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2003 Subaru Baja – Head Gasket replaced once ~40,000 miles ago.
I am also looking for the source of consistent overheating issues. I’ve had no less than 3 mechanics do a combustion leak test and all came back negative. I’ve had the radiator replaced, thermostat replaced, radiator system flushed, and they’ve all done compression tests… Still I get intermittent overheating.. I hope that the mechanics have been competent enough to bleed the system of air each time.
This last time, I definitely heard a gurgling coming from behind the passenger panel where the heater core is. So air is getting in the system somewhere. The heater core is not showing any of the usual symptoms of a leak however. No smell. Heater works fine,
Not sure where to go next. I’ve ordered a no spill funnel to bleed the system myself. We shall see…
Any advice?
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The no-spill funnel is a good place to start, but Subie cooling systems generally self-bleed pretty well. When the engine was apart for the head gasket job, was the water pump replaced?
If you’re definitely getting air back into the system, and there’s no head gasket leak, here are some things to consider:
1. When the radiator was replaced, was the cap replaced with it? Is the current cap a known good OEM cap?
2. Crack in the hose from the reservoir?
3. Has the system been pressure tested?How can I tell if the cap is a good OEM cap? I mean it looks shiny and new like it likely came with the new radiator, but I have no idea if it’s a good OEM cap.
As far a the water pump, we think it was replaced with the head gasket as that’s standard procedure, but that’s next on the list to throw many at I suppose.
If you bleed and then find air in the system again, I’d check the reservoir hose first, pressure test second, replace the rad cap third.
It is possible for a combustion leak test to not show positive if the combustion leak is very small and is only occurring while under load.
Because the load conditions and pressures cannot be duplicated while testing in the shop bay. Those conditions occur only while driving on the road.
So a second test should be carried out after a brief highway drive.
If the result is still negative then there is likely some other issue such as a rad cap not holding pressure or allowing air to enter when the vehicle cools down.
Has the rad, flush and thermostat all been changed after the head gasket repair job?
If not then has stop leak been put in after the rad, after the flush?
Has the stat been replaced after the all the other work?
One needs to remember that just because these parts have been replace once that they can fail again after some.All repairs have been done within the last few months. (Except the HG repair)
Mechanic #1: Thermostat
Mechanic #2: Cooling system Flush
Mechanic #3: Radiator replacement
Each mechanic also pressure tested the system and did a combustion leak check. I don’t know if it was after a drive as you suggested or not, but I would expect so.In each case, the problems went away for a week until, I assume, air leaked back into the system from somewhere… I hope to get my no spill funnel today and I will replace the transfer hose from the reservoir to the radiator just in case. Might go ahead to replace the radiator cap as well – though I expect it came with the new radiator.
The thermostat is only a month or two old at this point.
Thanks for the suggestions!
Update:
Definitely air getting into the system. I bled the cooling system for about 20 minutes and the bubbles would stop temporarily but never cease. In fact, periodically, they would increase almost to a froth of tiny bubbles. And when I would release the gas or cut the engine, I would get several large bubbles for while as if the back pressure was pulling air in from somewhere in the system.I held the throttle at 2500-3000 rpm and the fan definitely was running for about the last 10-15 minutes.I doubt I just didn’t bleed it long enough, but I suppose it’s possible.
I hope someone is going to tell me that the periodic frothing could be a leaking water pump as it’s pulling air in when the thermostat opens. I don’t want to hear about a head gasket… Especially when 3 mechanics have all performed the combustion leak check.
In any case, just to be on sure, I did replace the reservoir hose and the radiator cap. I’m doubtful they are the cause…
Any thoughts?
More tests:
1. With the car completely cold, start it, run it for 2 minutes, turn it off, and immediately remove the rad cap. Is there pressure?
2. Power balance test.
3. Leakdown test. Should have been done long ago but I don’t see it mentioned above.What will these tests tell me? I suspect these are test for a blow head gasket?
I should also note that I’m not having any coolant loss, oil loss or milky oil. I do get a gurgle noise in the heater core…Yes, they are tests for a bad head gasket or cracked head. The power balance test should not turn up anything unless you’re having substantial performance problems, but it’s quick, easy, and free, and we’d feel silly to find out we completely overlooked a non-firing cylinder.
Having watched some of the combustion leak videos, the bubbling is nothing like what I’ve seen in those. If it is a head gasket leak, it’s a small one, which might explain why the overheating is so intermittent…
spark plugs on this car are hard to get to..
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