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  #1  
Old 8th February 2008
moxwell moxwell is offline
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My Saabs: 2000 saab 9-5. 1997 saab 9000 cse
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Default overheating

Hello
I have a 97 9000 cse and lately it has been overheating. I took it in to the local indy and he diagnosed a ruptured heater core which he bypassed. On the way home today it got into the red again. Luckily though it happened as I was getting into my driveway, anyways I popped the hood and both my top hose and the overflow looked as though they were about to pop. I mean they were stretched out pretty good, fearing they were about to burst I closed the hood and let the fans do their job of cooling the engine. I was wondering if someone had a diagnosis or had gone through a similiar problem, I am thinking the heater core burst due to the immense pressure the cars cooling system is exerting. Any possible reasons why I am overheating? Other than the overheating the car runs great.
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  #2  
Old 8th February 2008
Superaero Superaero is offline
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Don't use that mechanic again. His diagnosis is just dumb. Heater cores that rupture leak all over the place. A clogged heater core might not flow coolant but that won't cause overheating. Only a clogged radiator could have that effect. Your mechanic might have incorrectly bypassed the heater core.


The number one cause of SAAB engine overheating is a failed thermostat. The number two reason is a failed thermostat, so are numbers three, four, five and etc.

Other rare and obvious causes include an inoperative radiator fan, usually a relay stuck somewhere, a failing water pump (really rare as they usually pump well enough even when on the brink of failure, they leak badly before they fail as a rule, a head gasket leak into the cooling jacket is another cause of serious overheating and overpressuring of the hoses. Leaking head gaskets are serious and expensive to fix. The other causes are cheap to fix.

Also, as part of the fix I strongly recommend you replace ALL the coolant hoses, and there are a lot. Don't forget to do any hose, including the throttle body heater hose and the turbo coolant hoses. The only one you might get away with not changing is the PCV heater hose which is weird and is steel inside the rubber crankcase ventilation hose.

Like a chain the cooling system is only as strong as its weakest point. Unless you know that all the hoses are good change them all out. You can save any good ones that come out in case of emergency repair. Cooling hoses last between five and ten years. Newer SAABs seem to have poor quality hoses, due I think to GM's cynical "build 'em to last for the warranty" business practices. My 86 had hoses that lasted 15 years, the ones in my 97 last 5 if I'm lucky.
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  #3  
Old 8th February 2008
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MoreBoost MoreBoost is offline
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Do was superaero said and check the thermostat first, then its not a bad idea to change the rad temp sensor, but do this when ur out side next time, it worked for me,

When the car is cool, start it up and let it run in your driveway. see when the fan comes on, ur 9k is a 97 so i presume its a 2 speed fan, your low speed may not be working, just like mine. I was only getting the high speed fan when the car was near the red. If you dont notice two fan speeds, it could be very possible that the little resistor on your fan shroud may have gone bad. Give it a try next time ur out side

Imran
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  #4  
Old 9th February 2008
moxwell moxwell is offline
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Default

thanks for the info, I went ahead and ordered a new thermostat.

as far as the fan, upon initial start up, should a the fan kick in immediately or does it need to warm up a bit before it does? I am going to check on that next. as far as switching out the fan resistor, where is it located and where can I get a new resistor.


Thanks for the help, this site is great for the do it yourselfer.
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  #5  
Old 10th February 2008
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MoreBoost MoreBoost is offline
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The fan should not kick in at start up as far as i know, the fan doesnt really start up till the thermostat opens and the coolant flows through the radiator. The resistor im talking about is the gold one with two wires coming out of it one on either side. it sits ontop of the fan shroud. Its a quite pricey though, and most people dont recommend getting used ones, as they are likely to fail too.CLICK

Imran
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  #6  
Old 10th February 2008
Superaero Superaero is offline
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When the ambient temperature is above freezing I think the fan may kick in when the ACC cycles the AC to pressurize it initially on start up. I think ten seconds after the engibe starts the ACC triggers the AC to cycle. I have not checked this though.


Otherwise the fan only operates when the temperature sensor reaches a pre-set figure and also kicks into high speed when the temperature sensor reads even higher or the AC cycles.
Older cars had two single speed fans which performed the same function. The AC rad fan came on when the AC cycled or the temperature rose to a pre-set higher level.
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