When doing leak-down test how much pressure

[Rolm]

I want to do a leak-down test on one of the cylinder that have a 30-psi. How much pressure should I pump in the cylinder.

Is this the metod

bring piston up to tdc on compression stroke and then compress the sick piston and then listen, if air comes out of crank case then the rings are shot, if air comes out of exhaust then the exhaust valve is shot, if air comes out of the intake then the intake valve is shot. I hope I can rent a compressor or can I use a propane tank as a pressure device.

[Guest Albert]

Also remove the rad cap too,and check for bubbles ther, you may have a problem trying to keep the motor from turning off TDC.

[Guest imported_PackardV8]

First things first. Check valve clearence or for sticking valve on the offending cylinder. Otherwise, if u only have 30 pounds of compression then the head will have to come off anyway even if the rings are bad.

For leakage test i prefer to rig up a hose and spark plug hole adapter and blow thru the offending cylinder wit h lung power and later with some compressed air at say 20 pounds continuous pressure and then listen and look for air or bubbles. I also light a cigarrette and blow smoke thru if the leak is bad enuf and at 30 pounds i'm guessing u'll see smoke fast from somewher. Don't forget to set the parking brake or use some other suitable method to keep the car from jumping and the engine from turning when the higher air pressure is applied.

[Rolm]

Thank you for the info, I also found the following site, great info

http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/index.html

[Rolm]

I do have a nice set of tools and I also have an electric impact wrench with has served me well over the years. The one thing I do not have is an air compresor. What do you think if I were to use an inflated tire as a compressed air source. I was thinking of inflating a tire around 40psi and using that.

[Rolm]

Well I used tire pressure to do the leak test and sure enough I could hear the air come from the crank case at a pretty go rate. It's amazing what one can do by improvising. I wish I had done this before I rip off the head hopping the low 30-psi was a burt valve. The leak test would have saved me 12 hours of work. I guess I learned a lot. Thanks for all your support.

[Guest Albert]

I have changed those motors in under 6 hours in the GMs, have you checked at Standard autowreakers or Jones at Victoria Park and the Danforth? there is a place out here that is around $200 for a motor or less a friend picked up a toyota motor complete for $100..

[Rolm]

Thanks for the info. I would not want to attemt a motor swap. I will ask around and see what it will cost for a used installed price