W124 Coolant foaming and overheating, with video

[elbistan]

Hi,
My Mercedes has recently started to loose coolant. Upon inspection it was loosing it from the hose in the expansion tank. The car has not overheated at all and the low coolant light comes on. I then noticed that the coolant was foaming. As seen in the video please watch. Mercedes W124 Coolant Foaming - YouTube I have googled and read few posts and it seems that it is the head gasket. Is this right? However there are no oil traces in coolant and not white residue present under the oil cap. Will this be a complete head gasket job. Would anyone know any MB specialist in North London please. Thanks

 

[millo777]

The foaming is likely to be coolant boiling. Under normal circumstances the cooling system is a sealed and hence can reach temperates over 100c and remain in liquid state, however as soon as the cap is taken off the expansion tank, it will boil. The same could equally happen due to a large enough coolant leak.

Any mechanic should be able to pressure test the coolant to trace a leak properly and if need be do a compression test to confirm whether the head gasket is leaking or not.

If it's the expansion tank thats the problem, replace it with a used one and see if that cures the problem first? it might be an easy fix.

Good luck with it.

 

[panason1c]

Looks to me to be a definite head gasket failure, the bubbles are caused by gasses escaping from the combustion chamber and into the water jacket (cooling system).

In your case, the head gasket has probably failed at a point between one of the cylinders and the water jacket, which results in the cooling system to be 'over pressurised' by gasses escaping from the combustion chamber(s) at the point of gasket failure...........

It is when the gasket fails between an oil gallery and the water jacket that you get the 'mayonaise' in the oil and oil in the coolant, etc.

 

[Beno]

If you take it to an Indi they can check the coolant if there's a head gasket leak it contaminates the coolant with combustion gas. They should have a test kit to check it.

 

[elbistan]

Thankyou for your replies I will take it to an Indie to check it out. cheers

 

[markjay]

If you take it to an Indi they can check the coolant if there's a head gasket leak it contaminates the coolant with combustion gas. They should have a test kit to check it.

Yes, also an MOT testing station can test for presence of exhaust gasses in the header tank (if they're not too busy) by placing the probe inside the expansion bottle (but not actually immersed in the coolant). Other useful checks are cylinder compression test, and you could also try placing your hand (carefully) behind the exhaust when the engine is warm and see if any water vapour forms on your palm - especially if it smells of Ethylene Glycol.