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What to do first:

  • Replace the clutch

    Votes: 2 25.0%
  • Diesel tune-up and fix leaks

    Votes: 4 50.0%
  • Something else

    Votes: 2 25.0%

Bad vibrations: which to do first

4K views 35 replies 9 participants last post by  PlaneCrazy 
#1 · (Edited)
Greetings, all

I am trying to eliminate the last vibrations from my car. There are primarily two remaining task that I have to complete:

1. I have to replace the clutch. And I might just have it done rather that doing it myself, lest the flywheel needs to be machined. I would prefer to purchase and supply the clucth myself, but I will enquire from the shop what clutch they supply.

2. The engine needs a tune-up. I have new nozzles, I have had the injectors pop-tested and leak-tested, and I have adjusted the valves, but there's no guarantee that nothing could have affected the injection system just because I didn't move or remove the pump. Also, there are some pesky diesel leaks.

The questions is: Which should I do first?

The tune-up will probably cost less. But if some of the vibrations remain, they might tell me there is something seriously wrong with the engine.

The clutch will be much more expensive. But if that doesn't solve the vibration problems, it will make diagnosing the clutch and clutch installation that much more difficult.

What would you do?
 
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#3 · (Edited)
Noticeable at 1200-1400rpm, with or without clutch depressed.

Can be felt in 1st, 3rd and 4th, will tear everything apart in 2nd, independent of vehicle speed but absolutely related to engine speed. Slightly more noticeable during acceleration/deceleration.

The engine can be seen rocking from left to right at these speeds, even if the fuel injection smooths out. I'd say 2mm-3mm. (I couldn't see if it were yawing around the vertical axis as well, but it was definitely rolling around the crankshaft axis.) The fuel injection also causes some bad shaking, which is visible when looking at the engine but not felt through the steering or chassis, complements of the new engine and transmission mounts.

I should mention that I did not have the flywheel machined this time around, because it seemed fine and I was in a bit of a hurry to finish. I also did not replace the clutch because it seemed fine. But the clutch has suffered some stall stops, twice when I broke first the clutch fork, then the clutch slave cylinder, and a third time more recently when the clutch master cylinder broke. (I make it sound like I drive like a maniac - or worse, an idiot...) The clutch also judders (sometimes) during a standing take-off.
 
#4 ·
Loving the enthusiastic response from all you guys.

(I'm guessing this whole password debacle is really going to hurt the forum in the long run, with many knowledgeable members not returning...)
 
#5 ·
Holy sheet I managed to remember my new password!

I didn't think that would happen...


...your problem is so not the clutch if you get the vibration with the clutch in or out.

Always sort out leaks on a diesel engine!
 
#9 ·
The tyres were balanced as soon as the car hit the road. The prop shaft centre bearing is brand new, as are the flex discs and engine mounts. I checked the prop shaft for straightness in the horizontal plane and in the vertical plane. I placed the car on the ground, rolled her to and fro and shook this way and that way, before scraping myself underneath to tighten the last bolts.
 
#12 ·
Yes, I had the prop shaft positions marked when I had it balanced. How can the prop shaft be upside down when it is a revolving component?

A question or two for you ,,,,,, does the engine shake and run rough at idle while the car is not moving ? If the answer is yes and you have the proper size wrench that will fit the fitting where the high pressure fuel lines to each cylinder exit the injection pump crack each fitting loose one at a time . If there is no change in the shaking condition after cracking the fitting loose and retightening each one at a time . Post a reply here .

Geo

PS feel free to ask if you have any questions
Yes, the engine shakes quite visibly when the car is not moving. At idle one can clearly see the motion at the injection frequency. If I throttle up a little, the injection vibration subsides, but the engine rocks visibly from left to right. I haven't touched the IP side of the hard lines. Are you talking about the multispline fitting of the delivery valve, or the 17mm hex fitting of the line itself? (I prefer not to tamper with the delivery valves myself.)
 
#11 ·
A question or two for you ,,,,,, does the engine shake and run rough at idle while the car is not moving ? If the answer is yes and you have the proper size wrench that will fit the fitting where the high pressure fuel lines to each cylinder exit the injection pump crack each fitting loose one at a time . If there is no change in the shaking condition after cracking the fitting loose and retightening each one at a time . Post a reply here .

Geo

PS feel free to ask if you have any questions
 
#33 · (Edited)
...does the engine shake and run rough at idle while the car is not moving ? If the answer is yes and you have the proper size wrench that will fit the fitting where the high pressure fuel lines to each cylinder exit the injection pump crack each fitting loose one at a time . If there is no change in the shaking condition after cracking the fitting loose and retightening each one at a time . Post a reply here .
It looks like desmodromic may be on to something.

My father helped me discover a vibration on Injector #1 that sounds like there are gas bubbles moving through the hard line. I'll take a look soon, but not today.
 
#14 ·
I'll check again, Nutz. But so far, every time I reach any speed where the vibration is perceived, and I disengage the clutch, the vibrations disappear. I am 90% certain this is not related to driving speed and only to engine speed.
 
#16 ·
Sorry, I still don't understand.

The old flex discs were replaced with brand new flex discs, and the prop shaft was removed to be shortened and balanced. The prop shaft halves were marked before removal, and reassembled with the markings still aligned before balancing.

Are you suggesting that I move the prop shaft one hole at a time on the transmission and final drive to see if it makes a difference?
 
#22 ·
Sorry, the car isn't with me this week, and I can really only spend weekends. But I will check on Saturday and report in.

Does the engine have to be cold or at operating temperature? I'm somehow thinking that I should crack the nuts loose and tighten them again before starting up.
 
#23 ·
What desmodromic is trying to have you do is release an injector feed line one at a time at the injector to see if engine miss increases or stays the same. Like on a gas engine when the spark plug wire is pull off of a spark plug. Loosening the nut on the feed line will not harm anything. Do have a rag or paper towel available to clean up the little amount of diesel that comes out. Less than a teaspoon full.

If it vibrates in idle, trans in neutral, clutch is probably not you problem.

Also check the motor mounts!

Have you had a compression check done lately.
 
#24 ·
Timing chain?

How is it? Stretched?
Injection pump? Off a tooth?

My '79 240D had the pump advanced a little-like the marks on the block and the pump of over 1/4 inch, advanced. The injection lines were bent enough to make installation of the valve comer difficult.
I didn't get to check the stretch of my timing chain as the tensioner and tension rail were shot. After installation, the car wasn't running right, so I removed the valve cover and discovered the crankshaft bolt resisted turning. I used an inspection mirror and could find nothing blocking the chain. I removed the rocker arms to prevent collisions, removed the oil pan- and found some link plates in the pan, along with ground chain pieces. When I cranked the crankshaft bolt, the chain had broken, but not separated- glad I didn't run it any longer! When I got the new IWIS chain I recognized the chain was from a gas engine-the chain components measured about 30% lighter, so this chain needed to come out whether it was damaged or not.

I had to remove and reinstall the injection pump to get it to run right again, and now it is on the marks.

I think the timing chain/injection pump may be suspects.

Later,


snapped_bolt

The shaky idle I had before is now gone- and I still need to adjust the valves, they are waaay overdue!
 
#25 ·
WHOA!! Slow down.

I thank you for all the feedback, but it looks like most of you don't know this car, this engine, or me.

The car has been off the road for nearly 18 months, being converted from gasser to diesel. That involved fixing all the problems I had after converting my original 240D to 300D.

The flex discs are new. The engine mounts are new. The prop shaft has been balanced while it was being shortened. I replaced the injector nozzles (220's, although they should have been 240's, considering the engine is an '82) with new nozzles (261). I had the injectors leak tested and pop tested, before re-installing them. Yes, I used a torque wrench to properly torque them. Yes, I used new heat shields. I replaced the valve cover gasket, also using the opportunity to adjust the valves.

I didn't touch the injection pump, or the chain. Those were fine when the engine was tested 5 years ago. The chain had been replaced then. Besides, these are things that I can only pick up on during a tune-up.

Most of my effort to yield a clean and smooth car have been successful: New engine rubbers, harder unit on the left, stock unit on the right; new-ish transmission mount; prop shaft straight in the horizontal and vertical planes; new prop shaft flex discs.

The clutch failed on me three times since being installed back on Donkey, my former car. Once the slave cylinder broke, and I had to stall the engine to stop; once the clutch fork broke; and most recently the clutch master cylinder's push rod snapped. There is no doubt that I will have to replace the clutch. But it will be expensive. If it doesn't immediately solve the vibration issue, it will set me back a good long while before I can take the next step. If, on the other hand, a proper tune-up will solve the vibration issue, then I can confidently wait until the December holiday to replace the clutch.
 
#26 ·
Well, I couldn't buy a 12-slot deep hex socket to modify to loosen the injector hard lines.

Fortunately she's scheduled for a diesel tune-up on Tuesday.
 
#27 ·
So, they couldn't exactly tune the car. But they could install a chip and add boost to the turbo... if I had a turbo... or a computer...
 
#28 ·
I'm up to ears with work, but I've decided to fix the W202 first.

Then I'm going to put my W123 back on the ramps and jack stands. I'll put the jack stands under the trailing arms, in order to allow the suspension to work as if on the ground. Then I'm going to put the car in 2nd gear and see what happens under the car. I'll crack the hardlines and see if there's any difference. I'll also check the valve clearances and chain stretch again to see if they could be the cause. If not, then I'm going to remove the clutch, then put the transmission back on without the clutch - again, to allow all the suspension components to work as if on the ground.

If it is the clutch, I'll have to cough up sooner rather than later. If it isn't the clutch, and it isn't the fuel or valves, then I guess I'll need a full engine balance.

Fun, fun, fun.
 
#29 ·
I haven't disassembled the car yet. Which is just as well, as I could drive her to town today. I had a collection for work, but while I was there, I stopped at the Bosch diesel service center that I frequent.

Three of their diesel experts came to look at and listen to the engine. After detecting no leaks:D, and following a short drive with me, they all agreed that the vibration is unlikely to be fuel system related. While such rocking can be caused by the fuel system, the symptoms will appear throughout the operating range of the engine, not just at some RPMs. Also, it appears that most of the MW pumps used in South African 300Ds were equipped with the vacuum bit behind the ADA, since they were similar to the US-spec MW pumps. This means that the auto tranny vacuum bits on the pump does not mean the pump or the engine was ever used in an automatic car.

The oldest technician mentioned that the engine runs a bit loud. I told him that he should've heard it with the previous nozzles. So she's definitely due for a proper tune-up.
 
#30 ·
Well, I'm still looking for a 12-prong socket to modify. But I did eliminate the clutch as source of vibration.

I guess the next, easiest and cheapest things to check are the cylinder compression and the IP.
 
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