Thermostats, which one?

[Diesel-do-nicely]

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When the stat is closed, there is about 2 litres of water in the head, header tank and matrix, and thats what cools the cyl-head. Not the radiator.
The turbo stat opens earlier due to the fact it can heat up very quickly , with its extra power = more heat and more pressure on the system.
The reason for the turbo stat opening earlier against the same non turbo car in the same country in the same weather ect ect, is as i have mentioned.
When the stat is fully open, be it 82/87/92 it makes no difference.
Its the transition period that the manufacturer has guarded against.
Thats all i wished to point out.
I would say to anyone with a pre 95 smaller metal rad on a turbo, don't do it.
after 95 the rads were larger and ally/plastic , and shed heat much better when masked by the intercooler.

[Clan]

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The thermostat is rarely if ever fully open due to their being so much reserve cooling capacity in the radiator whether copper or aluminium , if there was no thermostat at all the gauge would not get above 1/4 when driving , so you need the thermostat to regulate the running temperature to 87 or 92 what ever the thermostat is rated at .. I havent heard your theory before , there is a huge mass of cold metal to absorb any extra heat when warming up of course .. The 5 C buffer may be useful when the turbo is flat out at 130 mph for long periods but this doesnt happen ..

[Diesel-do-nicely]

you cannot say the thermostat is never fully open , you have never seen one working in situ.
Or maybee you have.
We built an IRIS type stat , linked to a stepper motor , that flowed the coolant through a modified housing at engineering colledge as part of the practical exam, way back in the 80's.
Its advantage was in a component failure situation a spring held it fully open, unlike a waxstat that can remain fully shut.

[stephend]

Originally Posted by Clan

The thermostat is rarely if ever fully open due to their being so much reserve cooling capacity in the radiator whether copper or aluminium , if there was no thermostat at all the gauge would not get above 1/4 when driving

That was certainly my experience when the thermostat jammed open on my old Maestro: no cabin heat, and the needle didn't shift off the bottom of the temperature gauge throughout a 50-mile journey at motorway speeds...

[James_N]

Christ this is confusing! So do I fit the 92 or buy an 88? Needs to be done this week.

[Clan]

Originally Posted by James_N

Christ this is confusing! So do I fit the 92 or buy an 88? Needs to be done this week.

There is no differention between the two now in the volvo parts system , so 92 C for colder climates and 87 C for warmer climates .. common sense really ..

[James_N]

Originally Posted by Clan

There is no differention between the two now in the volvo parts system , so 92 C for colder climates and 87 C for warmer climates .. common sense really ..

Thanks, so the 92 will be safe to fit?

/edit - just seen this on the VOC FAQ bit:

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
Note that your owners manual may vary: 87 to 92 degree thermostats may be prescribed. The differences are insignificant.

[Diesel-do-nicely]

if volvo spec a 87deg stat.
My question to you is, "whats your problem with following the manufacturers advice ? "

[Forrest]

I have researched this topic before and there are far more opinions on the subject than there are thermostat options. The ones available for the UK market are 87 and 92 deg C and both are readily available. One school of thought is that a cooler thermostat boosts performance whilst a hotter one improves fuel economy. The other is that the 5 deg C difference isn't noticeable.

I did recently try (briefly) replacing an 87 with a 92 in a B230FK which was returning very poor mpg, had a broken thermostat and seemed to be lacking power. Within a month I was having the head gasket replaced. I suspect the head gasket was on the way out anyway and was the cause of these problems; but I also think the hotter thermostat may have hastened its demise.

Since I currently run three 940 estates, two with 2.3 LPT (87 deg stat) and one with 2.0 HPT (92 deg stat) my own conclusion is just to replace like with like. I've thought about trying the cooler thermostat in the 2.0 to preserve engine life. But I've had the head gasket on that one done during my ownership, and if it ain't broke ...

[Diesel-do-nicely]

i have done nearly a hundred head porting jobs and well over a hundred head gaskit replacements.

All the turbo cars have had 87 or 88 deg stats put in during the re-build.

how many subsequent failures ?, 1, 328 e34 . cause...bmw o/e stat stuck shut after 3 months.

and it was a 92deg funnily enough. Bought from the main dealer at huge expense !!

But they (bmw uk) did cough up for the job to be done again. Albeit after the customers solicitor got involved.