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[cyrusthevirus]

Hi, I have just taken possession of a 2.5 Omega automatic which my old man was going to scrap- I thought the old girl deserves another chance as it is such a nice straight car!

Basically the car is using coolant (approx half a litre on a 150mile drive back home) but there are no leaks which I can spot and no signs of a head gasket failure (no coolant/oil mix or overheating). The car recently had the cam cover gaskets changed which I'm thinking might be related. Is there a particular place which is prone to leaking on this model which I should look for? (my knowledge is of old Mercs, no idea where to look!)

Would be nice to solve the leak and re-MOT as I like the car. Thanks for any tips 

[Entwood]

Check the neck and fitting of the coolant header tank cap. Not unknown for small cracks in the neck, ot the seal in the cap to leak. This causes the pressure in the system to be lower than optimum and the water "evaporates" at a higher rate.

One way to check is to run the car to normal temperature then paint a soapy solution around the neck/cap looking for bubbles if the pressure is escaping.

Another way of finding small leaks is to add a bright food colouring to the coolant... bright yellow works    .... makes the leaks more "seeable" and leaves a trace of colour as the water dries....

HTH 

[jb]

check hbv a common fault

[The Red Baron]

check hbv a common fault

+1

[Andy H]

And for very thorough instructions V6 Change Heater Bypass Valve

[omega3000]

Check the radiator drain plug , some only drip after being pressurised and car parked up overnight 

[cyrusthevirus]

cheers

Is there a way to work out if the heater valve is dodgy without removing it? thanks 

[omega3000]

cheers

Is there a way to work out if the heater valve is dodgy without removing it? thanks 

Try different heat settings , bit of a blighter to see if its leaking ...have you felt underneath the hbv to see if its damp , leakage maybe from hairline crack that only noticeable with different heat settings . I replaced mine as a precaution as not knowing how old it was 

[tidla]

from memory, which aint great. cold and it should leak. mine sprung a leak miles from home. stuck the heater on hot(windows open) on the way back it lost next to nothing.

[albitz]

Remove the wiper scuttle and shine a torch on the HBV.You will probably be able to see if its leaking.

[jiho102]

Another place to look is in the 'V' of the engine where the oil cooler sits.
I think mine leaks from one of the pipes that run near the thermostate but not as much as yours though, justs needs topping up once a week with about 1/4 of a litre of anti freeze if that.

[JimE]

Another place to look is in the 'V' of the engine where the oil cooler sits.
I think mine leaks from one of the pipes that run near the thermostate but not as much as yours though, justs needs topping up once a week with about 1/4 of a litre of anti freeze if that.

I have been told by my father in law that his leaks a little coolant from the rear of the engine somewhere  and he has to to it up by about the same amount (1/4 ltr a week). He had it in the garage and for an oil change and they apparently had a quick look and said "Oh yeah it's coming from somewhere around the oil cooler area!" (very helpful LOL). Is there a way of determining/eliminating where without stripping everything out? The weird thing is he has since had the engine flushed and coolant changed and thinks it leaks less now?

[albitz]

you really need to remove the plenum and inlet manifold if its suspected to be from the oil cooler area.It will probably be obvious then.

[omega3000]

you really need to remove the plenum and inlet manifold if its suspected to be from the oil cooler area.It will probably be obvious then.

 

Especially if it stinks of old drains , coolant bridge seals need to be checked as well ...mine were weeping due to the washers perished 

[Johnny English]

I also suffered with mysterious coolant loss for a time at the end I found a quite small split on the rear end of the throttle cooler pipe. Good luck with it, mate!