[plain OM]

I wonder about the driving conditions under which the engine begins to overheat. Also, could it be the fans? Could it be the thermostat?

 

[plain OM]

Just to update this thread my mechanic is challenging that it's a HG issue because theres coolant in the exhaust when he did a compression test,

Diagnosing from a distant is challenging, and sometimes little bits can be missed. This statement is one. What does it mean? Was the compression test on the cooling system, or cylinder compression? And, where "in the exhaust" as coolant observed?

There's a "cracked head" thread here: http://www.subaruoutback.org/forums/88-head-gasket-issues/45341-still-smoking-after-hg-repair.html

This doesn't preclude the possibility that the HG's are seeping/leaking, but I wonder if there's more to this statement that might be related to the apparent overheating.

 

[plain OM]

Those are all good questions I don't answers to but, could you expand more on your last sentence.

A crack in the cylinder head, between the coolant jacket and the exhaust side of the head, could lead to "coolant in the exhaust" which is what the mechanic said was found. This is also what appears to have happened in the thread to which I provided a link earlier.

If there is a crack allowing coolant to get into the exhaust (subject to clarification as to where), the overheating could be caused by the loss of coolant, or perhaps the effect the coolant in the exhaust has on the air/fuel and O2 sensors at the catalytic converter. That was why I asked for more information on the driving situation when the car overheated.

Also, in many if not most threads on overheating, the symptom appears under specific conditions -- it might be while idling, or while ascending a long, steep slope, or while driving down an interstate at a constant high speed, etc. Sometimes, this information can be used to narrow down causes.

Information, indeed, details, that might be overlooked can be quick leads to a solution. That's also why I asked about the fans; do they come on when the temperature gauge goes above normal? They should, but if they don't, that itself could be the cause of the overheating.

The point is there's many possible causes of overheating, and we need to look at the possibilities to try to diagnose from a distance. When someone observes coolant in the exhaust, that should be considered, at least, delved into in order to understand exactly what it refers to. It might not be something to discount summarily. That's why I said

I wonder if there's more to this statement [about coolant in the exhaust] that might be related to the apparent overheating.

Hope this helps clarify . . .

 

[plain OM]

As to the fans coming on I noticed a few months ago that they where coming on when I started the car and let it idle also when I put it park after a drive.

Normally, the fans should not come on when the engine is first started and not yet up to operating temperature; an exception, however, is if the AC is turned on, or the heater is set to one of the two windshield defrost positions with the heater fan running.

Although unusual, if the temperature gauge is indicating above normal temperature right off the bat, the fans could be on because the fan control, the engine control module, is sensing an overheat situation, but I wouldn't expect that after an initial start unless there's a problem in the sensor.

Temp gauge rises after about 20 minutes of driving to about the three quarter mark on the gauge and moves back and forth from somewhat normal back to that mark.

Interesting. When a HG fails internally between a cylinder and the water jacket, the reports here suggest the temperature gauge would tend to spike up rapidly and then fall just as rapidly, but I don't recall mention of it cycling back and forth continuously. Internal HG failures are rare in the 2000 - 2004 Gen. The continuous cycling, if I understand it correctly, seems more like a thermostat that can't regulate properly.

I pulled over and checked to seen if the radiator was hot or the coolant was low. The radiator gave no indication that it was running hot and added about two pints into reservoir.

I would imagine that the radiator would certainly be hot if the engine was up to operating temperature and the coolant was circulating through the radiator. By "running hot" do you mean overheating? How did you check the radiator temperature to conclude it wasn't running hot? Not sure how you would do that without some instrumentation.

Also, when the engine is up to temperature, the coolant level in the external reservoir should be higher than it was when cold. If with the engine hot the reservoir level was 2 pints low, there could be a shortage of coolant in the engine cooling system because there wasn't enough in the reservoir. The coolant level in the radiator itself should be checked by removing the radiator cap, but this can only be done safely when the engine is fully cooled down. The level in the reservoir with the engine cold should be between the COLD and FULL marks. When topping up, it should be set at the FULL mark. It will rise an inch or two from there when the engine is fully warmed up.