Temp gauge rises - no cabin heat

In my limited experience with an American car, this is caused by low coolant level.With the engine at idle, the level is too low to reach the heater core. As the RPMs come up, the water pump flogs the coolant more strongly, and some of it reaches the heater core inlet.

Possibly also the water pump itself - or the belt driving it.

Bill

The cabin heater matrix has a thermostatic valve in. When the temperature comes back down (while driving) it is allowed back into the cabin. Does the temperature rise up to an indicated red on the gauge? Is the radiator fan working? Check this by baring back the terminals on the radiator thermostatic switch and bridging the terminals with something metal (insulating yourself from the voltage, of course). Does it come on at about 2/3 - 3/4 up the gauge? Check the fuse. One final things - there is a small hose that runs from the top of the radiator to the coolant expansion tank - feel it. Is it cold? If so, it's blocked ... most likely at the expansion tank end spigot. That may cause an airlock where the radiator thermostatic switch is, so the radiator will not work ... overheating.

You can change the thermostat - go for an 89 degree one. Might as well anyway for what they cost - check out the things above and report back. We should be able to get this one sorted between us.

"John" Jan 26, 2008 at 09:13 AM

I second the previous comments about coolant levels, temp senders, fans and the like. It may also be worth checking for a collapsed hose - especially the very long one. Cheers

-- Message posted using

John ("John" ) gurgled happily, sounding much like they were saying:

No, you've got the RIGHT 'stat installed.

The genuine Saab 'stat has three stages, not the usual two.

1. Block only, warm-up.
2. Full circuit, normal.
3. Rad & block only, over-temp. Heater is cut out of the loop.

First call would be to change the coolant and flush it all through - there's a block drain under the exhaust manifold (probably seized) and the rad drain under the RH (US passenger side) of the rad.

When you've got nice shiny new coolant in, turn the ignition on (don't start the car), unplug the two plugs from the rad temp switch (top LH of rad) and short between 'em. The fans should come on. If not, that's your problem. If they do, then start the car, and run it up to temp. If the fans don't come on as it gets to half-scale on the temp gauge, then the switch is at fault.

I agree - possible low coolant (easy enough to check) but likely a bad WP or belt.

Turned out to be a slow coolant leak, which then turned out to be a much faster leak during diagnosis.

Thank you!