[cesedy]

Hi.
I have a heat issue on my SAAB 9-5 MY1998.
When the car has reached its working temperature (needle in the middle), and I am parked, the vents are blowing cold air and fan speed builds up. Once I start driving (without changing anything) not fast ~45-50km/h, the fan starts to slow down and it starts to blow hot air.
Then again, without switching off the engine, when I am parked, the heat gets colder and fan starts to speed up.
I have changed thermostat this April, but if that would be faulty, it would be other way around - when parked, it would get warmer, and while driving - colder.
The coolant valve I changed last year October.
The coolant fluid is a little bit over the Max when hot.
I have run Climate control calibration with 0 errors.

I am not sure when this appeared, because I was not driving the car for 2 months and in summer I was not keeping an eye on heat.

What I changed today is the dump valve with aluminium one, because in May I bought an aftermarket one from Professional Parts Sweden and it was already broken after 2 months (drops RPM to/almost stall when let go of peddle).
This valve comes with 3 spring, with one pre-installed. I left the default spring in, because, when I applied suction with my mouth, I could feel a little movement on the valve opening.
But, as this dump valve is connected to vacuum controller by the firewall, which is also controlling vacuum for heater valve, could it affect the performance of heater valve?

So, has anyone had this symptoms before? Because google is not much of help here.

Are these the symptoms of air in heater radiator?
Should I replace the dump valve spring, because it is too hard?
Or, should I do a vacuum mod, eliminating dump valve from the vacuum controller by the firewall?

Thank you.

 

[Mimmi]

Replace thermostat. You now have wrong type of it.
Replace your dump valve to original by-pass valve ASAP.

 

[cesedy]

There are no problems with thermostat. Engine reaches normal working temperature fast and there are no drops while driving.
What do you mean by wrong type? It is a regular 88C thermostat meant for SAAB.

As for dump valve - I made a mistake, it is by-pass valve (RECIRCULATING DUMP BLOW OFF VALVE - as stated in description).

But, it seems, the problem sorted itself out.
Today I wanted to do more diagnosis, was idling about an 1hr, but the problem did not appear.
I reached to feel if all hoses coming and going from heater core are hot, which they were.

Might be there was air in the system.
But strange is that yesterday it was cold while idling, and hot while driving. Would have expected only cold.

 

[Mimmi]

Wrong type of thermostat shuts flow to heater core when engine coolant is warm enough to open thermostat fully.
I persnally use only original thermostat, because they are cheap and reliable (and 3yr warranty).

 

[cesedy]

Sorry, I am lost.
Are you talking about thermostat or coolant by-pass valve?

 

[bob3000]

Sorry, I am lost.
Are you talking about thermostat or coolant by-pass valve?

Mimmi is referring to the thermostat.
.

 

[unclemiltie]

If you replace the coolant bypass valve and put the hoses on wrong you'll get no heat. FWIW it's easier just to replace the hoses and eliminate the damned thing.

 

[EdT]

If you have the coolant bypass valve, pull the vacuum hose off the valve. I suspect that then you will have heat. That would point to some problem in the vacuum lines to the bypass valve, as it is only supposed to be activated when ACC requires no heat at all from the unit. Probably just a mixup in hoses.

If you don't have the heater bypass valve, then I would look at coolant flow through the heater core. When the car is fully warmed up, check both of the hoses going to the heater core. If it's bad coolant flow, one hose will be hot and the other one pretty cool.