frag Posted August 12, 2007 Share Posted August 12, 2007 A few days ago I made a compression check on my engine to confirm I had a leaking valve in cyl no 2. While I did the check (around 8 revs of the engine for each cyl) I heard, each time and only once) a loud TACK! after the second or third rev. (like a sharp blow on a hard wood table with a steel ruler) It did it for each time and only once each time. Has anyone an idea of what this could be? All the plugs were removed during the check and I had the intake butterfly fully open. I was using a manual starting switch, so ignition and fuel were off. When I normaly start, it does'nt make the sound. Link to comment Share on other sites More sharing options...
nipper Posted August 12, 2007 Share Posted August 12, 2007 Could it have been the bad valve? A bad tooth on the flywheel? nipper Link to comment Share on other sites More sharing options...
frag Posted August 12, 2007 Author Share Posted August 12, 2007 Could it have been the bad valve? A bad tooth on the flywheel? nipper Thanks for the answer. Could it be a sticking valve instead of a burnt valve? The sound would be the valve closing suddenly after having stuck open for a fraction of a second? Is there a way to decide if it's a sticking valve or a bad valve? What is the best method to get a sticking valve unstuck? I have all the parts for the clutch and belt change and the valve repair, but If I could I would be very glad to not to have to remove and replace the head. I remember reading here about an instrument to look into the cylinder. Is this something not overly expensive? Thanks in advance for your answers. Link to comment Share on other sites More sharing options...
nipper Posted August 12, 2007 Share Posted August 12, 2007 Put a vacume gauge on the car and tell us what the needle is doing. DO a wet/dry compression test and show us the numbers. nipper Link to comment Share on other sites More sharing options...
frag Posted August 12, 2007 Author Share Posted August 12, 2007 Put a vacume gauge on the car and tell us what the needle is doing. DO a wet/dry compression test and show us the numbers. nipper Just found the vac gauge. Had been looking for it for days. Il trow it at the engine tomorrow. If by wet compression test you mean after having spayed oil into the cylinder, i've already done it. Cyl no 2 : dry = 120 psi; wet = 140 psi. All other cyl are 195 psi dry. I'l get back with the vac numbers tomorrow. Link to comment Share on other sites More sharing options...
nipper Posted August 12, 2007 Share Posted August 12, 2007 hrmmm do you have wet numbers for the others? nipper Link to comment Share on other sites More sharing options...
frag Posted August 14, 2007 Author Share Posted August 14, 2007 hrmmm do you have wet numbers for the others? nipper Here's a recap of all I know about the problem including the vac figures. Vaccum readings. 1) At idle, the needle vibrates about 1/2 inch Hg on each side of the 20 inches Hg mark. Not more than 1 inch Hg in all. 2) At around 2K, 2 1/2K rpm, the gauge shows 22 inches of mercury. when I let go of the throttle, the needle jumps to 25 inches Hg and comes back rapidly to 20. At those rpms (2K), the rapid fluctuation of the needle stops. Compression tests readings 1, 3 and 4 = 195 psi dry. 2 = 120 psi dry and 140 psi wet. Additionnal test When i disconnect the plug wires or the injector one by one, the rpm slows for every cylinders, but the effect is less at cyl no 2. EXTERNAL SYMPTOMS THAT LED ME TO INVESTIGATE 1)The car drives perfect except for a medium but very distinct shake (when I look at the external mirror at idle I see it shake and I feel the shake thru the seat of my pants) at idle rpm (700). That doe'nt throw a misfire code. 2) At higher idle rpm (750-800) the shake subsides almost completely. 3) At idle I distincly can hear and feel (at the tailpipe) a very audible put, put, put that sound like a miss About the wet numbers for the other cylinders (those at 195 psi) What do you have in mind ? Just would like to know what I'm doing before removing all the plugs again. Thanks. Link to comment Share on other sites More sharing options...
nipper Posted August 14, 2007 Share Posted August 14, 2007 actually 195 sounds high, as it should be 180. Wet vs dry will tell us the condition of the engine rings. http://www.secondchancegarage.com/public/186.cfm How old are the plugs? nipper Link to comment Share on other sites More sharing options...
frag Posted August 14, 2007 Author Share Posted August 14, 2007 actually 195 sounds high, as it should be 180. Wet vs dry will tell us the condition of the engine rings. http://www.secondchancegarage.com/public/186.cfm How old are the plugs? nipper When I made the compression test, the plugs were all of a light tan color and the gap was at .045 just one mil out of specs (Ngk iridium) About the wet test on cyls no 1, 3 and 4. Just the fact that they are à 195 dry and that this is high, is that not proof the rings are good ? Just want to understand what and why I doing things. Maybe the fact that I reved the engine until the compression would not go any higher ( 8 to 10 revs IIRC) is responsible for the high figure. I think I remember having read somewhere that one should no go over 4 revs of the engine to have a significant compression reading. Is that so? Link to comment Share on other sites More sharing options...
nipper Posted August 14, 2007 Share Posted August 14, 2007 That would do it. Also too high a reading can indicate a jumped timing belt. I am getting more and more convinced that you have a valve issue and not a HG issue. nipper Link to comment Share on other sites More sharing options...
frag Posted August 14, 2007 Author Share Posted August 14, 2007 That would do it. I am getting more and more convinced that you have a valve issue and not a HG issue. nipper[\quote] That's also what I think. Is there a way of distinguishing between a bunt valve and a sticking valve beside lookin into the cyl thru the plug hole with a special instrument? I've already added some special cleaner to the oil to try unsticking it whitout any effect. Also too high a reading can indicate a jumped timing belt. [nipper[\quote] Would'nt it cause some drivablility problems other than a shake at idle? It starts, cruise and accelerate perfectly even from a low speed. The fuel milage is also good. Link to comment Share on other sites More sharing options...
frag Posted August 15, 2007 Author Share Posted August 15, 2007 Anyone knows the answers to the questions asked in my last post? Link to comment Share on other sites More sharing options...
nipper Posted August 15, 2007 Share Posted August 15, 2007 If your not overheating its a valve. My guess is that its burnt. nipper Link to comment Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now