5VZ-FE Head Gasket Gone Wrong

[cruisercorner]

I've been working through a head gasket job on a 1999 4runner with the 5vz. Everything seemed to go great until I cranked it up and it ran for a few minutes. It ran fairly smooth on initial crank for about 2-3 minutes. Then I heard a bang coming from cylinder 1 area, then 5 seconds later, same bang. As I was going around to turn the engine off i heard it a third time. Definitely not a normal engine sound.

It sounded like it came from cylinder #1 area, so I pulled right side valve cover, everything looked ok on the top side. I did noticed what looked like coolant down by the exhaust manifold (like it was leaking out of head).

I followed Timmy's HG videos (which are awesome), as well as my own copy of the FSM and the only odd thing was that after lining up the cam gears with 2 dots on right side, and 1 dots on left side, I still had to rotate the right cam pulley (where the timing belt rides) 180 degrees to get the timing set.

I rotated the timing belt through several revolutions to confirm the timing was correct per both outer cam pulleys and the crank. Everything looked great.

I ran a scope down the #1 cylinder and see marks on the piston and on a couple of the valves - im assuming something hit something, or perhaps a nut got dropped down in there.

I'm thinking my next steps are to check the timing again, check the valves on #1 to make sure they're not stuck (using the rope trick), put it back together and try starting up again.

Anyone have thoughts? Maybe it ate a spare nut that fell down in there when i wasn't looking...

 

[brillo_76]

Being these are non- interference engines. Need to find what feel into the cylinder 1. I take it you didn't tape off the intake ports when you were working on the heads?

 

[JohnMc]

If you see impact marks, that's almost certainly what happened, something loose in the intake system that went into one of the cylinders. If you've got a bore scope, I'd look at all of the cylinders, and also maybe take the upper and middle intakes off and make sure there's nothing still hanging around in there.

If it made it into the cylinder, it might still be there, the exhaust valves are a little smaller. Or it may be spat back into the intake, and it was just holding the intake open briefly causing a backfire into the intake.

If you can't senything in the intake ports or in any of the cylinders, maybe it made it out into the exhaust, not sure if it's worth fishing out of there. It could probably damage the catalytic converter if it's bouncing around on the ceramic core for a long time.

Do a compression check to see if whatever it was damaged a valve or two on its way through.

 

[cruisercorner]

Being these are non- interference engines. Need to find what feel into the cylinder 1. I take it you didn't tape off the intake ports when you were working on the heads?

well that would make too much sense to tape off the cylinders, why would i do that?

So yes they are non-interference engines, but I've also read if you get the timing way off you can still have interference. However, i highly doubt that's what happened here. I triple checked the timing - should be good on that.

 

[cruisercorner]

If you see impact marks, that's almost certainly what happened, something loose in the intake system that went into one of the cylinders. If you've got a bore scope, I'd look at all of the cylinders, and also maybe take the upper and middle intakes off and make sure there's nothing still hanging around in there.

If it made it into the cylinder, it might still be there, the exhaust valves are a little smaller. Or it may be spat back into the intake, and it was just holding the intake open briefly causing a backfire into the intake.

If you can't senything in the intake ports or in any of the cylinders, maybe it made it out into the exhaust, not sure if it's worth fishing out of there. It could probably damage the catalytic converter if it's bouncing around on the ceramic core for a long time.

Do a compression check to see if whatever it was damaged a valve or two on its way through.

I'm now planning to basically do all of this. I need to find out the cause, even if I have to pull the head again. I do have a bore scope, did get pictures and video. There are marks on the #1 cylinder, in the middle. doesnt look half moon like contact (which is unlikely anyway). There are a couple of nicks on the valves. I'll pull right side exhaust see if the supposed nut got ejected down in there. Need to figure out how to upload pics/videos here... that's next.

 

[cruisercorner]

not sure how to add photos in this forum... not very intuitive. Here are pics from #1. #3 and #5 look clean. Havent looked at #2 #4 #6 yet, but will soon.

4runner cylinder - Google Photos