Timing Chain...help!

[BadMojo]

I posted a bit about this on the General Forum, but wanted to get a bit more in depth. This seems like the right place to do it.

I've been hearing an arrythmic tapping sound on startup while idling. This seems to happen more often on a cold engine. The noise comes from the front of the engine, right underneath the valve cover. I can't hear anything lower in the engine.

This definitely sounds timing chain related...

1) Could it just be the upper tensioner or the now useless upper chain guide? If it's the guide, is removal of the guide just removing the symptom and not the problem?

2) Could it be a bad tensioner? If so, is the fix simply replacing the part?

3) Should I look in to having the timing chain and all associated parts replaced?

4) If we're doing the total replacement, is there any other kind of preventative maintenance that should be done while we're in there?

Thanks!

[jam149]

Chances are, the tensioner has worn out. If you are going to pull it apart to replace the tensioner, tho - you might as well replace the chain itself.Courtesy Nissan sells the chain and tensioner. You can go in and remove the guide while you are at it.It's not a hard job. You have to remove the valve cover, and the upper front cover only. Mark things well. (you can learn from my mistakes: <http://www.negative-camber.org/jam149/240cams.html>

[jivehonky]

i just got done fixing my '91. the upper chain guide had broken off and was just sitting on top of the timing chain. she sounds fine now!and it only took 15 minutes!pull the cover off and take a look at the upper chain guide.

[BadMojo]

i just got done fixing my '91. the upper chain guide had broken off and was just sitting on top of the timing chain. she sounds fine now!and it only took 15 minutes!pull the cover off and take a look at the upper chain guide.

I'll definitely check on the chain guide, but this concerns me a bit. If the chain is hitting the guide, it seems like there could be other causes. The cracked guide may just be a symptom.

I'm thinking it's just a bad tensioner as mentioned above, but I suppose it could be low oil pressure due a failing oil pump. That would suck.

I'm gonna have Nissan do as much diagnostic stuff as they can for cheap, then do as much of the work as I can. I hope my FSM comes in soon...

[DAEDALUS]

I think the reason the guide is there is to keep the chain from flopping around. I totally agree you might need to replace a weak tensioner, and that this would probably help quiet things down, but some play in the chain was always assumed. When you check the oil pressure make sure the car is warmed up to normal operating temps, and check it at various RPMs.

[jivehonky]

the chain is tight when the car is not running. when the car is sitting at idle i can still hear a little tap/squeak noise coming from the timing chain area. maybe becasue of low oil pressure? how do you check oil perssure?i'll i have is a darn dummy light.or is the a normal noise for a rebuilt moter?are there any other guides the might have be rubbing other then the top one?any input would be helpful, thanks.

[jam149]

There are 2 guides. One directly on top, and one along the side, opposite the tensioner.

The chain may appear tight after the car is off and you check. My tensioner, though, even tho tight when I opened the motor, could EASILY be pushed back. With the new tensioner, it was VERY hard to push back to get the holding pin in.