Slow warm up 2.0T Aero

[phoenix]

This one has been bugging me for some time.

When I got the car, I noticed it was slow to warm up. Changed the stat for a non-OEM one and still the same, so swapped it for a genuine Saab and replaced the temp sensor. Checked the temp sensor resistance at 20 deg C and OK.

Still slow to warm up compared to our other one (yes we have 2) yesterday (not  avery cold day) it struggled to get above 74 deg C  cruising at around 50mph.

Have I been unlucky and had 3 faulty thermostats and 2 faulty sensors? I'm thinking maybe a thermostat issue as the cabin heater takes some time to warm up. I was wondering if there's any possible bypass circuit? 

WIS isn't terribly clear other than saying that (unlike the B2x5 and B2x4 heads) the stat is in the return from the radiator, not the flow, which probably accounts for it being 80 deg C not 89, but even running in summer it never seems to really get up to the high 80s.

Ideas?

[sgould]

The highest temperature should be reached with the car stationary and just relying on the fan for airflow.  Does it heat up quicker when sitting on the drive?

Have you checked the thermostats with a thermometer in a saucepan of boiling water on the stove?

[sgould]

I've had a look at the WIS and I can't see anything unusual  in the cooling system layout.

The only other thing I can think of is that's the system is OK and it's the gauge tht's reading incorrectly.  High resistance in the electrical connection and wiring?

[phoenix]

No, I haven't tried the pan test yet. But it would be odd for 3 of them to be faulty. The fact that the cabin heater is slow to warm up suggests to me that it's not a sensor/reading issue. I suppose what I could do is disconnect it and measure the resistance with the engine warm and compare it to the spec.

[aerojon]

how much was the oe stat

[phoenix]

The list price is daft- circa £50 but you can get them for around £25 delivered. Still over twice the price of a genuine one for a 900, 9000, 9-5 etc.

https://www.ebay.co.uk/itm/171503751067

[phoenix]

So, resolution. I bought a new stat, and removing the old one I found that I'd managed to not align it properly when fitting, so the seal ring had become torn and presumably water was leaking past there. Odd why it's deteriorated though.

Checking the temperature of the heater matrix hoses with an IR thermometer, it would appear that the temp sensor is reading a degree or two low. I can probably live with that.

[sgould]

Interesting comment about the seal.  This was the state of the seal in my 9-5 when I replaced it four years ago.

[carrera]

Good to hear you have found the source of the problem