overheat question

[subegrl]

Here's the story:

 

Forester, 230k miles.

 

I was driving in town this morning and noticed the engine temperature going up.I stopped and popped the hood and added coolant to the reservoir. Infact I added too much and realized it was full to the top. I called my brother and asked if I had messed anything up by doing that and he said not to worry about it.

 

I got back in the car and drove it about a mile and it started trying to overheat again. Called my brother again and he said to twist the radiator cap open and drive it over the hill to his mechanic (I was in my old neighborhood which is where he still lives and works).

Radiator cap is Subaru OEM btw and about a year old.

 

I twisted open the cap and it spewed coolant everywhere. We were thinking bad thermostat. The thermostat on my car is underneath the car, making it a pain to replace. It didn't over heat as I drove it over the hill, again about 2 miles to the mechanic.

 

I parked it and talked to the mechanic; he asked me to drive it around to the garage doors. When I drove it around it overheated (not to the red). He expressed surprise and said it got so hot so fast he suspected head gaskets.

 

But - he put water in the radiator itself, not in the coolant reservoir, and it stopped overheating. He told me to drive it around 15-20 minutes and see if it did it again. I did and it has not done it again. I drove it in stop-and- go traffic, a brief stint on the interstate, and ran the air on high the whole time and the temp didn't budge.

 

I am going to get it pressure tested but in the meantime, what do you think? Head gasket? Or was just that the fluid in the radiator was low and did my overfilling the reservoir cause this somehow prevent it from flowing into the radiator when it needed it (vapor lock?)

[NoahDL88]

Depending on year, the headgaskets are a possibility. I remember someone on this forum having a similar issue with their Forester, it would overheat and they would have to add coolant every few months until the headgaskets finally failed catastrophically.

[subegrl]

It's a 2001. It's never had a head gasket replacement. I've been good about adding the Subaru coolant additive when I've had the coolant changed.

[Fairtax4me]

Get a block test / combustion gas test done. That will tell you if there are exhaust gases in the radiator, a solid indicator of a bad HG.

[SchwarzeEwigkt]

That's what happened to me when I blew a hole in my radiator recently. It kept overheating because there wasn't anything in the system. It won't suck the coolant back in from the bottle because it needs to be full up already to do that; it needs to make a syphon. If there's air in the system, there's no way for the coolant in the bottle to get back in. You have to put coolant in through the top and bleed it via the bleeder screw. You might have a leak someplace and it finally ran down enough to make a difference.

[EVOthis]

WOW! an 01 with 230k miles and the HG have never been replaced...Perhaps your radiator was just low on coolant, in 2001 you have the SOHC EJ25, 95 % of the HG on these, well really Subarus in general leak externally and for the most part dont really cause overheating problems, Pressure testing the system is a good idea as well as a combustion leak test of the coolant as mentioned...

[idosubaru]

you're likely loosing coolant somewhere. these engines are notably hard to get air out of once they've lost coolant. the radiators tyipcally have a bleeder screw on the passengers side to aid in getting the air out. if not it causes overheat as the bubbles prevent proper circulation.

[mdjdc]

You have the typical SHOC head gasket leak. It is external and the coolant got low and you got hot. Once you fill her back up you are fine. You just need to watch the level of coolant.

 

By the way, these motors DO NOT have a bleeder screw on the radiator. It has a different design than the earlier models and doesn't need one.

[subegrl]

Well, on the suggestion of a friend I took off the hose that connects the radiator to the over fill tank, and blew it out, poured some water thru it to made double sure it wasn't clogged; reattached it and drove the car all weekend - about 400 miles - without the coolant level in the radiator dropping. hmmm. I can only wait and see I guess.

[idosubaru]

thanks mike, good to know on that bleeder screw.

 

you can drive these all day long, they won't over heat...until they run low on coolant. keep it full of coolant and you have no worries on overheating, on this year motor it's strictly about coolant level.