Tapping noise, I'm stumped...

[JNErotten]

I have developed this tapping noise. It's totally happens randomly but when it does, it seams steady. It sounds like it's coming out from somewhere low. I made a make-shift hearing aid with a bolt and 1/4 inch tube and did not hear anything from the oil pan, valve covers, exhaust, or transmission. They all sound smooth (though my method is primitive). It really seams to be comeing from the transmission around the ring gear. Either way, any time it starts, if I give it gas in gear with my foot on the brake it goes away. I think it goes away on the road while acceling too. Sometimes it will do it in neutral and go away in drive. It dosen't seem to do it while cold though at all. I brought my timing up to 5 degrees to see if that would help to isolate the problem but i hear no difference. There isn't any meatal on my dip stick so im hopeing I haven't killed a bearing. I'm going to do an oil change and drop the pan so I can check the rods. And check the old oil for metal. Other that that, I'm not sure what else it could be. I'm wondering if one of the rod bolts have lossened 'casue this vehicle sat for like 4 years and then was run considerbly. I still have great oil pressure and runs good. i know my valve seals are gone and I have one bent pushrod. could that be makeing the noise?

Thanks In Advance,
J

[Joe's 89]

First thing I thought was collapsing valve lifter; your comment on having a bent push rod confirms it. Sounds like the pushrod has beaten your lifter into submission.

[JNErotten]

Ya know, that was my first thought too. But the noise just really sounds like it's comming from underneith. Who knows though, strange noises def do seem to travel. Would I be able to replace that by pulling my intake and valve covers? Aslo, can an old cam take a new lifter (same as tappet right)? I aslo noticed when I had my intake off, that six of my drivers side push rods had what seemed to be like a thin black carbon on them. Anyone know what would cause this? The rest were clean.

Thanks for the reply.
J

[ecjammer]

You said that your jeep was sitting for 4 years, and the noise goes away with your foot on the brake. with the increase of RPMs it seems like your lifters are bleeding down at lower RPMs. How many miles are on the cam? You could put new lifters on it, but I would look at how many miles, and the condition of the lobes. As for the 6 lifters with black carbon, look at the valve seals.One more idea on the noise, this may be far fetched, but how is your exhaust? Any loose connections? That's all I can think of.

[JNErotten]

My exhaust seems solid enough. When you say lifters, are you refering to the pushrods themselves, or the tappets? Lots of people have different names for different things and it helps me make sence of it if I am sure I know what your refering to.

Thanks,
J ;)

[Michael]

Lifters are the cylinder looking thinks that the pushrods sit on under the intake. It is very possible you have a sticking lifter which would not happen all the time. Mine does the same thing at times. I would say the best fix is new cam,lifters, timing chain set. That is if the noise is coming from there for sure. One way to check... The next time it does it take the valve covers off and see if any of the rocker arms are loose and then check and see if you have any up and down travel on the pushrod. And also spin them to see if one or more spin more free than others. Good luck... Just my .02. ;)

[porchpiggy]

Don't forget to check the heat riser, a common cause of a click or tap noise..just one of those easier things to eliminate. :cool:

[JNErotten]

Well. I have the oil pan off now, I notice that the rods that don't have much pressure on them have a slight and I do mean VERY slight play. Is it normal for the rod to have a slight (not even a millimeter) of slack on the bearing? Oh, and my heat riser is a-ok.

Thanks,
J