Topic: Excessive "blow by" cyl 2+3

[stan98tj]

Finally took the jeep in to get all the leaks taken care of. Had a rear main and oil pan leak. This would be the 3rd time the oil pan gasket had been changed in 2yrs. Keep in mind the Jeep sits during the 4 months I'm at sea. Other things that have been changed: valve cover gasket, front main (2 times). They also changed the distributor seal as it was leaking as well.
The shop then held on to the Jeep to do a cylinder test and found cylinders 2+3 had "excessive blow by." The figures they gave me were 81 on cyl 1, 51 cyl 2, 55 cyl 3 and 61 cyl 4. They explained to me this was causing excessive crank pressure and would blow out the seals in the engine and to therefor expect it to leak again. They figured this would also contribute to my rough idle/misfire.

What do you guys think? Pistons wore down and not allowing for good compression? This is a rebuilt motor from 2007. Is it on its way out?

[VA_YJ]

FSM lists 120 psi for new engine - maximum difference between cylinderss 30 psi.  Your numbers are low, and you are right at 30 psi difference.  You need to have this rechecked, also have them do a "wet" compression check to determine if the leakage is at the rings or valves.

[Jeffy]

Those are all really LOW numbers.  At minimum you need new rings.  Might need a hone to clean things up a little.  If it's a lot of wear then you'll need to bore it.

[stan98tj]

FSM lists 120 psi for new engine - maximum difference between cylinderss 30 psi.  Your numbers are low, and you are right at 30 psi difference.  You need to have this rechecked, also have them do a "wet" compression check to determine if the leakage is at the rings or valves.

Wet compression test, is that when you fill oil up in the spark plug port and take a reading? I think I did this waaaay back when I got the jeep. I knew nothing about nothing then and was merely following directions.

[stan98tj]

Is this thing going to grenade on me? I feel like this is where it's alllllll  headed to. Catastrophic failure like the first engine. Kind of ticks me off, though. It's a completely rebuilt long block and isn't that old and doesn't have that many miles on it. I'm not sure I really wanna tear into it (again) and replace pistons and whatnot. I feel like if it's going to require extensive work, like the head coming off, then I may as well gut it and replace with something better and stronger...TDi or 4.0 at the least-though I really want the TDi.

Perhaps I should take a wet test? Wonder how much longer I have left with this thing....

[Jeffy]

Is this thing going to grenade on me? I feel like this is where it's alllllll  headed to. Catastrophic failure like the first engine. Kind of ticks me off, though. It's a completely rebuilt long block and isn't that old and doesn't have that many miles on it. I'm not sure I really wanna tear into it (again) and replace pistons and whatnot. I feel like if it's going to require extensive work, like the head coming off, then I may as well gut it and replace with something better and stronger...TDi or 4.0 at the least-though I really want the TDi.

Perhaps I should take a wet test? Wonder how much longer I have left with this thing....

No, it usually leads to burning oil, poor mileage, a lack of power and bad emissions.  Not to mention smoke out the tail pipe when you romp on the throttle.

[sharpxmen]

like others said, the numbers are so low that i am suspect it would even start -  i think they might have done a static pressure test rather than a cranking compression test (unless they forgot to open the throttle). on a cranking compression test you should be at about 150 for a decent engine, nowhere below 120.

[stan98tj]

You guys think this is what is leading to the misfire/near stall I am experiencing every time I start up. Happens within a min or two of starting, idles fine then goes into a spasm and idles poorly. If I start driving before it does this, the motor begins to stall, experience severe loss of power and then it finally catches itself. If i'm not getting good compression in the cylinders, would that contribute to it?

What sort of test should I do to gain some actual understanding of what is going on?

[Jeffy]

Do a compression test then follow it with a wet compression test.

[aw12345]

I take it they did a cylinder leak down test? In essence what that means is you pump 100 psi of air into the cylinder and you measure on the second gauge how much pressure remains in the cylinder which is in your case was 85 psi, 65 psi and so forth in percentage cyl one has 15% leakage which is to much the rest are worse. 10 percent is the acceptable limit. Now this is a test you do with a hot engine with the cranckase ventilation system disconnected. Each cylinder has to be in top dead cneter with both valves closed. Doing one of these tests is a pain in the butt to do right, but will tell you condition of valves, piston ring sealing better than any other test available. If this test got done correctly then your engine is due for a rebuilt

[stan98tj]

I take it they did a cylinder leak down test? In essence what that means is you pump 100 psi of air into the cylinder and you measure on the second gauge how much pressure remains in the cylinder which is in your case was 85 psi, 65 psi and so forth in percentage cyl one has 15% leakage which is to much the rest are worse. 10 percent is the acceptable limit. Now this is a test you do with a hot engine with the cranckase ventilation system disconnected. Each cylinder has to be in top dead cneter with both valves closed. Doing one of these tests is a pain in the butt to do right, but will tell you condition of valves, piston ring sealing better than any other test available. If this test got done correctly then your engine is due for a rebuilt

Yikes. Fan-friggin-tastic. Deja vu all over again. Maybe it will hang on for the time being and let me run it into the ground. Now if it's valve related, could it be valves sticking or need a valve train replacement or something more complicated? If it's pistons, then I am wondering how the rings could have worn so quickly. I fear it could be even worse than that and perhaps the cylinder walls are fouled?

[aw12345]

First find out if they did this correctly, they should be able to tell if there was air leakage at the intake or exhaust

[sharpxmen]

buy a $20 compression tester, warm up the engine, take the plugs out and test each cylinder (remove the fuel pump relay, disconnect the coil and crank it a few times to clear the pressure from the fuel rail, then test each cyl with the throttle fully open).

[Bounty Hunter]

Who rebuilt the engine last time?  Was the head rebuilt?

[stan98tj]

Who rebuilt the engine last time?  Was the head rebuilt?

S&S out of Spokane Washington. Bought the long block from them for 1500 in 2008