W124 300D Severe judder

[bennycb]

Hi guys,

Just bought a W124 1987 300D Saloon. It´s a manual car and displays the following behaviour:

When the car is in gear and you are (very) gentle in pushing down or lifting off the gas, the car accelerates or decelerates nice and smoothly. However, if you change the throttle position without careful planning (either sudden lift off or suddenly press it a bit) the whole car judders back and forth (similar to clutch judder) and the lack of constant velocity is picked up through the speedometer (unfortunately rev counter doesn´t work).

2 mechanics had a quick look (but i live in Spain where they aren't too thorough) and they both said it was just the engine being old and wasn't worth investigating the problem further - just drive it smoother!

As a novice could someone tell me the following as i´m trying to piece together next course of action:

1) Could severe juddering be caused by a drivetrain problem (my possibly incorrect thoughts are if any part of the prop shaft or diff is this loose to allow such judder it would have broken altogether)

2) Could it be caused by the clutch even though the clutch doesn´t cause juddering when starting unless you release it suddenly during a gearchange. any definitive test to rule out clutch?

3) Assuming we can rule out 1 and 2 as the main cause and it is the engine, what could be done? I´ve greased all the throttle linkages. it needs a air filter fuel filter oil change and thermostat but mechanic said none of these were likely to solve it? The engine takes a few seconds to start on all cylinders from cold. From hot it´s instant and idles/revs smoothly in neutral.

I´d like to add im not fussy and my previous W124s were workhorses and had their faults...but they were atleast very smooth and easy to drive. I bought this very cheap as it hadn´t ran for a while and has done 200kms in a year and a half and have got all the electrics working smoothly and want to service it, but can´t justify servicing it if this problem will be unfixable as not sure i can live with it (and assume it must be putting a lot of wear on the whole drivetrain even if that is OK now!).

Any advice appreciated!

 

[Giantvanman]

Someone who's owned will be along but I am wondering if it's the engine mounts or prop shaft joints.

 

[dinoy]

i believe u right proshaft more likely but engine mounts i believe

 

[trapperjohn]

Hmmm Barcelona - Nice warm weather - bugger from drying out any rubber based mountings or rubbers if you will excuse the expression.

Have a good look at the gearbox mounting, diff mounts too.

 

[carat 3.6]

Sounds like a faulty crank sensor to me, it's mounted at the back of the engine looking at the flywheel teeth.

This sensor provides a signal to the idle speed control, and rev counter. But on a manual om603 it also feeds the "anti jerk control unit" or ARA fitted to the back of the injection pump.

 

[balge]

Sounds like a faulty crank sensor to me, it's mounted at the back of the engine looking at the flywheel teeth.

This sensor provides a signal to the idle speed control, and rev counter. But on a manual om603 it also feeds the "anti jerk control unit" or ARA fitted to the back of the injection pump.

Could be the ARA itself then? My auto 603 had a failed tach sensor, and it was a bit rougher, but in no way 'severe juddering'.

Easiest check for engine mounts is watch the engine while someone starts it up?

 

[bennycb]

Thanks for the interesting replies. Here´s some other observations I´ve made:

1) The first mechanic had to attach the exhaust which fell off while parked and didn´t line up properly so i asked him to specifically check engine mounts. He said the exhaust had been impacted and was bent and this was the reason it didn´t fit and that the engine mounts were fine and had not caused this. If i bounce the engine around it does not seem loose or to have any play and moves with the rest of the car.

2) I also asked the mechanic to check the drivetrain which he said was fine, however I can crawl under the car and turn the rear prop shaft a little with car is in gear and handbrake on. Also with handbrake off and car in gear I can push car back and forth a few cm. The rear rubber donut doesnt look that bad and the play i see isn´t here. Can´t get under it properly to have a full look or test more parts. When depressing the clutch when the car is accelerating, say just about to change from 1st to second there is a "clonk". Do these suggest a drivetrain problem grave enough to cause extreme juddering. When I say juddering I mean if I suddenly slam the accelerator down in 2nd at 20km/h there is a good 4 or 5 seconds of jerking back and forward, with the speedo jumping everywhere and each jerk is slightly less pronounced. Even in 5th at 70mph suddenly jumping off the accelerator (when you see a hazard for example) and the car judders once or twice for half a second. It is in every gear at every speed.

3) The rev counter has only worked at idle for a few seconds since i bought the car. As above I say the jerking is severe, could this anti jerk control really cause this? Also when i cold start it takes a few seconds to get all cylinders firing, could the failed crankshaft sensor cause this?

It must be hard to diagnose by here i know but if there are other little things i can try in order to rule more things out it would be great and the mechanics really aren't too helpful, they just say it's a 28 year old car and will have problems so anything i can self deduce the closer i´ll get to diagnosis. If I can fix this everything else seems to work/no leaks/no rust/good mpg so I´m sure it could be a good car.

 

[bennycb]

Hmmm Barcelona - Nice warm weather - bugger from drying out any rubber based mountings or rubbers if you will excuse the expression.

Have a good look at the gearbox mounting, diff mounts too.

And a bugger for finding mechanics who take any sort of problems seriously. My last W124 needed wheel bearings 2 years ago. Using forums and wikipedia I worked out quickly that the right front wheel bearing was on its way out (hum at 35 increased with braking and turning left). Got told by two garages it was absolutely fine and had to wait 6k miles later when it was louder and hummed all the time, even then they only did it because i explained i had a 3k mile roadtrip to do and didnt want to worry about it!!

Sorry if it's a stupid question, how would i go about checking the gearbox and diferential mounts.

 

[trapperjohn]

You know when someone said - Good Question. You just know you are going to get a rubbish answer.

I had mine changed because my buddy was doing a whole load of preventative maintenance and said they could do with doing and he did them. Carat will be along to tell you how Im sure.

 

[balge]

Easiest way to check diff mounts is to stick a jack under to see if there's any slack when you jack it up. Had to do my 230TE, crummy job but nothing too complicated if you have/make a puller for the bushes.

Any visual evidence of wear or damage on the dough-nuts I replace them immediately. Had one break, not risking that again...

If you test the crank speed sensor, it should have 0.4 - 2.5kOhm resistance at rest, and 4V ac or above at tick-over, increasing with revs. The sensor is down by the starter.

 

[Tim203]

I reckon it's an engine mount as well. They always look ok 'cos there's a large amount of gravity holding the engine in position but the torque reaction from the engine easily lifts it off the main mount. Assuming clockwise rotation looking at the front crankshaft pulley the N/S ( in England!) or left hand ( viewed from the drivers seat) should show signs of separation when letting the clutch out with the handbrake on and obviously getting an observer to view from the side to avoid any accidents! Its worked for me as a quick test. The movement allowed from a broken mount could well cause exhaust system damage so it does stack up.

 

[carat 3.6]

Could be the ARA itself then? My auto 603 had a failed tach sensor, and it was a bit rougher, but in no way 'severe juddering'.

Easiest check for engine mounts is watch the engine while someone starts it up?

Yep, it could be the ara control unit at fault, but with the tacho also not working the sensor is the most likely.

The ara is only fitted on cars with a manual gearbox, the auto's don't need it because the torque converter absorbs any jerks.

Any om601/2/3 and the non turbo 606 that have been converted from auto to manual will do what the op is experiencing. I have an e300 diesel that does it most days. Short of retro fitting the ara setup, I just depress the clutch and feed the power back in.

After a while you get a feel for when it's going to do it, so I've adjusted my driving style for that car so it wont do it.

 

[carat 3.6]

The engine mounts could well be worn, but I don't think they will solve the problem.

New engine mount vs old collapsed mount.

 

[Smiley]

Thanks for the interesting replies. Here´s some other observations I´ve made:

1) The first mechanic had to attach the exhaust which fell off while parked and didn´t line up properly so i asked him to specifically check engine mounts. He said the exhaust had been impacted and was bent and this was the reason it didn´t fit and that the engine mounts were fine and had not caused this. If i bounce the engine around it does not seem loose or to have any play and moves with the rest of the car.

The engine should move around a certain amount INDEPENDENT of the rest of the car - if the car is "locked" to the engine then the mounts are kaputt. If they look old and grimey change them, not too expensive and make a big difference.

 

[bennycb]

Another drive, Another problem and more observations

Not sure if related but started car and went for reverse yesterday and all i got was a thudding vibrating gearlever where reverse was (despite the clutch being down fully). Eventually inching forwards and retrying with force finally got it in reverse and then all worked as normal. After driving 20 minutes it all went in reverse fine and couldn´t find a problem. The other gears worked fine although i wouldnt ever have described the linkage as "positive".

I´ve tried to adapt the driving style to the car as said and i´m getting better at not juddering it so much. However, when turning left and accelerating any slight vibration is accompanied by some banging and clonking from the rear right of the car. It´s silent when going straight, right or not on the power.

Finally if the car is going very slowly in 2nd or 3rd so the engine is close to idle there is a resonance through the whole car. You can´t feel it and it´s insignificant compared to the other problems but it brings out any rattles (of which there are a fair few) and might be more evidence for engine mounts?

I have time this weekend so will get someone to help me check the engine mounts and will also try and see the wiring for the tachometer/antijerk - liberally WD40ing things and twisting the fuses has got the wipers, fuel gauge, and cluster instrument lights working so if i could just get the tachometer to work enough time to see if it makes the engine smoother i´d be happy. Anyone know where the various anti jerk stuff, tachometer and wiring is?

Other than that got the MOT equivalent in 2 weeks time so will be interested to see what happens and won't be spending any money on it until after then. I'm not even sure if drivetrain things are included in the inspection here.

 

[carat 3.6]

linkage as "positive".

I´ve tried to adapt the driving style to the car as said and i´m getting better at not juddering it so much. However, when turning left and accelerating any slight vibration is accompanied by some banging and clonking from the rear right of the car. It´s silent when going straight, right or not on the power.

Finally if the car is going very slowly in 2nd or 3rd so the engine is close to idle there is a resonance through the whole car. You can´t feel it and it´s insignificant compared to the other problems but it brings out any rattles (of which there are a fair few) and might be more evidence for engine mounts?

Sounds like you have more than one problem going on there.

Your suspects list is now: Knackered diff, worn engine mounts, injection pump electrical problem, worn gear linkage and/or gearbox.

 

[bennycb]

Sounds like you have more than one problem going on there.

Your suspects list is now: Knackered diff, worn engine mounts, injection pump electrical problem, worn gear linkage and/or gearbox.

I'm beginning to think that...oh and it wanders/is sensitive to camber angles on the motorway but all my W124s have always done that so i´m used to it. and it also needs a new thermostat, service and two rear tyres have 3mm.

In other words fit for the scrap heap? Or just drive it if it passes the MOT until it dies completely? I'd happily spend 5 or 600 Euros on it if it could solve all or atleast the main problems (and labour is only 40 Euros an hour here) but that sounds like quite a list of expensive things that could easily go over budget and still not be completely sure of solving it?

 

[Smiley]

It does sound like several different faults; potentially rear suspension, prop joints + mounting bearing, engine + diff mounts; also sounds like the clutch is dragging. Rather than crunch the gears getting it into reverse - you could turn the engine off; foot on clutch, engage reverse and then start the car in gear (with clutch down obviously); at least you won't wreck the gearbox whilst you find out what is wrong.

 

[bennycb]

OK so been on a few more drives and no new problems...I´ve found on start up and when rocking the car on it´s suspension the engine does not move independently of the car at all. I assume this confirms the engine mounts are gone, and as such possibly some of the judder and the resonance through the car should be solved by replacing them?

Can anyone give me a rough cost (hours/parts) that a garage might charge as i'm not too sure about spending a lot of money on this when i don't think it's the full problem. Also what else should be done at same time whilst the mechanic is doing the engine mounts (good time to change thermostat or other things?)

So my current plan is

1) see if it passes the MOT.

2) maybe get engine mounts done and see if it solves any problems

3) ignore the reverse gear selection issue as it hasn´t happened again. The selector is smoother now i WD40d where it is attached to the linkage inside the car.

4) the clonking from the back right on acceleration and turn left - does this sound like the differential and if so could this be causing the judder. Does this mean the differential will break very soon or could it just be ignored and probably not get any worse. I´m assuming a differential is expensive to buy??

5) the rev counter works for a few seconds at idle occasionally and correctly reads the rpm but pretty quickly fails to zero again so I am hoping this will work whilst driving one day and then can see if it eliminates any judder.

Sorry as always if silly questions. I just need to make a decision on what to do with it. It has no rust, is in good overall cosmetic condition for here, does over 35mpg on cheap diesel, and because it is over 25 years has no tax and insurance/breakdown is 120 EUR per year.

However i want a car mainly for holidays and big road trips and I have never had so little faith in a car to get me where I am going. Would anyone just recommend scrapping it and buying something else (though bear in mind cvars a re generally more expensive over here than the UK)

 

[balge]

I rather doubt just trying to shake the engine by hand will prove much about the engine mounts, unless you use a very long bar - just watching it being started will tell you more accurately.
Again, jacking up the diff will be the easiest way to check the diff bushings.
Clonking off to the side sounds more like the drive shaft than the diff .
If the tach sensor tests ok I would suspect the OVP relay.
If you can't fix it yourself or afford to pay someone else to...no twenty year old car is a cheap run-around.