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belt tensioner

I've had this problem before and here it is again. The tensioner for the hydraulic pump was "bouncy" and squeeked a lot so I tried to replace it. Took the old Dayton off and put the new Gates on. This coach had a Dayton on it when I bought it 60k miles ago and I'd replaced it a couple of times. I tried a Gates and the belts kept running off the side of the pump pulley so I put the old Dayton back on and had no more trouble. Now, when replacing the Dayton I've tried another Gates. Correct cross number and all and the belt wants to roll off the pump pulley again. When laying a straight edge on the two pulleys they show daylight on the rims next to each other. Why does the Dayton not have a problem with he rolling and the Gates does??? Really tired of this.
Larry
1996 U295 36'
Build # 4805
Actually we sold it but just like to lurk

Re: belt tensioner

Reply #1 –
If the tensioner pulley, the engine pulley and the pump pulley are in alignment and at the same VERTICAL angle, you won't ever have a problem. Use an angle finder to check angles. About $6 at a hardware or Home Depot.

Ours jumped quite a bit and the advise was to replace it. I aligned it, got all three pulleys the same angle and have never had a belt problem since then. The tensioner was off 3 degrees. Now, the tensioner does not jump, makes no noise, etc. The tensioner bearing was a little dry so I just lubed it. 100,000 miles on the OEM tensioner.

When the alignment is off, the belt tries to take a longer path, goes to the side a bit but then jumps back causing the tensioner to jump. It repeats this several times a second and you see "jumping" for the tensioner roller. When everything is in alignment, the belt should ride in the middle of the tensioner roller. If you see any fraying on the edge of the belt, it is also a sign of mis-alignment.

I know you have a Cummins but Foretravel never updated the belt info for the Detroits when they went from the vertical side radiators on the 1992 to the horizontal radiators with two fans on the 1993/94. The pulleys are now 8 groove and take a different belt.

Go to my old belt alignment page for all the photos. Alignment method will be the same for the Cummins as the Detroit.

I can repost if you can't find them.

Proper alignment means a happy tensioner, belt and owner.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: belt tensioner

Reply #2 –
Quote from: Pierce & Gaylie Stewart –
Go to my old belt alignment page for all the photos. Alignment method will be the same for the Cummins as the Detroit.

I can repost if you can't find them.

Proper alignment means a happy tensioner, belt and owner.

Pierce

Here is one post with the photos C8.3 Cummins 325 Belt Tensioners
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: belt tensioner

Reply #3 –
When we replaced our original hydraulic idler with an improved style Gates, I at first failed to notice that behind the original idler was a black spacer plate that seemed to be part of the original idler.  So the replacement Gates would not have been correctly aligned if I had not reused the spacer plate.  Our coach probably has Larry's same engine.  BTW, both new Gates idlers are still working great with almost no hydraulic belt movement, and much less alternator belt movement.
Replacing Hydraulic Pump Tensioner

Re: belt tensioner

Reply #4 –
The tensioner on my hydraulic pump was very bouncy. The problem was the crank pulley was not concentric and had run out. Dial indicator and loosen bolts, centered it and no more bounce
1998 U270 34'

Re: belt tensioner

Reply #5 –
Michelle, thanks for finding and posting my old Detroit tensioner photo. The other link shows a spacer being fabricated to center the tensioner roller. On our Detroit the problem was the tensioner was out 3 degrees in the vertical plane so a flat shim would not work. I have seen new replacements off between 1 and 3 degrees. When we bought our coach, the previous owner was relating the times they had been stuck waiting for the tow truck to bring a new belt out On the way home from North Carolina, the belt gremlin struck again but I had a couple of spares. And still once again before I thought it out.

If the belt does not line up in the horizontal plane, you can loosen the four pump pulley bolts and it will slide on the shaft. On a Detroit, there are four bolts holding the pump/tensioner mount to the block. The tensioner can then be aligned by moving the mount fore or aft with the final pump alignment being done by moving the pulley on the shaft.

Some owners on the later twin fan Detroits have used the 6 rib belt instead of the 8 rib and just allowed it to jump a groove on one of the 8 rib pulleys. Auto parts or Truck stops don't normally carry the 8 ribs so pays to have spares onboard.

And yes, my preference is toward the Gates Green Stripe Fleet duty belts. If you order online, they are just a couple dollars more than the standard duty, otherwise $10 more each. Tensioners require either a 3/8" or 1/2" breaker bar to release the tensioner to replace the belt.

When on the road, if you are stuck on the weekend, John Deere warehouses are huge and stock millions of parts and open 7 days a week. Made up my hydraulic line quickly on a Saturday afternoon. Said they would do the same on Sunday.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: belt tensioner

Reply #6 –
Thanks for all the input. If you are looking at my assembly from the rear the drive pulley is on the right on the engine shaft. The driven pulley is on the left on the pump shaft. With a straight edge across both pulleys it shows light at the 9 o'clock position on the drive and light at the 3 o'clock position on driven pulley. Vertically they seem to be the same. There is a spacer behind the tensioner with a hole to help line up the button on the tensioner and the "index" hole in the bracket. With the Dayton tensioner there is no problem while with the Gates it keeps rolling the belt off the driven pulley. It would appear that it is necessary to unbolt the pump bracket and shim it into the same plane as the drive pulley. Groan!
Larry
1996 U295 36'
Build # 4805
Actually we sold it but just like to lurk

Re: belt tensioner

Reply #7 –
Quote from: Pierce & Gaylie Stewart –
If the tensioner pulley, the engine pulley and the pump pulley are in alignment and at the same VERTICAL angle, you won't ever have a problem. Use an angle finder to check angles. About $6 at a hardware or Home Depot.

Ours jumped quite a bit and the advise was to replace it. I aligned it, got all three pulleys the same angle and have never had a belt problem since then. The tensioner was off 3 degrees. Now, the tensioner does not jump, makes no noise, etc. The tensioner bearing was a little dry so I just lubed it. 100,000 miles on the OEM tensioner.

Proper alignment means a happy tensioner, belt and owner.

Pierce

Pierce,

I can attest to this simple but effective solution you posted four years ago for the same problem I was having.  The hydraulic belt was only a six ribbed one and the tensioner pulley was out of alignment and bouncing.  When I replaced the six rib with the correct Gates 8 rib belt it kept jumping up on the edge of the engine pulley.  Using your procedure with an angle finder and a small washer I was able to re-align the belt travel path along the pulleys to accommodate the correct belt and stop the tensioner bouncing.  After four years no problems and the belt is not frayed.  The bearing on the tensioner squeaks sometimes from sitting up but a little oil takes care of it.  I have a spare belt but I don't think I'll be needing it for quite some time!  I know now that changing the tensioner without the alignment fix probably wouldn't have solved the problem and I would be back to a six rib belt again.  ^.^d  ^.^d  ^.^d

Jerry

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Jerry and Cindy Maddux
1993 U300/36WTBI DD6v92TA
build 4271  "Miss Lou"
1995 suzuki sidekick 4x4 toad
Gulfport, Ms

"Pride of Ownership"

Re: belt tensioner

Reply #8 –
Regarding belt squeak, after much research I have found and just replaced my belts with Continental Elite (formerly Gatorback) belts, marketed  as "the quiet belt".  They have a sequential cog tooth profile which helps reduce slipping, squeaking and noise up to 15 db (decibels) compared to Gates. Since it is so cold here in the Northeast, I have not started the engine yet to test them, but will as soon as the temperature rises.
1997 U270 34FT Build 5140 Cummins 8.3 Allison 3060R
Solar 1920Watts, 14KWH lithium. Orion BMS.

Re: belt tensioner

Reply #9 –
Only start and run engine if you can drive 25-30 miles.
The selected media item is not currently available.Bill&Doris 97 U270 36'
University of Parris Island Class of 66
Semper Fi  Build# 5174 MC#17094