Brickboarders,

I am changing the thermostat on my 89 740GL 8 valve.

Yesterday it was boiling over.... Just a few weeks ago it was the heater control valve that I replaced with a plastic one that seemed to work.

The car was boiling over out the filler tank. I have a relatively new black cap lower pressure top on it. No loud sounds like the water pump failing or anything like that and no leaks that I could see around water pump or hoses or under car.

I have a new OEM Vuarnet thermostat and am wondering which direction the little check valce faces. I would assume up.

Any help greatly appreciated. Hopefully this is the cause of the overheating but not postitive.

Maui

Actually the black, lower pressure lid, will boil off much sooner than the green, factory specified cap. In your case you are losing the coolant sooner.

How's the temp on the gauge?
--
Paul NW Indiana '89 740 Turbo 110,000

Hi Paul,


I replaced the thermostat with a Vernet and that solved the problem.


I see your point about the lower pressure cap letting heated coolant boil off sooner. It has been my experience that it vents sooner preventing boil over.
It also does not keep the closed system under as much pressure so should be
easier on hoses, fittings, seals. They all seem like advantages and did make quite a difference on my car.

Using a green cap the system stayed pressurized even after the car was cool sitting overnight. If I removed the cap it would cause coolant to spill out when cold!

The black cap totally fixed this problem.

Thanks for your help.

Maui

If you are referring to the "jiggle" valve it goes up, pointing towards the highest point so as to vent any trapped air in the cooling system.