M998 rattling noise was not my fan clutch.....dang

[kane2018]

Thanks for checking out my thread. Looking for information on the rattling noise on my 998. Its an original 89 6.2 truck. Been driving it a year and a rattling noise has gotten worse. It seemed to be the fan clutch as it was only really noisy at 50 to 55.

Then hitting 50 got noisy also. Its noticeable at idle sitting but not terrible. It definitely is coming from the front of the engine area and not the alternator bearing.

A ex military 998 mechanic suggested the belts, saw on SS that 998s had a lot of slack anyway, Did tighten up the alternator more but did not help.

Putting the fan clutch on in the field sort of, was a pain. Any thoughts are welcome.

 

[simp5782]

You need to use a socket extension and place it on different parts of the engine/body. To try to isolate a location.

You may put a prybar on the engine and pry it to put it in a bind to see if its actually the motor or body.

Does it happen at idle while cold starting? or does it take a minute to start after being warm?

Checked your water pump pulley? Could be a bad bearing on the impeller.

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[NDT]

Welcome to the forum. Does your truck make the rattle if you rev the engine in neutral? If so, remove all the belts to eliminate engine accessories.

 

[gcbennet]

There's all sorts of things that can cause noise up front. Heat shields can rattle, the oil dipstick tube where it secures to the manifold can come loose or snap and vibrate, loose brackets, the fan blades can rub on the shroud, etc. I had a nasty phantom rattle once and it turned out to be a broken weld on the exhaust pipe shield causing the shield to vibrate against the pipe, but only at certain resonances. Took me the longest time to find that one.

 

[Bighorn]

Check your harmonic balancer.
Also see if you have the rubber isolated front crankshaft pulley and if that has failed.

 

[gringeltaube]

Cracked power steering pump bracket...

 

[Dock Rocker]

Before you dig to deep check the heat shields on the exhaust under the dog house. Every truck I have ever spent much time in rattles there. Get some of the metal zip ties used for exhaust rap and tie them all down. If they aren’t rattling yet they will one day so go ahead and strap them down.


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[papakb]

I was on the creeper under my truck doing a routine inspection when I looked up and saw that my power steering pump was getting ready to fall out. I had no indications anything was wrong beforehand but when I saw it I realized the new noise I had been hearing was coming from there. You might want to check it.

 

[charlietango]

I was going to say harmonic balancer. I had a rattle in my M1009 6.2 - all belts tight and couldn’t find it. Finally one day I found that the 2nd alternator bolt bushing was loose to the housing. One phantom down. Don’t rule anything out, could the the strangest thing


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[Milcommoguy]

Sometimes call a Hummer, should have been called the "rattler" While hard to tell from the thread here / hear... these are some of the noises I had from under the hood. Split flywheel cover "Buzzing", Smarty pants mechanic tossed bolts and washers into exhaust system and found there way into muffler. Broken lower front alternator ear. Same muffler mechanic ( government employee?) left the rear spacer out and tighten lower mount to the pinch point. Fuel pump rocker arm bushing exploded and bouncing around inside pump cavity along with elongated metal to metal on pump arm. Side tension spring on E brake hanging loose causing cable noise when released.

All these noises harmonically showing up at different engines speeds. Now it PURRS and smokes a little. HAha

Think what's going on, moving, turning, spinning... all eyes and ears, keeping your finger out of the mix and the E brake ON, wheel chocks in place. One by one or two you can find the gremlins.

Good luck, CAM

 

[parklandtrans]

Mr.kane2018,
I will have to agree with NDT...by removing the belts and starting engine up..you very quickly and effectively remove (or include ) a large number of possible suspects right off the bat. If your noise is totally gone, like stated in earlier postings...check all brackets, bushings, bolts..and list goes on. Repair the issues as you go and install (1) belt at a time and see if problem pops back up. Now, this may sound very labor intense but really doesn't take that long..!!! Just swap belt to the next location..!!

NOTE: THIS IS VERY IMPORTANT AND SHOULD NOT BE TAKEN LIGHTLY..with ALL of the belts off VERY CAREFULLY AND WITH NICE BRIGHT LIGHTS, LOOK AT EVERY PULLEY ON EVERY COMPONENT, THE COMPONENT ITSELF, BRACKETS, LINES, SHROUDS, HOSES ETC ETC...ON AND ON. THIS TAKES TIME BUT IT IS TIME WELL SPENT..!!! VERY THROUGH VISUAL AND "HANDS ON"..INSPECTIONS ARE REQUIRED.
IMAGINE FINDING OTHER PROBLEMS BEFORE THEY BECOME BIG PROBLEMS...JUST BY AN INSPECTION..

Noises and rattles are some of the most aggravating problems in the world to deal with...but sure is satisfying when found and "ELIMINATED..!!!

Happy Hunting and let us know what you find or discover,

Bob (Parklandtrans)

 

[kane2018]

Thanks for the reply. Thats a good thought also for the socket extension. We used to use like sounding rods to check motors on my ships for problems

.

You need to use a socket extension and place it on different parts of the engine/body. To try to isolate a location.

You may put a prybar on the engine and pry it to put it in a bind to see if its actually the motor or body.

Does it happen at idle while cold starting? or does it take a minute to start after being warm?

Checked your water pump pulley? Could be a bad bearing on the impeller.

Sent from my SM-G935P using Tapatalk

 

[kane2018]

I got great replys in only a day. Still at work but will thanks everyone. going to back up and take a better look this time after the work of installing the fan clutch.

 

[kane2018]

Think this will be my next inspection. Going to inspect everything this time before jumping in with parts.

 

[cucvmule]

Cracked power steering pump bracket...

Having welded two already that is a very good place to look, or grab and pull on.

 

[charlietango]

Find anything yet?


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