Stuck thermostat?

Oneeyeblind · Oct 8th, 2023, 18:34

Pretty sure I know what this is so please excuse me for asking what I think is possibly a silly question !

Car gets to temp bang on when idling and through town. On motorway the temp gauge falls down to about a 1/4.

I'm assuming my thermo is stuck somewhat open?

Chris1Roll · Oct 8th, 2023, 21:52

I'd say that's the first thing to change.

Laird Scooby · Oct 8th, 2023, 22:16

It's gone weak rather than stuck open i would think, either way like Chris says, renew it.

Mertz · Oct 9th, 2023, 08:30

2 different temp specs to choose from.. 87C and 92C IIRC.

Personally I favour the 87C. Volvo dealer had it in next day and was a reasonable cost. Also looked much better quality (Brass?) than the steel one i removed.

Laird Scooby · Oct 9th, 2023, 09:24

In terms of engine efficiency, the 92C is much better, especially here in the UK and the heater will be much better in the winter too.

Rversteeg · Oct 9th, 2023, 10:10

There is a little pin in the thermostat that should close the breather bore. I had a thermostat where the bore of this pin had worn to such extent that the pin could wedge itself between the thermostat valve, so it stayed halfway open. See attached picture.

Just replace the thermostat. It does not last forever and should be regarded as a wear part anyway. Replacing is quite easy, as it is located high up in the cooling water circuit, meaning that you will hardly loose any coolant.

Rob

360beast · Oct 9th, 2023, 10:37

87°C is for turbo cars and 92°C is for N/A cars.

Mertz · Oct 9th, 2023, 10:54

Quote:

Originally Posted by 360beast

87°C is for turbo cars and 92°C is for N/A cars.

Thanks, knew there was some reason to my madness!

Rversteeg · Oct 9th, 2023, 12:24

See attached according Volvo parts manual. It appears only the 2 ltr Turbo does not like a 92°C thermostat; for the other engines both are used.
I do not think it is a real issue whether the engine is running at a minimum temperature of 88°C or 92°C, the cooling capacity is the same.

360beast · Oct 9th, 2023, 13:00

My 940 was fitted with a 92°C thermostat by the previous owner and the temp gauge sits slightly past 12 o'clock so I will be fitting an 88°C thermostat when I change the coolant and hoses.

Oct 8th, 2023, 18:34	#1
Oneeyeblind Junior Member Last Online: Dec 23rd, 2023 20:37 Join Date: Jun 2023 Location: Dunstable	Stuck thermostat? Pretty sure I know what this is so please excuse me for asking what I think is possibly a silly question ! Car gets to temp bang on when idling and through town. On motorway the temp gauge falls down to about a 1/4. I'm assuming my thermo is stuck somewhat open?

Oct 8th, 2023, 22:16	#3
Laird Scooby Premier Member Last Online: Yesterday 23:55 Join Date: May 2012 Location: Lakenheath	It's gone weak rather than stuck open i would think, either way like Chris says, renew it. __________________ Cheers Dave Next Door to Top-Gun with a Honda CR-V & S Type Jag Volvo gone but not forgotten........

Oct 9th, 2023, 09:24	#5
Laird Scooby Premier Member Last Online: Yesterday 23:55 Join Date: May 2012 Location: Lakenheath	In terms of engine efficiency, the 92C is much better, especially here in the UK and the heater will be much better in the winter too. __________________ Cheers Dave Next Door to Top-Gun with a Honda CR-V & S Type Jag Volvo gone but not forgotten........

Oct 8th, 2023, 21:52	#2
Chris1Roll Senior Member Last Online: Today 11:22 Join Date: Aug 2006 Location: Cannington	I'd say that's the first thing to change.

Oct 9th, 2023, 08:30	#4
Mertz Member Last Online: Yesterday 21:15 Join Date: Nov 2022 Location: Peterborough	2 different temp specs to choose from.. 87C and 92C IIRC. Personally I favour the 87C. Volvo dealer had it in next day and was a reasonable cost. Also looked much better quality (Brass?) than the steel one i removed.

Oct 9th, 2023, 10:37	#7
360beast Go redblock or go home Last Online: Today 10:52 Join Date: Feb 2012 Location: UK	87°C is for turbo cars and 92°C is for N/A cars.

Oct 9th, 2023, 13:00	#10
360beast Go redblock or go home Last Online: Today 10:52 Join Date: Feb 2012 Location: UK	My 940 was fitted with a 92°C thermostat by the previous owner and the temp gauge sits slightly past 12 o'clock so I will be fitting an 88°C thermostat when I change the coolant and hoses.

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