Hydraulic Pump Tensioner making noise

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Hydraulic Pump Tensioner making noise

October 02, 2019, 11:33:21 am

I just got home(Lufkin, TX) from the Davis Mountain State Park. Its was a great, awesome, fun, cool, 8 day round trip(1300miles). I was checking on things(U-240 Cat 3116, Allision MD3060R, 180K miles on this trip) and a tweety bird sound(belt tensioner). I found it. The Hydraulic Pump Tensioner has contacted/touched the pump pulley. In the pics, you can see the back side of the pulley is flatten and shiney. You can also see that at rest the tensioner does not touch. I did notice that at idle there was no noise, but off idle there is a tweety bird/squeeking sound. I think that it must be bouncing hitting the pulley. So far the pulley is working and the belt is staying on. I will replace the tensioner. I did check the bearing on the roller and it is used, seams ok. My question is why did the tension roller touch the pulley?

Re: Hydraulic Pump Tensioner making noise

Reply #1 – October 02, 2019, 11:44:36 am

Pat,

Before just replacing belt and tensioner (which you need to do, pull HARD on the upper part of the belt.

Look carefully for any movement of the pump bracket. I have seen them cracked which allows the pump to move closer to the crank pulley and also at an angle.

Let us know what you find.

Re: Hydraulic Pump Tensioner making noise

Reply #2 – October 02, 2019, 12:12:58 pm

Brett,
Thanks for your response. I did pull on the belt and the tensioner moves. I did not see any thing else move. The bracket seams to be good. I did start the engine and noticed that the tensioner moves and does come close to the pulley. No noise at idle.

Re: Hydraulic Pump Tensioner making noise

Reply #3 – October 02, 2019, 02:04:54 pm

Replace the belt and tensioner. Make sure they are in absolute alignment, as that short a belt off even a couple of degrees will wear quickly/make noise.

You may or may not have to add/subtract tension from the tensioner to get it "right". Easy to do, as the bracket the tensioner is mounted to is mild steel. Drilling a new hole for the detent pin on the tensioner allows you to fine-tune tension.

As I recall, no that installation, the belt is so short that I had to loosen the tensioner bolt, slip in the belt, then use water pump pliers to twist the tensioner so the detent went into the hole. Sounds more difficult than it is if you have large pliers.

Re: Hydraulic Pump Tensioner making noise

Reply #4 – October 02, 2019, 03:02:05 pm

Brett,
How do I know that I have the right tensioner? Do we have a part number for that?

Re: Hydraulic Pump Tensioner making noise

Reply #5 – October 02, 2019, 05:22:16 pm

Pat,

Need to check with MOT or Foretravel. The 1995 may be different than the 1993.

Here is what I have for the 1993 U240:

Replace engine belts: 11/07 127k: Goodyear Gaterback. Serpentine: 4070735 7PK1865. Hyd: 4060445 6PK1130 replaced 9/09 145k mi. Water pump belt Cat 7E0744 (½" X 34.5"/13mm X 876 mm). Replace belt tensioners 5/20/10 149,090 mi. Serpentine Tensioner Caterpillar 7E3999= Gates 38509. Hydraulic Tensioner Cummins 3937553= Gates 38504. Gates belts: water pump 9345HD, serpentine K070735HD, hydraulic: K060445. Belt idler bearings (2 each) for Cat 7E3999: NTN 6203LU. Fed Mogul BCA203-FF. 5/1/11 154,661 miles, replace water pump idler bearings (2- 202FF).

Re: Hydraulic Pump Tensioner making noise

Reply #6 – October 02, 2019, 06:32:49 pm

It's really hard to see the polishing on the rear side/engine side of the pump pulley as most of the pictures are either out of focus or have bad lighting. If the smooth side of the tensioner roller is touching the pump pulley, it's because the belt has stretched and is too loose allowing the tensioner to jump up and down. Gates Fleet Green Stripe don't stretch and last longer than any others. In other words, your belt is too long.

Do you know how to stick either a 3/8" or 1/2" breaker bar in the square hole on the tensioner to remove the belt?

Jumping at any speed is either because of the tensioner being a different angle compared to the crank pulley and the pump pulley or because the belt is too long. $5 buys an angle finder with magnetic base at any hardware store. The coach can be at any angle. See my old posts on how to do it. Use a straight edge to make sure the pump pulley is in line with the crank pulley. The pulley on the pump can be adjusted in or out on the shaft. You can see the bolt heads in one of your photos. I had to shim one side of the tensioner where it mounted to get all angles the same.

Your belt is riding just about right on the tensioner roller.

Only takes a few seconds to remove the belt with the breaker bar. Tensioner is also easy to remove. You should spin the roller to make sure it does not have rough spots or make a dry whirring sound. I injected some oil in both the back side and front side of the roller's bearings. Well over 100K and original.

If the roller on the tensioner is out of line, the belt will move sideways on the roller face and then snap back several times a second creating the noise and the jumping you see. Essentially, the belt's path is getting shorter and then longer several times a second. This was our problem.

Again, if the belt has stretched, the tensioner will not have enough spring strength to push hard enough on the belt and the flat roller surface may contact the pump pulley flange as well as the tensioner jumping up and down.

The belt should ride on the groves and not rub much on the flanges of either one of the pulleys. A tale tale is seeing any fraying of the white cords on the side of the belt.

Always have a spare belt available as in case of one breaking, the belt may be a mile behind the coach and you will have no idea what length you need. Do NOT depend on listed specs for the belt.

Pierce

Re: Hydraulic Pump Tensioner making noise

Reply #7 – October 02, 2019, 07:32:07 pm

Thanks Brett & Pierce,

I have discovered that the pulley is damaged. The tensioner flatten and rolled the inside edge of the pulley and cut into the outside edge. This makes the new belt run funny and causes the tensioner to jump a lot. I guess that the belt stretched to let this happen.

Does the pump shaft turn smoothly and with even resistance over the complete 360 deg. ?? Mine seams to be a little like a compression engine with low compression.??

Here is more pics.
One pic is of the new tensioner stressed to be able to install. I just put it in a vice and use a ratchet to stress and then anything that will stay in the slot where the rusty wrench is.

Thanks for the help

Re: Hydraulic Pump Tensioner making noise

Reply #8 – February 26, 2020, 12:30:53 pm

Well today I was looking at the hydraulic fan motors and noticed the one on the rear of the MH is leaking(pretty good}. Looks like the leak is on the top, not the shaft seal. Maybe/i am hoping the leak is a connection(o-ring) problem. I had a o-ring start to leak at the high/low speed value. I got that fixed. While looking I also noticed that the hydraulic pump belt is starting to fray on the outside. I also noticed that the tensioner has started to touch the pump pulley intermittently again. As in the first of this thread, I replaced belt, tensioner, and pump pulley less than 10k miles ago. I did not know what caused the problem to start with and still do not now. The only thing I remember from the first fix was that I thought that the pump pulley kinda had a hard spot when turning by hand. Not every turn, but sometimes. Wonder what is going on???

Pat,

Re: Hydraulic Pump Tensioner making noise

Reply #9 – February 26, 2020, 06:31:06 pm

Pat,

Make sure the bracket that holds the hydraulic pump is not cracked. With belt installed, engine off, pull hard on the belt and see if the pump moves. That will cause all kinds of alignment issues.

Been there, done that.

Re: Hydraulic Pump Tensioner making noise

Reply #10 – February 26, 2020, 07:36:41 pm

OK, here are all the photos for how to align the crank pulley, tensioner and hyd. pump. This is for a U300 but the idea is the same. Did you use a Gates Green Stripe belt when you changed it?

Pierce

Re: Hydraulic Pump Tensioner making noise

Reply #11 – February 27, 2020, 12:47:54 pm

Thanks Brett and Pierce for the response. I will test those items today. I am concerned how the pulley should turn without the belt on. Should it be smooth, even and light pressure, or smooth, even and hard pressure, or smooth, uneven pressure within 1 or more turns, or something else??? I will test this also today.

Pat,

Re: Hydraulic Pump Tensioner making noise

Reply #12 – February 27, 2020, 03:58:52 pm

I checked the pump bracket for cracks, no to see and pulling on the belt shows no movement. I did check the pulley for alignment and found that the pump pulley was to far on the shaft by +/- 1/16". No problem I can correct that, but I still don't understand why the tensioner roller is touching the pulley. I do believe that I have the right belt. In the video, the contact point is at the bottom edge of the pulley. The light shines on the top edge, but that is just light.

The following is Google Drive Shareable link to a video of the pulley.
Video Link

Pat,

Re: Hydraulic Pump Tensioner making noise

Reply #13 – February 27, 2020, 04:51:23 pm

If the belt is too long, the tensioner will hit the pulley. That's why I asked about the Gates Green Stripe as they don't stretch. Now, picture the belt being about an inch shorter. Would that keep the tensioner away from the pulley?

You can see in photo 2 above that If the belt were longer, it would allow the flat idler pulley to hit the pulley on mine. Don't pay that much attention to what the part number is supposed to be. It's what works. I had to try several different belt lengths until I found the right length that show in photo 2.

Do you have a photo of the whole assemble like my photo 2? Perhaps we can figure out your problem then. The parts store was nice enough to loan me belts of different lengths until I was happy with one.

Pierce

Re: Hydraulic Pump Tensioner making noise

Reply #14 – February 27, 2020, 09:45:12 pm

I just changed both my tensioners on my 1996 8.3 Cummins. Got OEM Cummins off Ebay for $75 each and replaced all 3 belts with Gates HD. I bought a long 3/8 drive socket arm from Harbor Freight for $10 bucks and made the job way easier. You need to really move the new tensioner to put the belts on but didn't modify anything

Re: Hydraulic Pump Tensioner making noise

Reply #15 – February 27, 2020, 10:57:26 pm

Quote from: pthurman48 – February 27, 2020, 12:47:54 pm

I am concerned how the pulley should turn without the belt on. Should it be smooth, even and light pressure, or smooth, even and hard pressure, or smooth, uneven pressure within 1 or more turns, or something else??? I will test this also today.

On my coach (older and different pump than yours but should be similar) I was able to turn the hydraulic pump by hand. As I turned it a few revolutions the fan (I have a single fan) would turn showing it was working properly.

Pierce's response is correct. You want the belt to be aligned. If you don't have a gauge a long straight edge will get you close.

see ya
ken

Re: Hydraulic Pump Tensioner making noise

Reply #16 – February 27, 2020, 11:24:34 pm

Pat,

I annotated one of my photos showing the tiny washer I had to use to get the tensioner angle to match the other angles on the crankshaft pulley and the hydraulic motor pulley. It is a single washer and placed just in the right spot to correct the 3 degree difference. I experimented in the washer thickness and placement until all angles matched. Then I tightened the tensioner back down. And yes, the back of the tensioner is no longer is flush with the mount. The mount face was the correct angle but the 3 degree difference was somehow in the tensioner itself. I've seen other coaches where the back of the tensioner and the roller angle were off a little. Again, this was a three degree difference. The correction made all the difference in the world. The belt you see in the photo is the same one that is on today with 50K more miles. I have two more I carry with me.

I also used a long straight edge like Ken suggested so everything aligned in the horizontal plane. The four bolts visible inside the hydraulic pump pulley may be loosened and the pulley moved in or out on the shaft. (after using a Liquid Wrench type product)

Pierce

Re: Hydraulic Pump Tensioner making noise

Reply #17 – February 28, 2020, 12:12:54 pm

Good Morning Pierce,
I do have the same set up as yours. I have owned my U-240 for 13 yrs and 120k miles. I have never had any problems with this system. I have replaced the belts several times and the tensioner 2 times. I am thinking that all the alignment is fine. For some reason the tensioner must be bouncing and hitting the pulley sometimes. I can hear a noise while driving past walls, it is not continuously, it does sound like a rattle, very tinney(light metal sound).

Re: Hydraulic Pump Tensioner making noise

Reply #18 – February 28, 2020, 01:41:18 pm

Pat,

Make sure it's not your AC compressor clutch pulley. Ours rattled, stopped when I removed the belt.

Tensioner roller should clear the pump pulley by at least 3/4". Distance should increase if tensioner roller bounces. Check belt length.

My photo is off slightly with the arrow pointing about 1/2 inch from the back of the tensioner.

If you don't show any belt wear, you are in good shape. The PO of ours was stuck by the side of the road a couple of times with the belt problem before we bought it. Not all coaches have this problem but in case of belt wear, it's the first thing to check.

Pierce

Re: Hydraulic Pump Tensioner making noise

Reply #19 – March 06, 2020, 02:16:06 pm

Hi Pierce,
I have been working on belt length on my hydraulic pump. I have found that a Gates K060445 (13/16" x 45 1/8") will fit with very little slack to install. I also know that Gates K060448 (13/16" x 45 3/8") will fit, because that belt I have been running is a Gates K060450 (13/16" x 45 3/4"). I will see what the new K060445 belt does and go from there. Thanks for all the input.

Pat,

Re: Hydraulic Pump Tensioner making noise

Reply #20 – March 06, 2020, 02:45:16 pm

Pat,

Do not go any shorter than OE/absolutely necessary, as it can over-tension the belt, tensioner bearings and pump bearings.

Re: Hydraulic Pump Tensioner making noise

Reply #21 – March 06, 2020, 03:48:39 pm

Quote from: pthurman48 – March 06, 2020, 02:16:06 pm

Hi Pierce,
I have been working on belt length on my hydraulic pump. I have found that a Gates K060445 (13/16" x 45 1/8") will fit with very little slack to install. I also know that Gates K060448 (13/16" x 45 3/8") will fit, because that belt I have been running is a Gates K060450 (13/16" x 45 3/4"). I will see what the new K060445 belt does and go from there. Thanks for all the input.

Pat,

I would shorten the belt a little at a time untll happy with the idler pulley to pump pulley clearance. Check my photos for the approx deflection. I just checked the distance on ours and metal to metal, it's between 1/4" and 3/8" idler roller to pump pulley. It's been working great at this distance for many thousands of miles. As Brett says, don't shorten it too much.

Pierce

Re: Hydraulic Pump Tensioner making noise

Reply #22 – March 07, 2020, 12:08:16 pm

Good Morning Brett & Pierce,
I started with K060445 (45 1/8") to see if it would fit on and since it did I have not changed to the K060448(45 3/8") belt. I also noted when reading this post again that in reply #5 you said you(Brett) used a K060445 belt. I am not sure if I have ever known what the OE belt is/was. I have replaced this only a few times in 13 yrs and 100k miles. I only did that due to age. I have never had this problem before a few months ago. This may not help if the pump is having problems???!!!!

Pat,

Re: Hydraulic Pump Tensioner making noise

Reply #23 – March 07, 2020, 12:29:22 pm

You think that there is a possibility that the pump is starting to seize up and overheating the belt until it stretches and allows contact between the roller and the pump pulley? I think the pump would probably quickly fail and you would lose the cooling fans. Other possibilities for more pump drag would be if the hydraulic lines are having an internal problem and creating a restriction. How is the filter?

The belt wraps around over 75% of the pump pulley and at least 60% on the crank pulley on our coach. This is considered high in the belt business and slippage is not that likely. Serpentine belts also have a lot more contact area so are less likely to slip compared to one or two V belts.

Pierce

Re: Hydraulic Pump Tensioner making noise

Reply #24 – March 07, 2020, 12:56:55 pm

Pierce,
I really don't know what is going on. I know that over 13 yrs and 100k miles I have changed the belt a few times due to just age. The tensioner has never touched the pump pulley and now all the sudden it has and damaged the pulley. I have measured the old belt and it is still 45 3/4" long. I believe that the belt does no stretch, but flexes to the extent that the roller contacted the pulley, but why?

Pat,

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