99 4Runner 2.7L - 0 compression on cylinders 1 & 3 - possible causes? *Now with pics*

[Kanoe]

Toyota heads are reliable, I still think a used head will not only be cheaper but just as good and you won't have to piece it all back together.

I wonder how hard it is to find 3rz heads. I have been in a lot of wreckers from Canada to Mexico and firstly they are not common, and then every one had the head removed already. Maybe some of the bigger buisinesses with websites...

 

[iancbf32]

Those pics are confusing, I don't see a gap between the cam lobes and spring caps in the red-squared areas - perhaps it's a bad angle

If the valves are stuck open, the springs would have to be all the way collapsed into the seats, and there would be a gap between the cam's base lobe (valve closed position) and the spring cap.

If the valves are stuck in any position other than fully open (springs totally collapsed) then I would imagine there had to have been damage to the cam lobes of the same valve (cam wiped out) and you would probably want to replace the head.

I suppose I could have lit it a bit better. But 1 of the exhaust valves in cyl 1 and 3 are stuck at full extension (open).

 

[octanejunkie]

I suppose I could have lit it a bit better. But 1 of the exhaust valves in cyl 1 and 3 are stuck at full extension (open).

Whatever caused that to happen probably was due to, or caused, other damage; two springs don't just get stuck.

If it were me, I would resign myself to replacing the head and go from there. Pulling the head might reveal other issues in the affected cylinders. If that's the case I'd look for a replacement motor. You could just do that and go from there. Hopefully it didn't run lean in the past for long enough to detonate the pistons to bits and that's what stuck those valves open.

That being said, if you are industrious and have the means to read the cam lobes, like with a dial indicator, you could start with the head installed and measure a few other exhaust valve lobes and compare to the ones of the stuck values. This way you can see if the cams are damaged. If they are not then maybe you can salvage the head depending on what the issue is. I wouldn't be surprised if there wasn't significant damage waiting to be found.

Obviously mark and document your work if you start disassembling so you can put everything back together correctly; mis-timing the cams would be bad. Also be careful​ with the springs, seat pressure on valve springs is usually over 100# and a fully open valve is under more pressure than that. Don't get pinched.

Minimally, I would expect problems with the values, seats and/or guides. Unless you have a machine shop that specializes in heads nearby, it won't be easy to fix on your own; especially the guides and seats if new ones need to be installed. A refurb head might be best.

Sorry for the long post. May fortune be in your favor.

Sent from my Nexus 5X using Tapatalk

 

[iancbf32]

Whatever caused that to happen probably was due to, or caused, other damage; two springs don't just get stuck.

If it were me, I would resign myself to replacing the head and go from there. Pulling the head might reveal other issues in the affected cylinders. If that's the case I'd look for a replacement motor. You could just do that and go from there. Hopefully it didn't run lean in the past for long enough to detonate the pistons to bits and that's what stuck those valves open.

That being said, if you are industrious and have the means to read the cam lobes, like with a dial indicator, you could start with the head installed and measure a few other exhaust valve lobes and compare to the ones of the stuck values. This way you can see if the cams are damaged. If they are not then maybe you can salvage the head depending on what the issue is. I wouldn't be surprised if there wasn't significant damage waiting to be found.

Obviously mark and document your work if you start disassembling so you can put everything back together correctly; mis-timing the cams would be bad. Also be careful​ with the springs, seat pressure on valve springs is usually over 100# and a fully open valve is under more pressure than that. Don't get pinched.

Minimally, I would expect problems with the values, seats and/or guides. Unless you have a machine shop that specializes in heads nearby, it won't be easy to fix on your own; especially the guides and seats if new ones need to be installed. A refurb head might be best.

Sorry for the long post. May fortune be in your favor.

Sent from my Nexus 5X using Tapatalk

I appreciate the long reply. I've sourced a new head from a place in Clearwater that offers a multi-year warranty on their heads. I ordered a complete head with valves installed and new cams. Should be here on Monday or Tuesday.

It's been about 10-15 years since I last tore a motor apart - rebuilt the engine in my civic in my apartment parking lot back in college - so hopefully it's as straight forward as I remember. Mechanically, i know what I need to do, but I know i'll need to pay special attention to all of the vacuum lines and sensors that are in the head.

Any tricks to getting at the bottom header bolts? I plan on hitting them with pb blaster for a few days before I start working on it.

 

[Kanoe]

Any tricks to getting at the bottom header bolts? I plan on hitting them with pb blaster for a few days before I start working on it.

From memory, I don't think there is any issue with these. Take the heat shields off and things should be accessible with normal sockets.

I removed my cast header and put on the Tacoma mini-header in an Arizona campground and I did not encounter any issues.

Oh, do you mean the 3 that connect the header to the next down pipe? If so, long extension sockets and they can be reached from below the truck. Again, mine gave no problems.

Good Luck.

 

[diverscale]

I appreciate the long reply. I've sourced a new head from a place in Clearwater that offers a multi-year warranty on their heads. I ordered a complete head with valves installed and new cams. Should be here on Monday or Tuesday.

It's been about 10-15 years since I last tore a motor apart - rebuilt the engine in my civic in my apartment parking lot back in college - so hopefully it's as straight forward as I remember. Mechanically, i know what I need to do, but I know i'll need to pay special attention to all of the vacuum lines and sensors that are in the head.

Any tricks to getting at the bottom header bolts? I plan on hitting them with pb blaster for a few days before I start working on it.

There is one of the best how to on youtube on how to the heads on the 4runner, if it can help https://www.youtube.com/watch?v=voLBRDZL9fE

It will be more time consuming than your civic for sure, but with this you should get through it.

 

[iancbf32]

There is one of the best how to on youtube on how to the heads on the 4runner, if it can help https://www.youtube.com/watch?v=voLBRDZL9fE

It will be more time consuming than your civic for sure, but with this you should get through it.

Thanks for the heads up! I'll watch that series tonight/tomorrow.

 

[octanejunkie]

Thanks for the heads up! I'll watch that series tonight/tomorrow.

That series is for a 3.4L but it's a good watch

 

[iancbf32]

That series is for a 3.4L but it's a good watch

So I noticed, but I figure it wouldn't hurt to watch anyway.