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W5KVV 04-19-2014 10:39 PM

My poor 2.5 isn't happy
Guys, have a listen to my poor old 4 banger. It started making this hellacious squeal Monday. At first it was intermittent, but now it's there all the time & getting louder. I don't think she has many miles left in her.

At first, I thought it was a bad idler pulley or water pump bearing or maybe my new HO alternator. So I took the belt off to rule out something internal, but no dice. Even with the belt off it's still there. It's loudest right in the middle of the head around the intake/exhaust manifolds.

Any ideas? I figure it's a bearing fixing to seize, maybe a cam bearing?

NonRubicon 04-20-2014 12:35 AM

Sweet Jesus, those angry squirrels have gone rabid.

First thing I think of when I hear a squeal or whistle around the exhaust/intake manifold area is either loose manifold bolts, bad manifold gaskets, or even a cracked intake manifold. That the squeal briefly drops out right when you open up the throttle also makes me think intake leak. Still kind of hard to diagnose in a video.

If you haven't already, take the long cardboard tube center from a paper towel roll and use it as a redneck stethoscope to better narrow down the location. The tube will help focus the sound better and sometimes can point you directly to the problem without even turning a wrench. High pitched squeals and whistles can be deceiving as to where they originate.

Once you've verified the location of the noise and if it sounds like it is coming from the intake manifold area or the where the manifold mounts to the block, check for intake leaks. Don't forget about the underside of the intake manifold - cracks can hide here out of sight.

Just be careful of any moving engine parts when using the redneck stethoscope.

W5KVV 04-20-2014 02:11 AM

Great observation NR, I'm suspicious that the noise very well could be a vacuum leak. It won't make this racket under load when there is no vacuum, only at idle. It'll do it if I go up in RPM's VERY slowly with no load. (neutral).

I did take a can of carb cleaner to the intake while it was running, listening for a change in RPM. Nothing so far, but I will take another look at it. Let's hope that's all it is. I'm preparing for the worst tho.

It should be noted, the Jeep still runs like a top. No issues at all other than the noise. We drove it 100 miles today, ran great & got fairly good gas mileage.

EDIT: Usually takes 5 min for the noise to appear from a cold start. Pretty much once it come up to operating temp.

NonRubicon 04-20-2014 02:07 PM

Listen all around the engine using the cardboard tube trick, even in areas where you don't think the sound is coming from. This will help you narrow down where it is the loudest by ruling out where it isn't the loudest. Listen to the distributor, the head/valve cover, timing chain area, the intake manifold, the throttle body. Anywhere that has moving parts or where intake/vacuum leaks can potentially occur.

Also check for any codes for additional clues.

W5KVV 04-23-2014 01:01 AM

No codes, but I'm not surprised. Just my luck. At any rate I let the engine get good & hot & went to town with carb cleaner around the intake. Sure enough it started stumbling When I soaked the rear runners of the intake.

Long story short one of the intake bolts had backed off & a vacuum leak was the culprit. Snugged it back down & all is well. Thank goodness. Sure sounded like metal on metal from under the hood.

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