bmw e36 320i coupe

[gary5661]

i got a 320i coupe and recently put a new thermostat in it now i cant seem to get pressure in the coolant system i bleed the system thoroughly and im not loosing any coolant what so ever so i was just wondering what this could be and will it damage the engine if i continue to run it like this it doesnt overheat either
cheers

[darkhorse737]

pressure in a cooling system is the result of your water pump action and the expansion of water molecules as you engine heats up.

That in no ways means that your cooling system needs to "maintain" pressure. cooling systems are designed to hold around 12-16lbs pressure and any pressure built in the system over and above that is released through your radiator cap and into your reservoir(that is the reason for the spring loaded caps)

Bleeding you system on the other hand is done to eliminate air pockets in your system that can otherwise interfere with the efficiency of ur cooling. (this bleeding part isn't exactly the same as when u bleed a brake system) ;-)

you are not losing coolant; and you are not overheating... you are fine. no worries.

[gary5661]

so if theres no pressure behind the cap then does that mean the pump isnt working

[darkhorse737]

cold engine, thermostat closed. you will have little or no pressure. Once engine reaches operating temp, you should have pressure-both from coolant expansion and water pump pressure.

*highly unlikely for a pump not to pump, but it's known to happen especially in pumps using plastic vanes.(in such a case, your engine will definitely overheat)

I would rather suggest that u inspect your radiator cap for poor sealing-that is usually the reason why your cooling system doesn't build pressure. Check also for leaks elsewhere... esp where the hoses join to the metal tubes, pipes.