My Timing Chain Conundrum

[TriaxialBulls]

My 1994 FZJ80 with just 167k has quite a bad rattle, and I'm pretty sure it's coming from the timing chain. It has a steady RPM-correlated rattle that begins right around 1400RPM and finally stops around 3200RPM. Happens when the engine is cold, hot, whenever. When rebuilding my oil cooler, I found bits of plastic stuck in there, seemingly from the timing chain guides falling apart. I'm going to pull my lower pan on this upcoming oil change and look for more plastic pieces just to see how bad it really is. But basically I think that one or both of my guides is disintegrating (or, more likely, have already fallen apart) and this has caused a lack of tension on the chain, causing the rattle.

Unfortunately, I just am not able to tear it all apart and fix it right now, nor will I be for a couple years. My question is this: should I take the tensioner out (I think my 94 should have the ratcheting-type tensioner, right?) and re-set it so that it is providing more tension on the chain guides? Or should I just leave it to rattle? My fear is that if I re-tension it, it will just cause it to rub even more, and wear faster. On the other hand, having it rattling around isn't good either.

 

[Pin_Head]

The noise of a slack chain tends to change when revving up and down. The other thing that can rattle or knock in the front cover is the oil pump drive idler gear.. Sometimes this noise will go away when you remove the PS pump.

 

[TriaxialBulls]

The noise of a slack chain tends to change when revving up and down. The other thing that can rattle or knock in the front cover is the oil pump drive idler gear.. Sometimes this noise will go away when you remove the PS pump.

Interesting point about the gear, although the sound is correlated with RPM. It starts around 1400RPM, and then gets progressively more frequent until it eventually stops around 3200RPM.

 

[LINUS]

Slee’s site used to have a pic of how the chain guides loose their plastic sleeve & it slips down - it happens, most just never find plastic shards as it comes off whole from the metal arm & just “slides“ down a bit.

 

[TriaxialBulls]

Slee’s site used to have a pic of how the chain guides loose their plastic sleeve & it slips down - it happens, most just never find plastic shards as it comes off whole from the metal arm & just “slides“ down a bit.

So would that still be offering any protection, or would it be metal-on-metal contact?

 

[TriaxialBulls]

Anyone have any more advice? I'm going to be tearing a bunch of stuff apart to do the front main/oil pump cover seal within the next couple days and I have to decide if I want to re-set the tensioner while I'm in there.

 

[Kernal]

If you're thinking it's the timing chain tensioner, a new replacement part is only about $30. I took my original tensioner apart and cleaned it, put it back together, reinstalled, seemed to help quiet the short start up rattle. But then it sounds like you may have something else going on.

Other things to check while you're in there: water pump for noise or axial play
in the shaft, replace Tstat with OEM part, check alternator idler pulley, alternator bearings, AC belt tensioner pulley (bearing), replace belts. Fan clutch, check/modify as needed.

FWIW

 

[TriaxialBulls]

If you're thinking it's the timing chain tensioner, a new replacement part is only about $30. I took my original tensioner apart and cleaned it, put it back together, reinstalled, seemed to help quiet the short start up rattle. But then it sounds like you may have something else going on.

Other things to check while you're in there: water pump for noise or axial play
in the shaft, replace Tstat with OEM part, check alternator idler pulley, alternator bearings, AC belt tensioner pulley (bearing), replace belts. Fan clutch, check/modify as needed.

FWIW

I don't really think it's the tensioner, as mine has the ratcheting type (I believe) and there isn't a whole lot to go wrong there. Also if the tensioner was totally FUBAR, I'd expect more than just a rattle in a certain RPM range. I think the guides are just gone, and that extra clearance caused by their absence is what's causing a little play in the timing chain.

I'm replacing the water pump and thermostat, I'll check the bearings on the other parts of the accessory drive while I'm in there.

 

[ajax1]

You could pull the valve cover and use a borescooe to look at the guides or a small inspection mirror possibly

 

[TriaxialBulls]

You could pull the valve cover and use a borescooe to look at the guides or a small inspection mirror possibly

I thought about doing that, but it wouldn't really give me any actionable intel. If it is the timing chain, I am not able to fix it anyway, and if it isn't the timing chain, then I just spent all that time for almost no gain.

 

[1911garand]

I thought the engine was coming apart on my 1997. Ended up being just the AC and alternator tensioner / Idler pulley bearings.

Pull all the belts (alternator and AC) and start it up, how does it sound? The noise from the bad bearings travels into the front cover, I would have sworn the engine / timing components were fried - nope. It's worth a try. The bearings are very inexpensive and easy to replace as well.

Good Luck! YMMV

 

[BILT4ME]

Run a bore scope down through the oil fill hole on the front of the valve cover.

 

[TriaxialBulls]

I thought the engine was coming apart on my 1997. Ended up being just the AC and alternator tensioner / Idler pulley bearings.

Pull all the belts (alternator and AC) and start it up, how does it sound? The noise from the bad bearings travels into the front cover, I would have sworn the engine / timing components were fried - nope. It's worth a try. The bearings are very inexpensive and easy to replace as well.

Good Luck! YMMV

That's a good tip, I'll definitely check out the bearings on the stuff bolted to the timing cover. Although the plastic in the oil makes me strongly suspect the timnig chain guides.

Run a bore scope down through the oil fill hole on the front of the valve cover.

I just don't really see what that would get me? Even if I found an absolute smoking gun, that it is 100% the timing chain, I can't do anything about it.

 

[BILT4ME]

That's a good tip, I'll definitely check out the bearings on the stuff bolted to the timing cover. Although the plastic in the oil makes me strongly suspect the timnig chain guides.

I just don't really see what that would get me? Even if I found an absolute smoking gun, that it is 100% the timing chain, I can't do anything about it.

You can remove the timing chain cover without removing the head. You must remove both oil pans. Not an easy job, but it can be done in-frame.

CDan did it way back when. There have been a few timing chain failures and that's what prompted this possibility.

 

[TriaxialBulls]

You can remove the timing chain cover without removing the head. You must remove both oil pans. Not an easy job, but it can be done in-frame.

CDan did it way back when. There have been a few timing chain failures and that's what prompted this possibility.

I remember Dan also saying that it took about 27 hours of labor in total... I work on my truck in the street, so any job that’s gonna require it to be disassembled for more than 1 day is already pretty much out of the question. I have looked into it a lot and have watched OTRAMM’s YouTube videos on the job multiple times, and every time I watch them I get more dissuaded from doing the job in my conditions haha

 

[Wompom]

So... you're worried something catastrophic is going wrong with your timing chain.
You've been given advice to try to narrow down the source and pretty much ignored it since you don't think it'd gain you anything....
Why ask for advice?


If I were in your position i'd first follow @1911garand's advice and eliminate the bearing possibility.

Then i'd buy a $10 borescope on amazon and stuff it down the oil fill hole and make sure there wasn't disintegrating/slipping chain guides in there. This will at least validate that its a loose chain, and can be fixed.
If your tensioner isn't properly tensioning and the guides (you just inspected) are still good you can replace the tensioner easily and see what happens.
If you have an oil pressure driven tensioner you can also upgrade it to a ratcheting type (that wit's end carries) and see if that improves your situation.

My advice, listen to the guys above who have been on here forever who are giving you good advice, or don't bother asking.

 

[TriaxialBulls]

So... you're worried something catastrophic is going wrong with your timing chain.
You've been given advice to try to narrow down the source and pretty much ignored it since you don't think it'd gain you anything....
Why ask for advice?

I'm not sure if you read my original post or not, but I was never asking for advice on diagnosis or how to repair the timing chain. I am already thinking that the timing chain is the problem based on other things I've discovered. The post was asking a specific question concerning the timing chain tensioner.

If I were in your position i'd first follow @1911garand's advice and eliminate the bearing possibility.

I've already agreed that's a good idea.

Then i'd buy a $10 borescope on amazon and stuff it down the oil fill hole and make sure there wasn't disintegrating/slipping chain guides in there. This will at least validate that its a loose chain, and can be fixed.
If your tensioner isn't properly tensioning and the guides (you just inspected) are still good you can replace the tensioner easily and see what happens.
If you have an oil pressure driven tensioner you can also upgrade it to a ratcheting type (that wit's end carries) and see if that improves your situation.

My advice, listen to the guys above who have been on here forever who are giving you good advice, or don't bother asking.

I think I might have said this before, but there is absolutely no point to trying to diagnose a problem that I cannot act on. I could do all that and find that my timing chain is about to break and I still could do absolutely nothing about it. And if I'm just doing all that to inspect the tensioner, I could do that a lot easier by loosening 2 nuts on the side of the head and holding it in my hands.

Also, the 93-94 1FZ's came with a ratcheting tensioner from the factory, so there's nothing to upgrade to.

 

[Wompom]

I'm not sure if you read my original post or not, but I was never asking for advice on diagnosis or how to repair the timing chain. I am already thinking that the timing chain is the problem based on other things I've discovered. The post was asking a specific question concerning the timing chain tensioner.


I've already agreed that's a good idea.


I think I might have said this before, but there is absolutely no point to trying to diagnose a problem that I cannot act on. I could do all that and find that my timing chain is about to break and I still could do absolutely nothing about it. And if I'm just doing all that to inspect the tensioner, I could do that a lot easier by loosening 2 nuts on the side of the head and holding it in my hands.

Also, the 93-94 1FZ's came with a ratcheting tensioner from the factory, so there's nothing to upgrade to.

Wasn't trying to be a d*ck, just seems that you seem like you already know your answer.
I won't tell you what will happen if you tighten your tensioner as is because it's a gamble. If you're finding plastic bits, they're likely from the tensioner guides. If they're completely gone you'd have metal on metal contact which isn't ideal for fast moving parts. Guarantee the truck would probably run for a good while without the plastic guides, but if it were my truck and i wanted to be able to salvage the motor to rebuild i wouldn't drive it unless it was to get me home.

The point is, you can figure this out by properly inspecting the timing chain, tensioner, guides, etc. and then make an educated decision if YOU want to drive as is or wait til you can fix it. No one is going to tell you driving your truck with bad/disintegrating guides and cranked tensioner is a good idea.
If you inspect further you will figure out either:
A) guides are completely shot. Can't fix right now? make the decision to run the truck as is, or park it til you can fix it.
B) it's not the guides and is either a tensioner specific issue, or the sounds coming from somewhere else entirely.
C) the guides have slipped and it's not as big of a deal as you think.

It sounds like if you're willing to pull the pan you should want to fully diagnose the issue before rolling the dice.

 

[TriaxialBulls]

Wasn't trying to be a d*ck, just seems that you seem like you already know your answer.
I won't tell you what will happen if you tighten your tensioner as is because it's a gamble. If you're finding plastic bits, they're likely from the tensioner guides. If they're completely gone you'd have metal on metal contact which isn't ideal for fast moving parts. Guarantee the truck would probably run for a good while without the plastic guides, but if it were my truck and i wanted to be able to salvage the motor to rebuild i wouldn't drive it unless it was to get me home.

The point is, you can figure this out by properly inspecting the timing chain, tensioner, guides, etc. and then make an educated decision if YOU want to drive as is or wait til you can fix it. No one is going to tell you driving your truck with bad/disintegrating guides and cranked tensioner is a good idea.
If you inspect further you will figure out either:
A) guides are completely shot. Can't fix right now? make the decision to run the truck as is, or park it til you can fix it.
B) it's not the guides and is either a tensioner specific issue, or the sounds coming from somewhere else entirely.
C) the guides have slipped and it's not as big of a deal as you think.

It sounds like if you're willing to pull the pan you should want to fully diagnose the issue before rolling the dice.

My rig isn't my primary mode of transportation (it's actually not my secondary mode either), and I only put a couple thousand miles a year on it. It would suck if it eventually failed on me, but I do run 15w40 synthetic so even if it's metal-on-metal it should last me a couple years I think. At this point I think I've decided I'm going to replace the tensioner (it was only $30 for a new ratcheting one), install that and hope the noise goes away. I am planning on a total engine rebuild (or an LS swap, depends where I live) in a couple years anyway so it only has to last until then.