Engine getting warm

[dcarrb]

Originally posted by immortal_suby
I think it's the thermostat - but wanted to make sure.
Temperature climbing randomly (haven't seen a pattern), then before it gets more than 1/4" to below the red zone it drops back down quickly to normal. It will get warmer for a few minutes before it drops back.

Upper radiator hose hot and stiff during this.
Lower radiator hose only slightly warm.
Both fans working during this so I know it is not a temp sensor.

Local shop only had a thermostat and no gaskets. The T-stat didn't have the little bypass jiggle pin either - I think I'll order one straight from suby to be sure.

Anything else it could be?
I had the water pump replaced 100k ago as preventative maintenance.

The exact thing happened on my old Legacy. It was the thermostat. and, by the time I got around to changing it, the excess heat cracked the radiator.

I'd change the thermostat immediately (or just remove the old one and take a test drive); if the problem lies elsewhere, you're only out a few bucks.


dcb

[GreenMarine]

Originally posted by Subafreak
Sounds kinda head gasketish to me. Does it build an unussual amout of pressure in the cooling system just after starting?

That's what I thought of after I heard his story too... Hope all is well Matt...

[GreenMarine]

P.S. --- > If ya wanna change your head gaskets let me know... I wanna come help!!! You can do one cylinder bank and I can do the other

[UberRoo]

Your symptoms are classic "sticky thermostat" problems. This is not to say that this is your problem, but I'd be willing to bet on it.

Frequently a bad thermostat will cause "hot spots" in the engine, which will slowly boil off the coolant, which escapes through the radiator cap. This causes symptoms very much like a blown head gasket or leaky cap. A leaky radiator cap can make this worse because low coolant pressure lowers the boiling point. Running the wrong coolant mixture will also lower the boiling point. (Too rich is almost as bad as too lean.)

Also, the easy way to check for a blown head gasket it to start the cold engine with the radiator cap removed. Just watch for bubbles in the coolant. There should be a very steady stream of them. The coolant level may surge a bit at first, but it should stabilize quickly. The bubbles may take a minute to appear.

I would compare the lower radiator hoses on both cars for temperature. If your hose is significantly cooler but don't have a low coolant level, you simply have a flow problem. The thermostat or water pump causes this. If the coolant level surges (without the radiator cap on) when you rev the engine, it's probably not the pump, though some systems don't surge predictably so it only proves something if it does surge - and if it doesn't, you're still left guessing.

If it were my car, I'd just throw a new thermostat in and see what happens because I'm really lazy. Since it isn't my car, and you probably want to be sure, take the thermostat out and test it. Put the suspect thermostat in a cooking pot with enough cooking oil to completely submerge it. Stick it on the stove and use a thermometer to test it. You'll be able to see it move when it opens around ~200 degrees. Watch it closely - it may snap open or closed, which will tell you it was sticky. If the temperature it closes at is significantly lower than the temperature it opened at, this will also tell you it was sticky.

Here's the ugly part. EVEN NEW THERMOSTATS CAN BE BAD! I bought two from Schucks that didn't work and one from NAPA before I found one at WestBay that did work [for my Honda]. By "work," I mean open and close at the correct temperature and not have a large difference between the temperatures. (The first two bad thermostats were a pain because I installed them first, had problems, tested them, returned them, and then tried again. The last two I tested before I returned and installed respectively.) This isn't uncommon and some thermostats just aren't very accurate. Getting one from the dealer is probably smart.

Either way, just replace it. The part is cheap, even from a dealership. (Unless it's specially overpriced just for the SVX.)

[immortal_suby]

Originally posted by UberRoo
Your symptoms are classic "sticky thermostat" problems. This is not to say that this is your problem, but I'd be willing to bet on it.


Either way, just replace it. The part is cheap, even from a dealership. (Unless it's specially overpriced just for the SVX.)

Whew - I hope you are right, thanks for the calming words. I ordered the thermostat yesterday from subaruparts.com and even spent the 15$ for 2nd day air. I hope this fixes it.

Chris - if it's the headgasket I'll probably have to take it to porter's dealerhsip or something, I don't have an engine hoist . I appreciate the offer of help.

Thanks

[wawazat??]

You won't like the $$ associated with having a dealership do the work Matt....the sting drove me to doing it myself.

Todd

[SVXRide]

Matt,
I'm not sure whether this info is buried earlier in this thread, but you get have the coolant system pressure checked (not just the radiator cap). A shop will acutally hook a pressure fixture up where the radiator cap goes and apply pressure. Then you basically wait to see if the pressure drops ( a drop indicating a leak path somewhere - head gasket, coolant line, etc.).
Hope the thermostat does the trick for you!!
-Bill

[UberRoo]

The pressure check is a very good idea. I didn't even think of it until SVXRide mentioned it here. (One of those tools I forget exists.) It's probably the best test you can do. Often it won't expose a bad head gasket. (There is a chemical test that will tell you if exhaust gasses have entered the coolant. I think somebody already mentioned that in this thread.) A head gasket usually isn't a leak in the normal sense because it doesn't let coolant out, but rather forces exhaust gas in, which in turn forces coolant out through the radiator cap. The incredible pressure inside the cylinders can force its way through the smallest hole, which can act like a check-valve with the head gasket material. Aside from this exception, the pressure test is excellent. With some creativity, a bicycle pump and pressure gauge can work wonders. Just keep it under eight PSI or whatever your radiator cap it rated to. (Sometimes it's labeled.)

[CDG]

I can't remember who mentioned removing the thermostat and taking it for test drive. DON'T DO THIS, its dangerous. Many cars need the limitting of coolant flow to properly cool, a thermostat does this very well. i.e. older honda's will overheat if the thermostat is completely removed, coolant flows too fast thru system, never cools, cause thermostat causes some to flow back thru engine, and some to Rad.

Have you replaced the thermostat yet?

[immortal_suby]

Just got the thermostat today. Holy cow - that thing is huge compared to the one on my wagon and the one the parts store tried to sell me. I am glad I went with oem parts. This one also has the bypass jiggle pin.
I didn't know the gasket was a rubber type - cool, so I don't need RTV to seal it then?

I'll be installing it in as soon as the car cools down enough.

[wawazat??]

No RTV required Matt.

Let us know how it works out for you.

Todd

[dcarrb]

Originally posted by CDG
I can't remember who mentioned removing the thermostat and taking it for test drive. DON'T DO THIS, its dangerous. Many cars need the limitting of coolant flow to properly cool, a thermostat does this very well. i.e. older honda's will overheat if the thermostat is completely removed, coolant flows too fast thru system, never cools, cause thermostat causes some to flow back thru engine, and some to Rad.

Have you replaced the thermostat yet?

That was me. I based the suggestion on my experience with a Legacy (which I drove many trouble-free miles with no thermostat in place).

Hope no trouble results.


dcb

[CDG]

Like Dcarrb said, he completely removed his Thermostat in his Legacy, and didn't have a problem, but I still say, be very careful.

Don't forget to clean both surfaces well, and if there are any scratches in the aluminum where the gasket sits, you may need a tiny bit of RTV to fill those scratches, but as long as they are minor, the rubber gasket SHOULD fill them. Anything bigger than a hair is too big, so fill it.

[immortal_suby]

Installed thermostat - very easy job- so far so good it did not overheat today- as soon as I can get the wife out of the house long enough I'll pull out one of her good pots and boil some water to test the old thermostat.

Saw some bubbles after the initial fill while heating the car up to try to get air out of the system, hopefully that's all it was.

Thanks again for all the help.

[lee]

got my fingers crossed for ya