😭😭😭😭 So sorry for all this, Brian!… Don’t give up on her😞😞 When I deal with cooling systems I always watch the temp gauge and go back and forth between the engine compartment and the cluster. If the gauge reaches 100C I shut it off immediately. I hope your engine is fine but it’s usually never a good thing to reach 120C.
Hi Vito- it sucks for sure, but it's a learning experience. I don't think there's any major damage- but we'll see (could be small cracks that expand over time). Worst case, the block should be OK. I'm 100% with you that these are special cars and if needed I'll get a #22 head and install. Car does have 422k miles! So it would need a head gasket eventually
I've got agree with the air bubble diagnosis. Check the oil and see if its' frothy/milky, and the coolant to look for an oily film if you really think the head/gasket has failed. (oil-water mixing) Also: when you get the high temperatures and you are afraid of heat soaking it, I would NOT drive it, which adds stress/heat. Instead put a box fan on high setting to blow through the radiator with the car parked. (you see race teams do this all the time when cars are in the pits for an extended time.) Once the car has cooled, pull the thermostat and check it. (the old dangle-in-a-pot-of-boiling-water-on-a-string trick) If it opens, you are good there. Also: your model may have an air bleed screw/bolt at the top of the thermostat housing. You can open this while filling the coolant/running the engine to assist in driving out an air bubble. Park or tilt the car to make the fill cap the highest point in the system, set the heater controls to hot, and fill slowly with your coolant mix with the engine at an idle. I suspect the engine is fine, I didn't see any smoke/steam/liquids ejecting from anywhere. The idle didn't change. Also. look up the Waddington Effect and enjoy your initiation to the club.
Good call on the box fan - and the air bubble diagnosis. I think this is precisely what the issue was 🙂 I'll have a video coming up soon with a new thermostat / gasket and then showing a procedure to get the cooling system almost entirely full (it takes 10 liters - I got over 8 using this procedure). The way I filled the system (via expansion tank) only took 4-5 liters unfortunately - the bypass from expansion tank to water pump doesn't circulate enough volume of liquid. Much different than my experience on M104 and others LOL, RE: Waddington Effect. It's absolutely true (didn't know it had a name!). Anything not causing a direct problem, I've learned to leave it alone until it is causing a problem 🙂 In this particular case (ironically) I had to add coolant and didn't want to mix it. But in retrospect, should have just mixed G05 in with the pink/red stuff and pushed the flush until it was needed (doh).
@@bsclifton Excellent. No one is more pleased than I am that nothing extra-serious happened to the engine. Diesels have such high compression ratios that any water ingress to the cylinder wrecks things fast. The water is non-compressible so things like pistons tend to shatter. Or the moisture quickly flashes to steam which cranks the internal pressures destructively high.I figured if the head gasket had blown, there would have promptly been a trail of metal fragments marinating in an expanding pool of motor oil. but even the idle didn't sound bad.
@@FlashDriveFilms I'll have a follow up video soon I hope; I already filmed replacing thermostat and filling coolant. Will capture some of the car - like a walk-around. It's running great! Thanks for the kind thoughts and help diagnosing
Oh no. Drill a small hole in the thermostat's outlet plate. 1/16". Optionally another in the bypass plate. U had an airlock. Make sure the heater's bypass pump is working.
Do you know a good way to get the air out? I did open the petcock for the radiator, squeezed radiator hose. I have a new thermostat ready to go- will keep the old one and drill it like you're saying since I don't have the part mentioned in shop manual. Is the bypass the one used for circulating to cabin? That was working last night- but maybe it gave out. Should be easy enough to bench test that though- good idea
@@bsclifton There is a bleeding procedure. I don't know. It's in the manual. I always drill a hole in the upper plate of the thermostat. Small. Some have a rivet that works likes a one way valve. I cut off the rivet and have a hole. I don't think it's the thermostat. I think it was an airlock. U can't get the airlock if u have a leakage hole in the thermostat. IMHO thermostats either fail or work. Period. Be warned. MB diesels use lower temperature thermostats unlike the gas m103. Thermostat has two plates. Upper one moves down at opening temp and allows flow to the radiator. Lower one allows bypass to the pipe that goes down to the intake of the water pump. It moves downward. Good luck.
Thermostat bypass goes from below the thermostat to the intake side of the water pump. The cabin heater circuit also allows flow from the top of the cylinder head to the intake of the water pump. It has an electric pump to assist it. Unfortunately it is very susceptible to airlocks especially if there is any air in the engine block. Please check the rubber tube that goes from the top of the radiator to the reservoir. They often swell inside. Be real careful where it attaches to the radiator. Easily breaks. And sometimes leaks. I think u going to be ok w yours. Good luck.
@@ebutuoyebutouy thanks again for the tips! You nailed the diagnosis - air lock. Thermostat appears to be OK... but since I opened it up, it'll need a new gasket (I put back together and only after filling saw a leak). I'll order a new thermostat and gasket. I looked up the cooling system in shop manuals - it holds 10 liters of coolant. I definitely did NOT put that much in there previously when flushing (more like 4 liters max). Thinking things through logically, I filled car with coolant again but this time starting with the upper radiator hose (feeds directly into block). Slow and steady. And after burping out air, I was able to get almost 9 liters into the car. I turned it on and verified the circulation pump is working (to the cabin). That was loaded with air bubbles.
@@bsclifton Bottom line: why was there an airlock? That was because the air in the block could not escape because the thermostat's upper plate was blocking the escape route. And thermostat would not open for a while till steam got to it. Then all of a sudden it opened and car cooled. That's why u must drill a small hole in that upper plate. Period. Some have a loose rivet that acts like a one way valve. Then just chop off the rivet. IMHO u r brave to start off w new coolant. I would flush x3 over 3 days. First use tap water (preferably filtered w a Brita filter) and then distilled water that u buy in the baby section at the supermarket. Then put in the MINIMUM amount of antifreeze. Here in Hstn I protect down to 20f. Pure water is the best coolant but u do need a little rust inhibitor and anti cavitation mix. Good luck.
@@bsclifton Great! So, the issue was a stuck thermostat? HEY, while I am talking to you you are a smart guy when it comes to R129 :) right. I have a right rear tail light out ..92 500sl..It is not the bulb ALL other lights work on the right side..turn, brake,side marker lights all work. It does not appear to be getting power to the tail light socket? I was going to unplug and spray w/ electrical clearer and thoughts It is not the fuses...I tested them plus everything else connected to #1 fuse works? Hope it is NOT that N7 relay...what do you think?
@@rioraton I think the thermostat was fine actually- the root cause IMO was airlock. The cooling system takes 10 liters of coolant and in the overheating, I only really got maybe 4 or 5 liters in, because I was filling in the expansion tank. The thermostat would only open when it hits ~80C and there's not enough coolant on the other side to cool the engine, so it overheats. I filled the block completely from the upper radiator hose AND did the expansion tank (after replacing thermostat) and was able to get almost the full 10 liters in.
@@rioraton I've had issues with the rear tail lights on both the R129 and the W124. Try to narrow down if it's the wiring harness or the light assembly. In my cases, I had to replace the light assembly and that fixed the issue. Contact cleaner is always good to use - but you can also use a multimeter and test. Test against the other tail light (similar pins) and see what you get. Put positive on one pin and negative on the ground (in MB, brown is almost always ground), test one at a time. You might be able to take the light assembly from the left one and plug it in / try it on the right. The left has one more pin for the reverse fog but it should fit. Usually, the solder on the wires (from where harness plugs in to bulb) comes loose. Another test if you have the tools - test each pin on the light assembly for connectivity.
@@bsclifton Thanks. There is no power to the tail light bulb. But I was testing with multi meter I will use a test light and test again then unplug spray and test each pin with test light where it comes into the rear light assembly may be some corrosion may be bad solder joint like you said THanks B for the info
@@bsclifton after running that long in the red gasket most likely shot plus warped head. But you can probably replace the head and gasket and be ok. Worse case scenario you have a parts car.
@@w124mercedes7 maybe - it really does seem OK. Check out the latest video (JUST finished uploading it now) and let me know what you think ua-cam.com/video/SnsoRwolbOw/v-deo.html It's possible there are small cracks in the head or other damage, but it seems to be running fine enough for now. Will keep eyes open for a #22 head though.
😭😭😭😭 So sorry for all this, Brian!… Don’t give up on her😞😞 When I deal with cooling systems I always watch the temp gauge and go back and forth between the engine compartment and the cluster. If the gauge reaches 100C I shut it off immediately. I hope your engine is fine but it’s usually never a good thing to reach 120C.
Hi Vito- it sucks for sure, but it's a learning experience. I don't think there's any major damage- but we'll see (could be small cracks that expand over time). Worst case, the block should be OK. I'm 100% with you that these are special cars and if needed I'll get a #22 head and install. Car does have 422k miles! So it would need a head gasket eventually
Got a happy update! Check it out here: ua-cam.com/video/SnsoRwolbOw/v-deo.html
Thanks again for checking in
I've got agree with the air bubble diagnosis. Check the oil and see if its' frothy/milky, and the coolant to look for an oily film if you really think the head/gasket has failed. (oil-water mixing) Also: when you get the high temperatures and you are afraid of heat soaking it, I would NOT drive it, which adds stress/heat. Instead put a box fan on high setting to blow through the radiator with the car parked. (you see race teams do this all the time when cars are in the pits for an extended time.)
Once the car has cooled, pull the thermostat and check it. (the old dangle-in-a-pot-of-boiling-water-on-a-string trick) If it opens, you are good there. Also: your model may have an air bleed screw/bolt at the top of the thermostat housing. You can open this while filling the coolant/running the engine to assist in driving out an air bubble.
Park or tilt the car to make the fill cap the highest point in the system, set the heater controls to hot, and fill slowly with your coolant mix with the engine at an idle. I suspect the engine is fine, I didn't see any smoke/steam/liquids ejecting from anywhere. The idle didn't change.
Also. look up the Waddington Effect and enjoy your initiation to the club.
Good call on the box fan - and the air bubble diagnosis. I think this is precisely what the issue was 🙂 I'll have a video coming up soon with a new thermostat / gasket and then showing a procedure to get the cooling system almost entirely full (it takes 10 liters - I got over 8 using this procedure). The way I filled the system (via expansion tank) only took 4-5 liters unfortunately - the bypass from expansion tank to water pump doesn't circulate enough volume of liquid. Much different than my experience on M104 and others
LOL, RE: Waddington Effect. It's absolutely true (didn't know it had a name!). Anything not causing a direct problem, I've learned to leave it alone until it is causing a problem 🙂 In this particular case (ironically) I had to add coolant and didn't want to mix it. But in retrospect, should have just mixed G05 in with the pink/red stuff and pushed the flush until it was needed (doh).
@@bsclifton Excellent. No one is more pleased than I am that nothing extra-serious happened to the engine. Diesels have such high compression ratios that any water ingress to the cylinder wrecks things fast. The water is non-compressible so things like pistons tend to shatter. Or the moisture quickly flashes to steam which cranks the internal pressures destructively high.I figured if the head gasket had blown, there would have promptly been a trail of metal fragments marinating in an expanding pool of motor oil. but even the idle didn't sound bad.
@@FlashDriveFilms I'll have a follow up video soon I hope; I already filmed replacing thermostat and filling coolant. Will capture some of the car - like a walk-around. It's running great! Thanks for the kind thoughts and help diagnosing
Oh no. Drill a small hole in the thermostat's outlet plate. 1/16". Optionally another in the bypass plate. U had an airlock. Make sure the heater's bypass pump is working.
Do you know a good way to get the air out? I did open the petcock for the radiator, squeezed radiator hose.
I have a new thermostat ready to go- will keep the old one and drill it like you're saying since I don't have the part mentioned in shop manual.
Is the bypass the one used for circulating to cabin? That was working last night- but maybe it gave out. Should be easy enough to bench test that though- good idea
@@bsclifton There is a bleeding procedure. I don't know. It's in the manual. I always drill a hole in the upper plate of the thermostat. Small. Some have a rivet that works likes a one way valve. I cut off the rivet and have a hole.
I don't think it's the thermostat. I think it was an airlock. U can't get the airlock if u have a leakage hole in the thermostat. IMHO thermostats either fail or work. Period.
Be warned. MB diesels use lower temperature thermostats unlike the gas m103.
Thermostat has two plates. Upper one moves down at opening temp and allows flow to the radiator. Lower one allows bypass to the pipe that goes down to the intake of the water pump. It moves downward.
Good luck.
Thermostat bypass goes from below the thermostat to the intake side of the water pump.
The cabin heater circuit also allows flow from the top of the cylinder head to the intake of the water pump. It has an electric pump to assist it. Unfortunately it is very susceptible to airlocks especially if there is any air in the engine block.
Please check the rubber tube that goes from the top of the radiator to the reservoir. They often swell inside. Be real careful where it attaches to the radiator. Easily breaks. And sometimes leaks.
I think u going to be ok w yours. Good luck.
@@ebutuoyebutouy thanks again for the tips! You nailed the diagnosis - air lock. Thermostat appears to be OK... but since I opened it up, it'll need a new gasket (I put back together and only after filling saw a leak). I'll order a new thermostat and gasket. I looked up the cooling system in shop manuals - it holds 10 liters of coolant. I definitely did NOT put that much in there previously when flushing (more like 4 liters max). Thinking things through logically, I filled car with coolant again but this time starting with the upper radiator hose (feeds directly into block). Slow and steady. And after burping out air, I was able to get almost 9 liters into the car. I turned it on and verified the circulation pump is working (to the cabin). That was loaded with air bubbles.
@@bsclifton Bottom line: why was there an airlock? That was because the air in the block could not escape because the thermostat's upper plate was blocking the escape route. And thermostat would not open for a while till steam got to it. Then all of a sudden it opened and car cooled. That's why u must drill a small hole in that upper plate. Period. Some have a loose rivet that acts like a one way valve. Then just chop off the rivet.
IMHO u r brave to start off w new coolant. I would flush x3 over 3 days. First use tap water (preferably filtered w a Brita filter) and then distilled water that u buy in the baby section at the supermarket. Then put in the MINIMUM amount of antifreeze. Here in Hstn I protect down to 20f. Pure water is the best coolant but u do need a little rust inhibitor and anti cavitation mix. Good luck.
hope things work out let us know.
No update video yet... But it's all back together and everything seems great!
@@bsclifton Great! So, the issue was a stuck thermostat? HEY, while I am talking to you you are a smart guy when it comes to R129 :) right. I have a right rear tail light out ..92 500sl..It is not the bulb ALL other lights work on the right side..turn, brake,side marker lights all work. It does not appear to be getting power to the tail light socket? I was going to unplug and spray w/ electrical clearer and thoughts It is not the fuses...I tested them plus everything else connected to #1 fuse works? Hope it is NOT that N7 relay...what do you think?
@@rioraton I think the thermostat was fine actually- the root cause IMO was airlock. The cooling system takes 10 liters of coolant and in the overheating, I only really got maybe 4 or 5 liters in, because I was filling in the expansion tank. The thermostat would only open when it hits ~80C and there's not enough coolant on the other side to cool the engine, so it overheats. I filled the block completely from the upper radiator hose AND did the expansion tank (after replacing thermostat) and was able to get almost the full 10 liters in.
@@rioraton I've had issues with the rear tail lights on both the R129 and the W124. Try to narrow down if it's the wiring harness or the light assembly. In my cases, I had to replace the light assembly and that fixed the issue. Contact cleaner is always good to use - but you can also use a multimeter and test. Test against the other tail light (similar pins) and see what you get. Put positive on one pin and negative on the ground (in MB, brown is almost always ground), test one at a time. You might be able to take the light assembly from the left one and plug it in / try it on the right. The left has one more pin for the reverse fog but it should fit. Usually, the solder on the wires (from where harness plugs in to bulb) comes loose. Another test if you have the tools - test each pin on the light assembly for connectivity.
@@bsclifton Thanks. There is no power to the tail light bulb. But I was testing with multi meter I will use a test light and test again then unplug spray and test each pin with test light where it comes into the rear light assembly may be some corrosion may be bad solder joint like you said THanks B for the info
Blown head gasket or cracked head
It could be a cracked head- but so far so good!
@@bsclifton after running that long in the red gasket most likely shot plus warped head. But you can probably replace the head and gasket and be ok. Worse case scenario you have a parts car.
@@w124mercedes7 maybe - it really does seem OK. Check out the latest video (JUST finished uploading it now) and let me know what you think ua-cam.com/video/SnsoRwolbOw/v-deo.html
It's possible there are small cracks in the head or other damage, but it seems to be running fine enough for now. Will keep eyes open for a #22 head though.