All through October (I got the car in July), the temperature needle was at about half way on my dash -- I am in Philadelphia. Now since the cold weather came, the needle stays at about 1/3 and never goes above that. Is that normal? Shouldn't the engine temperature be always the same under same driving condition regardless of outside temperature? Could that mean that the temp sensor in the airbox does not work and does recycle hot air back in the system to compensate for colder outside temperature? Any ideas ? Any help greatly appreciated.
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'89 244DL M47 158K miles

Ok then I will not worry about the temp sensor in the airbox.

Now it's been raining all day with warmer temperature here in Philadelphia and my temperature needle is back to half way on my dash. So in the end what is causing this variation? Bad coolant thermostat? Should I replace it, or not worry about it?

Why isn't the needle at half way when it's real cold out anyway? It is consistently at 1/4 or 1/3, does that mean that the engine is not operating at the right temperature? Or that the thermostat is not reporting the correct temperature? Just want to get to the bottom of this...

Thanks.
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'89 244DL M47 158K miles

As stated by others replace that coolant thermostat, it is propably stuck partially open preventing the engine from reaching proper temperature. It controls the engine operating temperature which is reported to the guage by the temp sensor mounted on the side of the block.
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David Hunter

Thanks David.

ARe the coolant thermostat and sensors two different things? Or is it just one component on the side of the engine block

The part I need is the thermostat, right? And not the sensor.

New to me... getting somewhat confused.

Thanks.
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'89 244DL M47 158K miles

You need a new thermostat, it is mechanical device that regulates water flow through the cooling system according to temperature..... Low temp = Low flow Higher temp = higher flow. It keeps the engine at proper operating temperature. It can get stuck in any open/closed position and cause engine to run too cool or too hot. Many Bricksters will change it periodically as a preventive measure. It is located at the top front of engine in a housing at the base of the large hose coming from the radiator. Cost about 5 bucks and 10 minutes to install.

The coolant temp sensor is a separate electronic device that is mounted lower down on the drivers side of the engine with a wire to it. It's purpose is to tell the dash guage what to say. Rarely fails. Sometimes the temp and fuel guages will give false readings due to failure of a small electrobic device buried in the instrument cluster called a Temp Comp Board.

In your case CHANGE THE THERMOSTAT.
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David Hunter

..and have a look at this thread for more cooling system info...

http://www.brickboard.com/RWD/index.htm?id=719573&show_all=1
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Bob (81-244GL B21F, 83-244DL B23F, 94-944 B230FD plus grocery-getter Dodge minivan, MGB, and numerous old motorcycles)

Thanks for all answers.
I guess I might as well replace both

a) coolant thermostat that is in the engine block
b) temp sensor in the airbox

while I am at it put in fresh 50/50 coolant/water (should I use Preston? any other brand recommanded?)

a) and b) seems easy from what you say, but I am not too mechanically inclined...
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'89 244DL M47 158K miles

I would not worry about the sensor in the airbox. Especially when you say the hose is chewed up anyway. Really, you're probably better off with a chewed up hose, because if the sensor in the box freezes the fresh air gate shut, then you could fry your AMM with too much hot air from the exhaust. Fortunately, I have never had problems with that particular sensor through twenty years of Volvo ownership.

As for what anti-freeze, you will get many opinions here, but I always spring for Volvo OEM. Yes, it costs more, but again in twenty years and five Volvos, I have never had the first hint of cooling problem, and I have always used Volvo coolant mixed at 50/50. Call it superstition, but I'll stick with the Volvo Type C for my cars.

No need to replace air box themo. It just works during startup to reduce emissions. Once the car is warm it should be closed.

In fact, many people plug the hot air hose or lock the air flap closed in order to preserve the AMM. Ie. If the air flap fails to close, hot air will fry the AMM. And AMMs are expensive.
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1980 245 Canadian B21A with SU carb and M46 trans

Get a 92C thermostat from fcpgroton.com, about $8 with a new seal(gasket). Very simple task to replace. It'd be a good idea to flush the cooling system as part of the job, and refill with fresh 50/50 coolant mix.

The airbox thermostat would have no detectable influence on the engine coolant temperature - it's there to reduce exhaust emissions during warmup and cold weather. When it fails, it invariably does so in the "hot" position.

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Bob (81-244GL B21F, 83-244DL B23F, 94-944 B230FD plus grocery-getter Dodge minivan, MGB, and numerous old motorcycles)

Your thermostat is probably broken.

It's Jim (in Hartford CT)

Hi Jim,

Which thermostat? The one in the airbox? The one in the engine block for coolant? Probably the former. The metal hose that goes from airbox back to engine is a bit chewed up at the end (engine end). But I don't think a little leak there would matter too much, would it?
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'89 244DL M47 158K miles

He is talking about the coolant thermostat. It seems maybe it is opening too soon and not allowing your engine to heat up fully.

I'm 99% sure he means the thermostat that controls the coolant.

Just replace it anyway, it's not that tough of a job.