Temperature indications fine, but coolant forced from expansion vessel cap (I think)

[lim]

The car is an E Class (W213) with an OM654 2 litre diesel engine. In operation the temperature indicator rises steadily to 90C and stays there without any noticeable fluctuation. The other day I noticed signs of coolant loss from the cap of the coolant expansion vessel; there were salts stains around the rim of the vessel and pink coolant filled a dimple in the bracket that supports the vessel. On removing the cap the vessel was quite empty and took one whole litre to bring the level up to the indicator 'tongue'. Apart from a faulty cap is there anything else that I should consider.

Regards, lim

 

[Flyinspanner]

Check your cooling system cap isn’t
A) properly fitted.
B) actually seats well, check the ‘land’ on the reservoir neck for rough limescale/corrosion
C) check the rubber on the cap isn’t poor/splitting.

check all hoses when warm - any bulging? - could be blockage.

 

[Deleted member 65149]

It could be the pressure in the cooling system increasing such that the pressure relief valve in the coolant cap is opening until it stabilises, thus releasing some of the coolant. The pressure could be increasing as a result of a leaking head gasket. A "nicer" fault could be a faulty coolant cap that's not letting the system pressure raise at it should; too little pressure could cause the coolant to boil off.

 

[lim]

Thank you for your thoughts.
The sealing cap has been checked and is wholly sound as far as I can tell and it should be as the car is only 8 months old. There have been no indications of overheating so I am suspecting an over pressurisation of the system. Way back in February the engine did overheat drastically due to an inoperative coolant pump and I am wondering if some damage done then is allowing gases from the combustion chambers into the water jacket. The loss of 1 litre of coolant has happened whilst driving 4000 miles over 8 months - is that significant - should I be worried - is it likely to get worse?

Regards, lim

 

[markjay]

Thank you for your thoughts.
The sealing cap has been checked and is wholly sound as far as I can tell and it should be as the car is only 8 months old. There have been no indications of overheating so I am suspecting an over pressurisation of the system. Way back in February the engine did overheat drastically due to an inoperative coolant pump and I am wondering if some damage done then is allowing gases from the combustion chambers into the water jacket. The loss of 1 litre of coolant has happened whilst driving 4000 miles over 8 months - is that significant - should I be worried - is it likely to get worse?

Regards, lim

Given that it's an 8-months old car, I would drive it straight to the dealer to have it checked under warranty. And take photos of the leak before you hand over the car.

BTW I has the same issue on my car (out of warranty) and a new expansion bottle pressure cap fixed the issue. If I were in your place, I would try to get the dealer to replace the pressure cap under warranty.

 

[E55BOF]

Yes, you should be worried on an eight-month-old car. It sounds as though the overheating has reulted in a head gasket leak. Take it back to your dealer and have them repair it under warranty.

 

[optimusprime]

Take a trip back ,,like above posts,, you should not lose any coolant from bottle or through the cap .

 

[nsamasn]

The car is an E Class (W213) with an OM654 2 litre diesel engine. In operation the temperature indicator rises steadily to 90C and stays there without any noticeable fluctuation. The other day I noticed signs of coolant loss from the cap of the coolant expansion vessel; there were salts stains around the rim of the vessel and pink coolant filled a dimple in the bracket that supports the vessel. On removing the cap the vessel was quite empty and took one whole litre to bring the level up to the indicator 'tongue'. Apart from a faulty cap is there anything else that I should consider.

Regards, lim

Hello, in the end what was the problem? I have the same problem now and the same motor