Greetings from a newbie...
I have a 4D55 in an '86 Ranger. Recently, it has aquired a nasty vibration. At first, the vibration came and went with a periodicity dependent upon engine RPMs.
A few days later, the vibrations mostly faded away.
But it is now back (at least at some RPMs) and more of a steady vibration.

There are some other occasional noises - something more of a brief screech. Not horribly different than the sound of somebody dropping a screwdriver on the valve cover. (Nope, no miscellaneous screwdrivers lying around in there.) <img src="/forums/images/graemlins/shame.gif" alt="" />

Per mechanic advice (primarily a gas mechanic), the truck has a new turbo. The muffler has also been removed.

The vibration is present whether I'm in gear or not.
There are no obvious motor mount problems.
Motor was rebuilt about 40K miles ago, tranny about 2K ago.
Best MPG pre motor rebuild: 34 <img src="/forums/images/graemlins/kewl.gif" alt="" />
Best MPG post motor rebuild: 27 <img src="/forums/images/graemlins/frown.gif" alt="" />
Don't think it has the power it should have, either.

So now I come to all of you, looking for advice.

I'd take the rebuild back, sounds like something wasn't torqued to spec, and is coming loose. But don't quote me on it. Also see a diesel mechanic, he/she may have a better idea then my guess. Go to a truck shop, they mostly deal with diesel engines.

You might want to check your injection pump timing that can affect fuel economy and power. The earlier VW pumps (80s-90s) is adjusted the same way if you don't know how to do it (requires specialty tools) find a good VW mechanic who works on diesels he will be able to help. As for the Vibrations, it could be anything, maybe pull back the T-belt cover to make sure your balance shaft belt is still in place and OK, clutch fan frozen or bearing gone. The list could go on forever and you need to get a trained ear to listen sometimes. Preferably one you can trust. <img src="/forums/images/graemlins/cheers.gif" alt="" />

Ok, I've got it scheduled with the closest diesel shop that was willing to look at it. (I was pleased that they knew the little diesel ranger existed!) Hopefully I'll have a good report in a week. <img src="/forums/images/graemlins/cheers.gif" alt="" />

Hi,

I have the same '86 Ford Ranger diesel and here is what I would check first:

1. Turn off the engine and start checking all of the accessories attached to the drive belt. Wiggle them to see if anything has come loose. If you have A/C, check the compressor for being loose and also test the A/C clutch.

2. Inspect the drive belt(s) to see if there is any unusual wear. If it is worn in an area, inspect all pullies and tensioners.

3. Remove the drive belts and check bearings in all pullies to make sure they spin freely and without excessive noise. Reinstall belt or replace if worn. Make sure that you tension the belt well.

4. The 4D55 has a timing belt and a balance shaft belt and they both have their own tensioners. If the balance shaft belt slipped off track or broke, it usually takes out the timing belt and the engine stops when the valves bend on the top of the pistons. I guess it's possible that somehow the balance shaft belt is either off track or missing. This would cause excessive vibration that is normally dampened by the balance shaft driven by that belt.

If you can't find anything loose on the engine and the drive belt looks good, I personally would recommend tearing down the front to make sure those belts and tensioners are ok. It will be worth every bit of the effort if you end up preventing catastrophic engine damage from a broken timing belt. (this is an interference engine)

Good luck. Take good care of that truck and it will take good care of you. Those things will run and run and run and..

About the only things that will kill it are running it w/o oil in the sump or w/o coolant. (or letting the engine belts go too long between changes)

Powell

Thanks for the reply.

A mechanic noted that the fan clutch bearing is going out. I tested it by removing the two belts on the water pump/fan pulley and that seemed to get rid of much of the vibration. (I think the current lack of a muffler is also adding a few extra rattles.) I had tried the same test before the turbo rebuild without getting rid of the vibration, so it looks like I may have had two (or more!) problems. I should get time to replace the fan clutch this week and will report back then.

I know I can see the timing belt by removing the front plastic cover. Is the balance shaft belt also visible or does it require further tear down?

Truck has no AC. I will go through the pulleys/tensioners.

I'm the second owner on the truck and I've now owned it for 10 of its 20 years. It has been a fun truck, though not without its problems.