97 TJ unknown engine noise

[Quad City Jeep]

I have a new noise that started just the other day. I have a video where you can hear it:


The rhythmic ticking you hear throughout the video is what I'm talking about. I could not locate it's origin. Sound like anything anyone has heard?

 

[waynepope66]

Sounds like the clutch on the a/c pump hard to tell

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[Quad City Jeep]

No A/C on this Jeep. Thanks.

 

[Quad City Jeep]

Would a bad fan clutch make this noise?

 

[IronCity]

I'm no mechanic but it looks like the crank pulley is shaking a bit


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[RaymondT]

Sounds (and looks) like the belt shifting on the smooth surface of the fan pulley as the sideways tension builds up. A small shot of silicone spray on the smooth side of the belt would confirm this. Maybe an imperfection in the belt or a slight pulley misalignment.

 

[Quad City Jeep]

Great thought. I'll check that out. Thanks.

 

[Chris]

I agree with @RaymondT.

It could also be a bad bearing in the alternator pulley, AC pulley, or even a tensioner pulley. However, when one of my bearings went bad there it was howling.

 

[Quad City Jeep]

Thanks - I'm going to check the pulleys and see if that is it. Hopefully, because on another board they thought it was the timing belt.

 

[Chris]

Thanks - I'm going to check the pulleys and see if that is it. Hopefully, because on another board they thought it was the timing belt.

Timing belt... There is no timing belt on the 4.0.

Maybe they meant serpentine belt? Which if that is the case, that's a very cheap and very easy fix! It should be done as preventative maintenance anyways.

 

[Quad City Jeep]

I have the 2.5

 

[Quad City Jeep]

...and I mistyped...meant timing chain

 

[Chris]

A timing chain could cause a noise, no doubt. However, most timing chains are meant to last the life of the engine (meaning a lot of them will make it to 300k without issue).

How many miles are on the engine?

 

[RaymondT]

I've been thinking, maybe it's a 4-cyl thing. Our 4-bangers don't have a spring-loaded belt tensioner. Since it's gotten below freezing in the last month, mine sounds like two chipmunks doing the nasty under my hood when I start it up cold. I'm thinking the belt might have gotten tighter with the cold weather. I have a Burroughs gauge and when you set the belt tension to factory spec, it is very taunt. More so than any modern vehicle.

I might just loosen it off a little.

 

[Quad City Jeep]

A timing chain could cause a noise, no doubt. However, most timing chains are meant to last the life of the engine (meaning a lot of them will make it to 300k without issue).

How many miles are on the engine?

I've got 140,000 miles on it

 

[Quad City Jeep]

I've been thinking, maybe it's a 4-cyl thing. Our 4-bangers don't have a spring-loaded belt tensioner. Since it's gotten below freezing in the last month, mine sounds like two chipmunks doing the nasty under my hood when I start it up cold. I'm thinking the belt might have gotten tighter with the cold weather. I have a Burroughs gauge and when you set the belt tension to factory spec, it is very taunt. More so than any modern vehicle.

View attachment 8564

I might just loosen it off a little.

I think you might have nailed it. It was near zero here in Iowa recently. Now that it is warmed up (near 50 today) I don't hear it, so guess I'll write it off as no big deal unless I hear it again, and I'll check that tension on the belt anyway. Thanks.

 

[Ryan Thomas]

I think you might have nailed it. It was near zero here in Iowa recently. Now that it is warmed up (near 50 today) I don't hear it, so guess I'll write it off as no big deal unless I hear it again, and I'll check that tension on the belt anyway. Thanks.

I would bet you a nickel that its the idler pulley or the tensioner pulley if it is making the chipmunk sexytime noises... Easy to replace, and cheap! My idler did the exact same thing. I could actually wiggle it slightly, which is what verified it for me.

 

[Fire41fighter]

It also may be the power steering pump, especially since it happens when cold. You can do the old school mechanic trick and put a screw driver on the metal and put your ear to the handle of the screw driver to help locate the noise. Or get an engine stethoscope...really handy for localizing mystery noises. If you do the screwdriver routine...don't get your beard caught in anything moving...that's a mistake you make only once!

 

[Chris]

I think you might have nailed it. It was near zero here in Iowa recently. Now that it is warmed up (near 50 today) I don't hear it, so guess I'll write it off as no big deal unless I hear it again, and I'll check that tension on the belt anyway. Thanks.

X2. Probably just the cold weather.

When I start my 4.0 up (it has 80k miles) when it's really cold out, it ticks like crazy for about 30-45 seconds. Then it goes away and never comes back. It's done that since I got it, but it's pretty normal for 4.0s I hear.

 

[Fire41fighter]

One of the things I do with my older engines (67 Mustang, 48 Farmall tractor) and my wifes 98 TJ is that I substitute a quart of oil with Rislone ZDDP supplement, marketed as Rislone 3x Concentrated Engine Oil Supplement (not the standard Rislone). It has zink and phosphorus in it that quiets old lifters and valves. Modern oil removed those additives that the older or high milage engines like. I notice a difference in the valve tappet noise immediately. It also keeps the engine cleaner and reduces the sludge buildup. I swear by the stuff and used it on my race engines too.