Surp. Belt Vibration

[lmholmes11]

I noticed while checking everything out under the hood that on the very left hand side of the belt assembly, on the the second wheel down the belt has some vibration in it. Is this normal or do i need to tighten the belt? Also, when im inside the cab i can hear some spuratic rattling coming from the passenger side of the truck ( i assume its coming from under the hood). Is there anything that causes natorious rattling in 2001 duramax's?

Its driving me crazy!

[DmaxMaverick]

You can't "tighten" the belt. The tensioner is spring loaded, and keeps a specific preload on the belt. You probably have an idler, tensioner, or accessory pulley wearing/worn out. Remove the belt and check each of them for trueness and bearing drag/noise. They should be smooth and quiet, and have no play in them.

The rattle you hear may be the turbo downpipe mount tab. Look through the passenger side wheel well, at the rear and behind the fender liner for the tab bolted to the manifold. Many of them crack. If so, you can weld it in place (no need to remove the pipe or tab).

[Duramaster]

From experience, it sounds like the tensioner has bound up. The 2001 is the only year that uses your particular type of tensiner. An easy check is to simply remove the belt. Pick up on the tensioner with a 3/8 ratchet ( I believe it is 3/8" on that year only, if not then 1/2") and remove the belt from the tensioner pulley. Carefull let the tensioner down. It should go way past it's original position down to a built in "STOP" . After letting the tensioner down, try and pivot it further. If it continues to move, then you have a defective tensioner. Simple as that. the new tensioner usually comes with a new bolt. I agree with DMaxMaverick as well though on the broken bracket. I just don't hear them rattle as often as the annoying belt tensioner. ;)

[lmholmes11]

ok thanks guys, I'll take a look and post what i have found. I appreciate the help.

[lmholmes11]

Well i still cant figure out where the noise is coming from. I have narrowed it down though. It sounds like it is either coming from the air box/intake or the Bosch rail, they are located right next to eachother, so it is hard to tell which one. The noise isnt all the time either, once in a while while ideling. Strange...

[DmaxMaverick]

It isn't your "Bosch rail", and it isn't your airbox (unless something is really wrong). Check for anything in contact with anything else. Check the intercooler pipes, fuel lines, A/C lines, wire looms, etc. Could even be an engine mount. Get busy with a stethoscope. Remove the belt and spin all the idlers, the tensioner, and all the accessories. If you can hear it from the cab, you shouldn't have too much difficulty locating it. I'd start with replacing the belt (they can have glazed, sections, or even missing pieces, causing noise and/or vibration), if for no other reason, because it's 7+ years old. Did you locate the downpipe bracket? Was it cracked?

[lmholmes11]

Ok i'll get to looking real close at everything, yes i did locate the bracket, it was still good. Ill keep you posted, thanks!

[lmholmes11]

I think im going to replace the belt tensioner here in a few days, i mine as well replace it when im replacing the belt and it is already off. I priced a pulley out for $16.97 so why not. Is there any special protocols to follow while replacing it ( torque settings)? Or just tighten it on and go with it? Thanks

[DmaxMaverick]

$17? That sounds too cheap. Should be around $30, at best (GM list is like $80). Make sure you aren't getting just an idler pulley.

When I R/R tensioners, I use some anti-seize compound on the mating surfaces and the bolts. If you don't, corrosion can happen, causing issues in the future, including bolt seizure (as can happen on any aluminum accessory mount). I don't have the torque # on hand, but I just get it tight.

[lmholmes11]

Yeah i thought that was too cheap also, ill double check. Next week I plan to do some fluid changes/service to the truck. If Everyone doesn't mind, can you look over what i plan to do and make sure i am on the right track?

Oil+filter-easy

Front/Rear Diff- fluid hot to warm, fill until it overflows filler hole or a little bit lower than filler hole ( rear side of truck about half way up on cover).

Front Diff, are the drain plug and filler hole in the same places as in the rear?

External Tranny Filter- Unscrew, a little bit of fluid will come out with it, replace with new one, transfer magnet to new filter after cleaning off.

New Serpentine Belt/Tensioner Pulley- Get a ratchet or a breaker bar and insert in square hold on pulley, lift up to relieve tension take off belt, replace new one.

Change Fuel Filter- This is my concern. As DmaxMav. probably remembers i had some problems getting my fuel filter to re-prime after a filter change, and also after replacing the fuel lines going into and out from the fuel filter assembly. I eventually had to get it towed and fixed by the dealership. (Diesel Mechanic said it just took a looot of pumping) after i spend a good 2 days of priming it myself.) Was this amount of excessive pumping due to the fact that I replaced those lines? Im considering just taking it to the dealership to have THEM change it and see if they have problems getting it to prime, and if not then ill continue to service it myself.


Any tips would be greatly appreciated,
As always Dmax Mav. has been a big help

[DmaxMaverick]

Looks good.

The drain/fill plugs on the front diff are on the driver side, top/bottom, on the side of the housing (not like the rear at all). Remove the skid plate, if you have one. Not difficult, just potentially messy.

The loooong priming process may have had to do with replacing the lines. Don't know. Still, if there are no leaks, it should prime normally. It may take 1-200 strokes, at worst. I don't normally recommend this, but you can fill the filter prior to threading it on (careful--can be messy). Be careful to fill ONLY from the outside holes, and not the center. This will prevent unfiltered fuel from reaching the clean side. This will drastically reduce your prime process. Pump it up hard then loosen the bleeder (air escapes). Tighten the bleeder and pump again (with bleeder closed). Do this until you get fuel from the bleeder hole, then tighten the bleeder. Pump it up hard again, and it should start/run well.