Head gasket?

[trainbufftony]

My Land mate/ business partner/friend has a well used 300k tacoma.
Its got a 2.7l engine.
Its occasionally burning coolant. Blowing white clouds out the exhaust but not all the time.
I did a head gasket check for combustion gasses and came up with no evidence of combustion gas hot or cold. The head gasket checker says A-ok.

So I changed the idle air motor and gasket. Logical choice right? The gasket was dry and cracked. The symptoms didn't change.
I took off the throttle body and submerged it in water and pressure tested that piece of the coolant system.
No leak found. Whatever may have been leaking there, isn't now. My next step after breakfast is to pull the spark plugs for an inspection, then pull the (water cooled) egr valve and submerge it to check it for leaks.

Am I simply delaying the inevitable?

The truck has had the head replaced professionally once before he bought it but at 300k all bets are off.


What say the experts?

 

[aztoyman]

Did you get a look at the spark plugs? It would definitely help narrow thing down if you see a steam cleaned plug or plugs.

I had a 2002 Tacoma with that engine but I never worked on it so I'm not the expert you were hoping would chime in. Are there any coolant ports near an intake port? Like in the manifold. I vaguely remember one on the 22RE that could leak into one port. It's been many years so I may be wrong.

I've had corroded coolant ports (near the exhaust valves only) on a 22RE cylinder head that leaked into the combustion chambers.

Good luck with it. Scott in AZ.

 

[trainbufftony]

I pulled the plugs and #4 looked to have coolant burnt to it.
The EGR has a coolant passage which, would leak to that cylinder if it were leaking internally.
I removed the egr and the throttle body and checked them both for leaks by submerging them in water and pressureizing the coolant passage.
No leaks were found.
This morning (after borrowing a 14mm 12pt socket) I removed the head and found the cylinder head gasket pushed in on #4 far back coolant port on the hot side.
The head is off now so no point in simply slapping a gasket down . Its been 200k since the last head job so time to have another go at it. We'll take the head to my machinist and he will work his magic on it and that should get my land mate to the half million mile mark.
Glad to have found the cause of failure...

 

[aztoyman]

You definitely did some very logical troubleshooting. I'm glad you figured it out and updated this thread. I was wondering what you found.