Who does their own Compression/Leak down tests?
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Who does their own Compression/Leak down tests?
Im the type of person who likes to do everything on my own car. If I dont have the right tools then I will go out and buy them just for the job. I want to do a compression and leak down test on my car so I am wondering who here does them? Ive been reading online and it seems that the tools for both test's would cost about $100-$120 give or take a few.
This is what I have gathered from what I read
Compression test
1- Warm up car
2- remove coil packs
3- remove spark plugs (on all cylinders?)
4- remove the fuse going to the fuel injector
5- insert compression tester
6- have someone sit in the car and crank it over 4-6 times while you read the gauge
7- repeat the process for the remaining 5 cylinders
Leak down test
1- Warm up car
2- remove coil packs/spark plug for the cylinder that you are testing only
3- Insert leak down tester
4- Pressurize to the recommended PSI, Usally 100 psi
5- Read the gauge to see how much air is leaking
* If there is a greater then 10% leak then try to hear where the air is going through.
* Does motor have to be at TDC?
Is it possible to use the leak down tester tool as a compression tester also? Im assuming that a leak down test is more critical then a compression test?
This is what I have gathered from what I read
Compression test
1- Warm up car
2- remove coil packs
3- remove spark plugs (on all cylinders?)
4- remove the fuse going to the fuel injector
5- insert compression tester
6- have someone sit in the car and crank it over 4-6 times while you read the gauge
7- repeat the process for the remaining 5 cylinders
Leak down test
1- Warm up car
2- remove coil packs/spark plug for the cylinder that you are testing only
3- Insert leak down tester
4- Pressurize to the recommended PSI, Usally 100 psi
5- Read the gauge to see how much air is leaking
* If there is a greater then 10% leak then try to hear where the air is going through.
* Does motor have to be at TDC?
Is it possible to use the leak down tester tool as a compression tester also? Im assuming that a leak down test is more critical then a compression test?
Last edited by chopperman; Jan 4, 2009 at 02:28 AM.
In the compression test you actually want to do the fuel pump fuse right after warm up and actually let the engine run until it dies and crank a couple of more times to make sure all fuel is out of the lines.
And for 6 you really don't need someone else, the gauge reads and holds peak pressure
As for leakdown you need to add that you need to put the cylinder at top of the compression cycle, you need to do this for each cylinder when you test it.
Gauges for both tests are different.
And for 6 you really don't need someone else, the gauge reads and holds peak pressure
As for leakdown you need to add that you need to put the cylinder at top of the compression cycle, you need to do this for each cylinder when you test it.
Gauges for both tests are different.
Just make sure when you are doing the compression check to crank it the same amount of times for each cylinder..
For the leak down you wannt to have the cylinder that you are testing at TDC.
For the leak down you wannt to have the cylinder that you are testing at TDC.
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Thats what I have been reading. Someone told me that it is possible to jack up the rear of the car and put it into 6th gear and get someone to turn the rear wheels. They just busting my ***** or does that work?
it would be alot less work if you just used a breaker bar on the crank pulley and turned it by hand. The engine is pretty easy to turn when there are no spark plugs in it.
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For leakdown, the piston needs to be at TDC On the compression stroke so that both intake and exhaust valves will be closed.
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Last edited by Sharif@Forged; Jan 4, 2009 at 12:05 PM.
usually a leakdown is done after a failed compression to confirm where the loss of compression is
a leakdown requires air pressure source and takes longer so most diy'ers do compression and if it passes all is well
a leakdown requires air pressure source and takes longer so most diy'ers do compression and if it passes all is well
9:1 should be around 120-140. That's what my engine is.
To do a leakdown test you need to pull the valve covers off to check that both valves are closed then use a top dead center gauge to read when the piston is TDC.
To do a leakdown test you need to pull the valve covers off to check that both valves are closed then use a top dead center gauge to read when the piston is TDC.
Last edited by JETPILOT; Jan 4, 2009 at 09:31 PM.
Atmosphere pressure at sea level is 14.7 psi. 9 to 1 compression piston, compression should be 14.7 * 9= 132.3 psi and so on for whatever compression pistons you have. Someone please correct me if I am not right on this.
you cant really use multiplying by atmospheric pressure because you have to remember that the compression ratio of the pistons isnt the actually compression theres more factors. mostly what you should look for is equal compression across all cylinders.
Since this are built motors and built by various people you are going to have various results due to build criteria mainly ring gaps which will affect compression results. You will probably see from 130 to 160 depending on build the important thing is that they are consistent on all cylinders
Since this are built motors and built by various people you are going to have various results due to build criteria mainly ring gaps which will affect compression results. You will probably see from 130 to 160 depending on build the important thing is that they are consistent on all cylinders