Hello everyone! I have a 2006 M45 with lotsomods and have been messing with cars for quite some time.
Recently a friend's 04 Q45 starting running poorly so he dropped it off at my house and through doing some leakdown tests, cooling system pressure, compression tests determined that both headgaskets are blown. Left between 3 and 5, right 2 to coolant. No coolant in oil. Upper radiator neck cracked -- maybe due to headgasket or maybe it caused the headgasket failure. I know the heads may be warped but I'm pulling her apart to check everything as I have time to work on her.

I know what a pain the M is to work on for header work (made a set of headers for her with the snaking around the steering shaft and a bunch of other crap)--and hopefully the Q is not as bad. I have the front of the motor off down to the chain cover, and the top of the motor off down to the heads.

Can the heads be removed and re-installed with the motor in the car or does the motor HAVE to come out? Without a lift it is simply easier for me to leave the shortblock in the car, if possible. Plus if he decides to let me buy the car I will just build a motor and do a swap down the road. The "good" cylinders are showing 10-15% leakdown (cold, no oil on cylinder walls) so I am confident that the short block is "OK" for now.

Any help would be appreicated.

Thanks!

For the trouble you're going to go through taking the heads off, I would pull the entire motor and replace it with a low mileage junk yard motor. You don't know what other damage has been done or what caused the head gaskets to blow. Are the heads cracked, warped? Will they seal back up properly? What else will you damage trying to get the heads out?

Seems like a no-brainer if you have access to a cherry picker to pull the engine. Besides, who wouldn't want a 50K mile engine in their Q?

Just my opinion and my opinion is worth what you pay for it.

Tom

Yeah, makes sense but I do know what caused them to blow. Combination of overheating and head bolt stretch. Heads are both warped less than .05mm at the worst locations. Deck is fine. I'll button it back up with new head bolts and see how she does. If/when I pull the motor I will go through it or the replacement junkyard motor. That was the point, if I had pulled the motor I would just go through and freshen it up. Pulling the heads while in the car was not hard at all. Plenty of room to remove them, even with the exhaust manifolds still attached. Once the front cover was off it really was a "walk in the park". When I get back from Japan (work) I'll bolt her back together.

Sounds like you've got it figured out. I'm assuming you have it, but if not the FSM is available at www.infinitiservicemanual.com

Good luck!

Heath

Thanks Heath! I have links to all the FSMs from Nico. That plus the helpful people on the board are what makes this the ONLY forum for Nissan/Infiniti worth using.