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1998 Subaru Forester Head Gasket Failure (again)

Our 1998 Subaru Forester has head gasket problems (intermittent overheating, etc) and its time to do something about it. We already replaced the radiator cap and thermostat. The radiator has been ruled out as the source of our problem. We seem to have 3 options: 1) replace the head gasket; 2) replace the engine with a 1998 engine with <50,000 miles; or 3) rebuild the engine. We’re committed to keeping the car so we want a long-term fix to our problem. The first option sounds iffy because there might be other problems with the engine that we can’t know about till the mechanic looks at the engine. Or the gasket may fail again. It sounds like replacing the engine with a comparable engine is a risky proposition since Subaru engines have head gasket issues till about the 2005 model. That leaves the rebuild. Or are we missing something here? For example, can we replace the 1998 engine with a post-2005 engine?

The overheating likely caused the cylinder heads of this aluminum engine to warp. Warped heads do not mate properly with head gaskets, thus allowing a breach in the gasket.

If the engine overheated prior to the first head gasket replacment, and if your mechanic did not replace the heads, then that head gasket replacement was essentially a waste of money. In other words, the first head gasket replacement was doomed to failure if the engine had overheated and if warped heads were not replaced (or at least “planed”) along with the head gasket.

If this engine has had repeated episodes of overheating, I don’t recommend investing any additional money in it, as the internal problems could be numerous. Aluminum engines, like the one in this car, do not take well to overheating.

I think that the best option is to replace the engine, as long as it can be verified that the cooling system is operating properly. If the radiator or cooling fans are not operating properly, then the replacement engine will soon be trashed as well.

If you try to install a 2005 engine, you will also need a 2005 Engine Control Module (ECM), otherwise that engine will never run properly. Also, you would need to verify that this newer engine would mate-up correctly with the older transmission. All-in-all, you may be looking at a much more extensive job if you try to use an engine other than the same type as originally installed in the car.

Thank you! We very much appreciate your response. My bad - the “again” referred to a string of postings on this subject in 2007 that didn’t quite address our question. Our car has not had the head gaskets replaced though it did overheat once. The hyrdocarbon test says the head gaskets need to be replaced. Otherwise, it runs well and we don’t have evidence that there is much internal damage. Does rebuilding our engine make sense under these conditions?

Screw me once, shame on YOU…Screw me TWICE, shame on ME…

Cost per mile to own and operate. It’s the only thing that matters…

Yes, thanks, cost per mile… Without any repairs the car is basically worthless. The car is in excellent shape except for the head gasket. We’re willing to invest ± $4k to get it to the point where we can get 5 more years of good use out of it. If $4k won’t make that happen then I guess we start over. If $4k will make it happen then we’ll do it (yes, anything can happen…). A couple of scenarios we’re considering:

  1. do a simple head gasket job (with head getting milled) ± $2k
  2. do a complete overhaul ± $5k(?)
  3. get a 98 engine with less than 50k miles w/new timing belt and 1 year guarantee: $4k (we have a line on one…)

those 3 options leave us with the same possible problem down the line, but now that we’re sensitive to the problem (to say the least), I’m not as worried that we’d catch an overheating problem at an earlier stage next time. Or…

  1. find/install a post 04’ engine w/o the head gasket weakness. This is a pretty attractive option if its feasible - does the later engine bolt to the frame and to the transmission the same? Are there options that have to be installed that are prohibitively expensive? Can it be done for ± $4k?

  2. any other options?

When someone comes up to me and say’s “I’m going to to buy a Suburu.” I just poke them in the eyes and say, “Well? We might as well start here!”


Instead of diving in with a big bucks fix you should try to verify whether the car even has a head gasket problem.
A head gasket that is not leaking into the combustion chambers or allowing the coolant level to drop too low will not cause overheating.

What are the conditions when the overheating occurs? In city driving, on the highway, when the A/C or Defrost is on, etc.
Fans cycling on?

It’s taken a while for us to get to this point but once they stuck the meter stick in to the coolant and the hydrocarbons went from 60ppm to 350ppm we were pretty convinced. Also, they could see bubbles coming up from the bottom of the reservoir. Last, there is definitely a black smudgy surface on the reservoir, It’s a little perplexing. The car has either lost coolant after 2 hours of highway driving or its overflowed. Sometimes nothing happens at all. The overheating has really only happened once and truly it may have had more to do with a loss of coolant due to a leaky radiator cap but we don’t know for sure. Our recent experience with overheating is that the temperature guage started to go past the half way point after the car had been on the freeway for 40-minutes and then hit stop and go traffic. The car cooled down once it was moving again at 65 miles per hour. The fans come on. We live in San Francisco so we hardly use the A/C. No issues with Defrost. As for pros and cons of owning a Subaru, we’ve been pretty happy with ours and feel like we got 12 good years out of the car. Also, used subarus seem to be a hot commodity in our area - the AWD and higher suspension on the Forester is great for rural roads and snow.

Faithful bunch to the brand and they seem only attract more people with their lastest Forester, Impreza, Outback. I don’t think stuff like this matters. I believe one of the few car makers with a sales increase not decrease for 2009.

I love my turbo Subaru but the rest not my cup of tea.

Since you’re committed to a long term fix and you’ve done the proper steps to verify that the headgasket is blown, the next step is to remove the head and inspect it for erosion of the breech path (block too on this one) and for flatness. A machine shop can check the flatness better than you can, because they’ll have a reference surface to use, a granite table (literally). They can even teake specific measurements. The cost should be minimal.

Until you know the condition of the head and the top surface of the block (see the erosion comment) you can’t really make a proper decision on how to proceed.

If the head is warped you then have to look at the options of having the head reworked or buying either a boneyard head (which will need to be checked before installation but should come with a money back warranty) or reworking the head you have. The machine shop can give you a quote to do that. You may even be able to buy rebuilt heads online.

If you decide to change the motor, you may want to shop out a rebuilt long block. It’ll cost a bit more, but if you plan to keep the vehicle long term that may be your best option. I’d be hesitant to go with a boneyard motor for a long-haul fix on this one.

On 3) there are quality Subaru rebuilds out there if really needed.

This one has a good rep:

Personally I would give up on the car and move on. It is 12 year old and served a good life.