Help? Compression diagnoses from you experts

[mallet2442]

This is a 99 3500 with less than 80k miles. The problem is missing, blowing white smoke, no power, I did the compression test and cylinder 3 and 5 where 200lbs. and the rest where 380 to 400lbs. When I pulled the glow plug out of the 3 cylinder it had fresh unburnt fuel on it. The top radiator hose does not feel like their any presser and there no bubbles in the coolant tank.The oil stick is clean, no diesel or coolant? Is this head gasket or cracked head/block? Iv searched the forums and haven’t found any thing pertaining to these two cylinders like this.

[suburbanK-2500HD]

Do you have any unusual noise when engine is running with this issue.
knocking, ticking....
Maybe some valves are open, a colapsed lifter, ore valve spring..
Have you tried to apply air pressure in the glowplug hole when its suppose to have the valves shut, if you get leak trying this. there may be a valve problem. Maybe you need to pull the head cover off too check.

[mallet2442]

Thanks, that well be my next step!

[mallet2442]

If the lifter was calapsed wouldn't the valve still close? I would think it wouldn't open with a calapsed lifter. Thanks for the help.

[ronniejoe]

Broken valve springs will cause the symptoms that you describe.

[suburbanK-2500HD]

If the lifter was calapsed wouldn't the valve still close? I would think it wouldn't open with a calapsed lifter. Thanks for the help.

It could be stuck open if defect, but dont think that happends to often.
did you have any unusual noise from the engine. ?

[mallet2442]

OK, I removed the rockerarm cover and the rockerarm assembly. The valve springs look good nothing loose? So I connected shop air to the glowpug hole and put 120 psi to it. I can hear it leaking but it's not obvious where it from. I could not here any sound from the turbo exhaust. Tomarow I'll unbolt the exhaust manifold and see if I can make out where the leak is coming from. I think what I hear is coming from the ports around the push rods?

[ronniejoe]

Be sure to look very closely at the springs. Sometimes it is not easy to see if one is broken. I doubt that anything will be loose even with a broken spring.

[DaveBr]

OK, I removed the rockerarm cover and the rockerarm assembly. The valve springs look good nothing loose? So I connected shop air to the glowpug hole and put 120 psi to it. I can hear it leaking but it's not obvious where it from. I could not here any sound from the turbo exhaust. Tomarow I'll unbolt the exhaust manifold and see if I can make out where the leak is coming from. I think what I hear is coming from the ports around the push rods?

Take your oil filler cap off when you have air on it and see if you have a breeze blowing out the filler pipe.

[mallet2442]

Thanks for the help! I couldent tell where the air was going so I tryed the #1 cylinder that was giving me 400lbs of compression, well it did the same thang? I could hear air leaking just like the low compression cylinder #3. Well I was tired of leaning over the finder and figuerd the head as comming off to fix the problem one way or another. It was late when I got the head off but I was disapointed not to find anything abviously rong. I can see no cracks, head or block. I havent cleaned anything yet. I can see the lifters are not colasped but maybe there stuck open, I wont hold my breath.

[mallet2442]

OK, I removed the lifters and the where fine? I cleaned and reprimed them then put'm back. Then I checked the head. The heads are newly rebuilt but I pulled the valves and checked everything! No broke springs! Nothing! no signs of leak! The cylinders look great, the still have the cross hatching from the factory honing! I made a plate to bolt over the cylinder and applyed 125lbs of air to the cylinder, it does the same thang as it did when it had the head on? Just leaks, I'm assuming it blowbuy around the rings! Can a injector cause low compression? I can't think of what to check next!

[JohnC]

Try your air test on one of the good cylinders. I suspect you will find similar results. Take a very close look at the head gasket, head and cylinder deck between #3 and #5. Low readings in two adjacent cylinders often means there is a leak between the two.

[Robyn]

If you have a severe leak past the rings then you need to dig deeper.

Injectors will not cause low compression.

Any cracks in the tops of the pistons ??

200 is low and its going somewhere.

You could have some broken or stuck rings possibly.

Missy

[DaveBr]

When you air test make sure both intake and exhaust valves are in the closed position or you will have air flowing out the exhaust. Which might account for the air you hear leaking.

[mallet2442]

Thanks for the help. I made a plate to cover one cylinder at a time and pressurize them. Again heads off plate bolted over #3 and it's leaking into the crankcase not water jackets. So I tryed the #1 (witch had 400lbs of pressure) and it does the same thing? Is this normal blow by? I'm using shop air, 125 PBS 1/4" hose.

[DmaxMaverick]

Thanks for the help. I made a plate to cover one cylinder at a time and pressurize them. Again heads off plate bolted over #3 and it's leaking into the crankcase not water jackets. So I tryed the #1 (witch had 400lbs of pressure) and it does the same thing? Is this normal blow by? I'm using shop air, 125 PBS 1/4" hose.

No surprise, really. Continuous 125 PSI on any cylinder will leak a lot. At 125 PSI, you are placing about 1,500 pounds of force on the piston top, which pretty much removes the possibility of testing the piston at various cylinder wall positions. Normally, a leakage test uses only about 5-10 PSI. Harbor Freight sells a decent cylinder leakage tester. I have one, and it works well. A cylinder leakage test is best done with heads on, to determine where the leakage is occurring.

If your compression test indicated 400 PSI on some cylinders, and a leakage test with heads off shows all cylinders about the same, your compression problem was with the heads and/or head gaskets. Common gasket failures are not always obvious.

[mallet2442]

OK. well I was getting ready to do the compression leakdown test and and was turning the engine over by hand
when I heard a noise i had not herd befor. So I brought the #1 piston ( one of the good ones 400lbs ) up TDC, it looked flushed by eye
and the I turned it on over to bring the #3 piston to TDC. It stoped about .100ths or more frome the top? Then I continued to turn it over, I could hear a
clunk-clack and the crank turned a lot further befor the #3 piston starting to move. I turned it so the piston was about half way down then I
reached in and pushed down on the top of the piston and it moved about .200ths or more. I did the same thang on #5 piston, same thang!
What is this? Wrist pins or spun bearings?