Cracked head - Inside intake valve port

[Daisywheels]

Thanks to 2000Streetrod for suggesting a compression check. I finally got a gauge and cylinder number 3's plug looked as new as the day I put it in. My codes were P0301, P0302, and P0303, and P0300. I was chasing vacuum leaks for months.

Would anyone like to confirm the crack? I'll try to post some pics....

Also, why would a cylnder head crack in this spot? Any common reasons? It never overheated, and I don't think it gets that hot up there???

Compression readings were as followed: (cold test, both lower and upper intake off the truck)

Cylinder 1 165
Cylinder 2 165
Cylinder 3 0
Cylinder 4 155
Cylinder 5 165
Cylinder 6 165

Even though cylinder 4 is within the 10% range, I still suspect a valve problem in that cylinder, so that means taking off both heads. I just don't think I'm skilled enough to take that on.

Thanks - DW

P.S. Now I finally figure out how to post pics!

 

[Daisywheels]

Need someone to verify crack in head so I can call time of death and put this truck behind me. Thanks - DW

 

[ranger7ltr]

Before you call TOD...

Is the valve cover off of the heads? I would check the valve action on the dead cylinder to verify the valves on that cylinder aren't causing the problem...

If the valve are not sealing yes the head will need to come off but it doesn't have to mean the truck is dead... Unless you are done with it then...

Just a thought... And I have never seen a crack that high on a SOHC head cause a complete loss of compression...If you have an air compressor, adding air to that cylinder would confirm whether the valves are sealing or not when the valves show to be closed...

 

[Daisywheels]

Is the valve cover off of the heads? I would check the valve action on the dead cylinder to verify the valves on that cylinder aren't causing the problem...

If the valve are not sealing yes the head will need to come off but it doesn't have to mean the truck is dead... Unless you are done with it then...

Just a thought... And I have never seen a crack that high on a SOHC head cause a complete loss of compression...If you have an air compressor, adding air to that cylinder would confirm whether the valves are sealing or not when the valves show to be closed...

No, the valve cover is not off...will do your suggestions - thanks! I don't understand nor have I seen a crack that high either. It makes no sense it would crack there. If I had the head off, maybe it cracked from bottom up. Who knows - DW

 

[Daisywheels]

Just a thought... And I have never seen a crack that high on a SOHC head cause a complete loss of compression...If you have an air compressor, adding air to that cylinder would confirm whether the valves are sealing or not when the valves show to be closed...

Just to confirm: What am I looking to find with the air compressor? If the valve is closed and it continues to blow through the valve, then the seal is no good? Assuming the seal is still good, would I expect the air compressor to build up pressure until it can't release any more air? Thanks! DW

 

[boominXplorer]

I also suggest pulling the valve cover off. I have seen a valve spring break and cause the same issue.

A cracked head will show at least SOME compression. Heck you can loose part of a valve and still could get 30 psi on a compression test.

Also if you broke an intake valve spring then the unburnt fuel would come back into the intake and possibly flood out other cylinders (like 1 and 2)

 

[Daisywheels]

I also suggest pulling the valve cover off. I have seen a valve spring break and cause the same issue.

A cracked head will show at least SOME compression. Heck you can loose part of a valve and still could get 30 psi on a compression test.

Also if you broke an intake valve spring then the unburnt fuel would come back into the intake and possibly flood out other cylinders (like 1 and 2)

I saw "something" coming (possibly spraying) out of the intake port only on the cylinder 3 compression check. It could have been fuel or just air. I did not see this checking the other 5 cylinders. Also, there was a different "sound" on the bad cylinder. I was like the starter was turning with nothing else moving. I could at least hear "something" while testing the other cylinders. That confirms the 0 compression, plus I tested all cylinders twice.

I just got started on taking the valve cover off. Not going to drain the cooling system. I'll keep you updated - thanks! -DW

 

[Daisywheels]

I also suggest pulling the valve cover off. I have seen a valve spring break and cause the same issue.

A cracked head will show at least SOME compression. Heck you can loose part of a valve and still could get 30 psi on a compression test.

Also if you broke an intake valve spring then the unburnt fuel would come back into the intake and possibly flood out other cylinders (like 1 and 2)

I am having trouble removing the right rear valve cover bolt, but I have the proper tools now, so I should be able to get it off. Questions:


1) The head is cracked, so doesn't it need to replaced anyways? Prices aren't bad for a re-manufactured head ($200 - $300) including parts like head gasket and bolts.

2) I can't find a link here for the SOHC V6 motor on cylinder head removal. Does anybody know of one? Or should I just follow Haynes?

3) Will someone please talk me out of pulling the head? I'm already in over my head

I'll let you know what I find after pulling the valve cover. Thanks! -DW

 

[boominXplorer]

Its not cracked! Those are casting lines. Get the valve cover off and report back lol

 

[Daisywheels]

Its not cracked! Those are casting lines. Get the valve cover off and report back lol

Casting lines? I sure hope you are right! I finally got the valve cover off which isn't that hard with the right tools!

The valve spring is hard to see, but I can feel it in place. However, the rocker arm was loose and laying to the rear of head - NOT attached. Advice needed on where to go from here....Thanks......DW

 

[boominXplorer]

Your valve spring broke or lash adjuster(lifter) collapsed leaving play for the follower (the part in your pic) to pop out. See if you can move the valve spring around freely or up and down. Compare it to the others.

Note: If you can move the valve up and down the spring is indeed broken. There are 2 little wedges at the top of the valve to keep the top seat on. BE CAREFUL they don't fall out, the valve will drop.

 

[Daisywheels]

Your valve spring broke or lash adjuster(lifter) collapsed leaving play for the follower (the part in your pic) to pop out. See if you can move the valve spring around freely or up and down. Compare it to the others.

Note: If you can move the valve up and down the spring is indeed broken. There are 2 little wedges at the top of the valve to keep the top seat on. BE CAREFUL they don't fall out, the valve will drop.

Thanks boomX. Will do your suggestions and report back tomorrow. I know at least for now I was no able to move or spin the valve spring when feeling for it, but will check it again for up and down movement (carefully). Thanks again! -DW

 

[Daisywheels]

Your valve spring broke or lash adjuster(lifter) collapsed leaving play for the follower (the part in your pic) to pop out. See if you can move the valve spring around freely or up and down. Compare it to the others.

Note: If you can move the valve up and down the spring is indeed broken. There are 2 little wedges at the top of the valve to keep the top seat on. BE CAREFUL they don't fall out, the valve will drop.

I can't move the valve spring up or down, nor will it rotate. However, I cannot really inspect the spring unless I get some sort of dental mirror. Of course, I can see the other springs just fine - lucky me on cylinder #3 !

I did remove the lash adjuster (much easier than I thought), and I checked for plunger movement with a paper clip. I went about an inch down and noticed no plunging action whatsoever. The paper clip just stopped around 1 inch deep - no give at all. Thoughts? Thanks! -DW

 

[boominXplorer]

You might have to rotate the crank if the cam lobe is pushing down on the valve. The lash adjuster should not be easy at all to compress. It is either one or the other.

 

[Daisywheels]

You might have to rotate the crank if the cam lobe is pushing down on the valve. The lash adjuster should not be easy at all to compress. It is either one or the other.

There is nothing putting pressure on the valve. I pushed down from the top of the valve where the follower should be.

I just read that if a cam is not timed, this exact problem could occur. I have no idea how to time the cam without that expensive equipment in 2000StreetRod's post about timing.

 

[2000StreetRod]

all three cylinders

If the camshaft is out of time it will affect the compression of all three cylinders in the bank - not just the third one.

On occasion the SOHC V6 will throw a cam follower. The only thing that keeps the follower in position is valve spring pressure. Did you inspect the follower thoroughly looking for damage? You might try reinserting the cam follower and then performing another compression test. Unfortunately, you'll need a valve spring compressor or equivalent to reinsert the follower.

The photos below show using one on my DOHC V8 intake valve.

 

[Daisywheels]

If the camshaft is out of time it will affect the compression of all three cylinders in the bank - not just the third one.

On occasion the SOHC V6 will throw a cam follower. The only thing that keeps the follower in position is valve spring pressure. Did you inspect the follower thoroughly looking for damage? You might try reinserting the cam follower and then performing another compression test. Unfortunately, you'll need a valve spring compressor or equivalent to reinsert the follower.
View attachment 83920
The photos below show using one on my DOHC V8 intake valve.
View attachment 83919
View attachment 83917
View attachment 83918

Thanks 2000StreetRod. I was not aware of that. I did inspect the follower and there is no visible damage to it. It looks like I will need that tool either way - bad spring, valve, or just a thrown cam follower. Thanks again! -DW

 

[2000StreetRod]

valve spring compressor

Tools 303-581 or T97T-6565-A were designed specifically for the 4.0L SOHC V6. I purchased a universal (ST-126) that works OK on the 4.0L but also works on the 4.6L 2 valve and 4 valve V8s.

 

[Daisywheels]

Tools 303-581 or T97T-6565-A were designed specifically for the 4.0L SOHC V6. I purchased a universal (ST-126) that works OK on the 4.0L but also works on the 4.6L 2 valve and 4 valve V8s.

Thanks again 2000StreetRod for the good info. Obviously I will have to rent those.

I just spoke to a buddy of mine who said that pushing a paper clip 1 inch down into the lash adjuster doesn't make sense - that something maybe wrong with the lash adjuster; however, he readily admits he doesn't know much about my truck. BoominX said it may have "collapsed." How do I know if it is functioning properly? Thanks! -DW