All Pumped Up?

[Bulls99Sub]

Time to display a little diesel ignorance. I can hardly keep the serpentine belt from squealing on my 99 Suburban. I replaced the original with a Goodyear Gatorback (supposedly the best belt(?)) and it still squeals when the truck is cold and is worn shiny on the non-ribbed side in only 3000 miles. I happened to be poking around today and noticed that the accessory on the lower left corner (when looking from the front) does not appear to be turning. I guess that explains the squealing and glazed belt. It looks like an air pump of some kind and it will turn by hand but appears to go through some kind of compression cycle. I think the pump may be OK; it seems to turn with a reasonable amount of effort applied. However, the belt does not contact much of the pulley and the little contact that exists is with the back side (non-ribbed side) of the belt. The belt tensioner also has a healthy amount of spring remaining. Here is where the ignorance comes in. Is this a common problem? What does this pump do? Any suggestions? I would appreciate any help that can be provided. I am very good with gas engines, fairly new to diesel autos, but have had a few diesel tractors. I am trying to get the truck into vacation shape and I do not want this issue to restrict our plans.

Thanks,

Bull

[gmctd]

That is the vacuum pump, necessary for turbocharger operation. The pulley should rock back and forth easily at bottom of diaphragm stroke.

Your description seems to indicate the serpentine belt is installed incorrectly.

Locate the belt installation label on the vehicle and compare for correct routing. May also be in the Owner's Manual.

[ 04-04-2004, 09:21 AM: Message edited by: gmctd ]

[patrick m.]

or someone sold you the wrong belt, not that something like that ever happens :D

[Bulls99Sub]

Thank you for the replies. I checked and the belt is installed in accordance with the underhood diagram. The belt just does not contact much of the vaccum pump pulley, maybe 1/8 of the way around it. If this is related to proper turbo operation and it has obviously been going on for some time (judging by the glazing of the back side of the belt, shouldn't the ECM have thrown a trouble code? I would assume that fixing this should help performance? Thanks for all the help.

Bull

[triggerman]

I have found the gatorback will stretch a bit more than the OEM (Goodyear) belts. Check your tentioner to see if the mark falls between the two triangle marks. If the tentioner mark is past these marks, you can get back in optimal range by puting 4 washers under the AC pump (mount bolts). This jacks the AC pump up and tightens the belt. It's also possible you may have a alternator bearing ready to sieze. Good luck

[markelectric]

If you find that the pump is bad and one from a 94 will fit, I have one that I pulled out when I put a turbomaster in. It can be yours for the cost of shipping. Email at markpamelectric@yahoo.com if interested.

[Bulls99Sub]

Update,

Patrick, you were right on. The belt that was slipping (just put it on 3000 miles ago) was a 1020. Gates belt that was on the truck was a 1010. It seems that the extra length of the 1020 is just enough to reduce the belt tension and cause slippage of the vacuum pump. Picked up a new correct belt and truck even runs better, I gusee the turbo is now doing its job.

Thanks for the help,

Bull

[TurboDiverArt]

Originally posted by Bulls99Sub:
Update,

Patrick, you were right on. The belt that was slipping (just put it on 3000 miles ago) was a 1020. Gates belt that was on the truck was a 1010. It seems that the extra length of the 1020 is just enough to reduce the belt tension and cause slippage of the vacuum pump. Picked up a new correct belt and truck even runs better, I gusee the turbo is now doing its job.

Thanks for the help,

Bull Hum, that's interesting. I believe the "book" calls for the 1010 belt. My truck had a 1020 Gates belt on it when I bought it. I tried putting a Dayco 1010 belt on it (as per the parts book) and it wouldn't fit. The parts store didn't have a Dayco 1020 belt so I was given a Dayco 1030 belt. That's what's on now. It just fits but is really too long but doesn

[ANXIOUS-SUBMAN]

The first time I bought a serp belt for my sub (4/01) NAPA asked which alternator I have. I guessed at the larger option cuz my sub is pretty well loaded. It fit just fine with no problems. The NAPA part number I have in my maintenance record is 25-061020. I just picked up a Dayco Poly Cog belt from Advance Auto (before checking the old # in my maint log)and they gave me a 5061010. I asked about the alternator size and the clerk only saw one part #. Seeing the difference now, I guess I'd better take this one back for a 1020. Glad I saw this thread. Thanks guys.

[ 04-09-2004, 01:49 PM: Message edited by: ANXIOUS SUBMAN ]

[ANXIOUS-SUBMAN]

I exchanged my 1010 belt at Advance Auto Parts for a 1020 as it should be. (I'll put it on tomorrow) Out of curiousity I just checked the NAPA sight and selected my truck. It shows a 1010 for trucks with 100 & 105 amp alternators and a 1020 for the same trucks with the 124 amp alt.