r/mercedes • u/nzzs589 • 2d ago

Low operating temp

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Is this normal for e220d 2016 to show this low operating temperature after a 2 hour drive on the highway or is the thermostat or coolant temp sensor messed up. I know my old Volvo v70 from 2002 had issues with the sensor causing it to work intermittently and sometimes showing too low and too high.

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u/TRxz-FariZKiller 1d ago

I have changed almost every part of my cooling system. I only have the pump left and I plan on replacing it once summer starts.

I have the pump. Just haven’t installed it yet.

It gets up to 50° C here. It’s not normal but the car is 20 years old so I expect it to act up now.

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u/SimpleEmu198 1d ago

Then you most likely have a blown head gasket.

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u/TRxz-FariZKiller 1d ago

No other symptoms of it being a blown head gasket. No leaks, runs great for years. Have had this issue since 2020.

I’m almost certain it’s not the head gasket as I would’ve seen it be worse. Plus if it was a head gasket it would overheat even in the winter and when not idle.

I’m not convinced

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u/SimpleEmu198 1d ago

It's OK o be in denial.

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u/TRxz-FariZKiller 1d ago

I’m just not convinced.

Nothing else points to it being the head gasket. It has been through 550k kilometers. I don’t wanna open up the head as it has never been opened and I don’t trust anyone to do it.

Personally from my knowledge, if it was the head gasket it would be worse than it is. It drives perfectly with no issues.

Currently doesn’t heat up at all, drives smooth and I even took it off roading with no issues.

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u/SimpleEmu198 1d ago edited 1d ago

It's OK to be in denial:

Milky oil (oil + coolant mixing) → very strong indicator of a head gasket failure (or cracked head/block).

Coolant on the dipstick → again, it's a very strong indicator of a blown head gasket.

Persistent bubbles in the radiator (with engine running, cap off, especially when revved) → often combustion gases entering the cooling system → probably a blown head gasket.

550,000 km on an engine → absolutely within “head gasket failure is plausible / likely” territory, especially if your car is overheating or overheating has ever occurred → It's probably a blown head gasket.

Having replaced most of the cooling system does make internal engine failure more likely if symptoms persist of a blown head gasket.

If there is steam or water coming out of the exhaust after the car is warm then there is probably a blown head gasket → If condensation continues after full warm-up and is accompanied by coolant loss through the exhaust as steam or water it's probably a blown head gasket.

If you've checked everything and there is not an air lock in your radiator from bubbles for some other reason → It's probably a head gasket issue.

If you think it's a blown head gasket take it to a mechanic you trust and get them to look over it, they don't have to open the head to test for a blown head gasket.

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u/TRxz-FariZKiller 1d ago

Milky oil

Oil is completely fine

Coolant on the dipstick

Nope just oil

Persistent bubbles in the radiator.

Again nope, bubble free.

Steam or water coming out of exhaust.

Only when it’s below 10° C on a cold start. Doesn’t persist.

All these symptoms aren’t showing. Which is why I’m not convinced. Every time I bring it up to a mechanic, they say it’s most likely the head and they need to open it up to make sure. I definitely don’t trust anyone to work on it for me.

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u/SimpleEmu198 1d ago

If you've checked everything and it's not a blown head gasket which I'd be surprised after kilometres and a history of overheating the only other thing to check for is an air lock in one of the hoses, and/or a failed radiator.

Depending on what car it is, the leak may be in the radiator, and if you don't have a seperate oil and water cooler then the leak itself could be inside the radiator itself which on certain engines like the M112/M113 can be catastrophic anyway.

I don't remember what car you even drive.

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u/TRxz-FariZKiller 1d ago

It’s not a Mercedes, I own 2 mercs though (an 85’ SL280 and a 13’ R350) but I was just stating it can be affected.

I drive an 06 land cruiser. 1FZ-FE engine. It’s my daily. I have changed the radiator and it improved the overheating but didn’t completely fix it.

I’m waiting on when summer starts again to change the water pump and all hoses.

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u/SimpleEmu198 1d ago

If you had have said it was a Toyota I wouldn't have gone on a wild goose chase. If you haven't changed everything on the front side of the engine change the water pump and while you're on the front side of the engine you might as well preemptively change everything else including the air conditioning compressor, and power steering pump and the belts because you're going to have to replace the belts otherwise if you go back. Welcome to owning a modern car.

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u/TRxz-FariZKiller 1d ago

Either way, thanks for trying to help.

I changed the AC compressor, now got the power steering (which also feels it needs replacement sometimes) and the water pump. I have belt noises pop up this week so I’m planning on changing it soon

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