Leak Down Test Help

[mikejsmith1985]

Hi, Iv'e never done a leak down test, I got a tool from Harbor freight it's mad eby US General. I've read some reviews that say the tool isn't very great. But this is what I'm looking at any help woud be appreciated.

Compresstion Test
#4- 150psi #3- 148psi #2- 150psi #1- 0psi

I am pretty sure that the #1 cylinder is a result of bent/bad intake valves when I run the leak down test no matter what psi I run through the tool when I zero out the percentage meter and I then hook it up to the Piston I am testing which is at TDC I have 100% leakage and the psi guage drops to 0psi. I would expect that on cylinder 1 but I dont think there is any way that the car will run and the compression is that high in 3 cylinders and yield 100% leakage across all 4 cylinders.

One more note the head is new and so is the head gasket, I had mishap with the timing belt after the head install where a bolt backed out of the water pump and caused the belt to slide on the cam gears towards the driver fender but didn't appear to skip any teeth. I'm guessing that it must have as I now have a valve problem in cylinder 1. Gasket is good leaks detected during BLT and no oil/coolant mixes any where.

Let me know what you guys think about my leakage issue thanks!

 

[Nvisabl]

Hi, Iv'e never done a leak down test, I got a tool from Harbor freight it's mad eby US General. I've read some reviews that say the tool isn't very great. But this is what I'm looking at any help woud be appreciated.

Compresstion Test
#4- 150psi #3- 148psi #2- 150psi #1- 0psi


Let me know what you guys think about my leakage issue thanks!

Did you buy a compression tester or a leak down tester 2 different animals? Compression is compression leak down is apply air pressure of a know amount and see how much stays in cylinder at TDC 0 psi compression is obviously bad but a leak down will tell you where it is going, good luck

 

[mikejsmith1985]

I have both, Just figured the compression results may be helpful.

 

[delta448]

Pull the valve cover off and look at the valves, rockers and cams. You should be able to tell if they're bent.

As for the leakdown test, I think you're just using the tester wrong.

 

[TSIfreek]

To use a leakdown tester in our engines all of the rockers have to be out as all of the valves need to be closed.
From what you posted looks more like a compression test and #1 cylinder may have some valve problems.

 

[pboglio]

No, you don't need the rockers off to do a leakdown test, come on now. You simply need to be able to rotate the crankshaft manually until TDC, or until you can stop hearing a leak while you feed in some air pressure via the leakdown tester. I just this 2 hours ago.

 

[mikejsmith1985]

I have the pistons at TDC when I test, cylinder 1 and 4 are easy because the timing marks on the cams line up when you are at TDC obviously clinders 2 and 3 are a bit harder but the cam gear timing marks are about 90* out when cylinders 2 and 3 are at TDC.

I did the compression test and understand what the difference is between a compression test and a leak down test. I am doing the leakdown test because of the dead cylinder, I want to make sure that the other 3 cylinders won't need any additional work while I have the head off reapairing the valves.

I am using the tester in this manner:

1. Set piston TDC
2. screw the Tester hose into the sparkplug threads
3. Set compressor pressure ( anywhere from 15 to 100 psi always gives the same reesults)
4. close regulator on tool
5. attach tool to compressor
6. open regulator on tool till the Loss gauge reaches zero
7. lock the adjuster
8. attach the hose threaded into the spark plug hole
9. read the Loss gauge

these steps yield 100% loss on all cylinders, is it possible that all valves are bent and I am losing 100% I guess but I wouldn't expect 150 psi compression if that was the case.

Is it more likely that the tool is faulty or that even with good compression I have 100% leakage.

 

[boostforfun]

No, you don't need the rockers off to do a leakdown test, come on now. You simply need to be able to rotate the crankshaft manually until TDC, or until you can stop hearing a leak while you feed in some air pressure via the leakdown tester. I just this 2 hours ago.

+1 ... I have the harbor freight testor too, and it worked like a charm.

You may have to put light pressure in the cylinder and rock the motor back and forth until the valves are seated. This is easy enough with the plugs out. I know you think you have it a TDC, but it is prob off just a bit.

 

[pboglio]

You need to HOLD the engine at TDC. The 100 psi of regulated pressure will kick the motor over and open up the valves again. I take a 1/2" drive extension and a long breaker bar, rotate the motor into position, then lean that breaker bar at an angle on the ground until it wedges the crank from rotating, then reverse the ratcheting mechanism to lock everything in place. I don't even bother looking for TDC, just rotate by hand until the pressure in the cylinder stops bleeding out. I typically feed in about 30 psi, then rotate the crank by hand, then when it stops leaking showing all valves in that cylinder are closed, I turn up the pressure to 100 psi. Simple.

 

[Nvisabl]

You need to HOLD the engine at TDC. The 100 psi of regulated pressure will kick the motor over and open up the valves again. I take a 1/2" drive extension and a long breaker bar, rotate the motor into position, then lean that breaker bar at an angle on the ground until it wedges the crank from rotating, then reverse the ratcheting mechanism to lock everything in place. I don't even bother looking for TDC, just rotate by hand until the pressure in the cylinder stops bleeding out. I typically feed in about 30 psi, then rotate the crank by hand, then when it stops leaking showing all valves in that cylinder are closed, I turn up the pressure to 100 psi. Simple.

This is incorrect if the cylinder is TDC it will not "Kick" we do 3 -4 of these a month
I use leakdown more then compression as vital info , You can always turn the boost up if compression is low but a bad leak down will make for a not fun car
and anything under 15% is considered OK

 

[pboglio]

^^^Thats true, at exactly TDC the motor will hold still. A couple degrees either way and the pressure will push the motor over.

 

[Calan]

Compression And Leak-Down Testing

 

[mikejsmith1985]

Compression And Leak-Down Testing

Thanks, for the write up the only thing I haven't done that is in the write up is put the car in gear and set the parking brake. I am going to give that a try and see if it helps.

Thanks everyone for the input!

same results, I even tried pressureizing the cylinder slightly before TDC and slowly rotating the cylinder to, then slightly past TDC with no change in the leakage meter. I think I may try doing the Test on my girlfriends cobalt. I KNOW that motor has no problems, If I can make it pass then I say my motor must really be toast. If not I think I will go exchange the tester for a new one and try it to see if maybe I just have a faulty gauge.

 

[pboglio]

Don't bother returning the leakdown tester. The compression test has its uses as it will cross check the leakdown test. If your coming up 0 psi on the compression test, and unable to maintain any pressure during a leakdown test, then almost certainly it is a dead cylinder (i.e. holed piston, worn/damaged piston ring, intake/exhaust valve, head gasket, etc.).

I've been able in the past to reduce my cylinder leakage rates using a combustion chamber cleaner, but never attempted it with a completely dead cylinder reading. I think its time you pulled the head off to see whats up.

 

[romeen]

I have the pistons at TDC when I test, cylinder 1 and 4 are easy because the timing marks on the cams line up when you are at TDC obviously clinders 2 and 3 are a bit harder but the cam gear timing marks are about 90* out when cylinders 2 and 3 are at TDC.

Keep in mind that you need to have it set at TDC of the intake stroke when testing. #4 will be at TDC of the exhaust stroke when #1 is set up properly and vice-versa. When at TDC of the exhaust stroke you will leak past both the intake and exhaust valves due to overlap.

If you gradually turn up the pressure/regulator (over several seconds) the piston shouldn't move.

 

[mikejsmith1985]

Don't bother returning the leakdown tester. The compression test has its uses as it will cross check the leakdown test. If your coming up 0 psi on the compression test, and unable to maintain any pressure during a leakdown test, then almost certainly it is a dead cylinder (i.e. holed piston, worn/damaged piston ring, intake/exhaust valve, head gasket, etc.).

I've been able in the past to reduce my cylinder leakage rates using a combustion chamber cleaner, but never attempted it with a completely dead cylinder reading. I think its time you pulled the head off to see whats up.

I was just using the leak down test to discover possible problems in cylinders 4,3,2 before removing, I am 90% sure that the cylinder one problem is bent intake valves. I am going to pull the head and see what the pistons/ walls look like!

Kindof a stupid question here, I am new to the engine building stuff, I've always done my own repairs but this is the first "bad motor" I've had. Can I pull the Pistons out with the block still in the car? I havent looked at it closely enough to know if I can undo the rod cap, then rotat the crank and pull the rod/piston out throuh the bottom of the cylinder. Then replace the rings without the expense and more importantly the time of pulling the motor, replacing all bearings and machineing everything.

I know Idealy everything should be replaced but this is my DD and I need to get her back on the road, if I can't do that then I'll end up buying a beater to drive around for 6 months to a year and I'll bore the block and do a 1g rod evo 9 piston setup maybe even grab a 4g64 crank to do the 2.1 motor. I have a lot of reading to do still like I said still new to all of this but luckily this site is full of great knowledge!

 

[delta448]

Can I pull the Pistons out with the block still in the car? I havent looked at it closely enough to know if I can undo the rod cap, then rotat the crank and pull the rod/piston out throuh the bottom of the cylinder. Then replace the rings without the expense and more importantly the time of pulling the motor, replacing all bearings and machineing everything.

You can't pull the pistons out from the bottom. You can pull the head with the engine in the car though and take them out by the conventional method. This is obviously sub-optimal, since the cylinders will need to be re-honed for new rings to bed in correctly.

 

[mikejsmith1985]

You can't pull the pistons out from the bottom. You can pull the head with the engine in the car though and take them out by the conventional method. This is obviously sub-optimal, since the cylinders will need to be re-honed for new rings to bed in correctly.

That makes sense thanks! looks like it's time to shop around for a beater till I have the time to pull the engine and have the machine work done.

Thanks for all the info guys!