I have finished the head job on the 300D and today was the first day I have driven any distance so I will pull the radiator cap around lunch today to see if there is still any pressure. I did drive around town day before yesterday (about 10-15 miles) and when I returned home removed the radiator cap and there was not any pressure to speak of although the engine was up to operating temperature based on the temp gauge. The temperature did not get above around 90-95 dC on the freeway run into work this morning (75 mph). Car runs great although I do have some fuel leakage issues that are causing a little idle roughness during the first start up in the mornings. I will get these issues resolved this weekend.

For those of you with to much time on your hands, try the following:
Remove the temp switch that is located on the t-stat housing and install a temp sending unit. It looks like it should fit. Disconnect the temp sending unit on the cooling water return line near the fuel filter. Run both leads into the passanger compartment and attach to a switch. Then run the leads of the switch to the temp sending unit lead. Drive the car until it reaches normal operating temp and toggle the switch between the temp sending unit on the cooling water supply and return. THis will give the temp rise across the engine. This will give the true status of the performance of the cooling system. Do this on a hot car and one that runs normal. Once a base line is set for temp rise accross the engine, use this as a bench mark. IN conjunction with this test, attached a T fitting in the line on the air bleed line at the expansion tank, and run a tube into the passanger compartment and attached a 0-20psig pressure gauge. Then calculate the vapor pressure of the glycol and water mixture in the cooling system and compare it to the actual running temp vs. pressure relationship. If it is higher than the predicted value, this would indicate a leak from the engine into the cooling system. It should always run below the relief pressue of the radiator cap and within the pressure temperature relationship of the fluid. Remember the Molier diagram?

For those of you with to similiar cars, you can always check the temp gauge accuracy by cross connecting the temp sending unit from on car to the other. Make sure both cars are grounded together and compar ethe readings. As important as the cooling system temp is the oil temp. Have not figure out how to test this. But just give me time.

SO who is up for the challange?

Henry