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Discussion Starter #1
i want to have a go at replacing my thermostat .

is there anything i need to take care with?

thanks
 

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Saab Mad
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If you don't want to change the coolant at the same time then the thermostat can be changed on an 8v without losing any coolant, and on a 16v without losing much. They key is a completely cold engine, so leave it over night.

You'll find the bolts for the thermostat housing will be tight. I recommend a 2ft breaker bar and six-sided socket. They're steel bolts into aluminium and the two metals seize together.

Buy a genuine Saab (made by Motorad) thermostat. Just get one from the main dealer. It should come with a rubber gasket.

Remove the thermostat housing. On a 16v, be prepared for a bit of coolant loss so have rags postioned ready. Pull out the old thermostat. Clean up the mating faces, removing an corrosion or sealant which may have ben used in the past.

Put the new rubber gasket on the new thermostat. The thermostat's flange fits inside the gasket.

On the thermostat you'll see a small valve with a floating stopper (these valves have a special name, but I don't remember it at the moment). Fit the thermostat so that the valve will be aligned with the bleed valve in the thermostat housing.

Fit the housing, and tighten the bolts. The manual will list the correct bolt torque. Finger tight plus a bit should be fine.

Run the engine. When the top radiator hose gets warm, open the bleed valve to let air escape. Close it when there's steady stream of coolant. When the radiator fans begin to cycle, bleed it again.

Go for a drive. Keep an eye on the temperature gauge. Bleed the system again. Then you should be done.

You may need to top-up the coolant. Try to use the same antifreeze which is already in the system.

You may want to consider changing the coolant :D

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My thermostat housing was leaking, so I changed the thermostat, got a new rubber gasket and also added a little hi temp cooling system sealant around the rubber gasket for added security. These can be bought at almost any auto shop.
 

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I use Permatex 'Ultra Blue' sealant when I have problem with leaking thermostat housings, heater control valve bases, etc. and it works really well. It's fully tolerant of heat and doesn't break down when exposed to the chemicals in coolants (at least the coolant I use which is Australian-made Nulon Long-Life Coolant that meets the Saab spec).

It's a lot better than putting additives in the coolant to seal up leaks. I've got a few pics in this album that you're welcome to check out from when I sealed up the leaking thermostat housing of my 85 900i's 8V engine.

Craig.
 

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Saab Mad
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Sealant should not be required on the thermostat housing. Only resort to sealant if the housing won't seal without it.

Whatever you do, do not use silicone sealant. You need to use an anaerobic sealant - those types cure (harden) only where there is pressure. That means any excess which squeezes out won't block the cooling system and cause an engine overheat (blown head gasket, seized engine etc).

So many people have used silicone sealant, only find oilways and waterways blocked with flakes of cured sealant.

Permatex Ultra Blue is a silicone sealant, so is unsuitable.

Loctite 518 is an anaerobic sealant, which Saab themselves recommend for cam covers and the like. If you have to us anything, then use that.

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So you crack that bleed screw open until coolant is streaming out of it?
Drive once and then bleed again?
 

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jh180iq said:
So you crack that bleed screw open until coolant is streaming out of it?
Drive once and then bleed again?
Just sit the car idling, and crack the bleed open until you get coolant. Close it. Let it idle and warm up, and just crack the nipple open every now and then until there's just liquid. Once it's warm enough that the thermostat's been open for a minute or two, and you've cracked the bleed open again, you should have got everything out of there.
 

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What thermostat?

What thermostat should I get for my 900i 1989?

Should I get the 82 or 89 degrees celsius model? for the climate here in australia? I will be ordering it via PFS. thanks
 

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Yep,the blue oxy. sensor safe RTV sealant works well.
It got me into a real big jam a year ago and I never use it on engines anymore.
I have an old dear friend who has an 89 900T cabriolet.
He lives roughly 100 away.
He left the car with me to fix some items on the car.
One of the repairs was to redo the valve cover gaskets.
I used some blu sensor safe RTV on the new VC gaskets.
Well,he had the car back for a month or so when I got a call.
He said the lifters were hammering and the oil pressure lamp was staying on.
He checked the oil,OK.
No oil leaks and no appearent reason for oil pressure loss.
He trailered the car all the way back here.
I tryed to figure it out.
Changed the engine oil a couple times.
Added cleaners,etc.
Still no oil pressure.
The final time I pushed the car into the shop I was about to pull the engine/tranny unit out to get at the engine's oil pump.
Just then a voice from the far past crossed my mind.
It said,the oil bypass valve can become stuck with crud and cause engine oil pressure loss.
I decided for the heck of it to pull the oil pressure control valve assembly.
The valve itself was stuck in the timing cover and it took some doing to get it out.
Guess what.
A small amount of cured blu RTV was jammed between the plunger and it's bore.
I cleaned the bore and plunger.
But it back together and tryed to start the engine.
Immediately the was full oil pressure with a bang.
Lamp went off immediately and lifters went silent in a couple seconds.
My friend got a call from me.
He was expecting the worst.
When I told him I cleaned the pressure valve and all is fine again he was thrilled.
So,he and I went through alot of trouble and worry all because of the RTV I used on the valve cover gasket.
I only use Loctite anarobic sealent on engines since that bullflop.
I learned my lesson that time.
TrollMedic
 

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Don't depend on the type of sealer to save you.
Loctite Anaerobic Sealers (both 510 and 518) harden in the absence of air, such as when they're submerged in oil.
Try it for yourself on the bench. Then use all sealers sparingly.
 

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Talking about thermostats, I have here a Wahler one, with the check valve and the hole, and one that is supposed to be factory, still in a GM bag. At first glance, the Wahler looks better built; I will post pictures later. Both are 82C.

Oh, should the hole on the bottom plate point up?
 

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the townsend site mentions mercedes coolant and 82C stats making things trouble free. Good "upgrade" for any c900 turbo?


also, do you really flush with a garden hose/water? How does one collect and dispose of all that fluid? Or the coolant drained intitally?

finally, will the water from municipal systems do damage to the motor if there are high mineral contents?
 

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abdukted1456 said:
the townsend site mentions mercedes coolant and 82C stats making things trouble free. Good "upgrade" for any c900 turbo?
I have no clue if Mercedes-branded coolant is any different or better than any other decent quality coolant. But an 82deg 'stat is too cool. I put one in when I did my HG. I've changed it back to an 89.

also, do you really flush with a garden hose/water? How does one collect and dispose of all that fluid? Or the coolant drained intitally?
In a big pan under the car. You will spill some/plenty.

finally, will the water from municipal systems do damage to the motor if there are high mineral contents?
Depends on your local water. But bear in mind your car's probably had the coolant filled with tap water for the last decade and a half...
 

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abdukted1456 said:
so how do you dispose of spent coolant (properly)?
sewer drain :lol:

take it back where you got it, normally they have to take it from you

if it's still good maybe use it to top up your winter beater or something
 

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How does one collect and dispose of all that fluid? Or the coolant drained intitally?
Please do your best to find a suitable disposal place. Ask your parts shop, local garage, town office, etc.

finally, will the water from municipal systems do damage to the motor if there are high mineral contents?
Yes. Use premixed coolant (if you can find it) or mix on your own with distilled water.
 
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