Leak Down - 80% down via Exhaust Valves

[1990TSIAWDTALON]

Did you bleed the lifters of oil? That will hold the valves open and it doesn't take much at all to bend one out by the valve head. I did it on accident because I didn't bleed my lifters. Just FYI in case you weren't aware of the need.

 

[sacrileger]

Im sure you understand what you are talking about and just misspoke. Lapping valves will not fix anything, rather it would tell you if the valves are sealing or not. Machining would only fix this. Wanted to make sure the OP understood.

I understand the 'lapping' issue. Nevertheless, I am still struggling with what "fix this" is so I can fix it. Or tell the shop what to machine to "fix this". What happened between the testing and bolting down is the issue here that I struggle to diagnose and identify.

 

[AdR]

Did you do the leak-down with the camshafts removed and the lifters empty? You don't want any effort being subjected into the valves in a leak test. They should be in their fully closed condition on both in/ex sides.

 

[sacrileger]

Did you bleed the lifters of oil? That will hold the valves open and it doesn't take much at all to bend one out by the valve head. I did it on accident because I didn't bleed my lifters. Just FYI in case you weren't aware of the need.

Thanks, I actually was not aware that the lifters needed bleeding even if the cams were not ever taken out. Is that what you meant? Can the bleeding be done with the head fully assembled?

 

[livedsm4g63]

perhaps I knocked the valves out of alignment and there's a procedure to put them back where they belong w/i minutes.

Im sorry but that made me

So you didnt bleed your lifters...This could cause the valves to bend.

 

[sacrileger]

Did you do the leak-down with the camshafts removed and the lifters empty? You don't want any effort being subjected into the valves in a leak test. They should be in their fully closed condition on both in/ex sides.

I have done the leak down with everything fully assembled; just as if this was a running donor engine and I wanted to find out how healthy it was. But from your reply I gather that I could have bent the valves while the head with lobes sticking out was resting on the block. Is that what you are thinking? While putting the head on myself, I could not see where the anchors were and I did miss the anchors and put the head down on the block.

 

[AdR]

Lets do something then:

1. Unbolt all of the camshaft journals (using the proper sequence)
2. Remove the rocker arms
3. Take your hydraulic lifters and make sure you bleed them before re-installing.
4. Do the leak-down test again.

It can be very possible you bent valves if you let them rest in a solid surface or hit them while installing. Just a fraction of stem deformity will create a gap on the seat, that is why @livedsm4g63 suggested you do a lapping check on the valves to rule improper valve seating.

 

[1990TSIAWDTALON]

Thanks, I actually was not aware that the lifters needed bleeding even if the cams were not ever taken out. Is that what you meant? Can the bleeding be done with the head fully assembled?

Usually not needed on a head that wasn't disassembled but you saying that some valves were staying open either mean the lifters are full of oil and won't compress OR you have some valves with bent stems which will hold them open also. A little more investigation in needed.

 

[sacrileger]

Lets do something then:

1. Unbolt all of the camshaft journals (using the proper sequence)
2. Remove the rocker arms
3. Take your hydraulic lifters and make sure you bleed them before re-installing.
4. Do the leak-down test again.

It can be very possible you bent valves if you let them rest in a solid surface or hit them while installing. Just a fraction of stem deformity will create a gap on the seat, that is why @livedsm4g63 suggested you do a lapping check on the valves to rule improper valve seating.

I just finished what you suggested. There's been a notable change in percentages. Here are the result:

1) Leak down with cams installed. For cylinder 1,3,4,2 the drop was 80%, 80%, 60%, and 85% respectively.

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2) Leak down with cams OUT. For cylinder 1,3,4,2 the drop was 80%, 80%, 70%, and 80% respectively.

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3) Leak down with cams OUT and valves rotated and snapped. For cylinder 1,3,4,2 the drop was 70%, 55%, 60%, and 75% respectively.

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Clearly, there was an improvement b/w test #1 and #3 after the cams were taken out and valves "snapped". Intake valves are fine, rings are new and expected not to be sealed; however, something is going on with the exhaust valves. Any ideas?

 

[AdR]

Sorry to say but that is the telltale sign of improper valve seal, either the valves are bent or the valve seat is deformed preventing a proper seating of the valves. Take it to a machine shop and get a valve job done.

 

[sacrileger]

Sorry to say but that is the telltale sign of improper valve seal, either the valves are bent or the valve seat is deformed preventing a proper seating of the valves. Take it to a machine shop and get a valve job done.

Thanks for nailing the problem down for me. How does one end up with a valve seat deformation?
I guess we are both leaning towards valves being bent during installation time when I dinged the protruding lobes against the block? If that's the case, I sure did not think valves would be this delicate.

 

[1990TSIAWDTALON]

I was surprised that they were as fragile as they are and mine were aftermarket valves.

 

[sacrileger]

I was surprised that they were as fragile as they are and mine were aftermarket valves.

These are expensive and dumb mistakes - time and moneywise. Live and learn. That head I had was good to be used as it was for what I was looking for. I will make sure that does not happen again after this. I am surprised nobody else had run into this - my search "bent valve" did not lead to anything that would suggest guys bent their valves just by resting the head on the block or missing anchors and dinging extruded lobes on the block. Aw well, it's good to be first...

 

[1990TSIAWDTALON]

You're not the first ......

 

[sacrileger]

I was surprised that they were as fragile as they are and mine were aftermarket valves.

yeah, I just read your comment here:
https://tinyurl.com/y79pkmue
and I can now guarantee that is how I bent my exhaust valves. When I put my timing belt on really loose and was on the bottom of the car rolling the motor by hand, the belt jumped on me on the exhaust side by 2-3 notches and I kept on rolling the motor to align all timing marks. But I can tell ya, I felt no resistance or anything unusual. That sucks big time!!!!

 

[AdR]

Thanks for nailing the problem down for me. How does one end up with a valve seat deformation?

It's rare for it to happen and much more so on a lightly modified car but it does happen. Many factors can incur in valve seat deformation. Excessive heat, rings going through the valves when they break, sucking something into the intake valves, bent valves massaging the seat into submission (usually Ti valves will do this if they by any chance bend), head warpage and or extreme boost pressure detonations. To name a few.


Sorry your plans changed, things happen and trust me I know all about bent valves. Thankfully you didn't end up noticing after bolting everything together and running the car. That would have been more expensive to rectify.

 

[sacrileger]

It's rare for it to happen and much more so on a lightly modified car but it does happen. Many factors can incur in valve seat deformation. Excessive heat, rings going through the valves when they break, sucking something into the intake valves, bent valves massaging the seat into submission (usually Ti valves will do this if they by any chance bend), head warpage and or extreme boost pressure detonations. To name a few..

This is great info. One thing that caught my attention was your comment regarding "extreme boost detonation"! The head came off a blown engine with big turbo on it. When I pulled the pistons out, the ring lands on three pistons were completely cracked and loose. Here they are are in this comment:
https://tinyurl.com/yaoxvoy5

Even though I may have bent my valves by rolling the motor by hand when my timing belt jumped by 2-3 notches, perhaps there were other problems with the head to begin with and I dont have to feel so bad about it after all. It cost me only $90 and I got the turbo with it.

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[1990TSIAWDTALON]

Well that was dirt cheap!

 

[boostdawd]

Don't feel bad! It's happened to a lot of people then just don't post about it haha. Pull the head internals off and inspect everything. I'm willing to bet your valve guides are cracked too.

 

[sacrileger]

Sorry to say but that is the telltale sign of improper valve seal, either the valves are bent or the valve seat is deformed preventing a proper seating of the valves. Take it to a machine shop and get a valve job done.

Turns out I have 5 visibly bent valves. The other ones I am not sure how to properly measure how much off they are (if at all) and if they are w/i spec. Lapping might work if they are just a bit off - I am not quite sure how to make that determination. The search of this forum did not tell me how to make that call.

This has been a lesson for me, I tell ya.
1/ never install heads w/ cams in it.
2/ set timing marks dead-on even before turning engine over by hand
3/ do not turn engine counter-clockwise

 

[livedsm4g63]

#3
One time I was doing the rear breaks on one of my old dsms and while tightening the rear lugs I happened to rock the car backwards a few times. (This was before I did a timing job) Well to my surprise I then couldnt start the car. A compression check showed I had 0 compression in 2 of the cylinders. Pulled the head and sure enough, bent valves. Come to find out, the tensioner wasnt set right by the previous owner. Fun times.

 

[1990TSIAWDTALON]

Well what a life story now huh? I was afraid that was going to be the outcome but kept hoping for the best! It's gonna be ok!!

 

[AdR]

You live and you learn. We all make those mistakes and learn from them. Sorry to hear you found the culprit. At least the mystery is solved.

 

[1990TSIAWDTALON]

And we all shared our bad luck too so don't feel alone!!! I have had many failures, just like AdR said, live and learn and pass the info on to the next DSMer!

 

[sacrileger]

And we all shared our bad luck too so don't feel alone!!! I have had many failures, just like AdR said, live and learn and pass the info on to the next DSMer!

I am attaching three documents that describe everything about valves:
1) Quick, Illustrated reference

2) Damaged valve service bulletin; and

3 Valve Failures handbook - focus on valves' failures and search for the reasons causing failures.

Hopefully it will come to good use.