Testing piston rings with water

I did a cylinder leakdown test with a special tool hooked to an air compressor -- check the picture on the previous page -- i think it highly correlates with the compression test

 

The symptom was that cylinder #4 was leaking 75% and other cylinders 15-20-25% max -- which raised the red flag

 

Smoking? Loss of compression? Running rough? If you had a loss of 75% compression in a cylinder there would some symptom.

 

None of those but then again, you can go to a doctor feeling great and he can correctly predict that you're about to have a heart attack by looking at your blood work.

I hadn't driven the truck for many months prior to the work because of the VVT problem, which was also tripping the check engine light so the vehicle doesn't pass inspection. But there was no outward symptoms. Again, I invoke the doctor analogy

 

For all I know, that one cylinder leak might have been causing engine imbalance, which somehow introduced reverberation that broke the VVT phaser (this is just a wiiiiild guess but i think not an uneducated one).

 

But here is the thing: Does having the left cylinder head off, which is where I am now, help me any in doing the piston rings, should I decide to do? I was thinking that all the work would be from under the vehicle, removing the diff, oil pan etc and that I practically didn't need to reach from the above. Is that correct? If so, I can just do it partial now, see how it goes, and then do the ring work separately? IOW, the total amount of work/time would not be any different because the two jobs don't intersect in parts -- or do they?

 

The pistons will have to come out the top and have to be reinstalled from the top.

 

Ahh in that case it would make sense to do it now

 

You do know it's not that simple as removing the old rings and installing new ones !!!

1] unbolt rod caps making sure rod cap is replaced correctly and the connecting rod and piston phased correctly . Place rubber hose on rod bolts as not to damage the rod journal of the crank

Piston and connecting rod is removed thru top of bore

2] inspect bore check for scuffing or unusual wear , insert a bore gauge into the bore and check for unusual wear patterns . Check to see if bore is within spec or not , if bore still within spec then insert a hone tool into the bore and clean / ream the bore until a cross hatch pattern appears

If not within spec then the cyl block needs to be bored out such as .030 over ( ea cylinder)

3] need to buy new piston rings measured to whatever the bore gauge indicates or over bore size such as .030 over if the cyl block needs to be bored over size

Next inside the cleaned up cyl bore place piston ring into the bore using the piston to push the ring squarely into the bore , next measure the " ring end gap" of ea of the pistons rings of that bore . Using a ring file cut the rings to fit to spec


4] place rings on ea piston and place ea ring end gap in a staggered pattern . Next with a piston install sleeve tap piston carefully into the bore and install rod end cap and torque to spec

 

Ya know, earlier in this post I said I was out because of the initial dumb ass question.
I have to jump back in and say this is not going to turn out on any side of good. These questions being thought and asked are pointing to a disaster. I do wish you all the luck with this.

 

That ^^^

If the valves are where the leak is you can probably get away with just honing cylinders but measure anyway so you know. This is engine shop stuff and easy for them to do.

The rods/cap will be marked and the piston will only go one way to clear the valves.

It's a bit of a can of worms. At 150k, if you don't do it now when you have it torn down this far you might be doing it all again before too long... Or it might go another 150k.

 

OP, IMHO....you are a victim of analysis paralysis.

Judging by the amount of carbon on the heads and valves, there is a ring problem allowing significant oil to be burned in the cylinder.

You've tested all, and more, that is needed. You've got the engine half pulled apart.

Suggest to pull the engine, replace the rings on all pistons, run a ball hone to clean up the cylinder, remove carbon, lap the valves, reassemble.

Be careful you don't step over dollars to pick up pennies.

 

UPDATE: I did the water test on all the intake valves on the left engine bank and confirmed the same results as from the cylinder leakdown test:

Over a 24 hr period, 100 ml of water injected in the cyl#4 (which measured 75% leak) manifold leaked 40% of water.

Over the same period, the same amount of water in cyl# 2 and #6 (which measured 25%) leaked literally 0% of water (not even a drop in the tupperware, same level in the manifolds).

I will now do the same on the exhaust side but again, expect no leak on any cylinders there.

Which means that the 25% leaks are most likely piston rings (and some maybe the head gasket) except in cyl #4, which is confirmed to be leaking through the intake valves.

I am willing to live with having a few cylinders leaking more than the recommended 20%.

 

People who don't want to do the analysis often say "replace it all" and they throw the baby away with the bath water because they are intimidated by the sophistication of intelligent examination.

Not me -- I'm an engineer, not someone who just follows instructions.

 

Sounds similar to tuning the valve lifters (getting measurements and ordering correct sizes) -- but I don't think I will be doing it.

 

There are a lot of people on this forum who regularly advise throwing the baby away with the bath water -- or to replace the whole roof for a single leak -- because tHaT iS tHe rIgHt tHiNg tO dO...

In reality, it is cheap for them to virtue signal "doing things right" or "that's what I would do" when dishing advice to others.

What is rather obvious is that a person who would replace a whole roof for a small leak is simply incapable of diagnostics/analysis to pinpoint the exactr source of the leak and attending it and it alone.

 

FWIW, I am an engineer also.

You have evidence of the needed repairs in front of you. When the cause is discovered, an additional test to confirm is enough. More testing only burns time to confirm the confirmed results of the cause.

When a tire is flat, you discover the nail, then checking air pressure with a gauge won't add to the conclusion.

Your choice, your truck.

 

I am attending to all what there is evidence for -- but not going a step further.

What the "do-it-righters" are suggesting is basically replace all the piston rings while at it -- i am not doing that if I can get all the cylinders to within 25% max leak (using the air test) by just doing what I am doing now (grinding the 1-2 valves)

 

Consider.

All the valves and pistons have endured the same number of cycles.

Sure, you may save some pennies to just do the "out of tolerance" parts. But, the other parts will probably go "out of tolerance" in a short future. Then you are faced with repeating the work.

Stepping over dollars to pick up pennies. As the saying goes........

 

This poor engine will never run correct again. Both heads should be pulled and sent to a machine shop for inspection and or rebuild. This will rule out any leaks, micro cracks ETC that may be wrong with the head.

Piston rings need to be saturated in oil to function properly and create compression and a tight seal. Using water is 100% pointless.

At this point the motor needs to be pulled and gone through by someone who knows that they are doing.