1991 300te

[bigkevtaxi]

when i`m stuck in traffic the temp. gauge goes through the roof but if i put the heating on full it drops back to normal but then looses water and i have to keep filling it up but can find no leakes pressure is very high any suggestions

 

[brandwooddixon]

Head gasket.

Stuck thermostat.

Viscous fan failure.

Electric fan failure.

To name a few.

If you're absolutely certain that there are no leaks - test by standing the car on a dry surface and allowing it to overheat etc. and then check the surface underneath for leaked coolant - then it's probably the head gasket.

 

[supercharger]

I wouldnt rule out the radiator i had the same symptoms on my w126 v8 which did exactly the same no sign of a leak but needed topping up now and again.eventually the rad failed with a big leak. i replaced with a brand new one and the temp struggles to touch 80 degrees when doing 100 plus no coolant leak.and no more problems.


supercharger

 

[bigkevtaxi]

the top hose and the top of the rad get very hot but the rest of the rad is cooled by the fan and the bottom hose only gets luke warm

 

[brandwooddixon]

Are you certain that you've actually got coolant flow?

 

[television]

This does seem like no circulation, I would do the carrot test first on the fan.

It speeds up at 80c or it should do

 

[Bolide]

You need to work methodically through all the possible faults - water pump, blocked rad, blown CHG, etc. It will take some observation to diagnose properly and that can't be done remotely

On all W124s the radiator and water pump will need to be replaced at some point in the first quarter million miles

Nick Froome
www.w124.co.uk

 

[wireman]

Try the thermostat first about a tenner from GSF/ECP, from your observation of top hose temp I think that there is little water flow in your radiator, ie the stat is stuck closed and the only water path is via the heater matirices. If the rad was choked up the bottom hose would get hot.
The water pump tends to fail by leaking through its gland (and the bearing gets noisy), this can lead to sudden total water loss with early signs of the wear being occasional loss of a little water at irregular intervals, usualy this is difficult to find since the loss is small and only happens when the engine is hot and running (the lost coolant evaporates imediately on a hot engine).
The CHG will if realy bad stop the car, it will boil up in no time but an early sign may be presurisation of the coolant tank just after startup with the coolant still cold.