If heat is off, does coolant still flow through heater core?

[MJGunn]

I was driving around today, and out of nowhere, my feet started slipping on the pedals. I pull into a parking lot, look down.....theres a small pool (~ a cup) of coolant on my drivers side mat. Now, I'm not too good at working on cars, but even I knew that was a bad sign. Called my friend (who knows cars much better than I), and took it to his house.

He said its probably the heater core leaking, and I should not be using the heat until he can fix it......then he thought for a second, and said I should ask everyone here on the board, when the heat is off (the fans are off, and the temp is turned all the way to cold), does coolant still flow through the heater core? BTW, its possible I butchered the question, so if it makes no sense, please say so

[RM '92 SPG]

Hot coolant won't flow through it when the heater knob is off, but coolant will still sit in the heater core, and can still leak regardless.

[MJGunn]

Thanks for the quick response. Friend has another question

He wants to know if the coolant will be pressurised with the knob all the way cold... Basically is the valve before the input on the heater core, or after the output.

[Matthew]

That might depend on which around the heater hoses in the engine bay are connected. I have seen several C900s with the heater hoses reversed, which would have the effect of reversing the direction of coolant flow through the heater matrix.

[Jon1]

MJGunn, more than likely the problem is NOT the heater core. Classic 900s tend to leak at the temperature control valve and not the heater core. The photo is a new temperature control valve connected to the heater core, removed from the car.

There are photos here:

http://saabpics.org:3000/gallery/Jon1-Misc?page=2

near the bottom of the page and on the next page.

Good luck,

Jon
jon1..

[MJGunn]

Oh Jon, I hope you're right. New heater core = $150. New Valve (aftermarket) = $35

Hopefully I'll be able to prod my friend into tearing the car apart in the next couple of days, so we can find out which of the two parts is bad. Any tips/suggestions?

[Oil_Eater]

It is important to remember that the entire coolant system is pressurized no matter where the valve is. The only difference is weather or not you are seeling slightly higher pressure on the pump side of the loop or *slightly* less pressure on the return side of the loop.

In short, it really doesn't matter if the valve is open, allowing flow, or closed, stopping flow, since both ends go the to main coolant system, which is pressurized.

I second what Jon said about the valve. The valve is directly above the driver's feet, and is prone to leakage.

As far as tips... Try to keep your cool. I hear this job is a real bear!


Jay

[john-w]

This job is not to bad, you need to remove the lower bolster panel, then remove the 2 hoses to the heater. Remove the screws that hold the heater matrix in, this allows the heater matrix & valve to drop down a little, then you can get to the screws that hold the heater valve to the matrix!!

[MJGunn]

My friend took it apart today, said yeah, its definetly the valve.

Just a question, has anyone used this aftermarket valve

http://www.eeuroparts.com/dwos-bin/d...&code=8605388a

instead of the saab part? I ask because the bentley manual warns

"Replacement heater valves may interfere with throttle pedal operation and require a new throttle pedal arm. See an authorized Saab dealer for correct parts information"

Normally I would dismiss this as them just wanting you to buy a saab part, but 1) Its bentley, what do they care if you buy saab or aftermarket? and 2) My friend said that looking at the valve, it is very close to the throttle pedal arm, and he could see it interfering if its not the right size.

So, yeah, has anyone tried that one?

[Timmybung]

I installed the aftermarket unit from Eeuroparts.comabout six months ago and no problems so far. For the removal/installation job, you may want to have a set of t-handle ball drivers (long) handy. I used a small set (l-shaped) of hex drivers (not ball drivers) and it made it very difficult to get to the bolts holding the valve on. With a longer ball driver it would have taken about 2 less hours. That job on my 900 was the worst thing I've had to do so far, but I think with the right tools it'll be much easier. Also- remove the drivers seat (2 bolts, takes about 3 minutes)- you'll have a ton more room to lay on the floor for the job.
Good luck-

[MJGunn]

Sweet, glad to hear it. Ordered it earlier today, everything should be here tomorrow (also had to order a new exhaust header). Thanks for the help everyone!