Cooling system issues

[Legacy777]

Well ever since I got back from my trip, I've been having issues with the cooling system. The system is pushing coolant to the overflow bottle and filling it about 7/8 of the way. It does not appear to go over this amount in the overflow bottle.

I have tried bleeding the air out of the system a couple times now. When I dump out the coolant in the overflow and put it back in the system, it doesn't appear that I need much if any extra coolant.....if I've added some, it's been very small. After driving for a while I'll hear gurgling from behind the dash in the heater core when idling.

I've pressure tested the cooling system and the caps. I did find a hose that was leaking and repaired it. The system only lost 1-2 psi in a 70 minute or so time period. That could be contributed to the tester or something else (the problem).

I'm going to pull the plugs tomorrow and probably try and compression test as well. I bought a coolant hydrocarbon tester. So when I get that, I'll test the coolant for hydrocarbons.

Based on what it's doing, I'm kind of guessing it will be a head gasket, but am trying not to jump to conclusions.

I know I didn't really ask any questions, but if you have any thoughts/comments, let me know.

Thanks

[ericem]

Are you going to try replacing the thermostat and rad cap?

[Legacy777]

I tested the rad cap with a pressure tester, it's good.

Tstat has less than 10k miles on it, and shouldn't be causing the symptoms.

I pulled the plugs yesterday and they looked good.
http://main.experiencetherave.com/subar ... /ngkplugs3

Smelled the coolant and I thinnk it had a little bit of an exhaust smell to it...but can't be sure until I get the tester.

[evolutionmovement]

Sounds like a head gasket.

[Legacy777]

Yeah.....I'm leaning that way myself...

[entirelyturbo]

Definitely do the coolant-sniff test, as you mentioned in the other thread.

Mine was doing the exact same thing... occasional overheating and overflowing of the reservoir. Yet I had no compression loss for 500 miles.

[evolutionmovement]

Mine ran balls-out with a bad head gasket and, much later, until the last moment before an exhaust valve melted.

[Legacy777]

Did a compression test yesterday. Cylinder 3 is lower than all the rest, but still in the "std" guideline. It's not a smoking gun, but seems to coincide with the results from the coolant system test.

The cooling system tester turned from blue to dark green, indicating that there was a little bit of CO2 it detected. That would confirm the fact that the engine still runs ok, and that the compression test showed a little lower than the rest.

Here's the pressures

Cyl 1 - 162 psi
Cyl 2 - 162 psi
Cyl 3 - 140 psi
Cyl 4 - 165 psi

I don't know if a leak down test will really show anything different or if it's worth doing or not....

[Legacy777]

Did a leak down test yesterday. Had some interesting results. As expected, cylinders 1, 2, & 4 all only showed about 5-10 psi of air loss.

Cylinder 3 was showing about 40 psi of air loss. The odd thing was that air was leaking out through the intake valves and was slowly pressurizing the intake manifold.

I never saw any bubbles in the cooling system, but I kind of did not expect to see any.

I'm not sure if I had an air pocket somewhere in the head due to the head gasket, and cooked a valve......that's kind of grasping at straws.

Anyway, will be pulling the motor in the next couple weeks to see what's up.