Advice on OM617 Engine Mount/Shock Change
 

Yo!

So I have an 83' 300TD Turbo, it's running okay for 329,000 miles but has developed a hard shake in the engine once it's warmed up and idling. I did a diesel purge, changed the fuel and the fuel filters and cracked the fuel line nuts to force it to miss. When the nuts were cracked, each cylinder noticeably missed.

So after all that, I'm thinking it's the super worn out engine mounts. I'm going to attempt to replace these myself but I also noticed the engine shocks are totally shot. From my understanding, these shocks play more of a roll when killing the engine, not so much during idle

It seems the mounts are quite affordable, but doing the engine shocks is really expensive. So I'm thinking about changing the mounts and if it solves the rough idle issue, then I'm going to go back in and change the engine shocks. I've heard you don't need to jack the engine up to remove the engine shocks.

I know it's twice the work but I'd be really pissed (with this particular car and it's condition) if I spent all that money on the shocks and it didn't help at all. The mounts, those are inexpensive enough that I don't mind if they don't do the trick.

So my questions are as follows...

1) Can I in fact change the engine shocks without lifting the engine?
2) Is it so much work that it makes no sense to change shocks separately from the engine mounts?
3) Do the shocks end up playing that much of a roll in reducing idle vibration?

The shocks come out without lifting the engine. The Shock mounts are expensive for what you get. There are threads on taking them apart and filling with Flexane. I did that and the mounts are working fine after ~1 year.

I posted recently about engine mounts collapsing and letting the PS pump damage the oil cooler lines. There are instructions regarding filling them to prevent the collapse. I'm going to do that as soon as I get my water pump replaced.

My engine shook lots until I adjusted my valves. All my intakes except one were tighter than 5 thou. After I adjusted it, it was a Lot smoother. I think I need to do it again though, and I don't have two thousand on the car since I did it.

Fix all the cheap stuff that can cause the hot idle shaking

Adjust the Valve

Make sure there is no Air leaks, typcal sources the Oil Style Hand Primer, the 2 sections of inlet Hose and cracks in the Plastic Filter

The idles speed should be with in the normal limits

If you can take yours apart the Fuel Pressure Relief/Overflow Valve Spring gets compressd over time and the Service Manual has that you can stretch it back to 27mm of free length.

If it is shaking badly a new Rack Damper/Governor Idle Pin may or may not help.
At your Engine Milage is enough to have worn out 2 sets of Injector Nozzles. (The Valve adjustment and rebuilding the Injectors too away most of My hot idle shaking.)

If you change the Motor Mounts remember the Transmission Mount also supports the Engine and Transmission.

If you still have issues after the above stuff is fixed a Compression Test is in order because you would suspect uneven Engine Compression.

You didn't tell them it was recommend to adjust intake gaps closer to 0.008 " with warm engine.


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It is really recommended that valves be adjusted STONE COLD.... unless you have an emergency.....that is because of the variables in expansion due to temperature which we have no way to measure...

I assumed they could read the sticker. :P

I plan on doing a valve check but doing the engine mounts, at this point, is actually the cheapest, if not the easiest thing to do. I want to do that first mainly because I know they're shot and at least contributing to the shaking. If the shake is a valve thing, I figure it's really important to at least get it more supported so the shaking doesn't destroy the drivetrain while I save up for the kit to do the valves.

I figure it's not the rack damper because it doesn't have sort of a floating idle, it just shakes and holds idle at the exact speed.

My gut tells me it's either the injectors or the mounts or both. It could be that at idle the injectors are spitting fuel out poorly because of the lower pressure and the monte are so shot that it lets it shake way more than it should.

The mounts will not cause a rough idle. The RD will give a rough idle that feels like a miss, it does not produce a rolling idle. The symptom will get worse as the engine warms up.

Having said that, replace the mounts if they're bad, but don't expect that to cure the rough idle.

Interesting, I always read that if the rack dampener was off, it would more affect the consistency of the idle not cause engine shake. Could I potentially see by screwing it all the way in and backing it out?

You can mess with the rack damper. Keep track of what you do and you can return to the start.

I did a valve-adjust hoping to take care of a bad air-cleaner shake at idle - no major difference. My engine mounts are beyond shot, and I've got new ones, but first trying to find someone who can detail the crap out of my engine-bay without me just washing it down the street into the storm-drain.

But on a roll one day, I finally replaced my rack damper bolt after carrying the new one around for a few thousand miles and not putting it in ('cause I'd gotten the idea that there was a special seal in the locknut that might leave me spewing oil/fuel out or some such). Not so. This made a significant difference, in the two minutes it took to do. Pretty sure the air-cleaner mount had broken solely because of the old bolt's weak-a$$ spring - even the beefiest of reinforcements couldn't have stood up to that extreme idle shake for too long. As for 'adjustment' of the new bolt, well it seemed I couldn't have tightened it any further without getting rid of the jam-nut.

I keep extra air cleaner mounts on hand for when they break but will try making some te next time I have Flexane out. I'll make a mold out of some type of plastic pipe, screw a stud through a cap on the bottom and pour the Flexane then cut the plastic off once it sets.

My engine doesn't shake excessively & still periodically breaks the rubber mounts. The bracket has been broken on every car I've looked at but hasn't broken after I replaced mine.

Most people do not follow the instructions in the FSM for making the gauge to check to see that the engine is correctly positioned relative to the engine mounts... so they start out under undue strain...and fail prematurely....

There is an old thread about putting a piece of Heater Hose between the Intake Manifold and the Air Filter Housing. It limits the movement of the Air filter Housing and prevents the Housing from beating on the intake Manifold.
I can't remember if the Hose was 1/2 or 3/4 inch ID. You need about 6 inches of it.
When I did mine I glued the Hose to the Manifold but that may not be needed.

More advanced; some one made a bracket with a Rubber Bumper to do the same thing that the Heater Hose will.