I spent an hour or so reading SDL threads.

This is what I tried.

I went out to the cold car, and made sure that the coolant expansion tank had no pressure.

I started the car, and let it run for about 30 to 40 seconds. No temp showing at all.

I went out (this car has an aftermarket radiator cap, with a little release lever) and lifted the lever.

I can hear a rather loud "gurgling" sound from the lower pasengers side. Somewhere in the neighborhood of where the passengers feet would be. I THINK this is the sound of pressure being released.. Or is it?

Is it a vacuum? If it were pressure, wouldn't I hear it come out at the cap? Is it a vacuum, by design to keep the radiator topped up?

Thanks in advance

JP

__________________
________
1985 300SD
2001 Toyota Tundra - soon to be replaced with diesel truck
2006 Honda CRV

Feel the radiator hose for pressure insted of opening the cap.

I can press in the sides of the upper radiator hose. Doesn't seem to be any difference.

Also ran the car with the cap off for a few moments. no pressure coming out.. If anything... small suction.

JP

__________________
________
1985 300SD
2001 Toyota Tundra - soon to be replaced with diesel truck
2006 Honda CRV

The test is as follows:

1) Make sure you have a properly functioning cap.

2) Run engine to opeating temperature and make sure the thermostat opens.

3) Shut down engine and allow to sit overnight.

4) Squeeze upper hose the next morning. If unable to squeeze it closed with two fingers, open expansion tank cap. Try again to squeeze hose. If pressure was released from system, and hose is easier to squeeze closed, you've likely got head gasket/head issues.

In such a condition, you'll also generally see a loss of coolant over time. In some cases, you'll see oil in the cooling system and in other cases you'll see coolant in the oil if you do a test for it.