'94 900 overheating

My 900 Turbo seems to be overheating when in traffic. I topped off the coolant level after it was low. I don't seem to have a leak because at the end of a run, the level was as I left it. When I'm moving, the temp gauge is mid way and goes up higher as the car runs. Do the two fans behind the radiator run when the car is running? I noticed one running just as the car was shut off. Not knowing much about maintenance, is there something I can do before I take it to the shop?

Reply to
itten
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If the temperature is climbing into the red when the car is moving, the electric fan is not the problem. Instead it is most likely a thermostat problem. The electric fan does not come on until the temp climbs to about

10 o'clock on the temp gauge. It is only really there so it can move air thru the radiator when the car is stationary.

-Fred W.

Reply to
Fred W.

I'd agree. If it is overheating when the car is running on the highway, it's not the fans. My first guess would be that your water pump is not pumping an adequate supply, check the serpentine belt to see if it's extremely loose. If you have a '94-900 and you have not changed the belt or upper idler pulley in 50K miles, you should probably replace them. However, unless the belt is very, very loose, (problem with tensioner) you probably have another problem. I think you'd see other problems if it was that loose.

Does the coolant get used up every time you run it ?

Reply to
Bob

The car does not overheat at highway speeds, only when I'm stuck in heavy traffic do I see the gauge move to the hot side, yet not all the way hot yet. The coolant level remains where I left it: full. I did notice a squeeling noise when the car was first started in cold weather. The noise went away after 20 seconds or so and did not re-appear again once I got moving.

Reply to
itten

Ok, sorry. That was not clear.

In that case, if the engine runs cool enough when moving, but gets hot when at a standstill, it may be the fan, but probably not the fan motor itself. Most of the time, this kind of problem is caused by the temperature sensor/switch which is located in the radiator. Not sure about the 900's, but the 9000's of the same vintage had temp switches which turn the fan on too late (at too high of a temperature) which results in the symptom that you describe. If yours is a severe case, it may be that the sensor never turns on the fan (though you said you heard it run, which would indicate otherwise)

Some configurations from around that time period used a dual temperature switch / fan configuration. It may be worth investigating to see if maybe you fan works at high temp/speed, but not the lower temp/speed. There are lower temp switches available which are generally considered a good upgrade.

-Fred W

Reply to
Fred W.

Also, you can check if the fan is working by using a paperclip/screwdriver, or piece of stiff wire to bridge across the switch terminals If the fan starts when you do that, and stops when you remove the jumper, then either the switch no longer functions, or is too higher a temperature than you need.

Reply to
MeatballTurbo

Yes. This will test the *fan*

Not necessarily. This will only test the switch if : a) You have already determined that the fan works, and b) You conduct the test under sufficiently hot conditions when you would expect the switch contacts to be closed, but the fan is not running.

CAUTION: The fan is powerful and will remove fingers. The radiator and other parts will be hot and will burn. Always turn the engine off before adjusting the test configuration, then keep fingers well out of the way.

Adrian

Reply to
SAABurger

e.g., letting the car idle upto fan cycling temps on the gauge? And doing the bridging/shorting test while it warms up (just make sure that the fan works)

Reply to
MeatballTurbo

Yes. That'll do nicely.

I would recommend wiring a manually operated switch in parallel with the thermos-switch, on the end of a (2 conductor) cable which is long enough to be operated clear of the vehicle. This would allow the tester to throw the switch as many times as he feels necessary as things warm up, in safety, without having to turn the engine off/on several times.

Incidentally: This topic is close to my heart at the moment. My 1992 9000CS

2.3-16i overheated yesterday in heavy traffic. First failure, other than flat battery, in 9 years. I suspect a sticky thermostat.

Adrian

Reply to
SAABurger

My experience with overheating has usually ended up being one of two things.

  1. Fans not running due to faulty fan or the temp sensor on the radiator; or

  1. If the fans run when activated by the appropriate temp then it is the radiator. I would go there before the water pump any day of the week. Over time the radiator gets clogged and it just can't flow water through the channels as well as it used to, which means less water to cooling air contact. It is first noticeable at idle, but in time it is noticeable as running hot in slow moving traffic. Then progressively worse until the day it overheats and you've got a blown head gasket.

Reply to
saabturbo

The thermostat is far more common than a plugged up radiator *unless* the car was run with the wrong type of coolant. If you have been running the green stuff (or worse, straight water) then I would say #2 above is right on the money.

The electric fan problem has the very unique symptom of running perectly when the car is moving along briskly (>30mph) but overheating in slow or stopped traffic.

-Fred W

Reply to
Fred W.

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