Engine 850: B5234T/2.3/20v/T5: - High temperature reading

stevepcar · Jul 28th, 2022, 13:43

I expect my temp gauge to read quarter past 3 when at running temperature. However, mine has been reading 10 past 3 for a long time, so I changed the thermostat to one that opens at 90 degrees. As I believe that is correct for my car. But despite topping up the coolant and taking it for a run to expel air pockets, it still reads the same. The engine doesn't overheat & the fan kicks in if it idles for any length of time. I will try changing the temperature sensor on the thermostat housing, as I have a spare. Has anybody got any other ideas why this might be happening please.

t4johnny · Jul 28th, 2022, 16:43

Did you use a Volvo thermostat when replacing ?
Any visible coolant loss evident in expansion bottle....?
How long has the gauge been reading high ?

4x4 · Jul 28th, 2022, 16:56

Owner's Manual states the thermostat temperature for all non turbo engines is 90°C, turbo engines are all 87°C and diesel engines are 92°C

t4johnny · Jul 28th, 2022, 17:16

As far as i know, i may be wrong, but the 87 degree thermostats for the turbo engines are no longer available....only seen 90 degree ones as being supplied.

RollingThunder · Jul 28th, 2022, 18:35

I ordered an 87 degree one from FRF a few days ago

Baffler · Jul 28th, 2022, 22:08

Check also that the sensor wiring harness isn't making contact with any surrounding metal. I too would fit a new sensor for peace of mind and some of that black flexi conduit to protect the harness.

The genuine Volvo stat, manufactured by Wahler, has a built-in bleed nipple to prevent excess pressure on the cooling system and to speed up bleeding. I personally wouldn't fit any other type.

Luxobarge · Jul 29th, 2022, 07:51

All good information regarding the thermostat, however this isn't going to be relevant to the OP's problem, as a difference of 3 degrees won't give the symptom he's describing, and in any event this is just the temperature at which the thermostat opens, once it's open it's open, and won't by itself affect the reading on the guage on a fully hot engine to any noticeable degree.

Assuming there's nothing much wrong with the rest of the system my vote will be for the CTS - Coolant Temperature Sender too. The guage gets its information from the ECU, which gets engine temp info from the CTS, so if that sensor is erroneously sending a "too hot" signal to the ECU, the guage will read hot while the engine is actually fine.

You could use an independent method of measuring engine coolant temperature (for example I've got an infra-red thermal measuring gun - quite cheap) and compare it to another car that is giving the correct guage reading, I'd be surprised if the actual true temperatures weren't pretty similar, which would mean that it has to be something to do with the sender or the guage itself.

Clan · Jul 29th, 2022, 11:03

Quote:

Originally Posted by stevepcar

I expect my temp gauge to read quarter past 3 when at running temperature. However, mine has been reading 10 past 3 for a long time, so I changed the thermostat to one that opens at 90 degrees. As I believe that is correct for my car. But despite topping up the coolant and taking it for a run to expel air pockets, it still reads the same. The engine doesn't overheat & the fan kicks in if it idles for any length of time. I will try changing the temperature sensor on the thermostat housing, as I have a spare. Has anybody got any other ideas why this might be happening please.

the 850 temp sender with the wire has been known to fail .

stevepcar · Jul 30th, 2022, 10:02

Quote:

Originally Posted by t4johnny

Did you use a Volvo thermostat when replacing ?
Any visible coolant loss evident in expansion bottle....?
How long has the gauge been reading high ?

I didn't use a genuine Volvo replacement, but the gauge is in exactly the same position as it was with the old stat. No loss of coolant in bottle and the gauge has been reading high for at least 3000 miles.

stevepcar · Jul 31st, 2022, 12:27

Quote:

Originally Posted by stevepcar

I didn't use a genuine Volvo replacement, but the gauge is in exactly the same position as it was with the old stat. No loss of coolant in bottle and the gauge has been reading high for at least 3000 miles.

Sorry I just checked it was a genuine Volvo thermostat from Caffyns

Jul 28th, 2022, 13:43	#1
stevepcar Steve Last Online: Today 10:13 Join Date: Jul 2012 Location: Bristol	High temperature reading I expect my temp gauge to read quarter past 3 when at running temperature. However, mine has been reading 10 past 3 for a long time, so I changed the thermostat to one that opens at 90 degrees. As I believe that is correct for my car. But despite topping up the coolant and taking it for a run to expel air pockets, it still reads the same. The engine doesn't overheat & the fan kicks in if it idles for any length of time. I will try changing the temperature sensor on the thermostat housing, as I have a spare. Has anybody got any other ideas why this might be happening please.

Jul 28th, 2022, 16:43	#2
t4johnny Junior Member Last Online: Sep 20th, 2023 16:48 Join Date: Oct 2014 Location: essex	high temperature reading Did you use a Volvo thermostat when replacing ? Any visible coolant loss evident in expansion bottle....? How long has the gauge been reading high ? Last edited by t4johnny; Jul 28th, 2022 at 16:51.

Jul 28th, 2022, 16:56	#3
4x4 Premier Member Last Online: Today 19:58 Join Date: Dec 2017 Location: North of Hadrian's Wall & South of Antonine's Wall View Photos By: 4x4	Owner's Manual states the thermostat temperature for all non turbo engines is 90°C, turbo engines are all 87°C and diesel engines are 92°C __________________ MY2010 XC90 SE (M66-manual) Magic Blue (467) Sold MY1997 850 GLT (62,000 miles) Silver Sand (419) MY2005 V70 2.5T (66,000 miles) Willow Green (471) Volvo 850 GLT website

Jul 28th, 2022, 17:16	#4
t4johnny Junior Member Last Online: Sep 20th, 2023 16:48 Join Date: Oct 2014 Location: essex	Thermostat temperatures As far as i know, i may be wrong, but the 87 degree thermostats for the turbo engines are no longer available....only seen 90 degree ones as being supplied.

Jul 28th, 2022, 18:35	#5
RollingThunder Grumpy Old Git Last Online: Apr 19th, 2024 09:16 Join Date: Dec 2004 Location: South Yorkshire View Photos By: RollingThunder	I ordered an 87 degree one from FRF a few days ago __________________ S40 2.4i '07 Japanese import '96 850R - https://www.volvoforums.org.uk/showthread.php?t=312484 Ex Danish Embassy '96 940 GLE LPT - https://www.volvoforums.org.uk/showthread.php?t=326071

Jul 28th, 2022, 22:08	#6
Baffler Premier Member Last Online: Apr 21st, 2024 15:36 Join Date: Dec 2002 Location: Co. Limerick, Ireland	Check also that the sensor wiring harness isn't making contact with any surrounding metal. I too would fit a new sensor for peace of mind and some of that black flexi conduit to protect the harness. The genuine Volvo stat, manufactured by Wahler, has a built-in bleed nipple to prevent excess pressure on the cooling system and to speed up bleeding. I personally wouldn't fit any other type. __________________ Liam... '96 854 TDI SE, '99 V70 2.5D S, '05 C70 2.0T Collection, '05 S80 2.0T SE, '15 V70 D4 SE Lux Nav.

Jul 29th, 2022, 07:51	#7
Luxobarge Premier Member Last Online: Today 14:53 Join Date: Jan 2011 Location: Horne (Nr. Horley)	All good information regarding the thermostat, however this isn't going to be relevant to the OP's problem, as a difference of 3 degrees won't give the symptom he's describing, and in any event this is just the temperature at which the thermostat opens, once it's open it's open, and won't by itself affect the reading on the guage on a fully hot engine to any noticeable degree. Assuming there's nothing much wrong with the rest of the system my vote will be for the CTS - Coolant Temperature Sender too. The guage gets its information from the ECU, which gets engine temp info from the CTS, so if that sensor is erroneously sending a "too hot" signal to the ECU, the guage will read hot while the engine is actually fine. You could use an independent method of measuring engine coolant temperature (for example I've got an infra-red thermal measuring gun - quite cheap) and compare it to another car that is giving the correct guage reading, I'd be surprised if the actual true temperatures weren't pretty similar, which would mean that it has to be something to do with the sender or the guage itself. __________________ Some people are like Slinkies, they serve no useful purpose but they still bring a smile to your face when you push them downstairs.

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