Vibration at idle

[rd3war]

I have a M1078 with a CAT 3116 and at idle notice vibration coming from the motor sometimes. The cab seems to amplify the vibration and make it more noticeable as the door panels make noise against the door. If I give it some throttle the vibration goes away. I don't feel it while driving unless I'm stopped or moving slow (at idle rpm). With my foot on the brake when I shift to drive or reverse it makes a little more vibration than when in neutral. My throttle pedal does stick slightly so to get the rpms down to idle I push up on the pedal with the corner of my shoe. I can feel it through the cab when inside (fyi, my air ride does not work yet) and when out side if I put my hand on the bumper, etc. I don't know if this vibration is normal or not. This is the first diesel truck I've owned. I did a quick check to make sure the compressor bolts were tight, flywheel bolts tight and noticed very minor play in the fan. Let me know if you notice this in your trucks or if I should check something else on my truck.

I made a couple quick videos to show you what I notice:

https://www.youtube.com/watch?v=4Vyd_2vTCLc

https://www.youtube.com/watch?v=DVUhe9-YyJY

I had the door open in the video, so its not as noticeable, but good view of the inside of the cab (it was still light out):
https://www.youtube.com/watch?v=pTKsdrylpIQ

 

[simp5782]

Just sounds like loose paneling to me. I mean if you feel the vibration in the gas pedal it could be motor related. One way to tell is with the cab down. take a long 3/8" extension and put it to the side of the engine block and put it to your ear while someone works the gas pedal and see if you can hear it there. If its engine related you will hear it before the mounts take it away. Or a tone change in the engine. or transmission bellhousing as well.

You can check all your engine/trans mounts with a pry bar to check their play to see if one may be bad or missing parts.

I think awhile back someone said that the flywheel/torque converter bolts weren't locktited and backout, which could also cause a vibration.

 

[Moostang]

If you’re cab air ride isn’t working the cab can come in contact with the engine. Look for rub marks near the rear of the engine or underside of the cab

 

[Andyrv6av8r]

I would increase your idle on the stop just a little bit. I was playing with mine after I first got it and if I turned the idle down too low, it would vibrate exactly like yours. It won't take much at all.

 

[rd3war]

Just sounds like loose paneling to me. I mean if you feel the vibration in the gas pedal it could be motor related. One way to tell is with the cab down. take a long 3/8" extension and put it to the side of the engine block and put it to your ear while someone works the gas pedal and see if you can hear it there. If its engine related you will hear it before the mounts take it away. Or a tone change in the engine. or transmission bellhousing as well.

You can check all your engine/trans mounts with a pry bar to check their play to see if one may be bad or missing parts.

I think awhile back someone said that the flywheel/torque converter bolts weren't locktited and backout, which could also cause a vibration.

I will check with the extension as you describe.

I checked the motor mount bolts and all were tight and the rubber part looked to be in good shape.

I did check the fly wheel / flex plate bolts as described in Adventure Driven's video on here. They were all tight, none were loose.

 

[rd3war]

If you’re cab air ride isn’t working the cab can come in contact with the engine. Look for rub marks near the rear of the engine or underside of the cab

I ordered the rebuild kits for the air ride today from OHS. Air rushes right out of the bags now so I couldn't test with air ride activated.

 

[rd3war]

I would increase your idle on the stop just a little bit. I was playing with mine after I first got it and if I turned the idle down too low, it would vibrate exactly like yours. It won't take much at all.

I'm glad you get the same vibration too. I thought idle might be a bit on the low side. I'm used to having a tach that I can see exactly where it is, but I just have to go by feel on this one. I'll look to see where I adjust this on the motor.

 

[coachgeo]

Check air compressor/power steering pump bracket support for loose bolts. A known problem that causes crack in the front hou$ing. Also search in here on how to check the Fan and Fan Clutch. Another known issue. Both or either might could cause some vibration...... but even if not.... they are known issues to check.

 

[rd3war]

Check air compressor/power steering pump bracket support for loose bolts. A known problem that causes crack in the front hou$ing. Also search in here on how to check the Fan and Fan Clutch. Another known issue. Both or either might could cause some vibration...... but even if not.... they are known issues to check.

I did a quick check on the compressor bolts on the front and back bracket. I didn't find any loose bolts or notice any cracks in the front housing.

I checked the fan with the power switch off and then with the power switch on. In the off position it doesn't move at all or have any play. With the power switch on, letting it rotate freely, it has slight play front to back, maybe about 1mm at the base. Is this normal? I reached up and checked the bolts on the front of the fan and none were loose.

Checking the fan for play:
https://www.youtube.com/watch?v=SPNSEvwd15w

https://www.youtube.com/watch?v=TgDCYf3d7rI

https://www.youtube.com/watch?v=DcDq0pifS4c

 

[Suprman]

Second vid, a bit hard to tell from the vid but it looks like when you are moving the fan blade the clutch itself is moving a bit. If thats the case I would investigate further.

 

[rd3war]

Here is a pic to show where the movement is at (red line). Should there be no movement at that spot? What else should I check?

 

[Suprman]

If it was me I would at least take the fan and clutch off to inspect. See if you have the older or newer style clutch. If its ok then you have peace of mind and you can loctite the bolts well when you put it back together. If its the older clutch you should replace with the newer style. I have seen many fan clutches explode and toss the fan thru the radiator. Really ruins your day.

 

[rd3war]

What is the difference between the old style and new style fan clutches? I've seen newer fans (without clutch) on evil bay with steel centers, are the old ones aluminum?

 

[Suprman]

Newer design. The old style is discontinued. Your clutch may be ok. Just a good idea to take a look at it. Get the part number off it we can see which one it is.

 

[Awesomeness]

What is the difference between the old style and new style fan clutches? I've seen newer fans (without clutch) on evil bay with steel centers, are the old ones aluminum?

I was just replacing my old clutch with the new style today. From the outside, they look very similar - I don't know what's different on the inside. The way to tell them apart (besides the part number obviously) is that the old style has threaded bolt holes for attaching the fan, and the new style has studs. The old style fan does have an aluminum center with a rubber bushing, and the new style has a steel center. The two can not be mixed - old style fan clutch only fits old style fan, new style fan clutch only fits new style fan.

 

[rd3war]

Just wanted to post a follow up on this. Someone replied that I should make sure that the cab wasn't sitting on the engine since my cab air ride wasn't working. That is exactly what it was doing, the hose clamps on the uppermost hoses were touching the underside of the cab and made a little dent and run mark there. I spun the clamps down so they don't stick up anymore. So now the annoying vibration at idle is better. Next job... install the new cab air bags.

I also checked to see if my fan and fan clutch were the older or newer model. As per TM: "NOTE: Discard fan clutch assembly PN 1090-08000-03 and replace with fan clutch assembly PN 1090-08000-01." Luckily the fan clutch still had the sticker so I confirmed it has already been updated to the newer part number. Easy way to check, use your phone to snap a photo, no disassembly needed (if you still have the sticker on it). I did pick up a new spare fan on ebay in case I ever need it.

 

[yertnamreg]

Random question, did your truck come with the white face gauges? Those look pretty slick!

 

[rd3war]

The white faced gauges were in the truck when I got it. The previous owner probably added them, but I've seen some trucks come out of surplus with some gauges like that, usually not all, but some that were replaced during its service.