operating temp?

[87900turbo]

I just bought my first C900, an 87 turbo convertible with around 120k miles, that was converted to a manual transmission.


the factory temp gauge doesn't work, but it has a an aftermarket temp gauge. It seems to run hot in stop-and-go traffic. How hot should it run? I'm going to flush the coolant system and begin to track down the problem, but I need to know the operating temperature I should be shooting for.


Thanks!

[Dave T]

I gave away my 10+ volume Saab service manual and my service manual published by Cambridge, MA based Bentley. However, I remember the original coolant temperature gauge running hot and about 2/3 of the maximum in my 1982 Saab 900 with a 8 valve non-turbo even when new. My 1990 900 16-valve non-turbo was at the middle. I do remember that there was a hotter version of the thermostat available for retrofit and maybe for certain markets. I know that the temperature specification of the thermostat is not the same as the coolant operating temperature.

[peva]

The factory gauge when working sits around middle dial at operating temp. This equates to approximately 90°C, which is the same as the recommended engine thermostat. The top of the gauge is red equating to 100°C. Remember that with properly functioning radiator cap the water is under pressure when hot at up to 15psi. At this pressure the water will not boil until 115°C. So effectively the engine is not overheating until it reaches 100°C. The radiator has a thermostat that closes at 95°C which causes the rad fan to run. When the fan is running the water temp will fall until below 95°C and the fan will stop. If the car is left idling the fan will cycle on and off.

A common cause for the temp gauge not working is the wire that attaches to the sensor at the front of the cylinder head is detached or corroded.