I'm hoping the collective can help me. Our 300 TDi (RRC) has a few minor heating system issues but one I don't quite understand. It's collecting air in the thermostat housing and not bleeding it away. The pipe that runs to the expansion tank from the very top of the engine goes into a small round valve under the expansion tank along with a pipe from the radiator.
Sound familiar?
Well it connects to the off centre connection, the radiator connects to the central one. Now to my mind this pipe should allow air to be forced out of the thermostat housing into the expansion tank as the engine warms up (coolant expands) but possibly it's meant to prevent water of air returning ot he thermostat is the engine cools.
Am I right? because the thing seems to be blocked, from the thermostat at least, and I can't blow air through it at all.
Is this what's causing air to accumulate in the thermostat housing?
I'm worried it might be the head gasket, so I borrowed a pressure test from work. The system is not pressurising at all but I found about 5 slow leaks, now it holds 17PSi for about half an hour and the leaks I found would more than account for the small amount of coolant it's loosing.
So back to this valve. First thing I tend to notice is the heater blows cold because there's air in the top of the engine, the temp gauge is fine but I'm rather cold. Investigation shows the thermostat is exposed and topping up (with a little bleeding) restores the heater.
Any suggestions?
