Why we got rid of our radiator cap
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- Опубліковано 29 сер 2024
- For the last 10 years, we have always had issues keeping our Pikes Peak Subaru WRX cool. We have tried a number of things to increase the cooling capacity of the car, and we have had some success, but the car always seemed to find a way to overheat.
Then we went to Super Lap Battle at Circuit of the Americas this year, and we couldn't even get a lap in before the car would overheat and push coolant out of the overflow. We spent that weekend trying to troubleshoot the issue, and found a lot of odd issues (we have one video out on this all ready, and we are going to dive into the final results of the engine teardown here soon). But what came from all of that is that a big part of our problem was likely to have been our radiator caps.
As we looked into the differences between the 1-way and 2-way radiator caps, we also found that a down-flow radiator (which all turbo Subaru's have had here in the states) are also prone to cooling issues on track as well.
Everything is starting to fall into place and it is starting to look like simpler is better, and the old ways are better than the new ones.
So we have made some changes to our cooling system, and this video is a discussion about why we have removed one of the caps.
Thanks for watching and Stay Tuned!
And here is a link to the Professional Awesome article mentioned in the video. It is well worth a read:
professionalaw...
Anxious to see how these changes work out for you all. Keep up the good work!
Absolutely! Hopefully we'll have results here soon.
Thanks for watching and Stay Tuned!
Hi guys, I believe I may have an explanation for the overheating issues you are having.
As I don't have the specifics of what the circumstances under which you are overheating, that being the case I'll make the following assumptions:
1) Overheating comes on at high rpm
2) Appears to take place in a sudden onset, ie: temperature is ok, then suddenly you are overheating.
3)takes place when under sustained high load and in particular high rpm.
4)No underlying cause such as head gasket issues, thermostat working correctly, timing belt tensioner applying sufficient tension to adequately drive the water pump, correct Glycol concentration in cooling system, blockages or incorrect plumbing causing reversed flow within the system.
Based on those assumptions, I believe the problem is not in the outlet going to the radiator but on the inlet coming back from the radiator. May I refer you to the 3:00 time stamp on your video; take a look a the flow path of the coolant on the radiator shown in the window; the flow comes from the top, left of centre of the radiator. Coolant must then flow close to 400mm in one direction and 300mm in the other (14 and 12 inches) in order to presumably flow evenly across the width of the core (though in reality not the case), then when the flow gets to the bottom after passing the restriction to flow that is the radiator, all of the flow must then travel all the way to the far left of the radiator a path of 700mm at its longest to get to the outlet.
The flow rate through the radiator at high rpm becomes high enough that the radiator is unable to flow without a significant pressure drop; in essence we have the same scenario as an intercooler, greater efficiency due to greater surface area often results in an increased pressure drop across it. Should that pressure drop bring the suction side below the vapour pressure of the coolant, it will instantly boil. Remember boiling point is a function of both pressure and temperature, hence why we use higher pressure radiator caps to prevent overheating.
To a certain extent this can be addressed by increasing the pressure of the radiator cap or removing the radiator cap altogether. From a fluid dynamics if you are able to push a higher pressure (whilst maintaining the same flow rate) on the inlet and the pressure drop remains the same, we can hopefully force more water through in an attempt to maintain the pressure at the outlet of the radiator above vapour pressure, until you reach the same limitation.
A better option would be to improve the flow out of the bottom of the radiator. This would be a better option in my opinion as an added bonus it should help with pumping losses from the water pump.
An easy way to test this particular theory wold be to set up a video camera looking at the bottom return line from the radiator which might show the radiator hose collapsing if the pressure is low enough, or if you would like to take a much more technical and data based approach, set up pressure sensors to measure both inlet and outlet pressures at the radiator.
Whilst I would love to take full credit for this information and insight, ALL credit must go to Brett Middleton, former owner of MRT performance in Sydney Australia. I came across a technical video in his MRT channel on UA-cam. it is one of his much older videos where he goes into the finer details for what the original problem was in his then race car.
I hope this helps or at the very least provides some additional perspective. I will try to find the video and add the link later.
As I was reading it sounded familiar, I think I saw that video as well. Also, he's the former owner? Was this a recent change? I haven't followed up on their stuff lately but always did when I was working on my WRX.
Thanks for the suggestion. I'll have to see if we can find that video. Bret at MRT Definitely knows his stuff when it comes to Subaru's. In our case, there are a few other things going on, but improving the flow of coolant to the engine is never a bad thing.
Thanks very much for your comment and Stay Tuned!
Yes, I believe that Bret sold MRT to a new owner a couple of years ago.
This is one of those videos that makes you think:
"Yeeeeah, I'm gona add this to favorites. I'm gona need this one later"
Ha! Well, at least you know to go looking for it if problems arise.
Thanks for watching and Stay Tuned!
One common radiator for GC STI swaps from Koyorad is the VH090302, and it does not have a cap on the rad itself by design. It was originally for the 91-94 Legacy 2.2L Turbo I believe.
Great video, really helped answer some of the reasons why they were lacking caps back then for me, and also helped solidify my choice for using the above Koyo for my GC.
Thanks very much for the comment! Stay Tuned!
Scotty doesn't know .... Yeah I don't think we'll ever get that song out of our heads 😂
Ha! Well done.
these short videos are way better, i love em
Thanks very much! Stay Tuned!
Just letting you know, I run a wrx race car as well down here in Australia and I removed the opening flap of the thermostat years ago, resulting in a much more reliable cooling system back in the day. I run both 2 and 2.5 l forged engines in this car on e85 fuel. Hope that helps. Cheers and well done on the channel.
Excellent! We are going to be doing that on one of the shop cars here. The hard thing with the Pikes Peak car is that all of race week, we test in the morning which is usually below freezing, so we need to car to warm up at least a little bit. And we definitely don't want the water (required by the race) to freeze either. We're hoping to find a balance there.
Thanks for the comment and thanks for watching. Stay Tuned!
Warm ups have not changed for us in that by the time the oil temp comes up ready for racing, the water temp is well up. We are fine with ambient air temps zero thru 40 deg C. And if you have temps in the minuses that worry you, a piece of card blocking off a portion of the radiator front should fix that. I really doubt sub zero racing temps will be a problem with low coolant temps but at least you can deal with that. Data log cooling temps for a while. Cheers.
@@FlatironsTuning Sounds like you need an electronically controlled radiator shroud opening/closing panel that is temp sensor program from your standalone ECU.
But seriously it looks like that koyo radiator needs to be upgraded with a much higher quality efficient unit that comes with the cap delete option from the manufacturer.
@@DJ_Driven Thanks for the comment. The Koyo here was just for display. It has actually been sitting around the shop because it was damaged in shipping, but was handy for this purpose. That being said, we are definitely fans of Koyo radiators.
Thanks for watching and Stay Tuned!
Updating from my comment on the first radiator cap video. I installed the oem low pressure cap on the expansion tank rather than running 2 high pressure caps on my STI swapped GM6 (which just passed Carb :P ) and I was issue not with cooling but rather the cooling system pulling a vacuum and collapsing hoses after the engine had cooled. After installing the oem caps in the correct locations, that is no longer an issue and the system bleeds pressure to the correct areas. I never had an overheating issue but as the last video came up, I recalled just throwing both high pressure caps on with the mentality of higher pressure will yield a higher boiling point. So the video caught my attention as I had those hoses collapsing which cause the upper hose to come into contact with the alternator pulley and put a good groove into the brand new hose. But that one issue has been resolved and as the whole swap is stock im thinking it will be as reliable as a stock STI can be.
Very glad that we were able to help you get your car running properly cool again!
Thanks for watching and Stay Tuned!
The solution is really simple. Credit to MRT. Thermostat causes turbulence at the volute of the water pump and causes cavitation. Relocate thermostat to the upper rad hose and you'll never go over 200F ever again. I use the MMR with a 3/4 bypass line. Rad caps, crossflow radiators and all that are not significant enough to fix the root cause (high rpm + OEM thermostat location = cavitation).
Great vids guys. Effectively your set up is like the early GC8 WRX & STI (all be it that the earlier model is cross flow radiator) but they run a dedicated breather line from the top of the radiator end tank to the top of the expansion tank.
Yep, that is correct. And we do still have the connection from the upper tank to the expansion tank too.
Thanks for watching and Stay Tuned!
I run a one inch plate instead of a thermostat. Never ran into any problems now but I'm always racing in hot weather here in Thailand. Also run a custom cross bar and plate radiator with one expansion tank. Water temps never goes over 95 c in race contidtions.
Nice! Yes, a cross-flow radiator that allows you to put the cap on the low pressure side of the radiator would be a big help for sure.
Thanks for the comment and Stay Tuned!
Run a Stock radiator system on my 2002 WRX which has and APS IC, down pipe and exhaust with a tune done in 2005; all here in Phoenix AZ. The only time I have had issues with the car getting hot is cruising over 70mph in +115°F temps. So, if I keep the WRX at 70mph with AC on I don't have issues. As soon as I get up to +75mph overheating begins. Now, I drive my car like I stole it, and it does just fine with the stock setup, which is a single radiator cap on the tank near the intake. There is a stock expansion tank by the radiator as well. If this works here in Hell on Earth, then this setup should sustain some nasty beatings in lower temperature areas. Granted racing at altitude does cause cooling issues due to thinner air.
Thanks for the comment. Stay Tuned!
APS FMIC or APS Top Mount? Either way, some pretty rare stuff. Truly wish they had stayed in business. I've been running the DR525 FMIC on my '05 WRX since 2009, and I'm terrified of front end collisions: cars, animals, etc.
@@dullahan7677 Using TMIC. To your point, and the fact in 2005 I don't believe front mount were common on the street. I bought it from the original owner who is now in his 80's. 🙂 Going to install the JDM splitter and JDM custom painted scoop soon.
reading up on this for a while, first couple videos I found really talking about the problem. I am pushing coolant on high RPM. On one of my uploaded videos on the dyno you can see coolant on under the car after a few pulls.
Thanks for the comment. It definitely sounds like your cooling system isn't holding pressure properly, or you are moving compression gasses into the coolant.
Hope that our videos help you get to the solution.
Thanks for watching and Stay Tuned!
@@FlatironsTuningit was head gasket :-/
@@Zcypot Sorry to hear that, but hopefully you can avoid that type of failure going forward.
Hope you can get back on the road soon!
Good stuff as always I always have ideas like these
Thanks for watching and Stay Tuned!
Hey guys, thanks for updating us on your findings because they are very interesting and I hope your current configuration helps with your issues! However if I may ask, I have seen the other video but got kind of lost, so if you don’t mind just telling me what your guys’ definitive suggestion is for the cap setup on just a normal driven street car? Ex: 2 way valve 1.1 bar reservoir, single valve 1.3 bar radiator cap? I don’t believe I have cooling issues but would still like to maintain the proper pressures in my system to prevent issues down the line. Thank 👍🏻
Thanks for your question. At this point, we would simply recommend the factory caps. That is your best option I think.
Thanks for watching and Stay Tuned!
Is there any more info on these issues that y’all have figured out? I mean I don’t know if most people can have someone change the radiator they way y’all can? Did y’all do any more testing or have any other input on if you have to use the radiator and expansion caps, which seems to be most ideal? I’ve looked at both videos on the topic tens of times, I just kept waiting for a new one to come out to maybe help us more “common” non-mechanic type folks. Any additional input or info would be amazing if you have any. Thanks for all the amazing content!
Thanks for your question. Our cooling system is now working better than ever, so we haven't tried anything else because we are having good results currently.
For most applications, using the correct factory radiator caps is going to be your best bet. We talk about that here:
ua-cam.com/video/HzjBJz1Zdmw/v-deo.htmlsi=GNG-Qb-WIBqw5MyA
If you have the correct round cap on your radiator, the cooling system should be able to handle most of the hot conditions, etc.
Hope that helps and Stay Tuned!
this channel is excellent . subscribed, bell rung. Thank you
Thanks very much for the subscribe, and glad that the channel has been helpful!
Stay Tuned!
Keep us updated on this. Also since you removed a cap, what pressure rating is your main cap currently?
We definitely will let you all know how it works out. We are still using the 2.0 bar cap, but now that the configuration is correct, we should actually be seeing that pressure and raised boiling point in the system.
Thanks for watching and Stay Tuned!
Why not go to a custom fabricated radiator that is cross-flow instead? Even with how the Subie radiators mount, I don't see that as being overly difficult? Wouldn't that work better?
A cross flow radiator should be an improvement but since we have recently invested in the Killer-B radiator for the car, we need to stick with that for a while. And this change should make a good improvement.
It would be nice if there were more aftermarket cross-flow radiator options though, that is for sure.
Thanks for watching and Stay Tuned!
I cut the guts out of my thermostat because I can't find the cause of knock above 70°C in my un-tunable shitbox blobeye N/A SOHC EJ20.
I wired both the cooling fans to console switches and set up a digital coolant temp gauge on the dash and I operate the fans manually.
At 100kph on a 28°C day the car runs at about 70°C with the fans off.
I turn the Main Fan on if the car 'heat soaks' and pushes past 70° or when sustained hill climb is unavoidable I run both fans together.
Thanks for the comment. It is a bummer that the fans aren't working on their own for sure, but great that you were able to take manual control of them. Definitely helpful in hot conditions.
Thanks for watching and Stay Tuned!
@@FlatironsTuning fans have always worked but I need them to run well before 90°C.
My ecu turns the fan on at 95° and off at 90°.
That just isn't working for me until I work out why the engine is so knock prone.
You all have been killing it with the content. I have a question also. I had a local shop assemble and install my RA shortblock (that I got from you all) and when he installed it, he deleted the expansion tank. A few months go by and my car starts pushing coolant from the overflow. With the expansion tank being deleted, which cap should I have on my radiator? Should I use the OEM radiator cap or the expansion tank cap?
Thanks for your question James. With the expansion tank deleted, you would need a 2-way cap on the radiator. Definitely keep an eye on that and if you continue to see issues, you may well want to consider putting the expansion tank back on. If it was simply removed and you still have your turbo in the stock location, that would definitely make burping your coolant a bit more difficult.
For what it is worth, you may also want to take a look at this other video we made about the cooling system:
ua-cam.com/video/MBVNHON3d0w/v-deo.html
Hope that helps and Stay Tuned!
Maybe using gc8/sf5 radiator with horizontal flow core design would help as well?
It is an interesting idea for sure. I think that the plumbing is a bit different, but it may be possible to adapt to the newer engines.
For now, we are going to give this setup a try and see where it gets us.
Thanks for watching and Stay Tuned!
Hi, so it goes like this - use either OEM caps in OEM Locations (1.0 bar on expansion, 1.37 radiator) , OR use 1.5 radiator and 1.3 expansion tank?
Do not use 1.3 expansion tank and 1.37 OEM cap?
Awesome videos.
I like all that you said. I'd just add that it is ideal to have a 1-way cap on the radiator.
Thanks for watching and Stay Tuned!
@@FlatironsTuning thx!
@@FlatironsTuning so would you swap the one caps and do trimming the fins then? Though the holes aren’t the same size I think. If I use stock caps, I’ve got a lower rated cap on my radiator vs the expansion
@FlatironsTuning even if you don't have an expansion tank anymore? I have a rotated setup without the expansion tank now.
What about rotated turbo setups where the expansion tanks are removed? What's the best solution? 1.5 bar cap? Or? Thanks for such great information
Thanks for your question. Even if you put a rotated turbo on your car, you still want an expansion tank because you want to be able to bleed your cooling system from the highest point. If your turbo and coolant lines are higher than your radiator, it could end up being very challenging to get you cooling system to work properly.
Killer-B and IAG both make small expansion tanks that give you more mounting options if the stock one won't work. I'd recommend something like that to keep the cooling system functioning properly.
Thanks for watching and Stay Tuned!
@FlatironsTuning got ya... well I even bought the expansion tank but I have seen so so many builds without them that the local shop decided not to use one.
Seems adding an expansion tank is cheaper than an a radiator without plastic tanks. The only cooling problems I ever had with my Bugeye and TT BG Legacy, the plastic tanks splitting... 🤣
Yep, plastic end tanks on a radiator is not a great thing for any car I'd say.
Thanks for watching and Stay Tuned!
So if I'm currently running 2 koyo 1.3bar 2 way caps should I swap to the 1 bar 2 way expansion tank oem cap and the 1.3bar 1 way rad cap on the koyo rad? or can I just put the oem 1.37bar 1 way cap on the koyo rad and keep the 1.3 bar 2 way koyo cap on the expansion tank? I'm currently having a strange issue where I have to refill the overflow tank once every one or two months and I cannot figure out why since the system has been pressure tested multiple times and never shown a leak. I also never overheat. My theory is the 2 1.3 bar 2 way caps are keeping air in the system and everytime I fill the overflow it bleeds it a little. I never have overheating issues in the summer though so I'm kind of at a loss.
Thanks for watching and thanks for the question. I would recommend putting the 1.3 bar OE 1-way cap on the radiator as a starting point. Once that is in place, you know that all coolant coming back into the system will go into the expansion tank.
From there monitor your overflow and see if anything changes.
If you don't see any change, I'd say the next step would be to put the OE 1.1 bar cap on the expansion tank, and then monitor again.
If that doesn't get things working properly, then you need to do your best to find out where the coolant is going. Unfortunately at that point it could be the headgaskets.
Hope that helps and Stay Tuned!
What are your thoughts on electric water pumps such as the davies craig ewp150? With their digital controller you can remove thermostat completely and not have it affect the cars warm up. Plus you can run a water pump with no impeller reducing drag on the motor. Im also chasing heat issues being out here in the Arizona desert, but only in the hottest months, June, July, August. I wanted to give electric pump a go, but Gates seems to be the only company selling impellerless water pumps, and they have been back ordered for over 2 months now.... Sigh.
We actually ran the Davies Craig set-up for a while on the Pikes Peak car. Yes, you do have the ability to control the pump much more, but it never really worked well for us. Or I should say that it never seemed to work better than the conventional pump for us.
And we did upgrade to their highest flowing pump as well.
The main issue we had was once the car got hot, the electric system wasn't able to keep the temps below 200 deg. F, and the car would still overheat.
Knowing what we do now related to our radiator caps, it is possible that if we had removed the cap from the radiator when we were running the electric pump, it may have got us some improvement...
But having that sorted now, and with the improvements that we have seen in the cooling system since we have sorted out the radiator caps, I'd say that would absolutely be where I would start.
Hope that helps and thanks for watching.
Stay Tuned!
I run the the high pressure blitz cap on expansion and a cosworth high pressure cap on radiator....staggered...actually may have bought from you guys, lol. 20027842 1.5 bar cosworth rad cap...also have mishimoto tank and rad.
Nice! Yes, staggered is definitely the way to go with 2 caps.
Thanks for watching and Stay Tuned!
So as I understand, if I have 2 caps, should I put the higher pressure cap on the radiator and the lower one on the expansion tank? One is a 1.3 bar STI performance group N cap, and the other is the OEM.
Thanks for your question. That is correct, but the most important part is that the 1-way cap is on the radiator, and the 2-way cap is on the expansion tank.
Hope that helps, and Stay Tuned!
Are there one-way caps that go up to 1.5bar?
I see a lot of builders doing away with the expansion talk and using an IAG AOS in its place. Any thoughts on this idea?
Well, I would say that the IAG AOS isn't designed to serve that function. If it has a proven track record of working, then it may be okay, but I think I would really want the cap on the expansion tank.
Thanks for your question and Stay Tuned!
So I'm super confused now because I went to subaru of eugene oregon last year with the same issue and they sold me 2 different caps one looks like your stereo typical cap which goes on the upper coolant expansion tank and one that is completely round and its for the radiator. The one on upper area is supposed to be the higher rated of the two. I can give exact kulopascol when I get home tonight but is this not correct?
Thanks for your question. This is the cap that goes on the radiator:
www.flatironstuning.com/subaru-oem-radiator-cap
We go into detail about the differences in our last video here:
ua-cam.com/video/HzjBJz1Zdmw/v-deo.html
Hope that helps and Stay Tuned!
Thank you for the video 👍🏻
@@marcodg301 Absolutely! Thanks for watching and Stay Tuned!
Just curious, y not just modify the radiator cap to be a single valve? Seems ezer to do that then to cut a radiator up and weld on a bleeder screw on it. It would also be ezer for street cars to have this issue fixed also.
Thanks for the question. There isn't a good way to modify the radiator cap that I am aware of. And since we are trying to raise the pressure in the system to increase the boiling point, it is a much easier process with one cap.
Thanks for watching and Stay Tuned!
Bro what is the name of that rim on the car on top?
Fun fact my 91 legacy SS has no cap on the radiator and only on the expansion tank.
Yep, I think this only started in 2004 or so when Subaru was having issues with radiators failing on US spec cars.
Some of the earlier WRX's even had cross-flow radiators from the factory!
Thanks for watching and Stay Tuned!
Will you guys come out with a kit so we can do something similar?
Thanks for your question. That isn't actually something that we had considered, but I'll give it some thought.
Thanks for watching and Stay Tuned!
@FlatironsTuning so this setup still good? I just did this to mine.
@@cot998 Still works great for us!
@@FlatironsTuning next question. Why not use the old wrx radiator that doesn't have the cap instead of modifying that one.
@@FlatironsTuning also what cap are you using on your expansion tank?
Maybe try to use motorad thermostat 2094-170😉 as well
Thanks for the suggestion. Stay Tuned!
Is this necessary if u got a stock car with light mods? Koyorad or mishimoto radiator?
Thanks for your question. Nope, not at all. Just make sure you are running the correct radiator caps, and you should be good. This really would only be needed on track cars, etc.
Make sure you take a look at our video on the different radiator caps:
ua-cam.com/video/HzjBJz1Zdmw/v-deo.html
Thanks for watching and Stay Tuned!
i removed my expansion tank to fit my garret big turbo and made a custom reservoir., what can i do?
If you have a iag iOS race version check out how Josh at bbr bypasses the reservoir. You just need to keep the iOS at the high point of the system.
Thanks for your question. Take a look at the Killer-B Upper Turbo Reservoir:
www.flatironstuning.com/killer-b-upper-turbo-reservior-v2-barbed-fittings-02-07-wrx-04-21-sti
It is an expansion tank that is reduced in size. It may be easier to fit with a rotated turbo.
Hope that helps and Stay Tuned!