2010 5.7 Sequoia - I Messed Up...

Ok, I have not tested the leakage like I planned to yet, but I did get run a bore scope down into the pistons to have a look. I don't see anything that looks like new impacts or anything, but I also don't really know what these pistons should look like.

This engine has 240k miles on it.

I can get some better photos, but wondering if anything sees anything overtly concerning in these.

 

You can't bend all valves in the head, only one cylinder takes the hit. As many others said, check your timing. Could be you set it right, but the chain tensioner let it skip one tooth.

 

Ok, I pulled the valve cover on the driver's side today. I turned the engine over manually to find a spot in the cam rotation where both valves are closed on each cylinder and did a leakage test. All of the cylinders are showing acceptable leakage, which is good news. I think this debunks a head gasket issue.

I also took more photos of the tops of all of the cylinders and do not see any apparent damage. I am thinking this is a simple case of mistiming the engine.

Anyone else have theories that I am missing?

 

You are on the right track.

 

Ok, I pulled both of the valve covers and it appears that both cam gears on each side are indexed onto the camshaft as they should be. Probably just mis-timed it, I suppose.

 

It's taken me a bit to circle back to this project. I opened everything back up and re-timed the engine.

 

I shot a video with better detail to get a second opinion, and to just document this for later.

For anyone who has done this before, could you please let me know if you see anything awry here before I close this back up?

 

It looks like the chains are timed correctly in relation to each other, but the marks looks like they are off from where the service manual says to have them...see below:

 

Here's a good video on setting the timing after engine rebuild:

https://www.youtube.com/watch?v=oaDWBwmtVEE

 

Yeah, that's one of the videos I used to learn about this. I have it correct according to that video.

I think it's correct according to the manual. I will turn it into that exact position tomorrow to double check with the crank mark at the very bottom.

 

Ok, good deal, was hard to tell for sure with the video. If it rotates smoothly, the timing should line up every 28 rotations according to the video.

 

Ok, perfect. I did rotate it 28 times and it did line up again. The primary and secondary chains get out of sync and after maybe 15 more rotations, the secondary timing chains lined up with their marks again and I confirmed that the secondary chains are in the right spot. I am feeling pretty comfortable with this now. I appreciate the check-in.

I am still worried that I may have done some other damage and I want to check compression now that the timing is solved. Do you think I can reconnect the battery and turn the engine over with the starter for a compression test on bank 1? I had almost no compression before and it would be a really good confirmation if compression comes back.

 

I would think so, maybe leave the injectors unplugged so it doesn't start, and leave the other spark plugs out so it doesn't have to fight compression on the other cylinders.

 

Any slack in VVT hubs on the head where you have bad compression all across? I read somewhere it grinds the notch, the angle deviates.

 

@gunshipz hats off to you for being man enough to tackle this!

 

No, and the chains are tight and the tensioners are brand new.

Honestly, I wish I hadn't. This has been way more work than I was trying to sign up for. That said, it is what it is and I am trying to just make the most of it.

 

Did you ever figure out where the dust cloud blew out of?

 

No, still nothing, but I am probably going to find out sometime in the next 24-48hrs as I put this all back together. I am stull suspecting the secondary air system, which would be best case scenario.

 

Ok, I turned the engine over and am not getting compression on bank 1 (driver side) still. I am getting good compression on bank 2. WTF?

Head gasket time? I am glad that I didn't put the timing chain cover on before I tested.

 

It had compression before the timing chain change. Something seems odd that it lost the head gasket from that one startup run

 

Yeah, correct. No issue with compression before this, one very shaky startup run and I am getting no compression. I am scratching my head over this.

 

No washers or nuts fell under a cam lobe right

 

I am pretty sure there's not, but I was also pretty sure I timed this correctly the first time, so take that for what it's worth...

The one thing that is probably worth mentioning is that I took the cam tower off of that side (bank 1, driver's side) to reseal it. It was leaking near the cab. Everything went according to plan though and I don't think that would have affected anything. Regardless, I probably should pull that back off and start the tear-down to pull the head off. I am not looking forward to this.

 

So it’s been confirmed the timing was off previously when it ran rough? My guess is that head lifted whenever you got the big poof and smoked the gasket. Kind of odd it’s bad in all 4 cylinders but I don’t know what else could be going on assuming the timing is now correct.

Do you have a fancy digital torque wrench to check how much torque the head bolts are holding?

 

Honestly, no. I did not confirm that the timing was off when I pulled everything back apart. I should have taken the time to turn it over and confirm 100%, but I think it's a pretty safe assumption.

I think you're right about the head gasket. The only thing that is puzzling is that I was showing in-range (albeit bottom end of range) on the cylinder leakage test. I guess the only sure way to find out for sure is to pull it.

Anyone ever removed a head when the engine is still in the engine bay?

 

Before you attempt to remove the head, can you do a leak test like in this video? https://www.youtube.com/watch?v=kB78e5ga-iE Pour some kerosene and apply compressed air in the combustion chamber via spark plug hole. It will tell if the valves hit the piston and bent. Possibly some light leak is ok, you can compare it to a healthy head.

 

Do you see or can measure gaps between the lifters and the back of camshaft lobes? I.e. the valves are fully closed when they should?