Generation III Internal Engine 1997-2006 LS1 | LS6
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Leakdown results

Old Jan 4, 2004 | 08:38 PM
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Unhappy Leakdown results

Well I did the leakdown today and All of my cylinders were good except the # 3 which had 80 % leakdown. The rest ranged from 4-8%. I also have a couple of questions about some things I found when doing this.

1. I pulled all the valve covers cause I figured I may as well check my lifters since each piston was gonna be at TDC. From a previous post I read that you will not be able to push down on the pushrod side of the rocker and if you can it means you have a bad lifter. At TDC I was able to push down on all of my rockers a very small amount but enough to where they would just barely come off of the valve. This would mean I have 16 bad lifters?? I have the Yella terra's so Im not sure if maybe they act a little different than the stock rockers when doing this test.

2. Just to make sure I was at TDC I injected 20 psi (thanks larry) into each cylinder and then rotated the crank until it was not fighting me. This was right after the compression as turning the crank was very hard and then got really easy at this point plus I was able to hear that both valves were closed and could hear air going into the crankcase/oil pan. At this point both valves /rockers were visibly at there highest point when checking from above the car. I really believe this was TDC but if I am wrong please let me know because I would hate to think I have 16 bad lifters

3. On the #3 cylinder where I had the 80% leakdown I could hear a hell of alot of air coming into the crankcase but I could also hear it from the top of the car by what sounded like the valves or intake even though I know that there were closed because no air was coming out of the intake or valves.
I would think that this would point to an issue with my rings or piston on the #3 cylinder but I did find oil that was milky in color in the accordian hose and on my TB. This could mean a head gasket blew or a coolant leak but I only saw the milky oil on my accordian hose and the TB. Checking in my radiator the fluid still looked red and not milky and I have not drained my crankcase oil yet to check there. Also there was no air bubbles coming out of the radiator fluid while I was doing the leakdown on any of the cylinders.

So my question is do you guys think this is 100 percent a ring/piston issue or is it possible I blew a head gasket as I saw the milky oil in my TB and accordian hose?

Is it worth me pulling the one head just to make sure the gasket is ok before I pull the motor or should I just go ahead and pull the motor?
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Old Jan 4, 2004 | 08:55 PM
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What i would do is squirt some oil into the cylinder and turn it over a couple times to get the oil into the rings. And then loosen the rockers on that cylinder and then apply the air a see if the oil helps seal the rings if it does for a short time intill the oil works its way through rings are shot. and that will also make sure the valves are completely closed. as for the spongy rockers if the car sat with pressure without running for a while they might have just blead down. And milky oil could be from moisture in the motor on a cold start and not running long enough to burn out the condensation ive seen it alot on all my cars it won't hurt a thing.
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Old Jan 4, 2004 | 11:04 PM
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The car has been sitting for about 3 weeks so maybe the lifters did bleed down, I was kinda wondering that myself.
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Old Jan 5, 2004 | 10:25 AM
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Old Jan 5, 2004 | 11:02 AM
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As soon as the engine is running and there is oil pressure, those spongy lifters will firm right up.
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Old Jan 5, 2004 | 11:16 AM
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A spongy lifter after a long period of time is normal especially if it's trying to keep a valve open.
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Old Jan 5, 2004 | 11:21 AM
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If the engine has been sitting for a spell (3 weeks) and one of the valves on number three was open for that time and only closed when you pulled off the rockers, there could be some carbon/etc keeping it slightly open. I've run into this before. Put air on that cylinder again and use your valve spring compressor (with a coin inserted so you don't just pop the retainer) to open and close the valve a couple times. See if that seats the valve better.
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Old Jan 5, 2004 | 11:34 AM
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any more comments on the milky oil that I found? should I just go ahead and pull the motor or do you guys think I should try taking the head off just to be sure?

skonka I hear what you are saying but I had 80 percent leakdown and with the rocker installed I was able to easily turn the crank over even while injecting 100 psi plus I did not hear air coming out of the intake or the exhaust. so i think i have a bigger issue with that cylinder but Ill try what you said.
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Old Jan 5, 2004 | 12:49 PM
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Soft/bad lifters will make valvetrain slack and leave the
valves closed. They would only hurt a leakdown test if
they were bad in a way that made them stuck at full
extension.

Air into the crankcase is rings or a piston-hole.
Air into the exhaust or intake is valves or head
gasket (via adjacent, valves-open cylinder).
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Old Jan 5, 2004 | 01:53 PM
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Interesting, I just did a leak down on my motor and #3 was also the problem child. https://ls1tech.com/forums/generation-iii-internal-engine/125979-help-me-interpret-these-results.html

I only had 10% on #3 compared to 5-7% on the others. My car still runs pretty good, I just have quite a bit of blowby under boost.

I'm guessing that 80% leakdown means that something worse than a head gasket is blown.

I found that it was pretty obvious if you were not on TDC when doing the test. I hooked up the hose (but not the compressor connection) and just spun the motor until I could hear air coming out of the quick connect fitting on the hose. I then just turned the motor in little increments until the air stopped coming out. I found that the motor would spin in one direction or the other and open an intake/exahust valve if it was not right on TDC when I hooked the compressor up at 100psi ( I had the socket off the crank). I also marked the balancer on the 4 90* points (once I found one TDC). This made it pretty easy to move along the firing order.
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Old Jan 5, 2004 | 02:36 PM
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Yeah I figured I was close as well and I did not see the crank move while I was doing the test. 80% blowby is a sh*tload. You only had 10 % so maybe youll get lucky and will not have to rebuild the entire bottom end.
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Old Jan 5, 2004 | 02:54 PM
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I failed a leakdown on cylinder #5 and had milky oil all the way up into the airbox and it was due in part to a blown head gasket.
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Old Jan 5, 2004 | 03:06 PM
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Originally Posted by Hannibal
I failed a leakdown on cylinder #5 and had milky oil all the way up into the airbox and it was due in part to a blown head gasket.

Hannibal did you see air bubbles in the radiator or milky coolant anwhere else besides the intake track?

There was alot of it and it was all in my according hose and tb. Not to much anywhere else but the milky oil I saw was from 1 shakedown run that I made after a fresh oil change just to make sure my dipstick wasnt blowing out due to vibration.
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Old Jan 5, 2004 | 03:08 PM
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Originally Posted by QuickSilver2002
Interesting, I just did a leak down on my motor and #3 was also the problem child. https://ls1tech.com/forums/showthread.php?t=125979

I only had 10% on #3 compared to 5-7% on the others. My car still runs pretty good, I just have quite a bit of blowby under boost.

I'm guessing that 80% leakdown means that something worse than a head gasket is blown.

I found that it was pretty obvious if you were not on TDC when doing the test. I hooked up the hose (but not the compressor connection) and just spun the motor until I could hear air coming out of the quick connect fitting on the hose. I then just turned the motor in little increments until the air stopped coming out. I found that the motor would spin in one direction or the other and open an intake/exahust valve if it was not right on TDC when I hooked the compressor up at 100psi ( I had the socket off the crank). I also marked the balancer on the 4 90* points (once I found one TDC). This made it pretty easy to move along the firing order.

I just read your prvious post and its funny becuase on the #3 cyl I also heard alot of air that almost sounded like it was going to the intake but yet no air was coming out of it. weird....
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Old Jan 5, 2004 | 03:12 PM
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Mike,
If I was you I'd just go ahead and pull that one head before I went any further. That will determine the extent of your problem. Heck, pulling a head isn't a big deal at all on one of these cars. Let us know what you find. I'm betting on a blown HG
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Old Jan 5, 2004 | 03:41 PM
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Originally Posted by Mike K.
Hannibal did you see air bubbles in the radiator or milky coolant anwhere else besides the intake track?

There was alot of it and it was all in my according hose and tb. Not to much anywhere else but the milky oil I saw was from 1 shakedown run that I made after a fresh oil change just to make sure my dipstick wasnt blowing out due to vibration.

No bubbles as far as I can remeber. Only saw milky oil/coolant in the intake, TB, bellows, MAF and lid. There was enough to splatter the roof of my lid and leave some decent puddle in the bellows.

Have you done any WOT runs on the street just prior to discovering this problem or worse, since? Anything there? White smoke, loss of power?
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Old Jan 5, 2004 | 04:39 PM
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Like what was said before I would just put a tablespoon of oil into the spark plug hole and do another compression check. If it is rings your numbers should go up. Just because you don't have coolant in your intake doesn't mean there isn't a bad headgasket but I would tend to think that the problem lies someplace else. A loss of compression of that sort would make me tend to think that it is possibly a bent valve or a bad valve seat, or heaven forbid a hole in the piston but the only way you would know of that is to get the motor tore down to get a look at it, blowby with oil in the chamber should be relatively the same if it is one of the above mentioned. Eithor way good luck and we all hope it is something cheap and easy.
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Old Jan 5, 2004 | 04:49 PM
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I was doing a WOT run when I first noticed it and made one gimpy run in 1st gear a few days later just to make sure it wasnt a spoof. I did have the puddles in the bellows like you said and if I remember right a little tiny bit of spray on the lid originally from the first run but I dismissed it. Gomer I if this is a head gasket I will be very happy to say the least. I'll pull the head to see whats going on there.
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Old Jan 5, 2004 | 05:42 PM
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Originally Posted by Mike K.
I was doing a WOT run when I first noticed it and made one gimpy run in 1st gear a few days later just to make sure it wasnt a spoof. I did have the puddles in the bellows like you said and if I remember right a little tiny bit of spray on the lid originally from the first run but I dismissed it. Gomer I if this is a head gasket I will be very happy to say the least. I'll pull the head to see whats going on there.

That sounds like the same symptoms I had when I blew my HG. After I'd let the car sit for a while and start it up.. white smoke everywhere for a few mins. I have my fingers crossed for you.
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