low compression, help please

[blizz99]

Ok, so the other day I was going for a little drive and decided to punch it. Next thing I know, my dipstick pops out and smoke was everywhere. I put the dipstick back and went home. When I got home, I did a compression test and it read, 130-120-90-125. I know that is really low compression and I should replace something, but what? Can anyone help?

 

[ilikespeeding]

try adding a little oil to the 3rd piston and see if the compression jumps. If so, rings are bad. Are you burning oil? CEL?

 

[TSi Fury]

Sounds like bad rings. You're not supposed to have a drop any more than 15psi from cylinder to cylinder. Do what was suggested above and put about a teaspoon of oil in the cylinder and see if your compression jumps.

 

[Boosted4]

the CORRECT way to figure out whats wrong with the car is with a cylinder leakdown tester. You can make one yourself for around 30$ or you can buy one for 200$ your choice. it hooks to an air compressor, and obviously adds air in to the combustion chamber and tells you how much and where you are leaking from be it guide seals, rings ... whatever. another thing to remember is that normal compression for a slightly abused old motor is going to be around 145 150ish all the way across, if that number drops 10% from cylinder to cylinder, you have issues, which im sure you are already aware of.

hope that helps


Brandon

 

[ilikespeeding]

the CORRECT way to figure out whats wrong with the car is with a cylinder leakdown tester. You can make one yourself for around 30$ or you can buy one for 200$ your choice. it hooks to an air compressor, and obviously adds air in to the combustion chamber and tells you how much and where you are leaking from be it guide seals, rings ... whatever. another thing to remember is that normal compression for a slightly abused old motor is going to be around 145 150ish all the way across, if that number drops 10% from cylinder to cylinder, you have issues, which im sure you are already aware of.

hope that helps


Brandon

Why would adding oil be incorrect? If valve seals fail, you burn oil.

 

[blizz99]

Do ya'll think if I just bought a 6bolt shortblock that it would fix this problem? I was planning on doing that and putting some research into the "blown" one so I can learn more about the internals. But yea, would a 6bolt shortblock fix this problem or could it be the head as well?

 

[ilikespeeding]

Do ya'll think if I just bought a 6bolt shortblock that it would fix this problem? I was planning on doing that and putting some research into the "blown" one so I can learn more about the internals. But yea, would a 6bolt shortblock fix this problem or could it be the head as well?

If its your valve seals, then no a short block wouldnt help. But, if you wanted the short block, you could fix the problem while you're in there

 

[blizz99]

Ok, if it helps any, when I start the car the idle would go up to 1k rpms and then fall down until it stalls. Does this help anyone diagnose my problem?

 

[ilikespeeding]

Ok, if it helps any, when I start the car the idle would go up to 1k rpms and then fall down until it stalls. Does this help anyone diagnose my problem?

Not really. I want to know if your car is burning any oil at idle or when given gas.

 

[blizz99]

I'm pretty sure it doesn't. The only time smoke came out of my exhaust or anything at all was when my dipstick popped out. Someone said something to me about crankcase pressure and I needed a new shortblock.

 

[ilikespeeding]

I seriously doubt that pressure, unless in the hundreds of thousands of PSI could crack your block. And if anything, you relieved crankcase pressure.

 

[bjoseph04]

When you start the car up after letting it sit for awhile does it smoke out of the pipe? This is usually a sign of bad seals as the oil leaks through after setting for awhile.

 

[bjoseph04]

usually if your rings are bad your car burns off oil as your driving and you can see it out the exhaust thats for sure..

 

[blizz99]

When you start the car up after letting it sit for awhile does it smoke out of the pipe? This is usually a sign of bad seals as the oil leaks through after setting for awhile.

I can't get my car to idle long enough to see any smoke. It would turn on and stall out within a matter of seconds.

 

[blizz99]

Could it be possible that I have blown piston rings? I want to get a pretty good idea what I need to get before I buy anything and take everything out because I'll be taking it to the self help garage on base.

 

[Quasimondo]

You're not going to know what's wrong until you have a leakdown test performed. All you know right now is that your compression is bad, the leakdown test will tell you what's bad, whether it's the rings, valves, or head gasket. If you have an auto hobby shop on base, they'll definitely have a leakdown tester and somebody who can teach you how to properly perform that test.

 

[patty AT forge]

Look here:
http://www.xs11.com/tips/misc/misc3.shtml

A popped dipstick, 90 compression, and a poor idle all seem to add up to a cracked ring-land or some other failure in that cylinder...

 

[blizz99]

I'm a little strapped for cash right now, would I be able to just replace the pistons and rings without replacing the bearings and stuff?

 

[Quasimondo]

No.

Bearings are not reusable. If you pull it, you must replace it. If you're strapped for cash, just keep saving your money to do a proper rebuild, or at the very least enough to get a replacement shortblock. Trying to do a rebuild on the cheap by taking shortcuts will result in your car being down for twice as long and you spending twice as much to fix it.