I have an 81 Subaru DL wagon. The car passes smog easily and gets about 25-27 miles per gallon. My mechanic says the car runs cool. I thought the temperature guage was just aging and that was why it barely goes above the cold line even when it's warmed up.

 

Could my car be running cooler as it ages even though it seems to be burning the fuel, or is the catalytic convertor masking the unburnt fuel by burning it before it reaches the tail pipe?

 

Can a cat running too hot cause the rest of the car run too cool?

Maybe your thermostat stays open all the time. Our Brat wouldn't get about the 1/4 mark on the temp guage until I replaced the thermostat; not the guage is at just under 1/2 when it's warm.

I have an 81 Subaru DL wagon. The car passes smog easily and gets about 25-27 miles per gallon. My mechanic says the car runs cool. I thought the temperature guage was just aging and that was why it barely goes above the cold line even when it's warmed up.

 

Could my car be running cooler as it ages even though it seems to be burning the fuel, or is the catalytic convertor masking the unburnt fuel by burning it before it reaches the tail pipe?

 

Can a cat running too hot cause the rest of the car run too cool?

Interesting Theory.

 

What you are saying is if the water is always free flowing then the radiator is doing a super good job of keeping the water cool so it never heats up as much when it circulates into the engine.

 

Plus the radiator is only a two years old so maybe it is displacing more heat than the old one it replaced.

 

It's been so long since I replaced the thermostat I forgot where it's located.

 

Since I did have the radiator replaced perhaps I'm driving around without a thermostat??? Although the thermostat is located elsewhere I think.

 

If I take the radiator cap off and start the car and I see the water already circulating then that would mean there is no thermostat in the car???

 

But then the final question is, isn't the car running cooler actually a good thing in terms of engine longevity? In a warmer climate like California is the thermostat actually necessary?

the thermostat is in the housing where the top radiator hose connects to engine. as to keeping your engine cool this means within specs of the engine and not under. the idea behind a t-stat is that no heat is exchanged when the car is warming up so it all goes into the block and once its at bit above opterating temperature it opens letting fluid flow then closes when it gets too cool. without one the car would take longer to warm up (i possible) and always run colder than its sposed to. yeh and cold engines use more petrol, you know like how you need a choke for cold starts.

 

If I take the radiator cap off and start the car and I see the water already circulating then that would mean there is no thermostat in the car???

yeh that means a dodgy/missing t-stat, if it was cold.

From your description it sounds like your thermostat is stuck, open.

 

The engine is designed to run in a temperature range that the thermostat helps keep it at. From your mileage statistics and emissions testing it seems you are doing pretty well regardless of the possible thermostat problem.

This could also explain why the car idles so slowly when I first start it, it can't generate heat quickly because the water is circulating from the get go. Now if only I hadn't left my car at the mechanics this weekend I could actually check all of this out.

Too low a degree thermostat can also keep the engine running cool as well. I know one of my XT6s have a 180F thermostat while the other has a 195F thermostat. The temp gauge of the 195F thermo is right in the middle while the 180F thermo stays around 1/4 of the way up on the cool side, whether it's warm outside or not. But you would've already known if you installed a cooler thermo I assume so....:-\

That sounds exactly like a thermostat problem (If you brought it to a mechanic, i wonder why he didnt guess this?).

 

i have a thunderbird, and one winter I noticed it was running extremely cool. The temp gauge would never get above the C. Turns out the thermostat was broken and was always open.

I've had several STANT-brand t-stats (for various cars) fail as early as one month after installation. They don't fail hard (closed), but just seem to open far too early. And none were the "fail-safe" ones that stay open after an overheat.

 

My first thought, also, was that your cool running car was a t-stat issue.