Get a test kit to check for combustion by-products in the coolant. That will tell you very quickly if you have a head gasket on the way out.

 

There is something very wrong here. Coolant should circulate well through the heater core. Radiator should be hot all over at operating temp with thermostat open.

 

What if the heater core is blocked?

Should the bottom radiator hose be hot too?

Sorry to do your head in, lost my job recently I am so broke to take it to a mechanic who knows things about these cars, not any old cowboys.

Thanks.

 

The heater core might be blocked. Remove it & have it chemically cleaned.

When the thermostat is open both radiator hoses should be hot. Obviously there should be a temperature drop across the radiator but the bottom hose should still be pretty hot.

 

Thanks Glyn.

Will try what you have suggested.

In regards to removing the heater core to have it chemically cleaned or even replace, where can I get removal instructions etc. like the dash?

Thanks again.

 

In the spirit of not starting a new thread, I will use this to post some pictures and ask for some help and suggestions.

Long story, short: 01 C320, 142K miles on it. A few weeks ago it gave me the "Coolant - Check Level" warning. Two days later, I got it checked out at an European indy in NE DC and they said that, while my coolant was low, he didn't see any leaks. He did a pressure test after and said that it showed no leaks. He topped off the coolant and all was dandy like sour-candy. Heating worked perfectly.

Fast forward to this past Saturday and the "Coolant-Check Level" warning came on again. I drove it around for a bit, got gas, and the message never popped again while driving on Saturday. There were some decently long trips (15 miles) with 2-3 hours in between them. Sunday, though when I started my car cold, the warning popped on again. Didn't drive anywhere as I forgot something upstairs. Turned the engine on again, the warning came up again. Drove to dinner and after the warning didn't come on again. Tomorrow morning it will likely come on again. Coolant seems to be a little low, but not that low, I would say around one inch or so from the black top of the tank.

When I drive, both freeway or city or beltway traffic jam, temperature hovers in the mid 90s according to the bar graph.

I inspected for leaks, and while none seemed visible, there were some interesting stains on and around the tank. Heating works, but to a degree: engine has to be warm and I have to set the temp at 75F; last winter I could get steamy with heat at 71F. Thermostat got replaced by an indy in January after spitting a check engine light.

A few question: how can coolant leak when the pressure test is fine? Is the pressure test something that the mechanic can screw up and not do properly?

What could cause the stains in the pictures?

Final question, if coolant was leaking into the transmission, it would start shifting poorly right? The thing is that it doesn't; it's smooth and good, the way it always was.

Looking forward to everyone's wisdom. Thank you.

 

"Coolant - Check Level" warning is german for fill up your windshield washer fluid!

 

I filled up a few weeks ago when the first warning came on and didn't use much since, but I will add more and see what happens. Are those stains normal though?

 

No, Not normal. They happen when the cap is not properly tight or the seal is not good, or the pressure was too high in the system. That means it was too hot also.

Clean the stains off and see if it does it again.

 

+ 1

As Glyn said above have a combustion gas check to see whether you have a cracked head or head gasket leak.

You can loose coolant into the combustion chambers which may have caused the low level. Also combustion gases can over pressurise the coolant head tank causing the cap to leak.

The pressure test could miss a small leak when the engine is hot ie expanded. I always lost coolant in the past when the engine was cold & the gasket leak opened up.

When cold started does the engine miss slightly for a short period indicating water in a cylinder?

Have you noticed any water vapour from the tail pipe ?.

Check your water pump seal for leakage.

Good luck.

 

if coolant is being burned along with the gas in the combustion cylinders then wouldn’t the exiting fumes be thick white smoke?? which is a clear indicator of coolant leaking into the cylinder and mixing with the air fuel mixture and burning with the fuel.....

little confused here as I am facing the same issue.....

My story...

Recently got the "check coolant level" and also a Check engine light (don’t remember which came on first.....message on the dash of my 2007 C280 4matic....well was debating doing a complete flush which I did over the weekend.....drove around and topped off the reservoir......drove today morning to work and the "Check coolant level " message popped on again.....have read this entire post . but mine a more modern I guess M272 engine, do I also have the plagued Thermostat problem.....heating is OK not as warm as it used to be.....any direction.....

Would hate to start another thread.....sorry merclondon for hijacking your thread....

javvy

 

Thanks for the replies everyone! It's not smoking with cold start. A quirk i noticed today. Heating works like a champ on the freeway at 60 mph plus, but it is lame in city traffic or speeds below 40mph. Based on the spilling pattern, i would say the first culprit in my case would be the cap. So i'm going to top it off, clean the stains and replace the cap as a first order. Quick question: does any cap i could find ar autozone work or do i need to get one at a dealer?

Also when topping off, do i need to stick with the 50/ 50 mix?

 

I would get one from the dealer to be sure it is the correct one. Check the gasket for splits.

It is best to have some MB coolant at hand to top off but a small amount will not matter.

Make sure the water is demineralised or distilled . Crappy old mineral laden tap water is not good.

 

Check what brand your radiator is I doubt it is a Valeo as your transmission would have probably died years ago but it is worth a check.