Help identifying this timing belt noise?

[TajMan]

Finally, back to my '91 Talon project I've had waiting to be finished for YEARS literally.



I recently had an issue with a noise, kind of a rapping/tapping noise that got louder as the engine warmed up. [BAD serious once engine was warmed up] I had thought it was the cylinder head I had just done (second one I had recently put on this engine), I was way bummed about that.

Then I found something new, as the engine was running making this noise- if I used a prybar to put pressure directly on the bolt which mounts the timing belt tensioneer pulley... the sound would go away!
From this, deduced that the new tensioneer pulley bearing was probably bad (that part was only 1,000 miles used, but was re-used after car suffered that last bad overheat and warped cyl head. hmm)

I just installed another new timing belt tensioneer pulley, as well as a new hydraulic tensioneer this time! Started the car to check (before I even have the crank pulley fully assembled and the accessory/water pump belts installed).
PROBLEM: new squeaking/rubbing sound which increases with RPMs. I noticed immediately, turned off engine, and saw that there was a slight film of residue kind of waxy/greasy/plasitc-residue immediately building up on the engine-side edge of the timing idler pulley. Also that (outer engine-side) edge of the timing belt looked slightly lighter now like the belt IS rubbing against something.

You Tube

You Tube

You can wipe residue right off idler pulley with finger, but start the engine again for only seconds and re-check, residue is built right back up in a ring around that edge of the pulley.

I can NOT figure out where it could be rubbing or whats going on here.
(the outer main crankshaft pulley not being installed yet with the accessory belts couldn't have this effect could it?)

[TajMan]

Balance shafts & belts eliminated, also running no timing belt cover..

[90BLACKAWDTSI]

I can't really hear anything but the belt whining from being a little too tight.

What I do hear though is that motor is low in compression somewhere. May not be timed correctly or whatever but it is low.

[TSi4G63T]

Just a little fyi. That new tensioner doesnt look oem. I also just put a new head on my car and tried to use a parts store tensioner to save time/money. It failed before the engine was ever started. It would let the tensioner pulley bounce as the engine was turned over by hand. YMMV

[TajMan]

Yeah its a Cloyes or whatever brand tensioneer, better than the gates brand for less (O'Reily auto parts), this one has a $183 msrp. Better than the stock '91 98K mile tensioneer I re-used last time and never replaced yet.. I wasn't sure what was making rapping sound, decided to replace the bearing again AND the hydraulic tensioneer.


You really think that whining is just from belt being too tight? ok
maybe too tight belt is causing that residue to deposit on the idler.. yeah this is making sense... kind of rubbing off dirt/material from that edge of belt onto pulley..

But motor low on compression....
Engine internals are good, but I hate the timing marks on these engines (like down on the crank timing gear when the main crank pulley is off). Always looks like its 1/2 a tooth off, but if you try to move a belt/pulley one tooth different it just ends up being MORE off if anything. any suggestions about timing belt alignment?

The other thing to note, is I'm still on a all stock fuel system- except for an aftermarket fuel pressure regulator right now. Because of this, car has to crank longer at first to start because fuel pressure is building.. maybe this is 'low compression' sound you think you are hearing

I have both of the factory mitsubishi timing belt tools (the threaded rod, and the piece that turns the tensioneer pulley itself with a socket wrench)...

[TSi4G63T]

When i did my timing i had to set my exhaust cam half a tooth off and after being rotated it would be perfect. I think this is documented somewhere?

[MuffinMan7580]

When you string the belt, make sure you have ALL the slack on the tensioner side of the belt. Make sure you pull the belt tight before going over the intake cam gear. I usually end up using a wrench to turn the exhaust cam to line up perfectly, and then a tid bit more so the belt goes on without any struggle. If you can't get it lined up (there is no less than perfect or "close enough"), do a search here or on google for ways to check if everything's where it's supposed to be before you begin stringing the belt.

[TajMan]

but you obviously realize milling cylinder heads down is going to slightly effect alignment between cam gears and crank gear..
I'm no mitsu timing newb, 4G63's and 6G72's, and I'm still claiming like 1/4 tooth off as unavoidable...
but I'll try to re-do now and see how much better I can get it (and with the tension correct).

[MuffinMan7580]

Originally Posted by TajMan

but you obviously realize milling cylinder heads down is going to slightly effect alignment between cam gears and crank gear..
I'm no mitsu timing newb, 4G63's and 6G72's, and I'm still claiming like 1/4 tooth off as unavoidable...
but I'll try to re-do now and see how much better I can get it (and with the tension correct).

You had not mentioned that you had the head milled.

[TajMan]

2nd head I have ported so far for my engine...
yeah it has been milled, most likely more than once..
Shame that my engine had under 100K orig. miles, but this head I had to use now probably has twice that mileage total in its life.

[TajMan]

timing belt tensioned correctly, still almost the same noise, still seems to be leaving a slight ring/residue on that pulley.
I'm pretty stumped, but I'm also to the point I think its mostly ok and I ready to finish installing and run the engine to at least warm up, etc - see if things change at all.

Yeah I know my timing is on correctly, maybe the crank pulley mark only appears slightly like less than 1/8th of a tooth off..