compression test question
Thread Starter
Drifting
Joined: Jan 2004
Posts: 1,987
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From: Texas
compression test question
Sorry if this is a dupe, the search function isn't working for me right now.
Couple of questions:
1) Is a compression/leakdown test the same thing?
2) About what should I expect to pay to have one done?
Couple of questions:
1) Is a compression/leakdown test the same thing?
2) About what should I expect to pay to have one done?
Last edited by veni vidi vert; Sep 8, 2008 at 11:16 PM.
Le Mans Master
Joined: Nov 2005
Posts: 6,993
Likes: 25
A compression test is a pressure guage put on each cylinder (one at a time) to measure the maxuimum pressure a cylinder can build on the compression stroke.
A leakdown test has a guage with an air fitting. The cylinder has BOTH valves close for this test. The cylinder in filled with compressed air and the guage is timed for how fast it leaks the compressed air out. The faster the leakdown, the worse the cylinder is. You can generally listen from the intake/exhaust/oil filler to determin if the leak if from an intake/exhaust valve or leaking past the rings.
Probably at least 1-2 hrs of labor to do every cylinder.
A leakdown test has a guage with an air fitting. The cylinder has BOTH valves close for this test. The cylinder in filled with compressed air and the guage is timed for how fast it leaks the compressed air out. The faster the leakdown, the worse the cylinder is. You can generally listen from the intake/exhaust/oil filler to determin if the leak if from an intake/exhaust valve or leaking past the rings.
Probably at least 1-2 hrs of labor to do every cylinder.
Thread Starter
Drifting
Joined: Jan 2004
Posts: 1,987
Likes: 24
From: Texas
Thanks for the responses.
I noticed a bit of smoke coming from my oil fill and it concerned me.
I'm pretty **** about my car, and was thinking if it was something that could be done at a reasonable price would be a good Peace of mind..
On another note, would I have a loss of power or any signs if I had a problem associated with a compression leak?
I noticed a bit of smoke coming from my oil fill and it concerned me.
I'm pretty **** about my car, and was thinking if it was something that could be done at a reasonable price would be a good Peace of mind..
On another note, would I have a loss of power or any signs if I had a problem associated with a compression leak?
Le Mans Master
Joined: Nov 2005
Posts: 6,993
Likes: 25
Thanks for the responses.
I noticed a bit of smoke coming from my oil fill and it concerned me.
I'm pretty **** about my car, and was thinking if it was something that could be done at a reasonable price would be a good Peace of mind..
On another note, would I have a loss of power or any signs if I had a problem associated with a compression leak?
I noticed a bit of smoke coming from my oil fill and it concerned me.
I'm pretty **** about my car, and was thinking if it was something that could be done at a reasonable price would be a good Peace of mind..
On another note, would I have a loss of power or any signs if I had a problem associated with a compression leak?
During the leakdown test, pull the filler and listen for air. If all the cylinders measure about the same for compression and leakdown I would not be concerned. You should have both done since the plug(s) will be out and you can use the leakdown tool for compression testing too (at least I can w/ mine). Go buy the tool if you have a small comressor-they cast less than an hour of labor in most shops.
Low compression and/or leaks can be a power robber. In general it takes about 80-90 psi to fire well. Anything less will be a cylinder that's prone to misfire. All cylinders should be within 5% or so of each other as far as compression and all should leakdown at a fairly consistent rate. It they leakdown quickly or have low compression-you have "issues".
Last edited by dougbfresh; Sep 9, 2008 at 02:14 PM.
