Motor Mount Replacement

Topic: Motor Mount Replacement (Read 1069 times) previous topic - next topic

Motor Mount Replacement

May 02, 2014, 07:35:08 pm

I've seen a small bit of discussion about this but nothing in depth in other threads.

I'm getting a larger amount of vibration at idle than I did when I first bought the coach 2 years ago. This would be a very low frequency type of vibration that causes a rattle in the microwave and certain other cabinets on both sides of the coach.

I have ruled out the exhaust at this point since I still get the vibration when the exhaust tubing is disconnected between the flex pipe and the down pipe. I have also brought my idle speed back up to ~700 rpm after lowering it down last winter which does seem to help a bit but really only seems to speed up the vibration to make it less noticeable.

After looking at the motor/transmission mounts on both sides, there looks to be a difference between them. On the driver's side, I can slide my finger fully between the washer on the bottom and the frame mount but on the passenger side, I cannot. The rear motor mount looks to be different than the two front ones.

Has anyone had this issue and isolated it to the motor mounts? What are the procedures for troubleshooting this ? Has anyone tackled this themselves and have any advice as to upgraded parts other than the originals, or even just the original mount part number? How much vibration is too much for the C8.3?

I'll see if I can get some pictures.

Re: Motor Mount Replacement

Reply #1 – May 02, 2014, 08:27:17 pm

Added Lucas diesel fuel conditioner to my tank and my m11 smoothed right out at idle. Engine and gen both got quieter and smoother.

Re: Motor Mount Replacement

Reply #2 – May 02, 2014, 10:49:16 pm

Bob, you may want to look at this study done a few years back to see what Lucas does NOT do to fuel. It is worse than not using any.
JohnH
Lubricity Additive Study Results - Diesel Place : Chevrolet and GMC Diesel Truck

Re: Motor Mount Replacement

Reply #3 – May 02, 2014, 11:18:51 pm

Quote from: John Haygarth – May 02, 2014, 10:49:16 pm

Bob, you may want to look at this study done a few years back to see what Lucas does NOT do to fuel. It is worse than not using any.
JohnH
Lubricity Additive Study Results - Diesel Place : Chevrolet and GMC Diesel Truck

Beautiful. Ordered a gallon of the xpd. The idle smoothness is what i like from the Lucas.

Love the info here thanks john.

Bob

Re: Motor Mount Replacement

Reply #4 – May 03, 2014, 08:26:35 pm

Quote from: Caflashbob – May 02, 2014, 08:27:17 pm

Added Lucas diesel fuel conditioner to my tank and my m11 smoothed right out at idle. Engine and gen both got quieter and smoother.

I used Diesel Purge from Liqui Moly which was written about here
Lubro moly diesel purge
and noticed a smoother engine. I used a clear gallon carton as the tank for the return and supply so I could see everything that came out of the injection system.

I have been used the Diesel Kleen product for my fuel but just received my Fleetguard lubricity enhancing fuel filter setup but haven't had a chance to install it yet, probably in the next few days. I'm hoping for a noticeable improvement.

As for the vibration, it still isn't solved but I am happy to report that I have dampened it down quite a bit by creating some new brackets for the body panel to frame connections. I removed the poor bracket behind the driver's side rear tire which was nothing but a couple of small sheet metal screws sandwiching 3 thin pieces of fiberglass to the angle iron frame. You could shake it and hear it rattle which was vibrating the coach down the whole left side. I used a 90 degree bracket and neoprene washers to fix the issue but now I've noticed the same problem on the curb side. I will now regularly be shaking the body panels to see if there is any looseness to them, lesson learned.

Re: Motor Mount Replacement

Reply #5 – May 03, 2014, 09:25:06 pm

Definitely 2nd the motion on the diesel purge stuff. It was recommended to me by a mechanic I trust and yes it smoothed things out, most likely by cleaning off injector tips.

Re: Motor Mount Replacement

Reply #6 – May 03, 2014, 11:11:07 pm

This thread got off topic quickly, my coach does that at idle (causes things to rattle) when in drive. Goes away with a slight increase in rpm. Maybe I should look at the mounts. Last time I looked (several months) they seemed ok.

Re: Motor Mount Replacement

Reply #7 – May 03, 2014, 11:23:39 pm

I am not a mechanic, so..., I note this may not be great advice. I had a friend who is a dentist who has rebuilt several engines over one day and he wanted to see the FT. Anyway, I started it up and my 8.3 cimmins does pretty muçh the same thing you noted with the engine smoothing out at higher rpm. He suggested that I slightly increase the idle speed. I have not yet but think that may be a good idea or solution for me. With my 8.3 the idle does not have to go up much to really smooth out. It really has not been much of an issue for means I have not addressed my idle as of this time. Hope this is helpful.

Re: Motor Mount Replacement

Reply #8 – May 03, 2014, 11:43:07 pm

Quote from: Jerry Whiteaker – May 03, 2014, 11:11:07 pm

This thread got off topic quickly, my coach does that at idle (causes things to rattle) when in drive. Goes away with a slight increase in rpm. Maybe I should look at the mounts. Last time I looked (several months) they seemed ok.

I'm having a hard time remembering exactly but I don't think my coach vibrated like this when I bought it 2 years ago, maybe it did though. While I can live with the lesser vibration at idle in neutral, shifting into drive causes a noticeable low frequency vibration all of the way up to the driver's seat and dash area.

I do not have any issues, that I know of, while moving. My issues seem to only be at idle which leads me to think that it is the motor/transmission mounts. The vibration at idle, while in drive, was a symptom of bad motor mounts in a van I had years ago.

Re: Motor Mount Replacement

Reply #9 – May 04, 2014, 12:36:38 am

I would say that if you can see the engine moving while it's sitting there idling, that there's a mount problem for sure. That gap you describe doesn't seem normal but I really can't be certain.

Re: Motor Mount Replacement

Reply #10 – May 04, 2014, 12:03:26 pm

Related to an engine shaking condition: Grand Villas often have shaky miirors at idle, less so at speed. The cause isn't engine vibration. It's delamination. The glass on the front cap sides pulls away from the substrate. Foretravel can fix the problem. If you have a GV, knock on those sides. If they don't sound very solid, they are likely delaminated. We had this problem on both of our GV's and Foretravel advised me that it is very common. Anyhow, if your mirrors are shaking, give the sides a knock.
jor

Re: Motor Mount Replacement

Reply #11 – May 04, 2014, 04:37:25 pm

Engine idle more than 700? Thought I saw some discussion on 320's had a switch in the dash to set idle? Idk

Will the Allison enguage? $:-\$

Re: Motor Mount Replacement

Reply #12 – May 04, 2014, 04:51:59 pm

Quote from: fouroureye – May 04, 2014, 04:37:25 pm

Engine idle more than 700? Thought I saw some discussion on 320's had a switch in the dash to set idle? Idk

Will the Allison enguage? $:-\$

I've had no problem with the transmission engaging at 700 rpm. I did have an issue last winter with the transmission not engaging but it was a faulty dongle (zip tied to the King throttle box under the bed) that attached between the Allison and the King Control as troubleshot through 2600 Series Diagnostics

My problem was not fixed even by dropping the throttle down to 550 rpm though and the engine isn't very pleasant at that speed.

Here are the pictures of the bottom side of the transmission mounts. The driver side mount has 3/4" between the bracket and the bottom washer. The passenger side has slightly less than 1/2".

These may be famous last words but it looks pretty straightforward in removing the transmission mounts. There were a choice of 3 bracket mounting holes on the transmission and Foretravel went with the upper two. I believe that I can put my 20 ton jack on the bottom mounting flange to support the transmission and be able to remove the bracket and mounts to get a closer look.

In the meantime, I'll call Foretravel parts and see if they know the part number for the mounts.

I do have a question for Bob, since he sold new Foretravels, or anyone else who bought their FT new, about how much vibration there was when a coach was new? Perfectly smooth or a bit of a vibration that was livable?

Re: Motor Mount Replacement

Reply #13 – May 04, 2014, 05:31:34 pm

Robert,

All I know is that the Allison will not enguage at a preset rpm, my comment about the 700rpm was for Mr Scruggs, but alas iwasthinkingit but didn't mention it

My 8.3 vibrates until it warms up a bit. BUT when I rev to 1250 rpm for a few seconds it settles right down.

Just looked it up "set low idle". Better minds are in this discussion, much more experience that I have. DW says, keep it between the lines AND do what the Forefum tells you to do.

Re: Motor Mount Replacement

Reply #14 – May 04, 2014, 06:22:33 pm

Am I reading the above referenced report correctly? Does the Bio-Diesel that I'm getting sometimes at Wall Mart do the best job of improving lubricity? I know I get worse mileage but now so bad that the savings in price per gallon isn't worth it. Just thinking...

Re: Motor Mount Replacement

Reply #15 – May 04, 2014, 09:51:41 pm

If my engine ran rough when started cold, cleaned up when raised the RPM, I would be thinking Injectors, yes the fix in a can will make it smoother running sometimes. Not a repair, just a temporary at best, sort of like sticking our head in the sand.
On our 5.9 B Cummins (crane truck), when starting cold, missing & shaking until it warmed up a little, then ran great. The fix was new injectors, yes runs better and more power. Now starts, runs smoothly and still do not need new motor mounts.
Dave M

Re: Motor Mount Replacement

Reply #16 – May 05, 2014, 10:31:58 am

Quote from: lgshoup – May 04, 2014, 06:22:33 pm

Am I reading the above referenced report correctly? Does the Bio-Diesel that I'm getting sometimes at Wall Mart do the best job of improving lubricity? I know I get worse mileage but now so bad that the savings in price per gallon isn't worth it. Just thinking...

Should not notice the tiny loss of BTU/gallon in B-20 in overall mileage or power. Bio-diesel does go out of spec pretty fast and will absorb more moisture compared to 100% petro diesel. Would suggest you read the additive test results in the link toward the top and add a bit to your tank. I have gotten a couple of bad loads with very rough running that an additive cured immediately. The additives toward the bottom of the list operate on "placebo" effect.

Our diesels see ultra light duty. They are meant to be run hard. Babying an engine hurts it instead of helping it. I have run several used for towing at full throttle for several days at a time and they came back for more. This is especially true for engines with owners that idle them for extended periods.

Replacing injectors is a VERY expensive option on the later electronic engines. With the mechanical engines, a new injector (or injector/pump in our case) was only $50/ea. In the case of a bad injector on an electronic engine, a diagnostic tool can either manually or automatically shut off each injector, measure efficiency loss and tell you which one is bad.

Pierce

Re: Motor Mount Replacement

Reply #17 – May 05, 2014, 10:54:27 am

Quote from: rsihnhold – May 03, 2014, 08:26:35 pm

I used Diesel Purge from Liqui Moly which was written about here
Lubro moly diesel purge
and noticed a smoother engine. I used a clear gallon carton as the tank for the return and supply so I could see everything that came out of the injection system.

One of the best injector cleaners out there.

Re: Motor Mount Replacement

Reply #18 – May 05, 2014, 11:47:30 am

All 5.9 and 8.3 mechanical engines Shake Rattle and Roll at idle....Just the nature of the Beast

Re: Motor Mount Replacement

Reply #19 – May 05, 2014, 12:04:10 pm

Rough idle can also mean air in the system, high pressure injection pipe leak, valves that need adjustment, bad EGR, too low idle speed, etc. Raising the idle speed must be done within specs for the automatic transmission, as too fast an idle can result in creep while stopped for a red light, etc. I have had a couple of 5.9 owners in our neighborhood, but their engines ran very smoothly when warm. The early 5.9s are responsible for all the "turn off diesel engines" signs at fast food/bank drive throughs.

Pierce

Re: Motor Mount Replacement

Reply #20 – May 05, 2014, 12:55:18 pm

No shake rattel and roll on my 97,it did have that problem,one bad injector and run the rack fixed that,as long as she was in the shop I had the lift pump pressure checked and it was in spec,the tech that worked on our coach has 40 years as a Cummins tech

Re: Motor Mount Replacement

Reply #21 – May 05, 2014, 02:10:48 pm

Quote

I've seen a small bit of discussion about this but nothing in depth in other threads.

I'm getting a larger amount of vibration at idle than I did when I first bought the coach 2 years ago. This would be a very low frequency type of vibration that causes a rattle in the microwave and certain other cabinets on both sides of the coach.

I have ruled out the exhaust at this point since I still get the vibration when t

On some coaches or least the 97's there was a vibration damper mounted on the end of the drive shaft at the transmission. These have been known to fail and when they do they can destroy a transmission.
Look under the coach and if you see a round thick circular weight then you can go from there in finding if it is bad.

Gary B

Re: Motor Mount Replacement

Reply #22 – May 05, 2014, 06:12:38 pm

I do have the transmission dampener and have read the posts about the the P-3 carrier bearing not being torqued correctly at assembly but none of the posts mentioned anything about excessive vibration at idle. The posts all mentioned a vibration at speed which I do not have.

I'm probably going to change out the u-joints since I was getting a clunk when shifting out of neutral after I bought it since the previous owner had not been lubricating anything. If I remember correctly, the u-joints took an entire tube of grease since they had possibly never been lubricated in the previous 14 years and 90,000 miles. I haven't heard the clunk since as I've been keeping them lubed every 6 months as can be seen from the copious amounts of grease on the frame cross-member right above it.

While I've got the u-joints and driveshaft out, I'm going to remove the dampener and check for loose bolts all around that area. I'll try running the engine/tranny a bit without the driveshaft in place to check for vibration as was mentioned in the other post.

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