what exactly is a leak down test?

[cammed3800]

What are the steps in doing a leak down test?

[awesomeame]

step one...buy the tool [img]smile.gif[/img]

say you're checking it on #1 cyl....you've gotta put that cyl at TDC on the compression stroke, so both valves are closed.

then you install the tool into the spark plug hole, and add compressed air, say 120 psi. (number are example only) then you shut the valve off so no more compressed air can enter the cylinder. start your timer & after say 30 secs check the gage to see what the pressure is in the cylinder.

if after 30 secs the pressure is less then 70 psi, you've got a compression problem.

above numbers only used for example!!!!

--matt

[white96six]

just to add to that if you are leaking you will hear it in the exhaust pipe if it is the exhaust valve and the intake if it is the intake valve and oil fill hole if it is your rings. listen for the whisle :D

[cammed3800]

I bought a compression tester at advance auto, isnt this the same tool that will do the leak down test? when i do a leak down test i have to make sure each cylinder is tdc? to add compressed air i suppose i have to get an air compressor

[cammed3800]

Warm the motor up to normal operating temperature.

Remove all spark plugs. Put transmission in neutral. Block wheels.
Remove the rocker arms of the cylinder to be checked.
i found this on google search, why is there 10 people telling me to do 10 different things with a tester?

[awesomeame]

removing the rocker arms totally negates the purpose of doing this.

a compression tester will not work for this purpose. go to an autoparts store & tell them you need the tool to do a leak down test. it has a gage some lines & some valves. the tool should come with some better instructions then what i can provide.

yes the cyl in question needs to be at TDC, on compression stroke, so both valves are closed.

you have to be in neutral & remove all the spark plugs so that you can manually turn over the engine with a socket & powerbar controllably. no need to block the wheels--just set your emergency brake "on."

do what i said before. if you're at tdc on the compression stroke, both valves should be closed...when you add compressed air at that point, listen to your exhaust, intake & oil dipstick hole. if you hear whistling at the exhaust or intake, you know your timing chain is not lined up, becase one (or both) of the valves are open at tdc, when they ought to be closed. if you hear whistling from your oil dipstick hole, then you have bad rings. i really doubt you have bad rings tho, seeing as you have bad compression on every cylinder....honestly i'd check your crank/cam timing before i bought the leak down tool...

--matt

[awesomeame]

& thanks white86six for pointing that out [img]smile.gif[/img]

i've only ever done these on cold engines btw...haven't had any problems.

--matt

[cammed3800]

honestly i'd check your crank/cam timing before i bought the leak down tool

sorry but what are the exact steps in doing this? when i had my pcm programmed the guy alsoe advanced the timing, hope that didnt mess anything up, i also have a caspers tps enhancer which is supposed to advance timing, maybe i should remove the tps?

[ December 03, 2003: Message edited by: cammed3800 ]</p>