Flex Disc Replacement - Balance driveshaft?

[e500.org]

I recently had quite a few jobs done on my car. One of those was replacement of the front flex disc (which I was told by another garage was faulty but turned out it was ok - anyway).

Now I collected the car and frankly I am not completely satisfied because there is notable vibration in the driveline (which was not there before). This is at both at idle when in gear and also when driving. I assume the prop is not moving when in gear but it is probably under load/engaged. When in neutral the vibration reduced/is gone (I collected the car quite late last night so did not get to check it out properly). I will get a video up.

I am wondering whether the driveshaft needs balancing when you replace this part or whether the flex disc it is a simple remove/replace and install of the new bolts?

I am getting the wheel alignment sorted soon as well as full wheel balancing which should sort much of the issue(s) when driving as a number of suspension items got replaced (tie-rod assemblies, strut mounts, drag link, etc.).

Another issue: I also now have a misfire after replacing the ignition wires, coils, distributor caps. The insulators and rotors did not get replaced but have been removed and look ok. The FPR is original so I might replace this as I've had issues with this before. I am going to get the blink code ready plugged in and see if it reports any problems.

 

[e500.org]

BTW and I think this might be relevant - I only replaced the front flex-disc. We left the rear in place and did not replace it as it looked visually OK. I wouldn't have imagined both needed to be changed at the same time (like you do with shocks for example) but now I think about it more that may actually make sense: perhaps if one is "worn" and the other is tight/unworn, this would ultimately lead to an imbalance in the prop. I could test this theory as we kept the old flex disc (it looked fine upon removal/visual inspection) and see whether that makes any difference.

Edit: Original MB flex disc fitted.

 

[gerryvz]

If you are doing a flex-disc replacement, on one end only, then it should be pretty straightforward and not require removal of the driveshaft. You should not have to mark anything for a single flex-disc replacement.

When you remove the driveshaft (for example, if you are replacing the driveshaft center support bearing), then you need to mark the driveshaft's position before removing it, to maintain the factory alignment.

 

[e500.org]

If you are doing a flex-disc replacement, on one end only, then it should be pretty straightforward and not require removal of the driveshaft. You should not have to mark anything for a single flex-disc replacement.

When you remove the driveshaft (for example, if you are replacing the driveshaft center support bearing), then you need to mark the driveshaft's position before removing it, to maintain the factory alignment.

Thanks Gerry, I am not asking about removal of the driveshaft, as you note this is achieved with the unit in situ, however I am asking whether it needs to be rebalanced once the flex disc is installed. I think I know the answer to this question: no - but I did want to validate that position.

 

[gerryvz]

Let me restate more clearly -- my bad for not being clear in my first post.

If you are just removing and replacing one flex disc, then the driveshaft should not have to be removed. If the driveshaft is not removed, then its position does not have to be marked so that it is in the same (balanced) position upon re-assembly.

Therefore, replacing one flex disc should not create any situation where the driveshaft's balance is upset (as long as the flex disc itself is manufactured properly).

No driveshaft rebalancing is needed, required, or specified if one single flex disc is replaced.

I'm sure others can and will chime in.

 

[gsxr]

Now I collected the car and frankly I am not completely satisfied because there is notable vibration in the driveline (which was not there before). This is at both at idle when in gear and also when driving. I assume the prop is not moving when in gear but it is probably under load/engaged. When in neutral the vibration reduced/is gone (I collected the car quite late last night so did not get to check it out properly). I will get a video up.

Vibration while idling in gear and the car not moving, can not be from a flex disc.

I am wondering whether the driveshaft needs balancing when you replace this part or whether the flex disc it is a simple remove/replace and install of the new bolts?

Sometimes, yes, the driveshaft may need balancing when the discs are replaced. MB balances the propshaft with BOTH discs attached. Very few shops can do this. It's rare, and usually isn't needed, but it's possible the new disc is not balanced and causing problems. But it won't have any effect with the engine idling in gear and vehicle not moving.

Another issue: I also now have a misfire after replacing the ignition wires, coils, distributor caps. The insulators and rotors did not get replaced but have been removed and look ok. The FPR is original so I might replace this as I've had issues with this before. I am going to get the blink code ready plugged in and see if it reports any problems.

Ignition parts like rotors can LOOK ok but not function properly. Misfires almost never, ever appear in fault codes unless it's a "permanent" misfire where one or more cylinders never fire.

 

[gerryvz]

There are plenty of stories from people on the forum who thought they had fine-looking caps, rotors, and insulators, who replaced them and solved their issues.

These days, it does not make sense to replace caps and rotors, WITHOUT also replacing the insulators. All six parts should be replaced at the same time. No exceptions.

 

[maw1124]

Regarding that rough idle while stationary, how are your engine mounts? That's what gave my mounts away, nothing else. It just didn't idle like a ... ahem... Prius, anymore. I'd look at those + the misfire issue you're after already. But like @gsxr I doubt the flex disk has anything to do with it. Those tend to rumble under load when they're tired.

GL

maw

 

[Kyiv]

I recently had quite a few jobs done on my car.

I believe, vibration at idle could only come from bad motor mounts or engine working in an unbalanced fashion due to some issue.

 

[e500.org]

Thanks all for your thoughts. Engine mounts just got replaced actually, I assume there is no wrong way of installing them

Car got recovered this evening back to the garage so will find out more later and update this thread.

 

[e500.org]

There are plenty of stories from people on the forum who thought they had fine-looking caps, rotors, and insulators, who replaced them and solved their issues.

These days, it does not make sense to replace caps and rotors, WITHOUT also replacing the insulators. All six parts should be replaced at the same time. No exceptions.

Thanks. Issue with rotor arms is the rotor bracket needs updating and is currently NLA. Looking for a pair. As for the insulators, I'll replace these, but I do fail to see the issue with these if visually ok (seals good and plastic not damaged).

 

[JC220]

How fresh was the flex coupling? Eg SGF date of 2019 :



Only thing I can think of regarding the propshaft making vibrations when driving after flex disc replacement is that the part was incorrect/ malfitting (unlikely but still...) or they didnt fully locate and tighten up all the alignment dowels that locate into the prop and trans couplings. Maybe forgot to torque the bolts fully?

To be extra sure I now also mark the propshaft VS Diff or trans clocking with a paint marker before I pull the old flex disc. (Although the only clocking that should matter is the centre prop joint - I am extra cautious)

In short a SGF / MB flex disc correctly fitted should have zero vibrations.

 

[gsxr]

Thanks all for your thoughts. Engine mounts just got replaced actually, I assume there is no wrong way of installing them

There's sort of no way to install the mounts wrong, however the powertrain can be under tension, which can cause problems. To check for this you slightly loosen all engine mount bolts AND the transmission mount bolts, shake the powertrain around so it settles on its own, then tighten. In extreme cases I'd consider loosening the exhaust system at the manifolds as well. All the above is rarely needed, but when chasing weird stuff...

 

[JC220]

A new or proper engine ignition missfire also might give a false impression of a vibration.

Let the garage look at it again and resolve the misfire first and foremost I think.

 

[gsxr]

Good point, Joe! Any slight misfire can be felt as a vibration, which would explain the feeling when parked & idling.

 

[e500.org]

This has now been resolved. I am quite embarrassed to state: what felt like a vibration was actually the misfire itself. The solution cost me $0, it was as simple as the garage removing the spark plugs and realising they were not gapped. They did some research (perhaps this forum?) and noted the plugs need to be gapped to 1.0mm (they said from factory it seems like the spark plugs are gapped to 0.8mm). Now gapped to 1.0mm and reinstalled, the result is a perfectly smooth and strong performing E500, traction light on as you give it some down the road which always makes me laugh. Super happy with my car at the moment and a massive thanks to all the suggestions on this thread.

Note to all (which is admittedly a general comment all over this forum) - GAP YOUR SPARK PLUGS !

 

[JC220]

This has now been resolved. I am quite embarrassed to state: what felt like a vibration was actually the misfire itself. The solution cost me $0, it was as simple as the garage removing the spark plugs and realising they were not gapped. They did some research (perhaps this forum?) and noted the plugs need to be gapped to 1.0mm (they said from factory it seems like the spark plugs are gapped to 0.8mm). Now gapped to 1.0mm and reinstalled, the result is a perfectly smooth and strong performing E500, traction light on as you give it some down the road which always makes me laugh. Super happy with my car at the moment and a massive thanks to all the suggestions on this thread.

Note to all (which is admittedly a general comment all over this forum) - GAP YOUR SPARK PLUGS !

Glad its solved! That truly is a noob move for a garage. Spark plugs must always be gapped (excect iridium or specials) they are never right even if the box says pre gapped.

And in addition yes 1.0mm is recommended for the m119 over the 0.8mm spec so by virtue of that alone the spark plugs must always be gapped for the m119

 

[gerryvz]

Note to all (which is admittedly a general comment all over this forum) - GAP YOUR SPARK PLUGS !

Noted with emphasis here, as well as in MANY other places on this forum.

Although the Bosch plugs come pre-gapped at the "official" factory spec of 0.8mm, DO NOT TRUST this. You MUST gap each plug individually as it is installed, as plugs CAN and DO get jammed, jostled or otherwise disturbed during shipping, and this can potentially throw off the gap.

Not to mention the @Klink-approved wisdom on this forum that all M119 LH plugs should be gapped to 1.0mm, up from the factory-spec 0.8mm. This is expressly to help the running and idle characteristics of the engine, and avoid the issue that you had.

 

[e500.org]

Here is the video from the shop - thanks again all!

 

[a777fan]

In parking brake we trust!!!

 

[e500.org]

In parking brake we trust!!!

I know right, my reaction to that was OMFD !!!

 

[Funny Bunny]

I have vibration at idle and park too. New oem engine mounts didn't fix the problem.
My spark plugs are gapped at 0.8 so perhaps gapping to 1 might solve the issue?
My idle is fine though at 550-600rpm stable.

 

[gsxr]

It's easy and free to re-gap. Don't expect a major change, but it won't hurt to try.

 

[Funny Bunny]

It's easy and free to re-gap. Don't expect a major change, but it won't hurt to try.

I just finished doing this and there is no difference.
I did however notice this weird sound like a squeaky blowing sound while I change from P to R to D to N. I tried recording it but it wasn't loud enough to hear in the video.

Next thing I will try is "release the tension" on the mounting system as gsxr described.

Any other bright ideas?

 

[rayhennig]

plugs CAN and DO get jammed, jostled or otherwise disturbed during shipping

I haven't bothered to check gaps but I have noticed that my stock of genuine MB (Beru France) are not packed with that little cardboard cylinder that I've expected over the years. A bit shoddy?

RayH