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  #1  
Old 24th January 2008
Black Saabath Black Saabath is offline
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Unhappy 9000 Aero overheating

I just replaced the water pump on my 94 9k Aero when I noticed that the temp started to climb past 3/4. Before, it always stayed on or below 1/2. The temperature would go down while driving at high speeds, but would climb during traffic.

The fan works when the temp needle reaches about 3/4 but doesn't keep it at 1/2 like before.

I drained and replaced the coolant (which looked clean) and replaced the thermostat with a 82 C unit, and still the needle tends to go about 3/4 during traffic. I also noticed that the outside Temp on the trip computer goes up proportionally to the tem needle (funny, uh). I checked the fuses and relays for the fan and they seem to be OK. Like I said, the fan operates when the needle gets close to 3/4.

Do you guys have any idea what may be wrong? So far, water pump, thermostat, and coolant are new. Thermoswitch, seems to be stock. Car has 120K.

Thanks for your help.
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  #2  
Old 24th January 2008
eclipseproduction eclipseproduction is offline
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Do a search on this. I think I remember reading that a pocket of air can form at or near the fan switch on the radiator when the system is drained and refilled.
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  #3  
Old 24th January 2008
Black Saabath Black Saabath is offline
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Thanks for the advice. I remeber running the car without the coolant cap until the fan kicked in. I think that should have got ridden of any air, plus I don't remember seeing bubbles. I know tha the 82 C thermostat that I installed didn't have the nipple/bleeder, but I don't know how much that would affect the temperature.
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  #4  
Old 24th January 2008
Superaero Superaero is offline
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Leaving the "rad" cap off makes absolutely no difference. There's an air bleed hose from the top of the radiator to the top of the expansion tank which takes care of bleeding any air automatically, PROVIDED you have the proper thermostat installed which you don't.


First, use the 89 C thermostat as the 82 is too cool and will eventually cause unnecessary engine wear. The 82C is for Saudi Arabia and similar places. It has no beneficial effect in cooler climates than the tropical desert. Second that little bleed fitting in the stock theromstat is to help the air bleed out of the heater core. If you don't have it the air will stay in the system much longer and give you odd symptoms.

If it were me I'd put in a stock spec 89C thermostat and the problem will be fixed.
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  #5  
Old 24th January 2008
Black Saabath Black Saabath is offline
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Well, Palm Springs during summer time gets as toasty as Saudi Arabia or the Kalahari desert and that's where I drive the Aero.

I'm not sure about the thermostat. The one I removed was a 89 C with the nipple/bleder (made in the UK) and later I realized that it worked fine (boiled it). So, even with the thermostat that Superaereo is recommending, I go this high readings. What I don't get is why I would get high temps after replacing the water pump and serpentine belt

Any other thing that I should look at?
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  #6  
Old 25th January 2008
abusot abusot is offline
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The temp guage on these cars is pretty sensitive and will go up in hot, stop and go raffic and then go back down on the highway. Mine can get close to the red on a very hot day.

Later years have a guage that doesn't read the actual temperature because owners noticed the variation in temp and thought the car was overheating.

I don't think there's anything wrong with your car, but it would be a good idea to get the correct therm. with the bleed hole.
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  #7  
Old 25th January 2008
Black Saabath Black Saabath is offline
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After reading a few cases, I'm starting to think that high temp readings are normal on these cars. I still prefer the gauge to stay at or below 1/2 like before.

I guess I will revert to the original 89 C, nipple bleeder thermostat. I was also thinking of replacing the thermo switch even though mine still kicks the fan in, but with the unusual high temp readings on the gauge, I'm not sure if it kicks at the right time. What are the changes that the thermo switch may not be working properly?
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  #8  
Old 26th January 2008
BarryM BarryM is offline
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I would agree with other posters that your car is behaving pretty much as expected. But see below for some things to check.

My 9000 has the earlier non-placebo gauge like yours.

I recently changed the thermostat on mine. I was diagnosing higher than normal temperatures. The problem was actually fan switch related, but I changed the stat and did a coolant flush anyway as preventative maintenance.

The old stat was an 82C with nipple/bleeder made by Waxstat. The new one was 89C from a Saab dealer. Ignoring the fan issue, with the 82C stat normal gauge reading was below half, only getting to or just above 10 o'clock on a hot day. With the new 89C one it gets up to 10 o'clock, and drops back to half way when the stat first opens, or the fan kicks in (this is in winter). You can feel the stat opening when the top hose gets hot.

Excuse me if you have already read this, but there are known problems with the cooling fan, thermo switch and wiring. If you have a 2 speed cooling fan (3 wire thermo switch, low and high speed relays in box near battery, gold resistor on fan cage), it may be possible that the low speed is not working.
The thermo switch should cut in low speed at around 90C (if I remember correctly) and high speed at around 104C. The thermo switch connector (below radiator) can corrode, and the blue wire (low speed) has been known to break between there and the relay box. The gold resistor (low speed again) could also fail, but seems less common. To get good access to the thermo switch connector it is best to remove the undertray, middle and passenger side (US cars) sections. Testing is obviously easier if you can just put a volt meter on the fan connections, before pulling the car apart.

On my car, the pin for the blue wire had corroded away in the connector AND the thermo switch had failed

Have fun.
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  #9  
Old 26th January 2008
Black Saabath Black Saabath is offline
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This is great info, thanks.

I know the thermostat is working because the upper Rad hose gets pretty hot. The fan still kicks in when the car reaches the 10 o clock. But that's a good point, maybe is not kicking at low speed. Yes I have the 3 wire thermo switch. The connections look OK and don't see any corrosion, but I will look again.

Unless there's a way to test the low speed activation on the thermoswitch, it may be a good idea to replace it and see what happens. I want to make sure the car runs cool before summer gets here. On a "good" day, temps may reach the 40C over here.
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  #10  
Old 26th January 2008
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Well, im having similar issues with my car and this is what i have done so far, one day my car started to over heat and i mean it was in the red, i noticed the upper rad hose wasnt hot so i assumed it was thermostat, i did the same thing you did and i installed the lower temp thermostat, and i dont remember there being the little tiny balls in the bleeder hole, but i do remember the hole being there, so after that was changed the car was fine until about a week later and it started to heat up again but not to the point of getting into the red, so i assumed it was a bad fan switch (i also have a 2 speed fan) so i replaced that no luck still same issue. i was also told that the 2 speed fan may not be working properly so i let the car run in my drive way for like 20 min, no fan came on, and i let it run some more, then at last when the gauge was almost in the red, the HIGH SPEED fan came on for like 15 seconds then it shut off (high speed is extremely loud), it dropped the temp a few degrees but nothing substantial, so i let the car cool down and i did it again and again no fan until red, So im almost 100% sure its the little gold resistor on the fan shroud not turning the low speed fan on, im going 2 order the resistor in a few weeks, but for the time being i installed a toggle switch inside the car so i can manually control the fan, it works great, but yhea so you and i are pretty much in the same boat as far as cooling goes, so do what i did and let the car sit and let it run for a while and just stand out side and wait for the fan to come on, Try and detect the two different speeds, ur problem could be as simple as the low speed isnt turning on like my 9k, goodluck, when i order ill post my results

Imran
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  #11  
Old 26th January 2008
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Thirsty9000 Thirsty9000 is offline
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Quote:
Originally Posted by 9-3Aero
Well, im having similar issues with my car and this is what i have done so far, one day my car started to over heat and i mean it was in the red, i noticed the upper rad hose wasnt hot so i assumed it was thermostat, i did the same thing you did and i installed the lower temp thermostat, and i dont remember there being the little tiny balls in the bleeder hole, but i do remember the hole being there, so after that was changed the car was fine until about a week later and it started to heat up again but not to the point of getting into the red, so i assumed it was a bad fan switch (i also have a 2 speed fan) so i replaced that no luck still same issue. i was also told that the 2 speed fan may not be working properly so i let the car run in my drive way for like 20 min, no fan came on, and i let it run some more, then at last when the gauge was almost in the red, the HIGH SPEED fan came on for like 15 seconds then it shut off (high speed is extremely loud), it dropped the temp a few degrees but nothing substantial, so i let the car cool down and i did it again and again no fan until red, So im almost 100% sure its the little gold resistor on the fan shroud not turning the low speed fan on, im going 2 order the resistor in a few weeks, but for the time being i installed a toggle switch inside the car so i can manually control the fan, it works great, but yhea so you and i are pretty much in the same boat as far as cooling goes, so do what i did and let the car sit and let it run for a while and just stand out side and wait for the fan to come on, Try and detect the two different speeds, ur problem could be as simple as the low speed isnt turning on like my 9k, goodluck, when i order ill post my results

Imran
Check that the blue wire (low speed fan) to the thermo-fan switch has continuity all the way from the fuse box to the switch. It has a history of becoming corroded and losing connection on the 9000
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  #12  
Old 27th January 2008
Superaero Superaero is offline
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I agree that it sounds like the low speed fan circuit isn't working. Unlike the older cars which had two fans the later cars use one big fan with a high speed circuit that is essentially "straight trhough" and a low speed which uses an in line resistor to cut the voltage to the fan. the ECU knows when to switch on the low speed fan to keep the temp more stable, kicking to high speed only when necessary.


If the low speed fan circuit isn't working then the temp gauge will move up and down especially in heavy traffic or in very hot weather.
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  #13  
Old 27th January 2008
BarryM BarryM is offline
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I think it was from around 1995/6 onwards that the fan speed was controlled by the ECU, using the temp sensor in the engine block. Earlier versions (1994) like mine and Black Saabeth's just have the 2 or 3 wire thermo switch in the radiator. I don't know about the old shape 9000.

I am not sure anyone has worked out the logic behind all the different fan configurations. It could be those with a separate fan for the A/C were intended for hotter climates. Some of it may be the specification being defined by accountants, rather than engineers. It has also been suggested that the low speed was required to meet noise regulations in some markets. Even in the UK there seems to be a mix of single and two speed fans on the same spec of car. If anyone knows for sure please tell us.
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  #14  
Old 27th January 2008
Therealet23 Therealet23 is offline
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are u sure the connection is snug?? the connection is right by that gold resistor thing by the fan in the 93-94 cars....mine was loose and was the culprit...i solved this problem with a little bit of duck tape
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  #15  
Old 28th January 2008
Black Saabath Black Saabath is offline
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Thank you again for all the valuable info. I went back to check for continuity from the fuse box to the thermoswitch and sure enough, the cables were corroded (the blue wire had turned completely green). As soon as I toggled the connector, the blue wire broke (why is it alway the blue cable, and not the black one for instance?). So, I had to hard wire the thermoswitch.

I also noticed that the relay for the lower speed fan was a bit burn on one of the connectors. Luckily I had a spare relay "courtesy" of the local wreck yard.

I will see how the temperature behaves from now on. For the first time in my life I'm looking forward to be stuck in traffic, so I can observe the temperature variation.
Ah, and the temperature variation in the info display was due to an outside Temp sensor being out of place and closer to the engine.
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Old 29th January 2008
BarryM BarryM is offline
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Quote:
Originally Posted by Black Saabath
As soon as I toggled the connector, the blue wire broke (why is it always the blue cable, and not the black one for instance?).
http://www.corrosion-club.com/basictheory.htm

Perhaps sacrificial anodes and stuff.

The black wire is ground. I suspect that because the blue low speed wire carries current more frequently than the high speed it gets a bit warmer as the contact degrades. I assume this accelerates its demise. Other forum posters have suggested the blue wire gets stretched during manufacture, and that holes are poked in the insulation during testing. I have no idea if this is true.

Some chemistry and physics students will be along shortly to give us all a lecture.

The important question is whether the green stuff and remnants of pin/wire on your car were still sufficiently conductive to power the low speed relay coil. Even if it was, you now have one less 9000 problem to worry about in the future.

Thanks for the note about the external temp sensor, something else to watch out for.

You now need to check for connector corrosion on your ACC fan speed controller (plenty of discussion in recent threads).

Cheers,
Barry.
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  #17  
Old 30th January 2008
Black Saabath Black Saabath is offline
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Well, I thought that hard wiring the thermo switch and replacing the low speed relay would alleviate the problem, but the temperature needle continues to gravitate toward the 3/4 of the gauge. I'm running out of ideas as to what went wrong with the Aero's temperature. I think that I looked at almost any possible cause.

We have cool temperatures at the moment, so I hope I won't get any surprises when it start to get hot. I'll keep a close eye for smoke coming out from under the hood
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  #18  
Old 31st January 2008
BarryM BarryM is offline
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It is a difficult one to be absolutely sure. Your readings don't seem vastly different to those other posters report. But, they do seem a bit high compared to most cars running a proper Saab spec 82C stat. There is no obvious reason why the readings changed after you replaced the water pump, unless some scale or sludge was dislodged from the sensor.

Having only owned one Saab, I don't know how much the accuracy and linearity of the gauges and sensors varies between cars. When my car had overheated, the gauge got close to, but not into, the red zone. The only other evidence was that the coolant level had dropped below minimum. I assume it had escaped through the relief valve in the expansion tank cap. The heater core (since replaced) did have a minor leak, but there was no bad coolant smell or fog in the cabin. I now know that the thermo switch and connector had failed. I assumed, but never confirmed, this affected both low and high speeds.

With the fan not working the car would get too hot after being left to idle for 20-25 minutes. This was on a still day (no wind to simulate a fan) with the ambient temp around 4-5C. I switched off when bubbles started to appear in the expansion tank, and I could see coolant flowing through the overflow pipe (boiling point could be around 120-130C with an antifreeze mix in a pressurized system). The fan had not switched on.

Some other things to try:-

Confirm low speed wiring/relay by shorting the blue and black wires from the thermo switch (annoying if you just hard wired the thing!). Short the blue&white and black wires for high speed, you should hear the difference.

A new thermo switch (not from Saab) only cost me about 12 Uk pounds, not that expensive. You could do a boiling water test on the old one. Need to drain some coolant if removing. I managed to swap mine over quickly by just holding a thick cloth over the hole, and didn't spill too much. The part it screws into seems to be plastic on most 9000 radiators, so don't overtighten or cross-thread it.

Ensure the radiator fins, or the A/C condensor in front of it, is not clogged with dirt.

Partial radiator blockage - check for cool spots just after thermostat has opened, at least the parts you can reach safely. I did a 2 part chemical flush on mine, with the thermostat removed. Like with yours, what came out seemed relatively clean. I think it would take very poor maintenance or a serious failure to cause a blockage.

Temperature gauge sender (cylinder head, near thermostat). Haynes manual says resistance drops with temperature. It suggests disconnecting the wire and then grounding it to check the gauge moves correctly from min to max.
It also suggests that if other gauges show erratic readings, the problem may be a voltage regulator on the instrument panel circuit board.

Things like dirty or loose ground wires/straps could potentially cause strange readings. Engine management faults (fuel mixture etc.) can cause higher temps. If it were something like a head gasket I suspect you would have noticed other symptoms.

The car's ECU also reads the coolant temperature, via yet another sensor in the block. To access this though you need a very expensive TECH 2 diagnostic box, with Saab software. See the following for example use with a later Saab V6:- http://www.trollhattansaab.net/archi...-mechanic.html
Worth a try if you know a nearby friendly dealer or mechanic with one of these.

Personally, I would do the cheap and easy checks first. Like you, I would prefer not to wait until the next hot day to discover there really was a problem after all.

Good luck, and let us know how it goes.
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  #19  
Old 1st February 2008
Black Saabath Black Saabath is offline
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Thanks for the hints. I will give it one more shot and see if I can find the culprit. I'm ready to order a new thermoswitch and see what happenes. Now it's personal, I will make my Aero run cool even if I had to fill the engine bay with dry ice. I'll let you guys know if there is any new development.
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  #20  
Old 16th February 2008
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Quote:
Originally Posted by Thirsty9000
Check that the blue wire (low speed fan) to the thermo-fan switch has continuity all the way from the fuse box to the switch. It has a history of becoming corroded and losing connection on the 9000
Sorry to bring back an old thread but i forgot to ask about the blue wire you mentioned thirsty. Im a little confused on how to check the wire and where to check it from, i was going to order the resistor but i remembered something about the blue wire so i wanted to check before i order it. I just replaced my thermosensor but i didnt notice any corrosion on the other side of the plug, where does it tend to corrode. Right now i have the fan hard wired to the battery to a switch in side the car that i can now turn the fan on with. I know the problem is with the low speed fan,

Imran
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