C8.3 Cummins 325 Belt Tensioners

Topic: C8.3 Cummins 325 Belt Tensioners (Read 2179 times) previous topic - next topic

C8.3 Cummins 325 Belt Tensioners

November 23, 2011, 05:57:19 pm

I have one belt tensioner that is shimming and needs to be replaced. Can anyone confirm the spec. for the two belt tensioners on the Cummins C8.3 325 engine? I looked up in Beamalarm and the 1997 spec is not there. In fact it states that the 1997 engine is the 300 hp rated engine and not the 325 hp rating. I know for a fact the 1997 Foretravel U270 engine is rated at 325 hp.

The 1998 Foretravel specs. show the belt tensioner for a Cummins C8.3 325 is the Gates 38504. Is this correct?
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Re: C8.3 Cummins 325 Belt Tensioners

Reply #1 – November 23, 2011, 06:27:43 pm

BTW, here is a good short video by Gates on determining whether your tensioner is good/bad: Failed versus a good belt tensioner.

Brett

Re: C8.3 Cummins 325 Belt Tensioners

Reply #2 – November 23, 2011, 07:03:10 pm

Peter, That tensioner is used on all 8.3 engines for both belts as far as I know.
Gary B

Re: C8.3 Cummins 325 Belt Tensioners

Reply #3 – November 23, 2011, 07:54:39 pm

Great! How difficult a job is it to remove & replace the belt tensioners? Is there any special knowledge/tools about the way it is fastened to the engine bracket, or to whatever it is fastened?

Re: C8.3 Cummins 325 Belt Tensioners

Reply #4 – November 23, 2011, 08:19:26 pm

I didn't do it but I saw it done on my Cummins 8.3 (by two different mechanis within days). See: Kathleen & Paul Smith's RV Travelblog

It doesn't make sense since the tensioner is anchored to the (rigid?) block but the new tensioners needed to be shimmed (between the tensioner and the block) to stop shredding belts.

It's not hard, but our mechanic spent a LOT of time reving the engine and adjusting shims until he was satisfied.

best, paul

Quote

Great! How difficult a job is it to remove & replace the belt tensioners? Is there any special knowledge/tools about the way it is fastened to the engine bracket, or to whatever it is fastened?

Re: C8.3 Cummins 325 Belt Tensioners

Reply #5 – November 23, 2011, 08:27:36 pm

I imagine it is like mine and a really fast R&R. The photo below should show you the details with the single bolt/nut in the center. Pop the belt off first. I use a fairly long torque wrench with a 1/2" to 3/8" (some are 1/2" so no adapter needed) adapter to go in the square recess. Pull the torque wrench up until the belt is loose and off she comes. Good way to inspect the tensioner with the belt off. Check bracket for possible cracks. Should only need a couple of 9/16" wrenches to do the job. Check to see all angles, crank pulley, tensioner, pump pulley match before installing belt.

Use hardware store angle finder to compare angles. Bout $5

My photo shows the washer I added to bring all angles to match each other.

I think they may make a heavy duty tensioner for about $10 more.

Re: C8.3 Cummins 325 Belt Tensioners

Reply #6 – November 23, 2011, 08:47:44 pm

Good info Pierce, I only would like to add that one of the simple check is to look at the wear pattern on the idler pully, it should not be off the side of the belt or pulley. Have seen that issue on both the B and C series engines with a lot of hours. Have seen this happen before the tensioner starts to jiggle/wobble. Just another thing for a quick check. Once yu know where normal is, it becomes a quick easy check indeed.

Re: C8.3 Cummins 325 Belt Tensioners

Reply #7 – November 23, 2011, 08:49:49 pm

Here is more detailed photo showing where to insert the square drive and pivot the tensioner up so the belt comes off. The angles on the crank pulley and hydraulic pulley will probably be the same so you MAY have to adjust the tensioner to match. I just found a washer the right thickness so all the angles matched.

Good time to put on a new belt. I like Gates Green Stripe. They make a normal duty and the heavy duty Green Stripe. Don't let anyone talk you into a narrow belt. It should go from side to side on both the crank pulley and the hyd. pulley using ALL the groves. It should fit so with the tensioner rotated up out of the way, the belt slips on without prying, etc. With the belt on one pulley and lying flat, it should just clear the lip on the other pulley. My photo shows how it should look ready to go.

After the installation, check every so often to make sure one side is not fraying. Fraying on the belt edge is a sure sign the tensioner roller is out of alignment.

I put the 3/8" tool on, rotated the tensioner, installed the belt and removed the tool in 7 seconds after practicing a bit so its not a hard one to do (unless you have a rear radiator).

Re: C8.3 Cummins 325 Belt Tensioners

Reply #8 – November 23, 2011, 08:56:55 pm

With Dave's input, you now need to get out your checkbook. No need to make one for Dave as I will be sure to see he gets his half.

Hey, what a group.

Re: C8.3 Cummins 325 Belt Tensioners

Reply #9 – November 23, 2011, 09:13:43 pm

Thanks Pierce & Dave. Are the washers needed to ensure the alignment front to back on the tensioner along the rotating shaft or bearing? Is the alignment procedure always needed or does an OEM swap do the job w/o having to re-align?

Re: C8.3 Cummins 325 Belt Tensioners

Reply #10 – November 23, 2011, 10:26:42 pm

Peter and Beth,

No, the single washer I installed was to "tilt" the whole tensioner assembly. When I put the angle indicator on it, it was off 3 degrees. Three degrees really stands out and you can even eyeball one degree. I would not just bolt the new one on. Only takes a minute to check the three angles. Plus, the bracket/mount it bolts to could be bent/cracked so this it the time to check it.

Here is an example: The hand on the angle indicator read 12 degrees but the tensioner angle (measured with the indicator vertical on all measurements) on the roller measured 9 degrees so I had to shim until the roller also was at 12 degrees.

If no rain tomorrow, I will take a couple of fotos as words almost never are as clear. Should have added that I use one hand on the torque wrench to relieve pressure on the belt and the free hand to install the belt. A little awkward but easy once you get the motion figured out.

This misalignment triggered a lot of problems for the last owner with the incorrect belt installed, etc. Long story.

My tensioner was in good condition but I have no idea why it was off. Has been fine for 20K after correcting the angle.

With the engine running, mine just sits there without moving much.

Great Thanksgiving for everyone!!!

Re: C8.3 Cummins 325 Belt Tensioners

Reply #11 – November 23, 2011, 10:36:07 pm

Thanks, Pierce. A picture sure is worth a thousand words. Not ever having worked with these automatic belt tensioners, I have no idea waht angles your're talking about.

I did watch as the tech at TN RV changed the belts this past summer, so at least I know how to torque the tensioner out of the way to remove/replace the belts.

Re: C8.3 Cummins 325 Belt Tensioners

Reply #12 – November 23, 2011, 11:55:40 pm

Cindy & I replaced our tensioners in a campground long before they gave us any problems. We only recommend Gates tensioners which are different than all others we have seen as they have a sealed spring assembly. Alternator belt now has less movement and our hydraulic pump belt has no movement. Below is a link to Barry Beam's web site on our write-up & photos of our installation.
Replacing Hydraulic Pump Tensioner

Re: C8.3 Cummins 325 Belt Tensioners

Reply #13 – November 24, 2011, 08:47:52 am

Having a belt tensioner 3 degrees off from perfectly perpendicular to the belt (reason for the shim) is, to me, a red flag to check carefully that the pump bracket is not cracked or loose. Hairline cracks in the welded bracket are not that uncommon.

To check for a cracked bracket, with engine off, just grab the belt and pull HARD. The bracket and pump should NOT move even a little. If they do, the bracket needs to come off and be welded and often a gusset or added bracing welded in.

Brett

Re: C8.3 Cummins 325 Belt Tensioners

Reply #14 – November 24, 2011, 11:04:48 am

Brett,

I thought the same thing when I saw the 3 degree difference. I pulled the tensioner but noticed no cracks and even put a big crescent wrench to the mount but was OK and inline with the other pulleys. Bearing is in good shape, nice and smooth with no lateral play and the arm did not have any play either. Something amiss, possibly slightly bent from the several belt failures the last owner had. Once I found out how easy it is to release pressure on the belt and spin the roller, I check it before each trip but has been perfect for 20K. Is almost motionless with the engine running.

Barry and Cindy posted a link to the excellent photos of the 8.3 application. That is the new HD tensioner I noticed on the Gates site. For 8.3 owners, Amazon has it for $70 delivered. See: Amazon.com: Gates 38504 Belt Tensioner: Automotive Looks like a rubber/vinyl material over the steel roller. Going to make the Detroit version an "under the tree" present for xmas.

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: C8.3 Cummins 325 Belt Tensioners

Reply #15 – November 24, 2011, 01:12:12 pm

I bought 2 Gates tensioners last summer from Amazon when the price was $70. Later they bumped the price back up to about $90, and now it's back to $70. Be prepared for a long wait to get them, like 4-6 weeks, and they came in 2 shipments. Installation was just remove the belts, unbolt the old ones, and bolt in the new ones. One of the old ones had a spacer behind it that I reinstalled with the new one. The spacer was stuck to the old one, so it would be easy to miss. The new ones don't bounce up and down like the old ones did. The bouncing was more pronounced at idle than at higher rpm's.

Re: C8.3 Cummins 325 Belt Tensioners

Reply #16 – November 24, 2011, 01:14:21 pm

Peter & Beth,

Raining as you can see but shot some photos of my Detroit application. Yours will be different but principal is the same. The angle indicator is basically a level with a weight and an indicator pointer instead of a bubble. It has a magnetic base so you can place it against the steel parts and it will stick. Coach does not have to be level. You are just looking for readings that are all the same. A straight edge can be placed side to side on the tensioner roller pointed toward the crank pulley to make sure it is also aligned in the horizontal plane.

These angle indicators are available at most any hardware store. I use mine to check if the auto level is working. Works to setup satellite dishes too.

Re: C8.3 Cummins 325 Belt Tensioners

Reply #17 – November 24, 2011, 02:50:40 pm

Happy Thanksgiving--

I haven't been on here very often in recent months to post up, but if you have questions on tensioners or any Gates product for that matter, I'm happy to help. 25 years at the company and 15 of those in our heavy truck OEM business helps me navigate the questions pretty good...

The 38504 is a common Cummins replacement part for the alternator drive and is typical on B,C series engines. My ISL used the 38516 for the alternator drive. Usually you'll find a part number on the arm of the Cummins tensioner and our crossover resources can confirm its use. On the hyd pump, they've used the 38504 as well.

I applaud the efforts that Pierce is going to in order to confirm/verify alignment. He was measuring angular alignment, but there is also parallel alignment (fore/aft) to be concerned about as well . Parallel can be checked with a straight edge and a string. We normally allow approx 1/16" or approx. 1/2 degree for every foot of belt span between pulleys.

If you haven't been to The world's most trusted name in belts, hoses & hydraulics | Gates Corporation, there is a lot of technical information that is available for belts, tensioners, hose, etc. The fleet/HD products information is at Tech Tips - Fleet & Heavy Duty | Gates Corporation.

Mike O'Leary

Re: C8.3 Cummins 325 Belt Tensioners

Reply #18 – November 24, 2011, 09:14:56 pm

We paid $88 for each of our two new Gates tensioners at NAPA.

Re: C8.3 Cummins 325 Belt Tensioners

Reply #19 – November 24, 2011, 09:28:45 pm

I think we have paid about $130.00 at Cummins for the tensioner as we need them every so often for our generator users, will try NAPA next time.

Re: C8.3 Cummins 325 Belt Tensioners

Reply #20 – November 26, 2011, 06:53:38 pm

Quote from: wolfe10 – November 24, 2011, 08:47:52 am

To check for a cracked bracket, with engine off, just grab the belt and pull HARD. The bracket and pump should NOT move even a little. If they do, the bracket needs to come off and be welded and often a gusset or added bracing welded in.

I had to laugh at this. I can only imagine sitting there wondering how I'm going to grab the belt and pull hard with the engine running!

Re: C8.3 Cummins 325 Belt Tensioners

Reply #21 – November 26, 2011, 07:13:10 pm

Unless you beat it into them, people WILL try and grab it with their hands, neck tie, long hair, etc. They are usually the ones that put the RV on cruise and get up to get something out of the fridge. Or like me, back into a campsite way too short with the back tires against the log at the end and then hit the level button. I did watch a guy right ahead of me retract the landing gear instead of the flaps...with the engine running. A couple of pieces of hardwood and a couple of "C" clamps straightened the end of the prop pretty well.

Re: C8.3 Cummins 325 Belt Tensioners

Reply #22 – November 26, 2011, 08:20:12 pm

Pierce and Gayle you may have a mouse problem.

See your picture

Re: C8.3 Cummins 325 Belt Tensioners

Reply #23 – November 27, 2011, 03:32:55 am

Quote from: Donmystic1 – November 26, 2011, 08:20:12 pm

Pierce and Gayle you may have a mouse problem.

See your picture

You had me going for a while. I was trying to figure out what the computer mouse had to do with posting the photo. I use a trackball and started looking at it.

Yes we do or did have a huge rat & mouse problem the last few months. We live out in a very rural setting and they have come out in force in our county. Same thing has happened to friends and neighbors. We have looked outside and seen 20 big rats running on the deck rails at one time. They kept leaping for the bird feeder so we had to stop feeding the birds. They got into our friend's heater ducts and when they turned on the heater the first time in winter... We let the cats out at night and they brought 2 each in before morning. The kids have a cat with a cone on to keep it away from an injury. Even with the cone, it caught one. The kid's dog would also get one or two a day and the big guy in the photo caught a rat as large as a small possum. It even gave him a nasty bite before he finished it off. Perhaps it's the radiation from Japan or the Greek debt but whatever it is, they have been running rampant.

After driving home from trips, the next morning there are droppings in the RV engine compartment. Think they are almost gone but still see traces like you did. Have also been using traps but most are too clever.

Re: C8.3 Cummins 325 Belt Tensioners

Reply #24 – December 13, 2011, 05:23:00 pm

I hung up the phone on this guy! I called the nearest NAPA in Williamsburg, OH today and asked for a price on the Gates auto belt tensioner for the Cummins C8.3 #38504. He quoted $199.00. Nuff said...

JEGS has these for $99 + shipping. Don't know if there is a lower cost source...Help! Prices have really gone up! I'm so glad there is no inflation...can you imagine if there was?

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