6.7 Powerstroke Dual Thermostat?
Вставка
- Опубліковано 4 вер 2024
- 6.7 Powerstroke Dual Thermostat? #powerstroke #ford #mechanic #fordtech #f250 #f350 #flyingwrenches
Thanks for watching!
Contact - linktr.ee/flyi...
Amazon Shop - www.amazon.com...
👕Merchandise: my-store-d550a...
⬇️Ford 6.7 PowerStroke Recommendations-
Thermostat - amzn.to/3ZIfj3q
Radiator Hoses - amzn.to/3Hat6IW
Radiator (2011-2016) - amzn.to/3wcum82
Radiator (2017-2019) - amzn.to/3XgVRsU
Intercooler (2011-2016) - amzn.to/3Hat6IW
Intercoler (2017-2019) - amzn.to/3Hco1ja
Oil Catch Can (2011-2016) - amzn.to/3CX8
Oil Catch Can (2017-2019) - amzn.to/3XBvFsF
Secondary Radiator (2011-2016) - amzn.to/3XgWnHm
Intercooler Pipe Kit (2011-2016) - amzn.to/3wdaHEQ
Intercooler Pipe Kit (2017-2019) - amzn.to/3GOq5wn
Core Support - amzn.to/3XzrSw8
⬇️Ford 3.5 EcoBoost Recommendations
Sell It
⬇️ Must Have Amazon Tools
Pocket Scanner: amzn.to/3wjDaXi
Jump Starter: amzn.to/2TKp4B3
Pro Level Scan Tool: amzn.to/2SYdhi4
1/4” GP Socket Set: amzn.to/2TDramn
3/8” GP Socket Set: amzn.to/3dUBQDY
Extension/Adapter Set: amzn.to/3hXXNmV
Rachet Set: amzn.to/3r1EAow
GearWrench Set: amzn.to/3hMn432
⬇️Download ForScan For Free | Ford Specific Diag Software
1. ForScan Link: forscan.org/ho...
2. Recommended OBD Adapter: amzn.to/3yFLMZJ
⬇️ Gear Used To Make this Video
1. Camera: amzn.to/3jTcRVw
2. B Roll Camera: amzn.to/2VcYq45
3. Microphone: amzn.to/2UrGgeA
4. Tripod: amzn.to/3qTaQdg
5. Lighting: amzn.to/3i0hyu7
6. Editing/Upload: amzn.to/2SXw8dg
7. Gorilla Pod: amzn.to/3yBWe4L
8. My Brain Power - / @flyingwrenches13
⬇️Socials
Facebook: / flyingwrenchesauto
Instagram: / flyingwrenchesauto
TikTok: www.tiktok.com/@flyingwrenchesauto
⬇️Business Inquires
Email: maysondunsford@gmail.com
Disclaimer: Links included in this description may be affiliate links. If you purchase a product or service with the links in this description, I may receive a small commission. There will be no additional charges to you. Thank you for supporting my channel so that I can continue to provide you my best quality content for free!
Single thermostat working properly…
Ford: hold my beer
Yes. 😂
Duramax has it too
@evanwittig3976 also yes. 😂
Vw has entered the chat with a stepper motor to replace your thermostat.
Im sure others have too.
Lets take something that's worked for 100yrs fairly reliably and add some computer garbage to it.
Just wait until some fool thinks a broom needs a microchip.
This is a way better design.
The dual thermostat system was designed to accomplish the same temperature control under different load condition
That and coolant flow. one will allow x amount back to the radiator and two will increase it to max flow when engine temp caused by load or operation temp requirements it.
@@troyb5563the biggest issue with this is that higher flow doesn't immediately relate to cooler temperatures. if there is too much flow the coolant will not "sit" in certain areas long enough to pull heat from the engine. instead it will comtinue to flow and the engine will continue to heat up. I'm sure there's something with this system that has been engineered for these flow rates but in almost all cases this has not caused more cooling
@@FoxFabricationAndPerformance correct, that's why the thermostats are engineered with GPM in mind. I was referring to that as max flow.
Im surprised with all the electronic crap on engines these days that they still use a mechanical method (thermostat) instead of an electronic sensor/valve system🤷🏻♂️
@@Arknsawdave vw uses them on the ea888 and the newer 1.5L
GM did the same thing on older duramax diesels. The theory is, during light loads only 1 thermostat is needed to keep the coolant temp from dropping excessively. During heavier loads and or towing in the mountains the second thermostat is needed to flow enough coolant to prevent rising coolant temps.
The 6.5 in 98 got duals but they were the same temperature 🤣
And works perfect.
I'm making an educated guess.
Trucks need to have huge radiators to cool those massive engines under high load in hot conditions. You need to have as much flow as you can.
Under light loads like driving down the highway in -40° would cool the engine too much.
Bam dual thermostats.
So you do realize that a thermostat is not a open or closed binary device there's wax in there that as it heats slowly pushes the thermostat open
So unless something has changed on a standard thermostat 194 is when it starts to open it won't fully open for a while so you're not going to be like oh my God there's way too much flow all the sudden the motor got too cold.
So having the temperature differential you could have as many thermostats as you want they're only going to open slightly...
Sounds like over engineered garbage and as someone else said the 6 fives had dual thermostats it was the high flow literally was for extra flow same temperature thermostats two of them so that it would flow more to keep the engine cool Ford different temperatures why just why they are not open or closed devices they slowly open and they slowly close....
7 degrees is not going to make any significant difference.
Complete STUPIDITY
Love the cut to a 6.4 white smoking
😅😂
I almost bought a 6.4. Thank God that I researched engines before I bought a truck.
That poor 6.4 hope you fixed it. Something tell me not.
I still love my 2009.
Got a tractor with a 6.8L engine. It has 3 thermostats. Makes coolant flow a little more linear and keeps the thermostats from "hunting" if in a situation with variable loads.
well If you consider that dual thermostat 2, then that 6.7L has 4 t stats. has one on each side of the radiator and that dual t stat is on top of the motor in a housing where there is whats called the coolant crossover.
Hunting do we realize that thermostats don't just open and close.
A thermostat's not zero or 100 it's 0 to 100 they slowly open with temperature as the temperature increases the thermostat opens more so how the thermostat would start hunting doesn't make any sense there's a piece of wax in it wax gets hot wax expands wax pushes thermostat open as wax cools thermostat closes
Boil a stat, itd show you how it works. Pimping, dont embarass yourself talking stuff that dont make any sense.
Because the diesel engine dosent produce as much heat as a gasser and in order to maintain heater operation when ambient temp is low it allows less coolant through the radiator to keep Temps in the cab up. Older semi trucks employed an air powered tempature controlled radiator louver system to achieve this affect
Old Volvos also used to have a Louver system with no thermostat
It still gone take forever to get to 194.
Good guess, but no. A closed thermostat is a closed thermostat. Having 2 closed thermostats will not make an engine get to temp faster than just 1.
@@joec1995jcwhat? Dude its not about getting up to temp its about maintaining temp. So if I'm running empty on flat ground one smaller hole is open for coolant to pass. If I'm towing or working the mountains both open for maximum flow. Keeping one closed at low load when fluid imput pressure is low, increases output pressure keeping the fluid circulating but optimizing the fluid temp for the the heater core to utilize
@@mwiekhorst the guy I originally replied to was making it sound like that's the reason.
It gives more consistent thermal dissipation by creating a temperature controlled flow by doing this the engine doesn’t get a sudden rush of cooler temperature antifreeze which causes cycling irregularities this system allows ecu to more finely trim fuel to air mixes and also decreases expansion contraction cycling to help maintain torque on bolts and seals just about everything really
It allows a more finite adjustment of flow. Thermostats are not switches, they don't just open and close. The hotter they get, the more they open. So they let through an amount of water that is needed to maintain temperature. This is the same idea as a two barrel carburetor.
but surely you'd just design a different spec thermostat, reduce parts. This might pass muster by increasing maintenance costs ie profit margin but I don't get your tech reasoning.
@@DeepakKumar-lv4te like I said, same concept as a two barrel carburetor. If there is a large difference between the minimum flow you'll need and the maximum, then one large thermostat will not be able to modulate that flow as effectively at low flow rates. Just like one big butterfly drives less smoothly than the two stage butterflies that two and 4 barrel carbs use.
@@DeepakKumar-lv4teit makes sense to me, though I don't claim that it's actually the best solution to whatever problem they were confronting.
It's for additional cooling under load. When driving without a load my truck stays around 194~196 all day. However, when under a load not enough coolant flows through the one an the second opens, normally keeping temps (in my case) around 204~205. A heavy load in the mountains? It might get hotter anyway.
I've hit 250f with my 2015 in the mountains lol. Ran solid at 220,000 miles when I sold it
@@jeffhall768 I have yet to tow what my engine is capable of. My 250 is rated at 25,000 GCWR, but the same engine in a 450 is somewhere around 38,000. I bet it would get toasty like yours at that point!
My first guess was better flow. My second guess is it has to do with maintaining a more consistent engine temperature
You nailed it.
Basically ,emissions.
Yours sounds the best an wat I was thinkin
Cat had the same thing in the c7. The main reason for cat was GPM (gallons per minute) plus redundancy
But, the Cat C7 thermostats (or regulators as Cat calls them) are both the same temp.
@@tomthomas8004 yes funny the c7 the few engines cat made with no wet liner
It has to do with maintaining a more stable temperature with different loads on the engine, the 3521 Waukesha has 6 thermostats with three different temperature ranges and if you put them in the wrong order you will have temperature issues
Are the big Waukesha Engines 2 stroke? When I was first working on big drilling rigs back in the 80s I worked on a couple Slingshot Diesel Electric rigs with the 16 cylinder, 9.125 bore by 8.5 stoke, 8894.0 CI Waukesha engines running generators. The Cats were 4 stroke of course but the Stewart & Stevens, and Detroits were all 2 strokes. I can't remember if the big Waukeshas were 2 stroke or not. They were humungus engines. Thanks and be safe.
@@Big.Ron1 I don’t know if Waukesha makes a 2stroke or not, but the 3521 and 7042 are 4 stroke, the white superior engines run left hand or counter clockwise which was a surprise when I first started working on them, i have worked on a few big 2strokes but they were all Detroit’s, I’ve never worked on a Stewart and Stevens, i was working on a cat g399 16 cylinder today and I’ll be back there tomorrow as well
One for quicker warmup and the other one for quicker cooldown with heavyload by passing more volume of coolant.
I work for a Kenworth dealer and our understanding and teaching of our dual thermostat systems is for coolant pressure control. Helps with cavitation.
Limits coolant flow during normal operation to allow for smaller temperature fluctuations, keeping engine closer to ideal temperatures, but during excessive work loads allows for higher coolant flow for optimal cooling
Reduce thermal shock and you can actually have more surface area with two smaller thermostats in place one large one for more flow. Redundancy is another factor.
Heavy equipment engines have been running dual thermostats for a while. It’s to help prevent thermal shock when the engine is working hard. The lower temp thermostat opens first to bring in coolant slower and then the second opens up to move more volume of coolant
maintaining engine temp help with emissions and engine efficiency. this has been a thing in heavy duty engines for 40+ years. under normal and light work the single stat works fine. in hot temps and heavy work the second one opens up to keep the temps in check.
The only thing I can think of is diesels work better when they're warm,so you don't want to cool them too much,but you don't want to get too hot either to keep it at about 200 when running
they did this on the medium duty gas engine trucks as well.
I truly have no idea. But back in the day here in the cold we used cardboard or other materials to cover the grill because its hard to keep the cab warm when its -30f. So the carboard allowed it to stay warmer. So i fifure its to regulate the temp for the heater core. But im probably a mile off.
It's very common on medium duty and heavy duty engines. It's 2 things, more flow, and a failsafe. I'd imagine they are 2 different temperatures in that application because temperature and flow are lower rolling through town than pulling a grade with a trailer.
The big medium duty trucks from 80s and 90s were using this too. The primary or lower operates under normal conditions. If it fails, the second or higher operating temp thermostat will function to keep from overheating but alerts the driver that the primary thermostat failed. It's like a dual ignition on an aircraft, you can't afford to be broke down over a $5 part.
Mayson , I would believe from you more than any engineer because you are the one working on these trucks and you are the one that sees what works and what doesn't work and these engineers need to be in contact with people like you Because you guys are the one in touch with the customers and it's people like you Mason that keep these trucks on the road and Ford is thank you guys alot .
I think you hit the nail on the head brother.
Everyone else is banging on about the heat in the cab
Something somewhat similar is what I did to my 6.0 thermostat.
I drilled small holes around it. The coolant temp is between 150 and 170 when I am driving the F450 unloaded.
But when I am loaded hauling 40,000 pounds then it is around 180 to 200... And when I am going up hills the fan doesn't usually kicks in because it is not running overwhelmingly hot.
And if it gets all the way to 220 then it drops very fast too.
I love that trick. It makes the oil cooler to become a coolant heater.
It helps the cooling system get a head start on keeping the operating temperature at the desired target temperature, while keeping the coolant in the radiator for as long as possible, until the 2nd stat opens and rapidly allows cooler but not block cracking cold coolant to regulate the system temperature.
Makes perfect sense. Two t-stats will constantly cycle, while a single opens and stays open, then when the engine heats up enough to need more coolant flow, then it opens for more flow, without wearing them out from constant cycling. I've developed a dual tstat housing for a Cummins, and I get far superior cooling, even with a stock radiator. More flow makes better use of the radiator, especially when you get the small 1 inch id Cummins t-stats, though some are larger.
The only reason I can think of is the other thermostat is more for when the truck is running harder or in a regen. You don't necessarily want a higher flow rate in your coolant because if it's to much you will overcool which isn't good for optimal performance. It's all about trying to keep the engine at optimal temperatures depending on the loads
It's a flow thing... Start hi flow @194 & extra hi flow @201 cheeper than 1 big Tstat and holds engine temp @ best temp for clean burn
The reason for 2 thermostats being 7° apart is that if the engine is still not cooling enough and the temperature is still rising then more volume of Coolant needed so now 2nd thermostat opens and the potential volume has a higher chance to cool the engine.
During load conditions, the thermostat can open, but also during wintertime.That way you always have good heat inside the truck instead of having to block the raditor partially so you have heat
God I love the ford body style but watching this guy's videos makes me glad I have a cummins
Can’t knock a Cummins!
Not knocking it. All have their pros and cons
Watch Dave's auto center and you'll see they have issues too (and preventative fixes)
@@CGoody5642😂
I was in the same boat before I bought my Cummins. After dropping 10k on a built 68rfe to replace my blown one, I’m wondering if I made the right decision lolll
I suspect for the same reason your home boiler has a pressure relief valve. If for whatever reason the lower end fails the pressure will release at an increased temperature, your hoses won’t rupture, gaskets don’t blow, the block won’t warp and best of all it will let you know so you can replace it at your earliest convenience.
Duramax also uses two I believe it's allowed to help control the heat since they don't really build it idling or under no load but when working it build enough heat that it's two stats to help flow more and control heat under load and non loaded conditions it prolly overheating working under a heavy load with only one cause it would be restrictive pushing thru one t Stat. Easier to apply heat than it is to control it so it's bout maintaining coolant temp across the engine at the proper level.
Light versus heavy loads. Variable control over cooling system to minimize large fluctuations in temperatures depending upon engine load demands.
It’s the maintain consistent radiator temperatures under varying workloads
As thermostats tend to flutter in certain ranges
The guy that built the engine was a genius lol😂
To control engine temperature and keep it within the temperature range necessary for EGR to reduce nitrous oxide levels. If the engine is running too cold NOX emissions rise. If it's too hot stuff starts breaking.
The first thermostat opens when the truck is at operating temperature. When the engine gets too hot under a heavy load going uphill the second thermostat opens increasing coolant flow and the engine fan should go into high speed to bring it down.
It’s because if the primary fails the secondary prevents major overheating.
Same idea as a multi-speed furnace. Do a little bit of cooling if that's all you need. Or a lot if you need more. Probably helps reduce thermostat cycling in cold weather and low loads, and also acts as a failsafe against the thermostats failing closed; better to lose some cooling than all.
To maintain temperature better under any engine load or any ambient temperature, Paccar MX 13 uses the same dual thermostat design
It's so the engine will warm up faster...the top tstat is standard and controls passage to the radiator the bottom tstat has a bypass ( if closed ) to allow coolant back to the pump which allows coolant to bypass the radiator
Apart from redundancy it's meant to allow partial flow to give a more even, gradual warming of the entire system. Also it helps flow more when towing and keeping the engine under load compared to running around doing light driving where one open will be enough, especially on cold days!
It's to aid in maintaining an engine temperature between 194° and 201°. Most all diesel engines have had them since tier 3
Emissions? Quicker warm ups and then keeping the tempersture consistent/lower to reduce nox.
Usually any dumb idea on modern engines is usually for emissions
Back up for the emissions system for the lack of engineering.
Two for increased GPM and staggered temps to prevent a coolant surge that could overwhelm the surge tank and create a pushing coolant out of the overflow line condition.
At the time, caliper had 2 thermostats, one was to open at a 130. The old one was doping at a 195 is to warm up. The radiator so the cold war would not come in and hydrologic the Is water pump
I always thought it was to shorten cooling times after hauling a load helping the turbo cool so the oil feed line doesn’t get cooked off immediately
So when it opens the hot coolant, doesn't mix with the cold too quickly. Probably helps the engine get to operating temp sooner. I know Honda's stock thermostats open slowly as well.
To maintain consistent temperature This Also makes it easier on the gaskets since this will keep em from expanding and attracting.
Helps maintain EGT till coolant system is up to full temperature…
Restricting the flow of the system increases the heat build up, so the truck will actually warm up quicker.
Lead thermostat. Helps keep coolant temp from "waiving" up and down. Blends better
Dual thermostats kinda replaced radiator slats. It allows for a quicker warm up, helps control hot spots and theoretically gives better temp control. I know the old GM 6.5td had dual t-stats although I thought they were simply for greater flow. The first Duramax motors used offset temp and size thermostats to better control temps at different conditions and to increase coolant flow when needed.
Optimal operating temp is right around 194-201. Over 194 it starts to cool itself just a bit to drop back down, get too far over and cooling gets extra aggressive with an additional valve adding to the cooling ability.
Dual plane thermostats are common on diesel engines. Allison was great for using then, and since the Ford 7.3 is an Allison 466 it stands to reason it would have 2. Strictly for temp control under various loads.
It’s for proper cooling management. The 6.7 has like 7 radiators/condensers/intercooler (just a ballpark) so there’s not enough room in the grill to use active grill shutters, nor is it a cost effective and reliable option on what will more than likely be a work/tow truck
Lead and lag. One larger thermostat opening could allow the engine to cool too much and/or cause the thermostat to have to operate more quickly to maintain the desired temp. By staggering the open temps it allows the lower temp thermostat to perform the majority of the work and maintain a more stable operating temp but it still has the higher temp thermostat to help out in higher demand scenarios.
I love how ford fixes problems that never existed, in turn making new problems.
Most large diesel truck and off road equipment uses two thermostats so ford didn't invent the wheel.
One for heating up quickly, one for heating up optimally under loaded conditions.
Better for efficiency. Keeping the diesel engine more regulated for temp. If it gets hotter during the summer time, its best to keep a diesel engine below 205. So that 2nd thermostat will allow a much more flow with coolant to keep that temp regulated,
the first one is to reduce coolant flow, helping by keeping the engine warmed up during major winter months since diesels still need heat to operate to its best efficiency otherwise it will just run too rich on fuel.
If you have just 1 large thermostat set to a specific temperature the engine wont be able to regulate its temp as accurately as it would like as it would cause too much flow or not enough to keep it as its desired temp.
Not sure this applies to a cooling system with the capacity of the 6.7, but we had a similar setup on Mack E7 engines. When they first came out it was 2 195° stats. When under high load both of them opening at the same time would blow the upper rad hose off due to the volume of coolant. They the. Switched to a 185 and a 195 and didn't have that problem anymore.
The Duramax has 2 also and the way I understood it was to improve cooling under different load conditions.
The thermostat doesn't help cool it really helps heat the engine up it keeps the coolant from cooling until it reaches a certain temp
Dual thermostat is primarily for cold climates. allows coolant flow for heater since diesels take significantly longer to get up to operating temperature with such a large cooling system. It restricts flow to allow vehicle to get to proper operating temperature you know they have to keep EPA happy particulate filter is not operational until it get to proper operating temperatures as well.
Dual redundancy 1 reduces total failure and also modulates quick temp changes.
It's for coolant flow control, since diesel doesn't make as much heat as a gas, you need to limit the flow to allow it to warm up faster and hold temp better, then the second opens when its hotter to allow full coolant flow. I've only seem them on smaller diesels like 6.7s and as far as I've seen on hundreds of diesels, only cat has put duel thermostats on their commercial engines. Even Cummins has only had one which makes sense because its a 15l and it needs to be cooled fast as possible. Which is why older 6nz cats "overheat" to that 240f super easy. You need to switch the dual thermostats to single. Because it only works on smaller diesels
One thermostat allows coolant to flow to the radiator second thermostat acts like a re direct of the coolant to bypass the radiator and goes straight to the pump.
When working under heavy loads at temps over 110 degrees, you need LOTS more coolant circulating than if you are empty , luxury cruising
Extra flow under load helps cooling under tough conditions, reduced flow helps improve efficiency of the cooling system when not under load and helps it remain warm in extreme cold? I don't know if that's why, just my first thought
When you need enough coolant flow to go through that it requires two thermostats to open when you're at full tilt making power, you don't want both thermostats to be at the same temperature to flutter open and closed as the radiator cools the temperature too much at lower power levels.
I'm trying to think of a good analogy, but if both of them were the same temperatures they would open and close so much during normal driving that they would wear out.
I had one thermostat go bad and that kept the temperature below 140, it would not get up to 200°, so you only need the one thermostat to be functional at regular everyday driving, and you only need both thermostats working to get enough coolant flow for towing
To maintain coolant temps during after treatment regeneration when coolant will sit around 210°
Seeing all this plastic makes me happy I got my OBS 7.3 PS!
Because it was found that majority of EGR cooler failures were caused by lack of cooling system efficiency.
Just a humble guess, but i would say with the amount of power were making in the same design envelope as older generations. Plus the fact that we're pulling heat out of the exhaust stream with liquid cooled turbos and egr coolers while cranking EGTs to 11 with dpf filters. The 194 thermostat is sufficient to keep the heat in check under most conditions, but can't keep up under load or regen. Plus with the dual temp setup it probably helps to keep the thermostat from hunting in variable conditions or cold ambient temps. If the engine stays in a more consistent heat state it's also easier to predict and control the emissions. So, maybe easier to avoid a $2.6B lawsuit with the DOJ and EPA; or maybe that's just unavoidable.
Restricts flow, but allows some heat to get to the heater core. Then second opens to allow full flow. PLUS, if one fails.....unless fail open, which i think they fail closed.
If you think about this it sounds really complicated yes but with it being a diesel engine melt down temperatures are low 194 I would be assuming be getting warm n the 201 would keep the engine from huge failures such as a melt down
It gives diesels a more gradual temperature curve .
They don't like getting too cold and we dont like them getting too hot .
One thermostat opening at 201 will deliver a large amount of cool coolant to the block resulting in a significant and sudden drop in temp .
Not ideal . Hence why ,two thermostats
If I remember correctly they were having cracking with some of the plastic parts on the 6.4l due to the of the coolant shock when the tstats did open. Having one tstat open a little before the other would help prevent it.
First one is for most temp. Control second one increases flow to bring temp back down to the first one
For additional volume of cool water if the temperature continues to rise after the first opens if you look at the troubleshooting for coolant temp sensors the coolant temp will rise well past 201 indicating the are just trying to keep a desired temp without overcooling but sometimes under a load the flow of 1 may not be enough
My big truck engine uses the same philosophy and I've always understood it to be. It allows the engine to come up to the correct operating temperature and stay there. Even with varying load an engine heat production
This is why I live the electronically controlled thermostat on the 2028 and up Toyota Camry (probably on more models as well). It can adjust and send the right amount of coolant where it is needed.
The simplest answer is to better maintain desired temperature under all conditions
From my understanding Raymond has given the correct answer. And in my personal experience throw away the factory thermostat and upper radiator hose and get a good aftermarket set up. My truck has never gotten above 195 since and it doesn’t matter I do with it. And before everyone starts crying about heat that’s not a worry it does fine also heated steering wheel and seats make a difference oh and remote start.
My guess is it's to slowly warm up the engine so that the different materials don't expand too quickly.
It's because they're making too much power out of two small engines and the thermal expansion can't cope
Keeps a more consistent temperature and steps flow over as temp climbs.
Seems like a comfort thing to me. Warm for days it’s not working hard to cool, but add some volume when the thing actually starts building too much heat
In addition to the obvious more cooling at hotter temperatures, I think it also provides a nice level of redundancy. Thermostats are not reliable, so having two in parallel is nice.
Same reason cat and chevy 427 did it. Always have a back up
Eliminates the need for a bypass. In the motorcycle world the KLR650 had issues with it opening and immediately closing the thermostat as the radiator had as much coolant as the motor. A internal bypass would work but not as effective since the radiator at freezing temps could get much much cooler than the motor. That stress every time the stat opens isnt good for the heads.
I would assume it has something to do with the load on the engine. More flow to keep things good at high load, but the extra flow just cruising around would cause the engine to run to cold. But, remember Ford locks their engineers in separate rooms, and they're not allowed to speak with each other.
More water at higher temps for when towing or driving in low range when there's less wind to cool the engine
Temperature and pressure control. You need differential pressure. Best way to achieve that is get the minimum required flow to maintain cooling and keep the engine warm and open a second channel when that cooling isn’t adequate.
To keep the truck at optimal running temperature. The low thermostat is for the lower temperatures and wants to higher temperature. Thermostat cracks open to reduce the temperature back to the lower thermostat. It’s kind of like not towing and then towing, it produces excessive heat. Two thermostats open has a greater flow than one thermostat open, therefore, the temperature reduces
Better heat dissipation and keep it at peak performance temp easier is my guess. My 97 6.5td had identical dual t stats but that was cause early 6.5td has 87 gpm water pump and had overheating issues. 97 on had 130 gpm water pump and dual t stats without so much overheating issues
Thermostat only has a 20° differential by using two different thermostats get a greater temperature differential so when you're hauling that heavy load up a steep hill you have greater cooling capability
I think, without doing any research whatsoever, that when under normal driving conditions most likely 1 will open when needed, but when towing and under a load the second opens up to inrease the volume of coolant going through the vlock
Hot circuit/cold circuit. ECT on cold circuit, tranny, oil and turbo on hot circuit. SPE makes a great aftermarket thermostat. 171/180 open temps. I tow 10k daily in a 19 350. My hot circuit never even sees 200. ECT’s sit around 172 and EOT’s vary between 180-196.
It's a way to control the volume of coolant at different temperatures.
Basically more coolant flow when the engine reaches a higher temperature.. like drinking from a straw if you use another one you can consume more..