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Discussion Starter #1 (Edited)
Hi,

I'd appreciate some input. I've got a 2008 Tribeca. Has 142,000 miles on it.

Dealer has noted, on various occasions, both the head gaskets and valve covers are leaking. The engine is out and I can confirm it's only the valve covers.

Should I still replace the head gaskets? They look totally fine. Not even a hint of a leak.

Since I've cracked it open I'm doing the oil pump, water pump, valve cover gaskets, etc... Should I go all the way to the head gaskets?
 

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I hate to say this now, but I would have checked before pulling the motor. The oil pump and water pump are not known to cause issues, but if you are digging that far into this...you should replaced the timing chain guides and tensionsers since you will have to remove those to remove the heads. Seems like an awful lot of work to change gaskets that aren't an issue, though.
 

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Discussion Starter #3
I hate to say this now, but I would have checked before pulling the motor. The oil pump and water pump are not known to cause issues, but if you are digging that far into this...you should replaced the timing chain guides and tensionsers since you will have to remove those to remove the heads. Seems like an awful lot of work to change gaskets that aren't an issue, though.
Oh, I looked, but there was so much oil up front I couldn't be 100% sure until I removed it. Plus I was going to pull it regardless as a project. Yes, I intend to do the chain guides since they may wear. Was thinking about NOT replacing tensioners if they seem fine. I haven't taken them off yet to see if that's possible.
 

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Discussion Starter #4
Did a leak-down test. Cylinder 5 is the only one out of synch with the rest and has significant exhaust valve leakage. Looks like they're coming apart anyway.
 

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Replace the head gaskets, pure and simple. The leak your dealership is referencing is likely an internal leak, which typically cannot be seen with the naked eye, not the external leak you can visually ascertain by the presence of oil and/or coolant residue. The EJ25 is synonymous with "external HG leak," but when the EZ30 HG fails, it's almost always internal.

Whether you replace the timing chain components is up to you. Unless they're visibly damaged or heavily worn, it's probably not necessary. But if you want peace of mind, it's not a bad idea.

But whatever you do... MACHINE THE HEADS. Do not replace the heads unless they're absolutely flat, especially for an internal leak, or you'll be doing the HG's again in no time.
 

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I'd replace the water pump and seals/orings.

Unless there's an issue being addressed, I wouldn't bother replacing chains, guides, and tensioners again. I've done it in the past but on retrospect, never again. they routinely last the life of the vehicle and have nearly zero failure modes.

I totally understand the general notion, but all the data says it's unnecessary.
 
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