Oil Thermostat Operation
 

At what tempature does the oil thermostat open?
Should there be a small flow through the device when its cold?

There is NO SUCH CREATURE.

I was thinking the same thing, where on earth would that be lol. Please rephrase coolant thermostat!

actually I have seen oil thermostats before...they do not open or close persay, but talk to the computer and can be and sometimes are another gauge to look at.

On these I5 Volvo's?

I suppose multi-viscosity engine oil could be thought of as a passive oil thermostat...

I don't think this is what you are asking. :P

Do What ??

I did read that an 850 does have a thermostat but I can't remember if it's in the trans cooler circuit or the engine oil circuit ?? It might be engine oil since they only use the engine oil cooler on the turbos. One of those things I was curious about but hadn't yet tracked it down.
It's supposed to keep the fluid from circulating until it's reached close to normal operating temperature. In colder climates they want it to get up to temp sooner so they bypass the cooler when first started.

It was a dorky engineering joke.
Learn something new every day. Apparently the 850 Turbo does have an oil thermostat, its operation is limit flow through the cooler until the engine is warm. Found this thread where the poster discusses replacing the pressure hoses from the thermostat (which is bolted directly to the oil pan) to the oil cooler.

So to answer the original question here, he mentions in the thread's first post that he thinks the thermostat should only let about 10% through when closed (so 1.5-2 PSI at idle), but does not say that he found any particular documentation about that. Basically if you get full oil pressure when cold (not sure how to test this without some cost and time to rig a test hose and gauge) then the thermostat is not operating but is stuck open.

I'm not sure if this is a major problem unless you live in a very cold climate and/or do not let your car warm for a couple minutes before driving.

Maybe ,,,, but it's kind of funny and funny is good ;) Plus you never know how many people read that and really had to think about it !!

"From other research I have learned that 850 Turbo oil pump's capacity has been increased by a wider pump wheel and a modified profile. Yet, Volvo documents show that both pumps push the same psi pressure."

That's because the turbo (the turbocharger itself) uses up a lot of oil. The reason the part numbers are different is because the turbo pump will pump a higher volume of oil at the same PSI and RPM than the NA part will or needs to. The turbo's oil pump parts are physically bigger to pump that higher volume. The rotor in the pump is the main source of volume and the maximum pressure is usually controlled by a spring that limits max PSI.
It's like having a 1" hose running to a NA and a 2" hose running to a turbo. They both are running at 14psi at idle but you'll get a whole lot more out of the 2" hose. It needs that extra oil for all the oil that flows into and rapidly through the turbocharger to both lubricate the bearings and carry away heat.

Well that was an interesting read, I can assure you there is a oil thermostat on 850 turbo models. http://www.fcpeuro.com/products/volv...enuine-3528199
It is located in the 5:00 oclock position near the Crankshaft damper. If you have a
a non-turbo model there will be a block off plate installed there.
Attachment 18355

Well, I learned something NEW today. Now to my question... How in the world are you suppose to know when that thing is bad?