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Hello there, i’m alan. i’ve been on this site for a long time but never did post anything, but a lot of forums helped me here and let me know more about my car and how to fix it. i own a 2005 c230k, i have replaced the radiator 2 months ago because it was leaking, my replacement radiator was from an 03 c230 kompressor. the car ran fine after that and had no more leaks. 3 weeks ago i was driving and i had to accelerate to catch up to speed and suddenly the car didn’t wanna gain anymore speed so i looked at the temp gauge and it was 120c, i immediately pulled over and i was shocked, the car cooled down and it ran fine after that, so i went ahead and i replaced the thermostat and checked the t/stat but it seemed to be working fine, next thing i replaced the water pump twice and it seemed to be fine too. now the car overheats again when i got 80mph steady at high rpms with the ac on or off, the temp jumps to 100c then instantly to 120c. i don’t know what else could be wrong, i flushed the system so many times, i don’t know what else could be wrong with the car, i also use zerex g05 as my coolant. the car doesn’t overheat while driving around city at 40mph up to 60mph. only overheats when i go on interstate/higher speeds.
Last edited by Alan O Motran; Apr 4, 2020 at 12:19 PM.
Are you building excessive pressure in the cooling system?
Your description sounds a little what I saw in my 1999 C230K (W201/M111).
Water pump failed while daughter was driving it. It was ok for a while but gradually got worse. Head gasket.
I pulled the head, had it checked, replaced head gasket.
Originally Posted by Alan O Motran
Hello there, i’m alan. i’ve been on this site for a long time but never did post anything, but a lot of forums helped me here and let me know more about my car and how to fix it. i own a 2005 c230k, i have replaced the radiator 2 months ago because it was leaking, my replacement radiator was from an 03 c230 kompressor. the car ran fine after that and had no more leaks. 3 weeks ago i was driving and i had to accelerate to catch up to speed and suddenly the car didn’t wanna gain anymore speed so i looked at the temp gauge and it was 120c, i immediately pulled over and i was shocked, the car cooled down and it ran fine after that, so i went ahead and i replaced the thermostat and checked the t/stat but it seemed to be working fine, next thing i replaced the water pump twice and it seemed to be fine too. now the car overheats again when i got 80mph steady at high rpms with the ac on or off, the temp jumps to 100c then instantly to 120c. i don’t know what else could be wrong, i flushed the system so many times, i don’t know what else could be wrong with the car, i also use zerex g05 as my coolant. the car doesn’t overheat while driving around city at 40mph up to 60mph. only overheats when i go on interstate/higher speeds.
The break was between the cylinder bore and the water jacket. It did not get into the oil so no milkiness.
It would only leak a little when it was hot. I saw bubbles and excess pressure in the cooling system but nothing abnormal in the exhaust. It would also overheat.
You can also get a kit that checks for HC in the coolant to verify. These engines seem prone to popping head gaskets if you let them overheat. It might be fine for a while before it goes. 2 months and about 2000 miles for me.
If nothing is leaking and you have a good radiator and pump, the thermostat is not stuck shut and the coolant is circulating, there’s not much left to check.
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Thermostats fail open on these cars. The telltale sign of a failed thermostat is that the engine is running cooler than normal (<70C instead of >80C). This will also trigger a CEL. I am pretty sure your car does not have a failed thermostat. These do fail every few years though. Personally I'm on my 3rd one.
I second the opinion of checking the radiator for flow, especially if that's the only thing you changed out. The radiators on these cars are surprisingly cheaper than expected. Might be worth it to simply spend a few bucks more for a new one, considering you've already wasted money on the pump replacements. Coolant pumps are not known for failing on this car at all.
I assume your coolant level is where it should be.
Speaking of the radiator, did you have a Behr or Valeo installed? Valeos from that era (before 2004 I believe) are notorious for mixing coolant and transmission fluid (the transmission fluid is also cooled in the radiator). Many users on this forum have lost their cars this way when coolant got into their transmissions. If you have a Valeo, get rid of it ASAP and install a Behr. There should be a sticker somewhere and you'll need a flashlight.
Your engine is the M271 which is not known for head gasket issues, unlike the previous M111 buddy is talking about a few posts up.
Last edited by slammer111; Apr 5, 2020 at 09:47 PM.
With a recently installed new radiator, it's possible that an air bubble developed in the block on refilling with coolant. Depressurize the system by removing the cap and bleed the system. Also verify the cap is good. If the system repressurizes after bleeding then look at head gaskets.
i’ve read all of that, i’m not sure what type is my radiator but it came off of a 03 c230k that had a blown head gasket. and i did take all the air out, i took for a ride drove really nice, after that i let it cool down and then noticed that the coolant was low( because it circulated) so i opened the reservoir and suddenly it was just splashing coolant out of the cap that wasn’t open all the way, and from underneath the reservoir there was coolant going out. i topped then it was fine after that. this morning of april 6th, i found a puddle of coolant under the vehicle( driver side ) and the coolant reservoir was 3 quarters empty. here is a picture. do i need to lift the vehicle up and look underneath? coolant/antifreeze driver side
that’s out of my exhaust, i’m not sure if it’s residue from the old engine( it was hydro locked ) and the current engine was swapped in not sure what year but it has 87k miles on it. the body and tranny have 160k.
Thermostats fail open on these cars. The telltale sign of a failed thermostat is that the engine is running cooler than normal (<70C instead of >80C). This will also trigger a CEL. I am pretty sure your car does not have a failed thermostat. These do fail every few years though. Personally I'm on my 3rd one.
I second the opinion of checking the radiator for flow, especially if that's the only thing you changed out. The radiators on these cars are surprisingly cheaper than expected. Might be worth it to simply spend a few bucks more for a new one, considering you've already wasted money on the pump replacements. Coolant pumps are not known for failing on this car at all.
I assume your coolant level is where it should be.
Speaking of the radiator, did you have a Behr or Valeo installed? Valeos from that era (before 2004 I believe) are notorious for mixing coolant and transmission fluid (the transmission fluid is also cooled in the radiator). Many users on this forum have lost their cars this way when coolant got into their transmissions. If you have a Valeo, get rid of it ASAP and install a Behr. There should be a sticker somewhere and you'll need a flashlight.
Your engine is the M271 which is not known for head gasket issues, unlike the previous M111 buddy is talking about a few posts up.
Not sure what’s the radiator. i even have the old one that was bad, it doesn’t have any stickers anywhere, just a part number.
There should be a manufacturer stamp or logo somewhere, probably close to the PN. Not sure about the Valeo but on a Behr there is a sticker. Again you might want to look into this if you don't want your radiator potentially taking out your transmission in the future. 2003 is definitely within the danger zone. Besides the MB part number there should be a manufacturer part number stamped on it somewhere. A quick online search should tell you which brand you have.
See below for the quick and dirty way to tell the radiators apart. (not my picture)
Also just realized your car is now 15 years old. Plastic coolant pipes are known to go bad on this thing. The pieces (3 of the 4) break internally where the O-rings are. I know of 4 pipes that have been updated (they changed the grade of plastic) on this engine. The symptom is the car leaking coolant when the engine is cold, hence the puddle in your driveway. Change all 4 out, as 3 of mine failed one after the other within a few months. The small nipple piece snaps cleanly in half with no warning and will leave you stranded. Personally I keep a spare one inside the car. It's only a few bucks.
Is the overheating happening while your coolant level is at the proper level?
As for that wet exhaust, give your car an Italian tuneup and see if that goes away. I definitely do not have any liquid coming out of the exhaust after a drive. Any condensation inside the muffler should boil off rather quickly.
Last edited by slammer111; Apr 7, 2020 at 02:18 AM.
There should be a manufacturer stamp or logo somewhere, probably close to the PN. Not sure about the Valeo but on a Behr there is a sticker. Again you might want to look into this if you don't want your radiator potentially taking out your transmission in the future. 2003 is definitely within the danger zone. Besides the MB part number there should be a manufacturer part number stamped on it somewhere. A quick online search should tell you which brand you have.
See below for the quick and dirty way to tell the radiators apart. (not my picture)
Also just realized your car is now 15 years old. Plastic coolant pipes are known to go bad on this thing. The pieces (3 of the 4) break internally where the O-rings are. I know of 4 pipes that have been updated (they changed the grade of plastic) on this engine. The symptom is the car leaking coolant when the engine is cold, hence the puddle in your driveway. Change all 4 out, as 3 of mine failed one after the other within a few months. The small nipple piece snaps cleanly in half with no warning and will leave you stranded. Personally I keep a spare one inside the car. It's only a few bucks.
Is the overheating happening while your coolant level is at the proper level?
As for that wet exhaust, give your car an Italian tuneup and see if that goes away. I definitely do not have any liquid coming out of the exhaust after a drive. Any condensation inside the muffler should boil off rather quickly.
that’s interesting. the radiator that i removed from the car was a valeo (the damaged one) but the one in right now is a valeo too ! but i do not see any leaks from it or problems at all, but it might be clogged as mentioned above. but i will definitely invest into getting a behr radiator. and also the coolant leaks when the engine is cold (overnight) i found a topic/forum that was talking about coolant leaking when the engine is cold, turns out it’s the pipe behind behind the engine. but i have to check that out too. and yes the car overheats when the coolant is at proper level.
Going back to my recommendation about the head gasket test. Whenever there’s a vague overheating problem and no evidence where the coolant is leaking, I suspect the head gasket. You have a couple of other clues—it overheated with a bad water pump and you may have moisture in your exhaust.
It’s a simple test if you borrow the kit from your favorite auto parts store. I hope, for your sake, it’s negative. But if not, at least you know. You can decide whether to swap engines, fix the head gasket or drive it to the scrapyard. Or, try your luck with a head gasket sealer...
If negative, then pressure test the cooling system.
There are a bunch of coolant pipes in the vicinity. However it's misleading as the coolant can flow anywhere once it drips onto the plastic trays. Trace the liquid upwards. As mentioned, manually check each of the plastic pipes in the link. Any wet spot will be obvious.
There are a bunch of coolant pipes in the vicinity. However it's misleading as the coolant can flow anywhere once it drips onto the plastic trays. Trace the liquid upwards. As mentioned, manually check each of the plastic pipes in the link. Any wet spot will be obvious.
Hopefully it's not a head problem.
after looking and searching i couldn’t find the leak. i took the spark plugs out and looked into the combustion chamber but there is no signs of coolant in there or anything. i don’t know what else to do, but i’m sure it’s not a head gasket. i did the test and it’s negative.
That’s good news. I’m glad you don’t have to worry about the head.
Do you have, or can you get, a cooling system pressure testing kit? Auto parts stores sometimes have these for loan. There are lots of videos on how to use them to troubleshoot cooling leaks.
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That’s good news. I’m glad you don’t have to worry about the head.
Do you have, or can you get, a cooling system pressure testing kit? Auto parts stores sometimes have these for loan. There are lots of videos on how to use them to troubleshoot cooling leaks.
5
so i got the cooling system pressure and pressured the system at 13psi and had no leaks at all, went up to 15psi and totally nothing dripping, looked behind the engine and firewall and it was dry. i came to conclusion that it is a bad radiator, because that radiator was taken out of an 03 c230k that had a blown head gasket and it was parked for 2 years. i’m assuming the reason why the head gasket blew was because of the radiator ! i ordered a mahle behr radiator for $160 and it’s coming tomorrow, i will be definitely installing it and hope that everything else works fine. i will provide updates and see how things will go, thank you !
so i got the cooling system pressure and pressured the system at 13psi and had no leaks at all, went up to 15psi and totally nothing dripping, looked behind the engine and firewall and it was dry. i came to conclusion that it is a bad radiator, because that radiator was taken out of an 03 c230k that had a blown head gasket and it was parked for 2 years. i’m assuming the reason why the head gasket blew was because of the radiator ! i ordered a mahle behr radiator for $160 and it’s coming tomorrow, i will be definitely installing it and hope that everything else works fine. i will provide updates and see how things will go, thank you !
Hello did you ever find out what was making your car overheat? I have a 2006 w203 and my car temperature is at 90 degrees was at 75-80.. when should we replace the thermostat? Ive never changed it since I’ve had it... what should I check out as a prevention with it being an older car? I just had the radiator, upper and lower hoses replaced. Should I have replaced my thermostat? And spark plugs? Thanks
Last edited by valgal3x; Apr 18, 2020 at 11:00 AM.
Reason: Add more questions and spelling
Hello did you ever find out what was making your car overheat? I have a 2006 w203 and my car temperature is at 90 degrees was at 75-80.. when should we replace the thermostat? Ive never changed it since I’ve had it... what should I check out as a prevention with it being an older car? I just had the radiator, upper and lower hoses replaced. Should I have replaced my thermostat? And spark plugs? Thanks
when i meant by overheat, is when my temp gauge goes from 80 to 100 to 120 which is crazy. but in your situation if you’re not reaching these crazy levels that i have, it could be as simple as some air is in your system. remove the expansion tank cap, slowly because it could be pressurized if the car is kinda hot, then put your car in the ON position but don’t start it, put the heat on max and the fan level should be 1 or 2 then press the gas pedal for 10-12 seconds and then u will hear your auxiliary pump activated and you will hear water running through your dashboard/firewall. leave it running for 10 mins or so and you will notice bubbles coming out( if there is air in the system ) but that could be the case. if not, then i suggest take your t/stat out, carefully without breaking the house unless you you have a new t/star housing, then test it by getting a pot full of water that covers 3 quarters of your t/stat then let it boil, if you notice your t/stat opening and reacting fine, then you’re good, if it’s not opening quite enough or it’s not opening then u need a new t/stat. Also you can release pressure off your serpentine belt and spin the water pump, make sure it’s spinning right and you can’t hear any grinding or noise. For your note, after market T/stats take a little time to open than an OEM one and it doesn’t open as much as an OEM t/stat too, that’s just from my experience and testing. let me know how that goes for you.
when i meant by overheat, is when my temp gauge goes from 80 to 100 to 120 which is crazy. but in your situation if you’re not reaching these crazy levels that i have, it could be as simple as some air is in your system. remove the expansion tank cap, slowly because it could be pressurized if the car is kinda hot, then put your car in the ON position but don’t start it, put the heat on max and the fan level should be 1 or 2 then press the gas pedal for 10-12 seconds and then u will hear your auxiliary pump activated and you will hear water running through your dashboard/firewall. leave it running for 10 mins or so and you will notice bubbles coming out( if there is air in the system ) but that could be the case. if not, then i suggest take your t/stat out, carefully without breaking the house unless you you have a new t/star housing, then test it by getting a pot full of water that covers 3 quarters of your t/stat then let it boil, if you notice your t/stat opening and reacting fine, then you’re good, if it’s not opening quite enough or it’s not opening then u need a new t/stat. Also you can release pressure off your serpentine belt and spin the water pump, make sure it’s spinning right and you can’t hear any grinding or noise. For your note, after market T/stats take a little time to open than an OEM one and it doesn’t open as much as an OEM t/stat too, that’s just from my experience and testing. let me know how that goes for you.
Yes, my problem was the radiator. it was a used Valeo radiator from a 2003 c230k that had a blown head gasket, which i’m guessing was the radiator’s fault. i ended up buying a brand new Behr radiator, and it’s working so good with me.
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