Sorry guys, I searched the archive but couldn't find anything :confused:

Anyway, I dont' want to take the valve covers off, but I can turn the crank hub with my pry bar. I have an air compressor too.

What else do I need and what do I look for? i.e. results?

 

I just did a compression check with check and watched the gauge for any pressure drop as well as noting how it "pumped up" to final pressure.

To do it with compressed air you need to know when the valves are closed. So I think you would need to pull the valve covers.

I am able to turn my crank with an 18" breaker bar on the hub with all spark plugs and the serpentine removed.

 

What kind of gauge can I use? Is there a gauge I can pickup somewhere that goes inline to my air hose or something?

I would guess you can verify pressure simply by putting the gauge on and turning the crank until pressure builds up. Is it absolutely necessary to have the piston at or relatively near TDC?

 

What you need is a differential pressure gauge that measures the pressure drop in the cylinder by measuring the input pressure (usually 80 psig)and cylinder pressure. Any cyliner that has no more than 10 psig differential pressure is okay. Any more than that and you have either a valve or ring problem. Incidently these gauges are quite common in small airplane maintenance . One other thing this gauge comes in handy for applying pressure to the cylinder for valve seal replacement. It allows one to gradually apply pressure so that you don't inadvertantly turn the engine over if the piston is not exactly on TDC.

 

Do any of the major tool companies offer this? Where can I buy one?

Thanks for your help :cheers:

 

I bought mine from an aircraft supply house that caters to home builders but It's been too long ago to remember which one. (starting to suffer fron CRS in my old age). You might want check the internet.

 

To do a leakdown test the valves need to be closed, The quickest way to do that is to remove the rockers.

BTW, here's why. If you don't have the piston exactly at TDC when you presurize the cylinder you are going to kick that piston down to the bottom of it's stroke. Now if the rockers are removed the valves will still be closed when it reaches the bottom of it's stroke and the reading will still be fairly accurate.

If the rockers are still installed the valves will open as the cylinder kicks down to the bottom, and then you're gonna have like 100% leakdown.

Yeah it, sucks but I think you're really gonna have to remove the valve covers.


[Modified by Nathan Plemons, 4:08 PM 9/17/2003]

 

I prefer taking out the spark plug, and then turning on the hub until you build up pressure. I don't see why I should have to take the valve covers off.

Making sure the valves are closed is easy, checking for TDC is the hard part.

 

Why not measure the harmonic balancer diameter, then get a piece of tape, and mark TDC for every cylinder.

It seems like you'd be within a degree or so of TDC on every cylinder that way.

Or... Just put the car in gear when you think you've got TDC. The engine won't move then!

Just a thought. :seeya

 

Will something like this work? It's only $60
http://www.chiefaircraft.com/cgi-bin...ionTester.html

I was thinking about seeing if Autozone has one for rent. I know MacTools has one specifically for cars, but I don't feel like spending $120.

 

Snap on Part # mt324 I paid more than $60 though (don't remember how much)

 

:yesnod: You'd have to have a pretty loose engine to push the piston back to the bottom of the bore!

 

I don't think I have to worry about 80 or so psi turning the motor over no matter what.....all I have to do is put in gear and pull the emergency brake.

Just like when you torque the balancer down :yesnod: