Noise from the distributor cap

[thoughtpolice]

I am experiencing a strange buzzing/grinding type of noise that i can feel vibrations coming from the distributor cap. It isnt a constant noise, but it is more prevalent when the truck is first started then after a while it almost goes away. The noise is hard to describe but it is kinda like an buzzer from an old new york apartment noise.Deinitely "buzzy". The noise comes in bursts, is not constant. Truck is a 89 k2500 with a 350. The cap is not loose.

[JaVeRo]

I had that happen on a 2001 s10 4.3L. I have never heard of it happening on a 350 but it could.

The problem was the bushings worn leaving too much slack on the distributor shaft. The housing on it was plastic and not too expensive to replace the whole thing. I have never pulled one on the newer 350 but I have been told that those two motors are cousins.

James

[thoughtpolice]

Originally Posted by JaVeRo

I had that happen on a 2001 s10 4.3L. I have never heard of it happening on a 350 but it could.

The problem was the bushings worn leaving too much slack on the distributor shaft. The housing on it was plastic and not too expensive to replace the whole thing. I have never pulled one on the newer 350 but I have been told that those two motors are cousins.

James

When I roll into autozone what exact part should i be asking for?

[2000CAYukon]

If you pull the dist cap, can you move the dist shaft side to side. If you feel it move, then the upper shaft bushing is worn. I am not aware of a replacement bushing so you will probably need to get a replacement dist.

On your 89, the housing is not plastic.

//2000CAYukon

[silicon212]

My actual guess might be something like a rotor not fully pressed onto the shaft. These distributors have a pressed-on rotor, much like Ford/Chrysler etc., unlike earlier GM distributors where the rotor was screwed onto a weight plate on the top of the shaft. It is very easy to miss fully pushing the rotor onto the shaft, and when this happens, you will get noise and a vibration on the cap.

[thoughtpolice]

OK The noise will go away if I press against the cap very hard on the passenger side torwards the driver side. But it comes back after a few seconds.....Does this give any helpful info?

[silicon212]

Originally Posted by thoughtpolice

OK The noise will go away if I press against the cap very hard on the passenger side torwards the driver side. But it comes back after a few seconds.....Does this give any helpful info?

Either the cap itself is not fully seated, or it is the rotor. It could be the bushing shaft as well.

[thoughtpolice]

Is it ok to drive the truck to the store to get some parts or no?

[silicon212]

Just pull the cap off and make sure the rotor is fully seated, and then make sure the cap is properly seated when you put it back on.

[thoughtpolice]

OK I removed the cap. The rotor apeared to be tight, but the whole shaft has a bit of play and looks kinda shady. I can wobble it a good 1/8". Do i need to replace the whole distributor?

[silicon212]

I'd say so. That would be the upper bushing, new distributor time.