2G no compression in cylinder 4

[theoneandonlyg]

So I had a compression test done on my 97 gsx a couple weeks ago, no compression in cylinder four was the result. Today I finally pulled the valve cover off, and checked to see if all four valves were returning, and they were. I also pulled the sparkplug out, and couldn't see or feel a hole in the top of the piston. How can I tell whether this problem is being caused by worn rings? Or do you have any other suggestions on which direction I should go next?

Thanks,
Paul

 

[grothe3297venge]

Have you tried to do a leak down test?

In case you don't know how - http://www.dsmtuners.com/forums/articles-engine-fuel/338152-compression-leak-down-testing.html

 

[WES_393]

You could run a leak down test to get an idea of where the leak is. But with zero compression your going to have to pull the head anyways.

Edit- I'm slow

 

[compression]

I'm more of a cylinder 3 type of guy.

In all seriousness, drop a capfull of oil down into the cylinder then retake the comp test, if the numbers go up , its likely a bottom end issue, if no change top end.
Then check your coolant oil coloration, or pressurized coolant system.

Worn rings aren't going to cause a zero compression issue in a single cylinder, you likely had some failure of sorts in that cylinder.

TERRIBLE quality picture but sometimes it doesnt look like much on the top of a piston is its damaged.

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But then..

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[theoneandonlyg]

You could run a leak down test to get an idea of where the leak is. But with zero compression your going to have to pull the head anyways.

Edit- I'm slow

I guess i'm going to man up and buy a leak down tester from harbor freight. $45 isn't bad, compared to paying more just to have a shop do it. Once I get this test down, if it is the rings would you recommend changing them myself? Fairly new to DSM's, but learning very quickly due to how much maintenance they require, haha.

EDIT: @compression: never realized the piston could be that terrible yet look almost normal from the top down view!

 

[grothe3297venge]

Just rent one from a parts store. Then as for doing it on your own ya you can. Just make sure everything checks out and everything is all within specs.

 

[compression]

Actually installing the rings onto the piston isnt that hard, but i can see where it may be tricky putting them back into the block for the first time , youll need a special tool to compress the rings while you smack the piston down into the block. They make all kinds, just one random google

KD Tools Piston Ring Compressor - Tools - Mechanics & Auto Tools - Automotive Specialty Tools

Once you have the head off , you will obviously need a new headgasket, and its going to be a superb idea to install some sort of headstuds, the standard arp's are great until the super high hp mark, idk ,like 600+ then youll want the L19's from arp.

Headgasket wise, theres alot of options, im a cometic guy but ive heard excellent things from mitsu mls's.

And last but not least go ahead and throw on new rod bearings, It isnt very wise to put the old worn rod bearings back into the engine.

So new headgasket, headstuds, rings, and rod bearings would be your best choice, basically an entire engine overhaul.

 

[theoneandonlyg]

Only reason I'd rather do it myself is because I'm on a budget, and the last mechanic i took my car to told me he'd charge me like 1500 for all new valves. He told me this before he did a leak down test or anything, so basically just throwing parts at the car. That pissed me off. But I didn't know parts stores rented leak down testers, i thought they only had compression testers for rent?

And @compression: I definitely plan on installing headstuds along with the other parts you have listed. I appreciate the info from someone who actually knows! Just curious, how much do you think all those would cost me? I'm going to have another compression test done very shortly, because i believe on the last test another cylinder was below the "recommended level"(i know thats not the term) of 130. It read 125. So once I do another test I will post results and then we can go from there. If the other cylinder is still below 130, would a small loss of compression be caused by rings in that piston as well?

Also, this is all assuming that my piston isn't damaged on the side, which I can't see at the moment.

P.S. I really wish I could find someone in the Western Massachusetts area who would be willing to help!

EDIT: Lastly, the only thing that really scares me in regards to pulling the head off is messing up the timing. Any tips for that?

 

[WES_393]

I honestly wouldn't waste a whole lot of time on the leak down test. I would suggest getting a compression tester with a quick-connect fitting, like this one from harbor freight. You can use that to run a compression test yourself to make sure the shop wasn't bluffing. Then disconnect the gauge, hook up an air compressor, pump air into the cylinders, and listen for where the air is leaking. Just make sure the cylinder your testing is at TDC. But that will still just give you a basic idea of where to look once you get everything apart. It could be worn rings or melted pistons, I wouldn't assume anything but the worst until you have it apart.

In order to remove the head you have to remove the timing belt. So in a sense, you are messing up the timing. When it comes time to reinstall the head there are plenty of write-ups and guides to show how to properly time the engine.

Also, it's not recommended to use a Multi-Layer Steel headgasket without having the head and block resurfaced specifically for it. I'd suggest using a Felpro or Mitsubishi composite head gasket with ARP standard studs.

 

[Turbosnatch]

Definately do the leak down test. Because it may not necessarily be a piston or bottom end. I had the same issue and id bent and damaged a valve and came up as a 0 on the compression tester from where my valves had hit the piston

 

[theoneandonlyg]

I honestly wouldn't waste a whole lot of time on the leak down test. I would suggest getting a compression tester with a quick-connect fitting, like this one from harbor freight. You can use that to run a compression test yourself to make sure the shop wasn't bluffing. Then disconnect the gauge, hook up an air compressor, pump air into the cylinders, and listen for where the air is leaking. Just make sure the cylinder your testing is at TDC. But that will still just give you a basic idea of where to look once you get everything apart. It could be worn rings or melted pistons, I wouldn't assume anything but the worst until you have it apart.

In order to remove the head you have to remove the timing belt. So in a sense, you are messing up the timing. When it comes time to reinstall the head there are plenty of write-ups and guides to show how to properly time the engine.

Also, it's not recommended to use a Multi-Layer Steel headgasket without having the head and block resurfaced specifically for it. I'd suggest using a Felpro or Mitsubishi composite head gasket with ARP standard studs.

What do you mean when you say the cylinder should be at TDC when i test it? And I think a buddy has a compression tester, so this will be happening this weekend. I appreciate all your advice as well!

But I have another question. Could a coil pack have something to do with this issue at all? I know it wouldn't cause zero compression, but would it affect anything?

 

[OakStreetTuner]

Tdc stands for top dead center, when a piston is at its highest possible point during its revolution. A coil pack will have no influence on a compression test.

 

[theoneandonlyg]

Tdc stands for top dead center, when a piston is at its highest possible point during its revolution. A coil pack will have no influence on a compression test.

ah i see. you taught me something today, so thanks haha. i will be posting new compression test results this weekend so subscribe to my thread and help me out!