Coolant bypass valve failure symptoms?

[DanielZ]

Hej,

So my sedan started to leak a lot of coolant yesterday. I am aware of the CBV weakness and I suspect that this is the case here.
But:
All posts I've read so far would have the puddle form behind the firewall closer to the driver side wheel than the center of the car.
I have this leak almost dead center, just behind the firewall. It drips onto the exhaust system. It also leaks when the car is off, not just while driving/motor running.

I can't really see where the leak is but looking at the firewall below the wiring harness close to the throttle body it does look a bit damp/wet down there.
Oil is fine although the car uses a little too much of it.

Most likely the bypass valve? Please? I can handle that myself...but if it's not that or a pipe/hose...I'm hosed. badum-tish.

[nordwulf]

Classic CBV failure symptoms. You know what to do.

[Gen-X'er]

When mine went, it wouldn't leak when the car was off. It would blow the coolant out at start up.

[DanielZ]

I'll be trying to do the fix this week. It's acting a bit odd leak-wise. I have been forced to use it and it's not a catastrophic fluid loss. While driving it'll lose some, way WAY more than it should but not gushing. Then parked it'll sometimes drip and pool. Now, that's how it started. It's become less leaky over the week. Won't lose as much when on the road and will lose even less standing still.

It might not be that strange. Temperature and pressure is what controls the CBV and if it's cracked in one place it'll ac different when broken in another way. Anyway, gonna try 'n fix it this week. Picking up a 06 93 Vector combi tomorrow.

[Gen-X'er]

That sounds like the bypass valve. It would shoot out a decent amount on startup and then wouldn't lose much after that. If you fill it up, open your hood, and have someone start it, you should see it shooting out if you look at the valve. My mechanic quoted me $300 because that is what the labor and parts came to. I wound up buying the part online and did it myself. I think total cost was something like $25 and labor was about an hour.


Sent from my CB radio circa 1977. I'm 10/20 on the side good buddy.

[DanielZ]

Yep, seems to have fixed it. Had to let a mech//tech do it as I have no time and it also needed a fuel filter and a few other bits and bobs. Car is fine, my pride took a little hit tho.

[Issam266]

What is it the bypass valve or the hose cause im having the same issue

[nordwulf]

This thread has all the information: http://saabworld.net/showthread.php?t=674

[DanielZ]

Here is a youtube video to help you find it and perhaps do the swap as well.

[Kangaroo1]

Hi There - Just joined Saab World after owning a continuous line of Saabs from 1974 to the present.
Nine years ago the Coolant Bypass valve cost me a motza - primarily because of the intermittent nature of the leakage making it difficult to reproduce when taken to the radiator repair workshops. We don't have a Saab dealer or workshop in rural Wagga Wagga where I live.
It went on intermittently leaking coolant fluid from a spot that I/they couldn't locate.
They did a pressure test on the radiator and found no leaks but felt that it was worthwhile replacing the radiator.
When that didn't fix it they suggested a leaking head gasket - had the head taken off, reground and repalced - problem still there.
Problem also only appeared to occur in hot summer months - and generally only when I turned the car off after running the air-conditioner (although I didn't realise that at the time.
Finaly I checked from underneath the car and traced the drips- to the plastic device connected to the heater hoses hidden up against the firewall where no-one can see it!!
Cost me $45 for a replacement and half an hours labour.

Subsequently I realise that it only leaks in hot weather when the engine is turned off because when the air conditioner is working to cool the car, the sovalve is activated by the air hose to stop hot coolant from circualting to the heater. When you turn of the ignition, the vaccuum tube is no longer active and the valve is turned on by default.

If you open the top of a faulty Bypass Valve (which is easy to do) you will see that there is a rubber diaphragm with a pin in centre that is activated (lifted) by the vacuum. This opens up passage of hot coolant to the heater. However when the rubber diaphragm tears - the Bypass Valve fails - allowing coolant fluid to pass into the external chamber where it leaks out through a weep hole - dripping onto the ground.

Today (9 years later) I had the same issue - immediately knew the cause and purchased a replacement for $75 - an hour later all was fixed. I would suggest you put some tape or wire around the top hose on the side with 2 hoses so that you connect them correctly. Once you cut the plastic tie attaching the valve to the firewall (metal brake line?) then the assembly can be pulled towards the passenger side of the car for better access (but still cramped). I didn't disconnect the electricals from the solenoid below the valve but was careful not to pull on the wiring. Once you have the hoses unclamped the solenoid can be pulled off the back of the valve (I pushed the plastic sliding tab with a screw driver). Replacemnt is the reverse.
Good Luck,
Kangaroo1

The by-pass valve operates exactly like the solenoid operated watering system in-ground garden sprays.