Lesabre rattling noise

For over a year this car used to make a noise that was a mix of a sound of rattling and chattering. It did this at 2 different situations. When coming to a normal stop only when almost fully stopped. If you took your foot of the brake it would go away. AND. When you started taking off from a dead stop. If you took your foot off the gas it would go away. After getting up to speeds around 5 - 10 mph it would be gone. If took off slow it would not make a noise.

It stopped doing this a couple weeks ago. Now it’s making a rattling noise coming from the front of the engine. I took the belt off to check all the pulleys. They all are solid.

The exhaust is solid. A friend of mine is picking me up to do some drinking tonight. I believe he has a stethoscope. I will ask him to bring it along to do a quick listen to see if I can better pin point from where it’s coming from.

It is very quite when in neutral louder when in gear. Especially is sitting still in gear.

What year model is this?

And what makes you sure the exhaust is “solid” ? This sure sounds like a loose heat shield or something along those lines.

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“Solid” may not be the problem… Too close might be. The exhaust moves around when the engine rocks. If the exhaust, especially a heat shield is close to something on the car a rattle can occur.

Putting the car on a lift and shifting through the gears might expose what is touching.

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Could be a loose/broken motor mount allowing engine to flex the exhaust making it hit chassis

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+1 for above reply’s

When you did this, did you start the engine to see if the noise was still there or not??

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+1
When it was a couple of years old, my father’s '63 Plymouth began emitting a strange rattling noise underneath the car when it was idling. Our mechanic found that there was insufficient clearance between the e-brake cable and the exhaust pipe, due to a slight bit of slack in the cable. A simple adjustment eliminated the noise.

It’s a 98. I originally thought exhaust. I drove up the ramps and seen nothing wrong. It was my first thought because this began the second I dropped the gas tank. Having to drop the muffler to get the pipe out of the way.

So then that noise before this was also exhaust perhaps.

As for the heat shield. That has been removed a while ago as it was practically falling off.

Some shops will give a free estimate for a quick check. I’ll have to do that.

No I did not try running w no belt. Good idea. Will do.

Thank you Davesmopar. I ran w belt off not a noise at all. Put back on had the noise back. At least now I know it’s not in the motor.

The alternator has no slop but when I turn it it does make a bit of noise. It is charging good. At 14.40.

Did you spin all the pulleys by hand?

Did any of them feel rough?

what about the belt and tensioner?

Sometimes belts can make weird noises

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I’m going with a failing belt tensioner. I’ve been there and done that with the rattle.

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A failing bearing if still intact will not effect charging, if you have an impact or high speed drill and you can spin the alt pulley with it somehow, you can hear what the alt sounds like while spinning fast…

Like already mentioned by others, spin all your pulleys, but also put some side load pressure on the pulleys while spinning them, to see if they feel rough…

The belt tensioner if bad is a little more involved than your normal run of the mill serp belt tensioner (coolant passages)… But yes a belt and or tensioner can make some noise, especially if the tensioner is jumping…

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+1
The brake relationship you first noted could be an important clue. When stopped in D. brakes on, that puts a significant twisting force on the engine and transmission. If the engine or transmission mounts were beginning to fail, that twisting force could cause something to interfere. Suggest to ask your shop to access the condition of the mounts.

Yes by hand. None turned rough but the alternator did make a slight noise.

Also check your harmonic balancer (vibration damper) to make sure it is not coming apart or wobbling…

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My friend put a stethoscope on it while I had it in drive. He said it sounded loaders on the alternator.

At least those are easy to replace on your vehicle… Can you swap the one from your spare car to confirm??

It’s not the exhaust. I put on the ramps and blocked the back tires and put it in gear. With heavy gloves I grabbed the exhaust and nothing took the noise away.

I swapped the tensioner pulley still had the noise. I again removed the belt and the noise was gone. It does get a bit louder when I turn on the air conditioning. Im guessing either that or the alternator. The alternators are different so I can’t swap that.

As for the belt why would they design a belt that a engine mount would need to be removed to change a belt?

In gear at a idle makes it louder and the air conditioner increases it even more. And the noise is continues forever at a idle.

With time the bad pulley should start to show better.

With the rattle the tensioner pulley isn’t the issue. I’ll admit that I haven’t messed with it on a '98 LeSabre, but the rattling issue would be with a weak spring in the auto-tensioner body.

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I have no help on the problem, but I do think it’s a good French/automotive pun, ‘Lesabre rattling’.

How about this for a worn out Rabbit: ‘Golf shot’?

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