Stuck thermostat?

[griston64]

If anyone is after a gen Volvo 92c stat I have one boxed and brand new as I never fitted it to my ( Non Turbo ) 740

[Rversteeg]

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.

I went from an 88°C to a 92°C thermostat and it made no difference whatsoever to heater output or the temp gauge position. The temp gauge is so heavily dampened that it will reach the middle position at around 60°C and stay there until 105°C before going up further. You will not be able to see the 4°C temp difference.

[Laird Scooby]

Originally Posted by 360beast

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.

I'd stick with the 92C if i was you Luke

[griston64]

Originally Posted by Laird Scooby

I'd stick with the 92C if i was you Luke

87c is the normal recommendation for turbo cars Dave

Which Thermostat? [Editor/Bob] While you've got a choice, the Volvo specifications are:

Thermostat: begins to open at:
B 200/204/230F/FD 198° F (92° C)
B 230FTurbo/234 189° F (87° C)
B 6244/6254/6304 195° F (90° C) (changed from 87 for replacement thermostats)
D24/24T/24TIC 189° F (87° C

[Forrest]

The purpose of the thermostat is to keep the engine warm rather than cold. The rating sets the minimum rather than a maximum temperature. You want the engine to get up to temperature reasonably quickly in order to avoid excessive engine wear and fuel consumption.

I have heard one theory that Volvo used the 5°C buffer between the 87° and 92° thermostats to compensate for the lag in the waxstat responding to rapid temperature increases in the head of turbocharged cars.

In practice, for a road car driven with a degree of mechanical sensitivity, the difference is probably negligible.

[360beast]

Turbo cars run hotter hence the cooler thermostat to aid the cooling, my car is running around 200hp and over the winter/spring I intend to get that closer to 300hp so the cooler it runs the better as it doesn't get driven leisurely anymore. It is usually fully loaded to get to campsites and then ragged around race tracks.

[classicswede]

Originally Posted by 360beast

Turbo cars run hotter hence the cooler thermostat to aid the cooling, my car is running around 200hp and over the winter/spring I intend to get that closer to 300hp so the cooler it runs the better as it doesn't get driven leisurely anymore. It is usually fully loaded to get to campsites and then ragged around race tracks.

No the turbo engine runs cooler! Well it does if you have the 87 thermostat rather than the na 92!
What the turbo engine has is a higher thermal output (makes more power) Running a lower opening temp stat allows the cooling system to respond sooner

You dont want the engine running too cold as it increases engine wear

[baggy798]

My turbo had and has an 87°.

92° is for cold wretched horrible miserable climates, like Alaska or Scotland.

[Rversteeg]

I have heard one theory that Volvo used the 5°C buffer between the 87° and 92° thermostats to compensate for the lag in the waxstat responding to rapid temperature increases in the head of turbocharged cars.

That is the only theory that I have heard so far that makes any sense to me. With the cooling system running a little bit colder, there is some additonal "coldness" stored in the system when the system suddenly has to give its maximum output, giving it a little bit more time to respond.
The (maximum) cooling capacity itself is not influenced in any way by installing an 88 or 92°C thermostat as they will both be fully open when the maximum cooling capacity is needed. Even taking out the thermostat completely will have no influence on the maximum cooling capacity.

[Laird Scooby]

Originally Posted by Rversteeg

Even taking out the thermostat completely will have no influence on the maximum cooling capacity.

True and could cause HGF due to the temperature not being maintained evenly across the head............