Broken Engine Mount

[paulinbelper]

My son has recently bought a 1 year old Rapid 1.6 TDi S with approx 14,000 miles on the clock just over a month ago.

 

Within two weeks of ownership there was a loud knocking from the engine.  We called Skoda assist and the car was diagnosed with a broken engine mount (the nut and top of the stud had sheared off) the car was taken to a skoda dealer and a new mounting fitted under warranty.

 

Now two weeks later, the mounting has broken again in exactly the same way?

 

I've attached some pictures that I took this morning - you can clearly see how the nut has sheared off from the top of the stud which goes through the engine mounting.

 

Has anyone come across this before?  What could be causing the nut to shear off after such a short time of driving?  Is there likely to be an underlying issue with the car that should be investigated? should we be rejecting the car and getting our money back?

 

Any help or advice that members can provide would be much appreciated.

 

Thanks

 

Paul

 

 

[niant]

Hello! I had something similar. Since the first months we brought our Rapid (1.2 TSI) I heard a strange noise coming from the engine hood. It was diagnosed not with a broken engine mount, but with a broken transmission mount ( I think, I don't really know much about mechanics). But for sure it was some mount. Anyway, after that, and I mean, it has been more than one year and the car is perfect until today. no more breaking parts.

 

Do you know if the car had some kind of accident before?

[paulinbelper]

Hello! I had something similar. Since the first months we brought our Rapid (1.2 TSI) I heard a strange noise coming from the engine hood. It was diagnosed not with a broken engine mount, but with a broken transmission mount ( I think, I don't really know much about mechanics). But for sure it was some mount. Anyway, after that, and I mean, it has been more than one year and the car is perfect until today. no more breaking parts.

 

Do you know if the car had some kind of accident before?

Hi,  We've got the HPi checks and the car has not been written off or subject to accident repair, there's no evidence elsewhere on the car that suggests accident damage and nothing was highlighted when it was in the dealer a few weeks ago with the first broken engine mount.

[niant]

Hi,  We've got the HPi checks and the car has not been written off or subject to accident repair, there's no evidence elsewhere on the car that suggests accident damage and nothing was highlighted when it was in the dealer a few weeks ago with the first broken engine mount.

So that's awkward. The car's warranty was just one year? 

[paulinbelper]

So that's awkward. The car's warranty was just one year? 

It's still under warranty and Skoda will repair it again, however we're concerned that the new mount has broken after only two weeks use!!

[niant]

It's still under warranty and Skoda will repair it again, however we're concerned that the new mount has broken after only two weeks use!!

Yes, of course, it is a smart concern. I would say this: wait for the next repair, and if it breaks again then it is very very very odd. In that case, maybe the problem, as you said, it not in the mount part, but in any other place that, somehow, is forcing the engine mount to break.

[Breezy_Pete]

Make sure they check the other mounts while they're replacing it. That should be standard procedure, I would have thought, but I could imagine that if another mount were damaged/loose/not-doing-its-job-for-some-reason, it might cause a movement in this one that it wasn't designed to cope with.

I would have thought that bolted joint would be designed with a fair size safety margin though, to cope with all such eventualities without the engine dropping out, so I'd suspect a dodgy batch of mounts, or an incorrect pre-loading/tightening procedure.

 

Ask them what the torque spec. is that they will use when they fit the next new one.

 

Edit: Unless the rubber mount bit and that alloy casting get replaced 'as one' in which case they won't be torqueing that bolt themselves?

[chrisgreen]

Has anyone come across this before?  What could be causing the nut to shear off after such a short time of driving?  Is there likely to be an underlying issue with the car that should be investigated? should we be rejecting the car and getting our money back?

 

Any help or advice that members can provide would be much appreciated.

Hi Paul

The only things I can think of that would cause this to repeatedly happen are:

1) The engine mount wasn't all the way down on the bolt before the nut was screwed on, and so the nut wasn't gripping enough bolt to take the load (if it was just screwed on at the tip of the bolt, that's a lot of vibration and force to be subjecting the end of the bolt thread to)

2) The engine isn't mounted properly on the other mounts (it could be shifted too far overt the passenger side, causing it to pull on the driver's side mount), and needs to be slackened off on the other mounts to allow for a proper fit on the bolt

3) They over-torqued the nut

4) The grade of bolt being used is simply substandard and this is the first of many instances we are going to see of this happening

Do keep us posted please, as if its the latter two issues, we could be seeing a lot more of this.

Chris

[paulinbelper]

Hi Paul

The only things I can think of that would cause this to repeatedly happen are:

1) The engine mount wasn't all the way down on the bolt before the nut was screwed on, and so the nut wasn't gripping enough bolt to take the load (if it was just screwed on at the tip of the bolt, that's a lot of vibration and force to be subjecting the end of the bolt thread to)

2) The engine isn't mounted properly on the other mounts (it could be shifted too far overt the passenger side, causing it to pull on the driver's side mount), and needs to be slackened off on the other mounts to allow for a proper fit on the bolt

3) They over-torqued the nut

4) The grade of bolt being used is simply substandard and this is the first of many instances we are going to see of this happening

Do keep us posted please, as if its the latter two issues, we could be seeing a lot more of this.

Chris

Thanks Chris, we'll be taking those issues up with Skoda when it goes back into the garage tomorrow.

 

Regards

 

Paul

[eyegr]

This engine mount comes fixed with its base underneath from the factory. If they only changed the nut, it could be out of specs or over/under torqued.

Force them to replace the entire part, the part number is 6R0199167AE.

Also make them check the tightening torque for all other engine mounts' nuts and screws and adjust as follows:

M6: 10 Nm

M7: 15 Nm

M8: 20 Nm

M10: 40 Nm

M12: 70 Nm

 

After replacing the part and adjusting the torque, if it breaks again, there's something wrong with the car - demand a replacement.

Edited 1 July, 2015 by eyegr

[Breezy_Pete]

^ Those torque figures look a bit 'old-style'; but not necessarily wrong.

 

I'm reasonably sure the engine mount fasteners will be torqued to a lower figure than those numbers, and then angle-tightened for the final 90° of tightening. This gives more repeatable/reliable results than torqueing alone, as it removes the influence of friction for the angle tightening part of the process.

Is there such thing as a Haynes manual for a Rapid? If so that should have all the specs for each bolt/mount.

[eyegr]

^ Those torque figures look a bit 'old-style'; but not necessarily wrong.

 

I'm reasonably sure the engine mount fasteners will be torqued to a lower figure than those numbers, and then angle-tightened for the final 90° of tightening. This gives more repeatable/reliable results than torqueing alone, as it removes the influence of friction for the angle tightening part of the process.

Is there such thing as a Haynes manual for a Rapid? If so that should have all the specs for each bolt/mount.

I'm quoting the official Skoda workshop manual for the TDI engine, edition 05.2014. Wrong or right, I wouldn't know, but that's what the factory recommends.

[Breezy_Pete]

Oh, fair enough! Is that specifically the engine mount torques, or more general info though?

 

For example, on the Mk1 Fabia, a similar table of values exists, but then for the engine mounts, this page describes what I was talking about. Tellingly, there's no suggestion that one would undo the fastener that the OP has found broken (twice!) and replace the mount itself separately, which makes it less likely that error in the factory where the car was assembled, or at the dealers where it was first replaced, is involved. (Presuming that Skoda procedures aren't too different for Fabia and Rapid in this area).

[eyegr]

I hope I'm not violating any copyright by posting this.

 

 

As I wrote before, the aforementioned bolt is not specified at the factory workshop manual because it comes fixed. So it should be replaced altogether imho.

[camelspyyder]

Worrying that things are wearing out / breaking on cars so young.

 

We've had track rod end failure and engine mounts so far this week on here (both on diesels)

[Stormchaser]

Looking at the remains of the stud it looks like it's possibly been over tightened. Just using any old nut won't do either as normally the bolts/nuts are one time use on mountings.

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[paulinbelper]

Looking at the remains of the stud it looks like it's possibly been over tightened. Just using any old nut won't do either as normally the bolts/nuts are one time use on mountings.

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That's what I thought, but the unit comes complete with that bolt that's sheared off fitted at the factory and not adjusted during the fitment process (apparently).  The car's gone back to the Skoda today for a replacement mount and a more detailed investigation as to what's causing it to break.

[Breezy_Pete]

I'm intrigued by the depth of the 'sawtooth' indentations from the underside of the nut/washer in the alloy.  To my eye, that doesn't look to have been a 'cast-in' feature in the alloy. Makes me wonder whether some of that embedding happened after the nut was done up, for example because the alloy was softer than specified, coupled with thermal cycling in the engine bay, leading to loss of pre-load in the fastener? It's not clear to me how that would make the stud shear off with the nut, but a loose fastener is a vulnerable fastener, I believe.

[paulinbelper]

Well it seems that the first broken engine mount was just 'one of those things!", however Skoda Tech is investigating this as it is an unusual occurrence.  

 

However, it seems that the replacement mount broke within two weeks of replacement because the Skoda dealer that did the work (not our usual dealership - the nearest one which Skoda Assist towed the car to) had just jacked the engine up and put in the new mount without slackening off and adjusting the other mounts on the gearbox end.  This led to the engine/gearbox not being mounted correctly which placed the new mount under stress - so much so that it sheared off after two weeks.

 

We're getting the car back tomorrow, but it just goes to show that not all the dealers are the same, and also that some of the grease monkeys in the garage don't have a clue what they're doing!  Our regular dearer has been very helpful and made sure that the job was done properly.  Hopefully my lad will be back on the road with no further problems for a long time to come, fingers crossed!

[Breezy_Pete]

I don't buy either of those explanations, but sincerely hope that your new one fares better.  

[StevesTruck]

I'm intrigued by the depth of the 'sawtooth' indentations from the underside of the nut/washer in the alloy. To my eye, that doesn't look to have been a 'cast-in' feature in the alloy. Makes me wonder whether some of that embedding happened after the nut was done up, for example because the alloy was softer than specified, coupled with thermal cycling in the engine bay, leading to loss of pre-load in the fastener? It's not clear to me how that would make the stud shear off with the nut, but a loose fastener is a vulnerable fastener, I believe.

Someone put a shakeproof washer in, mullered it down (suspect buzzgun) then realised their mistake and took it out?

[Breezy_Pete]

Interesting contrast in appearance between the OPs pictures of the alloy casting and the used one in this listing. Same part numbers and manufacturers marks, very different appearance in the neighbourhood of the snapped stud.

 

 

Someone put a shakeproof washer in, mullered it down (suspect buzzgun) then realised their mistake and took it out?

 I think the nut used is a flanged nut, which will have that sawtooth profile on the underside of the flange part. Designed to embed a little, but nowhere near as much as in the OPs pictures, I wouldn't have thought.

[StevesTruck]

Possibly, I'm not an engineer, but it looks squashed in rather than rubbed in if that makes sense.

I wouldn't have thought using a fastener with a shakeproof finish on against a soft metal is worthwhile, I'd have thought it's need a plain washer in between.

[Breezy_Pete]

Yeah, I know just what you mean about squashed in not rubbed in, which I reckon either happened by the nut being held still while the mount underneath was turned during manufacture of the overall assembly (which seems very unlikely in my head) or because the alloy was much softer than intended at engine-bay temperatures (cheap fake part with substandard metal?) and that embedding really did happen in service, after it had been fitted to the vehicle. Once the pre-load is lost due to the depth of the embedding taking up all the stretch in the stud, movement of the joint becomes possible, metal fatigue becomes a factor and bang goes the stud. 

 

 

Maybe?

 

Dear OP,

When the new mount is fitted, any chance of a close-up photo, attempting to show how much the flanged nut is embedded in the alloy bracket?