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2001 Subaru Outback H6-3.0 overheating at 215k, fix at $2500?

My 2001 Subaru Outback H6-3.0 is at 215k miles (I bought it for $4k at 201k miles). It overheats only when I drive for a while on a hot day. I was trying to get to Yosemite with my whole family in the car, and rather than do the intelligent thing and go back home and get it repaired, I kept going, stopping when the gauge started going past the middle to let it cool down and replace any water it was missing (after the engine cooled, of course). Amazingly, we managed to use the car almost normally during the trip, as long as we did short-ish trips and kept some water in the car. Having to pull over randomly isn’t so bad when you are in Yosemite anyway.

There was a mechanic shop in the little town we stayed in, but they weren’t equipped to to do a head gasket job in the little time we were going to be up there, and we needed the car to get around anyway. So I tried putting some of that coolant leak repair gunk in there and it seemed to help. We made it the hundreds of miles home, no problem (but it was downhill, where the trip up there was uphill). Problem solved, right?

Well, about a year later of only driving the thing about 50 miles in any given run, and not terribly hot weather, we decide to go a few hundred miles south. Sure enough, it was a hot day and after about 60 miles I saw the temp gauge go past mid and immediately pulled over. After it cooled a bit, I drove it (in two hops, because it started heating up again quickly) to a shop. They tested it and sure enough it’s a head gasket leak. They said it’d be $2500 to fix it.

So far this car has been pretty good to me otherwise. Numerous times, I’ve taken it up 300+ miles into the snow and ice covered roads to go skiing and LOVE not having to put chains on. I am guessing that all the cold air up there kept it from overheating while I was pushing it pretty hard up some steep inclines without issue. It seems like there is a temperature threshold beyond which it starts to quickly overheat, and below witch, the gasket is holding fine, or something along those lines.

So, given that I like this car, is it worth another $2500 to get her back on the road? Should I just try the leak stopping junk again? Should I have been using “SUBARU cooling system conditioner” this whole time, even though it’s not one of the supposed head-gasket-problem engines? Should I just drive it until it finally overheats to death? It’s probably still fine to drive in moderate to cool temperatures (winter is coming), but I haven’t driven it since the leaking head gasket diagnosis. I don’t know if I did permanent damage to it that day, or if it’s just its usual self still. It didn’t get into the red, heat-wise.

If I get it fixed, can I really expect to get another, say, 10000 trouble free miles out of it? If so, then I think the overall $/mile ratio is alright.

Assuming the diagnosis of a bad head gasket is accurate, I would not sink that kind of money into an aged, high miles car that has been chronically overheating. That kind of overheating is tough on cylinder walls/piston rings and can lead to oil consumption problems.

Overheating only on extended highway use could point to a clogged radiator, weak pressure cap, or cooling fan issue; or all of those.
Even a clogged catalytic converter can cause overheating.

A head gasket will fail in one or more ways.
Leaking coolant externally. You should see spots and smell this.
Leaking coolant into the engine oil which may make the oil resemble sour milk, etc.
Leaking coolant into the combustion chamber. This will produce white smoke out the tailpipe.
If your car has none of those symptoms then the diagnosis may be suspect and you might consider another opinion as head gasket faults can often be misdiagnosed. Hope that helps.

Well, if you like the car and it is otherwise in good shape, $2500 is a lot less, like ten times or more, than the price of a new replacement vehicle. If you choose to buy a new one, be sure to consult Consumer’s Reports car guides, which give owner’s reliability report summaries. Avoid makes/models/years with a lot of owner complaints about major engine repairs being needed. Best of luck.

Get a 2nd opinion. This is similar to getting grave diagnosis.

Some folks are swayed that Subaru’s have short lived head gaskets however this is not true of the H6 and turbo H4 designs.

Andrew is correct about the H-6 engine not being subject to head gasket issues, but after this many miles, it is–of course–a real possibility, especially if the car has not been maintained properly.

Because the OP tells us that he uses “water” in the cooling system, that mistake could well have led to overheating, that in turn led to a head gasket problem. Any car will be subject to overheating if the owner uses straight water in the cooling system, rather than the correct 50/50 water/coolant mix, so this is a very poor way to try to save money on car maintenance.

Also, the H-6 3.0 engine will run too hot if regular gas is used, which is why premium gas is specified for it. If the OP has been using regular gas, that is another “economy” move that could have been an exercise in shooting himself in the foot.

Get a second opinion. If it turns out to be the same (don’t mention the diagnosis to the new mechanic) then sell the vehicle for parts.

For about $10 bucks, why not try the stop leak again. If you get another year or two out of it, how could you go wrong?

I’m pretty sure that there is something minor going on with the head gasket which could be triggered or exacerbated by driving it in the heat with the AC on. The shop I took it to did the pressure test thing, twice to be sure. Also, the battery had been fuzzy for over a year (I only replaced it a month ago or so after it straight up died). This may have caused that electrolysis thing which eats away at the head gasket. As much as I want it to be anything but the head gasket, I’m afraid that might be wishful thinking. As the shop that diagnosed it is 60 miles away, I’ll be taking it to another shop, if I decide to repair it, so the second opinion will come then anyway.

My understanding was that using water only for coolant is only ill advised in cold weather. I guess I was wrong about that. I’ve never had a mechanic tell me I was ruining the car with water-only coolant, and I’ve had at least two tell me to just fill it with water for hot weather.

The problem with trying the stop leak again is that I have no way to know if it was successful, given that it only overheats when I drive 50+ miles on a hot day (and winter is coming). I’m still on the fence about repairing it proper. But if someone told me that with proper maintenance I should expect another 50k miles without too much hassle, then I think I would go for it.

“I’ve never had a mechanic tell me I was ruining the car with water-only coolant, and I’ve had at least two tell me to just fill it with water for hot weather.”

Your first course of action is to find a qualified mechanic, as nobody with up-to-date mechanical knowledge and credentials has been of this opinion since…maybe…the 1970s.
No, I am not kidding.

Any mechanic who states that a modern car can be run with only water in the cooling system should not be trusted to be able to properly diagnose or fix your car.

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After all you have gone through with this car, I would not put any more money into it. Even with a head gasket fix, there will be other things that have deteriorated excessively due to the high mileage and overheating. Try the stop leak stuff again and just drive the car into the sunset.

Any problem caused by a head gasket should be present no matter if the A/C is on or not and straight water should never be run in a Subaru.

I just ran it again to test it out. Just a short 15 minute hop to work and back. It did not overheat, but after getting it home, I checked the coolant reservoir and it’s muddy. On that day I drove south 60 miles and it overheated, the reservoir was clear water. Unless the guys at the shop put something in there without telling me, it’s got an issue. I’ll call them tomorrow and ask, maybe they put some stopleak in there without telling me and that’s what I’m seeing, but I doubt it. So at this point, I think the problem was not big until that day, when I pushed it too hard, and now it’s big. Trying stopleak and driving it into the sunset is looking good. It’s too bad though, it’s a really nice car otherwise.

It is probably best if you simply drive this car until it croaks, which–unfortunately–is an unpredictable event. As long as you don’t mind the prospect of being stranded in an unsafe or inconvenient location, at an inconvenient time, then just continuing to drive it is probably the way to go at this point.

However, when you are in the market for your next used car, I strongly suggest that you do the following:

Only buy a car if it comes with full maintenance records that you can compare to the mfr’s maintenance schedule.

Even with evidence of flawless maintenance, you need to have a competent mechanic do a thorough pre-purchase inspection of the vehicle.

Find a new mechanic, as the ones who told you that it is appropriate to use straight water in the cooling system are WRONG and are woefully unqualified to call themselves mechanics. No matter what make of car you buy, it needs a 50/50 mix of approved coolant and water in the cooling system, and that mixture needs to be changed/flushed every 3 years or so.

Follow the mfr’s maintenance schedule faithfully, including both maintenance intervals and the correct types of fluids.

NEVER continue to drive a car if warning lights or gauges indicate overheating or low oil pressure. Both of those situations mandate that you immediately pull over to the road shoulder, shut down the engine, and either determine the nature of the problem (and fix it) before continuing to drive, or simply have the car towed to a reputable shop for diagnosis.

Get into the habit of lifting the hood once a week to check the level/condition of the coolant, motor oil, & transmission fluid. After you have determined that particular car’s rate of oil consumption and/or coolant depletion, it may be possible to stretch the checking interval to once every few weeks.

My understanding was that using water only for coolant is only ill advised in cold weather. I guess I was wrong about that. I've never had a mechanic tell me I was ruining the car with water-only coolant, and I've had at least two tell me to just fill it with water for hot weather.

Find new mechanics. Any mechanic who told you to run straight water in ANY weather has no idea what they are talking about. Besides the FACT that anti-freeze also raises the boiling point…it also lubricates the water pump. There are also rust inhibitors. Running straight water is just foolish.

Funny, I’m considering purhasing a 2001 Outback with the same engine and 215K miles. You wouldn’t have happened to have sold or traded in the car since you first posted this? The car I am looking at came from Wisconsin.

The car I’m looking at has been immacutaly mantained and runs fantastic. I’m wondering if you’ve had any issue since you bought the car, besides the above…?

About a year ago my 2002 Outback LL Bean H6 developed a hole in a radiator hose. Obvious fix. All good. Recently developed more overflow tank filling and blowing coolant out the top on a long drive. Changed radiator cap and burped the system. Still would hear gurgling on cold start up. Changed radiator cap again with OEM cap. And do check the overflow hose and make sure it is secure, mine was pushed to far in, and caused air getting into the system. Burping the system seem to relieve more bubbling, then it stopped. Long drives would occasionally increase overflow but not to blow out. Now at 214k miles all seems well. I concluded any bubbles in the system will cause a problem. The system seems to work well without constantly removing the cap to look into the radiator.