Engine Temp Question

Wolverine Fan · Post by **Wolverine Fan** » 10 Jan 2007, 07:32

Have a '94 850 with (I think since the odometer quit, have to change the gears like others have done) about 175k miles on it and just have an engine temperature question.

On mornings like this morning when it's cold outside (about 18 degrees), the temperature gauge will not move much higher than the lowest point on the gauge. Subsequently, the heater will not put out much heat. On warm days during the summer, the gauge will stay at the midpoint consistently. As the temp outside goes up, the temp gauge will rise as well.

My question is, is this normal? Do I have a thermostat issue and should it be replaced?

Thanks in advance for any help or suggestions.

chall · Post by **chall** » 10 Jan 2007, 07:38

It sounds just like a thermostat problem to me. When they fail, they usually fail open. On cold days if it is open continuously, the water never gets a chance to heat up. When stuck open, the water continuously circulates through the system, including the radiator. It's not an issue when it's hot, because the result is genrally that the temperature is where it should be (or very close).

Thermostats are cheap and pretty easy to change yourself. The parts are typically less than $30. If you go to VIP, they will hit for $100 to install (a process that takes a fumbling wrencher no more than 15 minutes).

Post by **MadeInJapan** » 10 Jan 2007, 18:04

I concur with a thermostat change. I did mine last year. I think you need a T40 torx bit, but it will need to be long (6 inches or so) to clear the fuel lines that is in the way. Other than this, pump all of the coolant out of the reservoir tank and be ready to catch just a bit of coolant (an old towel works well) when you open the thermostat housing.

CarVolvo · Post by **CarVolvo** » 10 Jan 2007, 19:26

I agree with the thermostat change.. but thermostats can also get stuck closed because the bridge support on the unit fails on some models and it cannot allow fluid flow to the radiator.

larryh · Post by **larryh** » 10 Jan 2007, 20:34

my indy volvo specialist told me to use nothing but genuine volvo thermostats. i proly got it mixed up, but i guess they have some (bipass?) feature that will still allow some water to the radiator if they do happen to fail closed? anyone else know about this?

Post by **JRL** » 10 Jan 2007, 20:59

Change it ASAP. Cold running is about as bad as hot running

Post by **luketrash** » 11 Jan 2007, 07:19

larryh: I think most thermostats, new or old have a hold in the body that allows the pass-through of coolant. It looks like a tiny hole, but I imagine when things get to 200F, the pressure alone is enough to get the juices flowing through there.

MIJ: Do you have a good lead on where to get an extended T40 tool to easily get at the bolts to remove the thermostat body?

Post by **MadeInJapan** » 11 Jan 2007, 07:42

Luke,
It is very important to use the right size (I have confirmed that it is indeed T-40) torx socket and that it fits firmly and squarly in the screw. If it does not, you will most likely bugger the screw up and then have to order new ones (fcpgroton sells new ones for about a buck a piece...ask me how I know). I have heard that others have ordered from here: http://www.mcmaster.com/
(you want part #6939A87). Although not the best, I have used the Autozone torx kit (not a socket, but an "L-key") to get mine in and out. If I have to do it again I will order the right tools to do this job.

nctlspider · Post by **nctlspider** » 03 Feb 2008, 19:26

I know this is an old thread, but you can also replace the TORX with regular metric stainless hexhead bolts or allenhead bolts. I only did this cause my car was without the housing and bolts when i bought it. Seems like they are M7 if i remember correctly.

Post by **MadeInJapan** » 03 Feb 2008, 19:49

You are correct...even heard of folks buying these at Home Depot.

Can you check and confirm the size?