Author	[Modern View]
wjkrostek 07-31-2012 13:37:08 216.137.195.243 Report to Moderator	I was working on a 4 cylinder engine and thought I would use compressed air in the spark plug hole to check the valves and rings for problems. I've done this before long ago but not on a 4 cylinder. So I made up a hose on a compression gage but no cylinder has the valves closed when it on the bottom. The question is is that true on all 4 cylinder engines? that a valve always opens before it hits bottom? I'm getting old and it may be all 4 cylinder engines have to be made this way and I just can't wrap my head around it so I thought I'd ask. And I can't remember if I did this on a 6 or 8 cylinder but it works. you will hear the air coming out where ever the problems are. leaky valves or bad rings will show up but I was hoping to check for a bad head seal. [Reply]   [No Email]
Indiana Ken 07-31-2012 15:57:46 66.249.232.45 Report to Moderator	Re: 4 cylinder question in reply to wjkrostek, 07-31-2012 13:37:08   It is not un-common for the exhaust valve to open BBDC (before bottom dead center) on the exhaust stroke and for the intake to close ABDC on the intake stroke. This has to do with the cam timing/duration and has nothing to do with the number of cylinders. For leak down testing you can position the engine at TDC on the power stroke or remove the push rods as another posted suggested.   [Reply]  [No Email]
ANON 07-31-2012 15:18:43 69.248.113.235 Report to Moderator	Re: 4 cylinder question in reply to wjkrostek, 07-31-2012 13:37:08   Did you remove the pushrods so the valves stay closed?   [Reply]  [No Email]
wjkrostek 07-31-2012 18:41:41 216.137.195.243 Report to Moderator	Re: 4 cylinder question in reply to ANON, 07-31-2012 15:18:43   no didn't but for some reason I figured that the valves would be closed at the bottom of the power stroke. what I did was put the air to it and turned the engine backwards to close the valves. I couldn't hold them closed. to much air. How is the best way to check for a bad head gasket. I tried the tdc idea but I couldn't keep her from turning. for some reason number 3 isn't burning right. The other three are nice. I'll change the wires and see if that will help.   [Reply]  [No Email]
CTucker 08-04-2012 15:10:49 64.196.47.4 Report to Moderator	Re: 4 cylinder question in reply to wjkrostek, 07-31-2012 18:41:41   If you lock the brakes and put it in first gear, the engine won't turn with air pressure on one piston.   [Reply]  [No Email]