Inconclusive Leakdown Test - Opinions please

[4UH8ERS]

Alright fellas, Havent been on here much do to business. Car is no longer Turbo sold my parts and returned it to stock because I need a dependable daily driver with good gas mileage. My last part to install was the complete EGR system to complete the return to OEM equipment.

Problem: 8 Days after the EGR install I am coming home from work and the car seems to be running great. Pull in a gas station to get some gas and the Idle is aweful! Look at my vacuum gauge and its fluttering between 10-13 in of vacuum which is way low. So i drive home and its great at high RPMS. Get home thinking vacuum leak and start testing the lines by pinching them off. No luck. So im like crap maybe its the IAC stuck open. pull it and its closed cleaned it with brake cleaner and re-installed. No reason to check tps cause it wouldnt cause low vacuum.

Compression results: #1 - 190 #2 - 185 #3 - 120 #4 - 190

add oil to cylinder #3 - 150

so my conclusion. is too much compressionm for rings, too much for a stuck valve and no burning oil so most likely not a valve seal. Possible a cracked valve so its time for a leakdown test

leakdown test results: Test with all valves closed. 140psi in the cylinder. no bubbles in coolant, no air coming out of the exhaust, none from the intake. Rings sealed great had to put a 1/2' drive on the crank bolt and brace it to the firewall cause the pressure would immedialty try to puch the piston down and turn the crank. There is a very slow leak you hear but thats natural because air slowly squeezes past the ring. I'm thinking headgasket fellas cause I dont know what else to do. i turned the crank 9 times and lined the timing marks up 3 different times. no oil in cooland or vise versa? no oil leaks at all! uhhhhg

please give me some opinions cause if I cant find the problem elsewhere I am pulling the head this weekend.

 

[adammethner05]

Have you checked the fluid levels in your radiator/overflow tank? There's always chance you're slowly burning coolant/water, meaning a possible blown headgasket of course. I don't know much about the leakdown test because I've never had to do one, but when I blew the headgasket in my Talon, my water level would be lower after only a 15 minute drive.

 

[Locke]

140psi is a bit excessive for a leakdown test, but the results would be the same.



If your gauge is mechanical, are you certain it is getting a proper signal? Check it's line first.

When you pinched the vacuum lines, did you pinch them nearest the IM and include the brake booster line?

Did you check the IM and TB gaskets, injectors, and MAP and IAT sensors for leaks?



Sorry to hear you felt the need to return your vehicle to stock, Jake. I hope you get all the little issues sorted out.

 

[4UH8ERS]

140psi is a bit excessive for a leakdown test, but the results would be the same.



If your gauge is mechanical, are you certain it is getting a proper signal? Check it's line first.

When you pinched the vacuum lines, did you pinch them nearest the IM and include the brake booster line?

Did you check the IM and TB gaskets, injectors, and MAP and IAT sensors for leaks?



Sorry to hear you felt the need to return your vehicle to stock, Jake. I hope you get all the little issues sorted out.

Thanks locke, Yeah 140 psi is excessive. I originally started at only 40psi but continued to increase the air pressure because it was inconclusive. I was not using a guage on the actual leakdown test itself only the compression test. The compression test gauge is mechanical and brand new, worked great on all other cylinders and I retested cylinder 3 to be sure it wasnt a fluke.

TB gasket is good and theres no leak at the MAP sensor as well. The car practically sounds like its missing at idle, I have a spare OEM coil and wires so I put them on to make sure thats not the problem. The low compression in the cylinder as well as low vacuum make me think headgasket or valvetrain which is why I have not cheked the IM gaskets. Could a leak in the intake manifold gasket cause low compression in the cylinder??????.

BTW: I did not check the brake booster line as a matter of fact, but i can do that soon as I get home. Thanks for the help keep it coming, I need all i can get as fast as I can cause Im bumming a ride with a co-worker at the moment to avoid driving it.

Also Locke, I just realized you might have been talking about the vacuum gauge and not the gauge for the compression tests. If thats the case I cant pinch its line cause its a hardline, but completely unplugged it from the IM and put my finger over the port and it didnt correct the Idle problem. The gauge reads fine when cruising or engine braking.

 

[Locke]

Thanks locke, Yeah 140 psi is excessive. I originally started at only 40psi but continued to increase the air pressure because it was inconclusive. I was not using a guage on the actual leakdown test itself only the compression test. The compression test gauge is mechanical and brand new, worked great on all other cylinders and I retested cylinder 3 to be sure it wasnt a fluke.

TB gasket is good and theres no leak at the MAP sensor as well. The car practically sounds like its missing at idle, I have a spare OEM coil and wires so I put them on to make sure thats not the problem. The low compression in the cylinder as well as low vacuum make me think headgasket or valvetrain which is why I have not cheked the IM gaskets. Could a leak in the intake manifold gasket cause low compression in the cylinder??????.

BTW: I did not check the brake booster line as a matter of fact, but i can do that soon as I get home. Thanks for the help keep it coming, I need all i can get as fast as I can cause Im bumming a ride with a co-worker at the moment to avoid driving it.

Also Locke, I just realized you might have been talking about the vacuum gauge and not the gauge for the compression tests. If thats the case I cant pinch its line cause its a hardline, but completely unplugged it from the IM and put my finger over the port and it didnt correct the Idle problem. The gauge reads fine when cruising or engine braking.

Yeah, I was talking about the vacuum gauge.

It is peculiar that you have low compression in the one cylinder, but a leakdown did not seem to locate it. Best I can figure, off the top of my head, would be perhaps the compression gauge wasn't completely secure in the plug hole (it has happened to me, especially with these deep plug wells) but that wouldn't account for the low vacuum measurement.

Did the vacuum fluctuate rhythmically between 10 and 13 inches at idle? If you hold the revs steady at 2000, does the vacuum still fluctuate rhythmically?


Any source of low compression should have revealed itself during the leakdown test. It all just doesn't quite add up. I'll ponder the situation tonight.

 

[4UH8ERS]

Yeah, I was talking about the vacuum gauge.

It is peculiar that you have low compression in the one cylinder, but a leakdown did not seem to locate it. Best I can figure, off the top of my head, would be perhaps the compression gauge wasn't completely secure in the plug hole (it has happened to me, especially with these deep plug wells) but that wouldn't account for the low vacuum measurement.

Did the vacuum fluctuate rhythmically between 10 and 13 inches at idle? If you hold the revs steady at 2000, does the vacuum still fluctuate rhythmically?


Any source of low compression should have revealed itself during the leakdown test. It all just doesn't quite add up. I'll ponder the situation tonight.

Thanks and ill bring more data to the table tommorrow. thanks a ton.

 

[pboglio]

Wait a minute, you ran a leakdown test WITHOUT a pressure gauge? That is not going to provide you with any useful information. The compression test is your first clue that something is seriously wrong and its also a test that is pretty hard to screw up. A proper leakdown test with a pressure gauge is the only way to confirm it.

I've had good luck bringing up a weak cylinder just by using Seafoam and running it thru the motor, but thats bringing a cylinder from 160 psi up to 172 psi. Looks like your in for a rebuild.

 

[4UH8ERS]

Wait a minute, you ran a leakdown test WITHOUT a pressure gauge? That is not going to provide you with any useful information. The compression test is your first clue that something is seriously wrong and its also a test that is pretty hard to screw up. A proper leakdown test with a pressure gauge is the only way to confirm it.

I've had good luck bringing up a weak cylinder just by using Seafoam and running it thru the motor, but thats bringing a cylinder from 160 psi up to 172 psi. Looks like your in for a rebuild.

I dont have a leakdown tester with the gauge. i use my compression tester hose and fitting, of course removing the valve stem seal. Why is a guage neccessary here?

 

[Locke]

A gauge is only necessary when measuring loss, the amount of leakdown. Knowing this won't really help us.

Jake, before removing the head for inspection, remove the rocker cover (duh) and inspect the valve train.

 

[4UH8ERS]

A gauge is only necessary when measuring loss, the amount of leakdown. Knowing this won't really help us.

Jake, before removing the head for inspection, remove the rocker cover (duh) and inspect the valve train.

I did remove the valve cover and take look with the cam caps and camshafts still in the head. There is no notable damage visible. I didnt get anymore data from testing last night, but I will have time to evaluate more things tonight.

Something is Just not adding up here. like you said.

 

[pboglio]

My point is to complete the diagnostic the PROPER way so people that are trying to help know what the facts are you need a leakdown tester to measure the stabilized cylinder pressure, THEN you detect where the leak is occuring. There are two parts to the test, severity of leakage and location of leakage. The first determines whether a rebuild is even warranted, the second where the failure occured so a rebuild can focus in the right area.

 

[Locke]

Yes, a proper leakdown test does use a gauge, (it's measure is to be used comparatively, though) but you should be able to easily locate a 10% loss with your ear. The "poor-man's leakdown test" in conjunction with compression and vacuum tests is well enough to locate nearly all sealing issues.

There will be no use to knowing the actual amount of leakdown - unless of course Jake is going deaf, but I give him the benefit of the doubt - in this case knowing the amount of loss will not help us determine where it is coming from.



I am curious about the nature of the vacuum fluctuations and how compression was built.

 

[bullettdsm]

Goofy stuff going on + previous turbo = possible ring landing. I have seen them show good on leak downs but bad on comp (or flip flopped). Depending on which ring landing and which way it broke. Just a yucky possibility.

MB

 

[4UH8ERS]

Well in regards to the Vacuum fluctuating I made a cell phone video to show you but my stupid phone wont send it because it says the file is to large. So anyways, I'll explain.

Fired it up and vacuum was holiding steady at -12. Let it warm up all the way and reved it to about 2000 RPM and held it. I was then pulling around 18-20 in vacuum which is where it should be normally. So i gave it some quick high revs, and then let it stable out again and it started to idle at about -15 in vacuum which is better and all I did was free rev it a few times. After letting it continue to idle another minute or too it would start to stumble a little but thats about it. Checked brake booster line also it was a little loose but not leaking so I caught that problem before it started. My mother in law then came by to take me and my wife to dinner to i couldnt pass that up. Work takes up most my day so I dont get to work on it much during the week days.

 

[4UH8ERS]

Goofy stuff going on + previous turbo = possible ring landing. I have seen them show good on leak downs but bad on comp (or flip flopped). Depending on which ring landing and which way it broke. Just a yucky possibility.

MB

Well, I understand where your coming from, just really uncharacterisitc really when I have driven a good 7-10,000 miles n/a now and I didnt put but an extra 10,000 miles on the boosted/built motor. Probably have around 25k on this rebuild now total. Only problem is the cylinder head was not rebuilt or milled or anything at the time of rebuild. I just changed the valve seals only. So the head probably has 160k on it. I know that was a big nono and although visual inspection is negative it could still be in the head I think.

 

[fhudsonjr]

With "...no bubbles in coolant, no air coming out of exhaust, none from the intake." and "There is a very slow leak you hear..." it sure sounds like a ring problem. Try your "leak down" test w/a couple of the other known good cylinders and listen for the air coming out past the rings. If you have young or good ears you may be able to determine if the sound is the same from the good cylinders and the bad one.
Good luck

 

[4UH8ERS]

With "...no bubbles in coolant, no air coming out of exhaust, none from the intake." and "There is a very slow leak you hear..." it sure sounds like a ring problem. Try your "leak down" test w/a couple of the other known good cylinders and listen for the air coming out past the rings. If you have young or good ears you may be able to determine if the sound is the same from the good cylinders and the bad one.
Good luck

Good Idea, Thanks buddy.

 

[4UH8ERS]

Something obviously was not adding up. So I started back from the begining. Re-doing all tests. Previous compression test was inaccurate because I re-did it after letting the car run for 15 minutes to make sure it was plenty warmed up. compression was great.
190-185-185-185. Did a smoke test looking for vacuum leaks and I noticed smoke is coming out where the tps is. I also tested the TPS and came back with the resistance starting at .562 KO and as the throttle is opened reaching as high as 3.8 ko at WOT. According to my Haynes the resistance should stay between 3.5-6.5 ko. i also noticed a little smoke coming from the EGR solenoid, but completely plugging all EGR vacuum lines made no differenct at all. I also just got a TPS high output code finally!, but i figured that might be from unplugging it while it was running.

 

[4UH8ERS]

Ready for more opinions. I have never had a problem I could not figure out on this crapper and its pissing me off. I had another TPS from a 420a avenger. i tested it and resistance results were almost identical. Installed it and it made pretty much no difference. I dont know what else to possible do other than re-check timing again? Cause of the low vacuum. If timing was off though then why would my cam timing marks line up over and over again? is it possible it jumped time by the crank causeing the marks to line up but not while the motor is at TDC? Sorry if im confusing anyone, its hard not to get frustrated here. Plugs also turning white after running, possible lean mixture.

 

[4UH8ERS]

Ohh my goodness, fixed my problem and feel like a total idiot . Thank you all for your help though. The actual EGR valve was stuck open making the recirculation tube be a huge vacuum leak. Cut out a coke can in the shape of the gasket and blocked it off and it ran awesome. I cant beleive i was blocking all the vacuum lines and forgetting the huge metal tube!!!! . How embarassing. 3 years w/o one makes you forget all they do. Anyways the smoke coming from the EGR when the motor was off was my dead giveaway cause the valve should have been closed. Got a new valve on the way, but the car drives great with the coke can inbetween the gasket and the head .

 

[Locke]

Hah Glad you found the problem. It usually is something silly that goes overlooked, it seems.

Appreciate the update as well.

You should come around more often.

 

[bullettdsm]

Lol, glad you found the problem. Balls points for admitting on the forum instead of making up something

MB

 

[kyanox]

I have the same issue, 13hg at idle and was having idle surge.

I'll check my EGR also, since I'm going to block it off anyway.

Thanks for the insightful post, VERY helpful.