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Discussion Starter · #1 ·
My 06' pilot would fill up coolant overflow bottle after about 300 miles of interstate driving. Replaced radiator / cap / thermostat based on everyones recommendations on the forums. Leak down test has confirmed, the front bank of cylinders (4, 5, 6) have a blown head gasket at 240k miles. The chemical test passed every single time I tried it. No white smoke out the exhaust, just a lot of condensation. I put air into one cylinder, #5, the air comes out #6 and bubbles the coolant and creates the same pressure situation in the radiator with the cap on. Clearly getting air into the coolant! If I did this test a year ago, it would have saved me soooo much time chasing fake electrical issues, blaming the computers programming, replacing coils, plugs, etc. etc. I wonder if more pilots on this forum don't have this same issue. A leak down test is so easy to do. I tried burping the system over and over, but it was always bubbling. When I KNEW i had a problem was when I took the rad cap off, and revved the engine and coolant shot out of the funnel about 6" on every rev!

Car never overheated on my watch (2nd owner) and it's been driving and idling perfectly even with the coolant issue. It would misfire on start up on cylinder 5 after sitting for 2 or 3 days, but would clear out if I restarted it. Seemed to happen more on cold days. Clearly there is coolant and too much air seeping into the cylinder(s).

The back cylinders, 1, 2, and 3 have tested perfectly on the leakdown, no drop in the pressures. The question is, should I replace only the front bank headgasket or both! I'm inching towards just the front one with this car having so many miles on it. I have it torn down to about ready to take the timing belt off.
 

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2005 Pilot EXL- 227,700 Miles
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Wow!!! Happy you found the issue and persevered 馃榿馃憤馃憤. Great write up too!! I鈥檒l defer to others who have more head gasket experience than I.
 

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If it never overheated I would throw the dice and only do the front side. The rear head will add a lot more work and it sounds like it is not necessary. This is a no brainer for me.

Be sure to check the front head for cracks.
 

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Discussion Starter · #4 ·
If it never overheated I would throw the dice and only do the front side. The rear head will add a lot more work and it sounds like it is not necessary. This is a no brainer for me.

Be sure to check the front head for cracks.
My thinking as well. If it isn't blown now, I just don't see it as being a future issue myself, if so, I guess I'll be redoing the rear one!
 
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