My 2000 legacy has 132K Miles. This spring it started overheating intermittently, now it is
a persistant problem. It will warm up and run at thermostat temperature for about 15 min.
at highway speed, then the temp, will climb.

The dealer has been fishing, replacing the radiator, thermostat, and replacing the head
gaskets. Their next step is to replace the heads, suspecting cracks, but the fishing
is getting too expensive.

The car acts as though the water pump is not working, at other than the heads and the
heater core, it's the only thing they haven't replaced. When it overheats, the heat
comming out of the heater is not very hot - leading me to believe there is no circulation.
Do cracked heads cause bubbles that stop the water from circulating?

My questions:

1) How to properly diagnose cracked heads vs. bad water pump?

2) Cost/difficulty of replacing the water pump - should that be the next step?

I'm looking to get some more miles out of this car with out spending money that would
be better spent on a new one. Ideas?

 

I'm surprised that replacing the head gaskets didn't resolve the problem. I have a similar car, and early last year, similar problems. I had it to the local dealer with one of the best service reputations in the nation...and they didn't fix it. Similar to your situation, the head gaskets were replaced, but the overheating still happened. It turns out that the radiator was all clogged up, and this wasn't the first time it'd happened on the car. The stop-leak that they put in to seal the head gaskets seemed to clog up my radiator, so they replaced it.

Still overheated, so they did what your dealer said and began to blame it on the heads possibly being cracked. The heads were not cracked.

I took it to a shop that works almost exclusively on Subarus and Saabs (in SLC), and was planning to do an engine swap to a low-mile 2.5, but ran into problems with the donor. We decided to remove the heads from my engine and see what was going on with it. No cracks, but the heads were warped from the repeated overheating. We had the heads sent out to get milled to spec, replaced the headgaskets, did NOT include the stop-leak, and hoped that might take care of it.

That was last March, and aside from a problem with the fan not coming on earlier this year, I've had no overheating since.

The advantage I had was that my car was under 100k miles, so Subaru was covering all service. What you need to do is go in and make absolutely certain that they checked the heads and confirmed that they were within whatever tolerance is allowed. If they didn't, you should be able to get them to check the heads without charging you, because it's part of the process.

The water pump is comparatively easy to replace, versus diagnosing the head issue.

 

Thanks for the info!

I don't have much faith in the dealer, so it wouldn't suprise me if they didn't check the
heads. I got the impression that they looked for cracks and didn't find any. I could ask
them to re-check them, but I really wouldn't trust the what ever they told me.

It sounds like my next step should be to find a reputable mechanic, see what they
think, and probably have them replace the water pump just to cover that possibility.
Any leads on good folks in the Boston, MA area would be appreciated.

In the long term, I'd love to replace this car with another Subaru, but I'd want to find
someone to work on it first.

 

Oh, and I forgot to mention, it does not leak or otherwise consume coolant, nor does it
appear to blow coolant back into the reservior.

 

After a number of calls, it's looking like it's the heads, with quotes for replacement running
in the $2K-$3K range. Given that the car has 130K on it, I'm considering selling it off as-is,
and getting a new 06 Legacy Limited Wagon.

 

There is no way to tell if the heads are cracked of just slightly warped unless you have them removed. Used heads can be had on many Subaru boards for less than $500. A cracked head can be welded, but that's a very skillful procedure. Warped heads can be made true, and that's not very expensive.

If the car still runs and the dealer will take it, the new car might be your solution.