Technical Driver's side engine mount studs damaged

[spleenharvester]

Hi all, really hope you can help, I can't find any other threads on this and it's going to be a really costly repair otherwise.

I haven't got my own picture to hand at the mo but my question relates to these posts on my 2011 Fiat 500 1.2 8v:

I tried to put new nuts onto these and I don't know what happened - I think they must have been out of spec or something - but they absolutely destroyed 2 of the 3 posts, and currently only one has a nut on it. On the other two threaded posts, one snapped while trying to remove the stuck nut, and I can't get a new nut onto it at all. It just won't even begin to thread. On the second one, the top 1cm or so is stripped and there's a bulge below that, as if it's been pushed downwards. This whole section seems to be welded on so if I can't fix these threads I am screwed.

Has anyone got any idea how to even begin to fix these? It seems like most people have bolts here instead of threaded posts so I can't find any other info about this problem anywhere at all. Only thing I can think of doing is taking an angle grinder to the top of the posts and hoping there's enough useable thread below that point to get a nut onto.

Thanks

 

[GettinBetter]

Sounds like you put the wrong pitch nuts on, maybe with an impact wrench? Am I close?
But you've probably almost definitely chewed the threads up and will need a die, of the correct thread to run down each one to recut the threads, if you've left enough to recover. Get some closeup pics so people can assess the damage.

 

[spleenharvester]

Thanks - it wasn't an impact wrench, it was M10 nyloc nuts - I think the nylon part must have been too thick and they just got stuck. I've got M10 non-nyloc nuts now and those screw onto the remaining working thread OK.

Here's the one that snapped while trying to remove the stuck nyloc

Here's the one with the destroyed thread (I currently can't get that nut off).

 

[GettinBetter]

I'm highly suspicious of that thread being M10, and if it is then more than like it's M10 fine, perhaps someone else can confirm?

Cut a bit of thread from a known M10 bolt (your spare bits) hold it alongside those you've just photographed and take another piccy to see if the pitches are the same.

That first pic looks cross threaded.....

 

[spleenharvester]

I did think this at first and bought some M12 nuts but they were too large. RE thread pitches I will take a look.

I am tempted to just take it in to be honest, think I am likely to screw it up even more if I try

 

[GettinBetter]

At this stage, if you don't have the tools to measure threads accurately, or prior knowledge of thread repairs, then I would agree.

 

[spleenharvester]

Thanks, will let you all know the outcome

 

[GettinBetter]

Yes, that would be interesting, thx. Oh and loads of pics

 

[John202020]

Get the right nuts, even if you have to go to the dealer, but suspect they're m10 1.25mm pitch.
Heat the nut up that's an issue to remove
I, think there's enough clean thread left at the base to be ok once the wrong nuts are off(begs the question why the original old ones not re used) ?
Clean up with a needle file the threads, use a correct nut, to help clean the threads(that you intend((nut)) to throw away)
Probably all good after?
Note M12 would just fall over stud, likely you bought m10, 1.5mm pitch, NOT, 1.25mm

 

[portland_bill]

As said, the studs are probably fine pitch, and will be grade 10.9, not the standard 8.8. Bolts have this on the head, nuts keep their grade a secret. The nyloc part is not strong enough to cause any thread damage. the pic does look cross threaded, probably a result of the wrong pitch.

To measure the pitch, without proper measuring tools, rub one side of the thread with a soft pencil. then press a piece of paper against it to make a 'rubbing' of the thread. The with paper on desk, measure the pitch from one peak to the next, or across several and divide by the number of peaks. A standard M10 will be 1.5, but these will probably be fine, so 1.25, as said above.
The studs, almost certainly being 10.9 grade will survive better than 8.8. A thread chaser, or thread cutting die run down the stud should clean it up well. Any doubt, fit a locknut on top. When fitting the nuts, ensure the engine is sitting on the car, don't expect the nuts to pull it down, they are there to hold, not pull.

If the studs are beyond repair, you have to see if you can get beneath them. If possible, then you drill them out, and replace with bolts, which will forever try to disappear when undone. You'd need to be able to get a spanner behind them.

I've created a note for myself, to look closely at the Panda tomorrow afternoon. I'll add more then.

 

[steveras57]

Might be worth using a socket 3 roller stud extractor ( if you have!, or have access to one!) to remove the broken /damaged studs completely even buying three new ones and nuts from Fiat aint gonna bankrupt you and then you will know that its done right and will be safe going into the future!

 

[spleenharvester]

Thanks everyone, appreciate your input. I think you are right about the issue being that the nuts were actually the wrong pitch. I managed to get the stuck one off and filed the topmost edges of the threads (couldn't resist). Now they start to thread and get stuck. I'll try and get some that are deffo the right pitch and see if they go on. If no luck then I'll just let the garage deal with it so as not to screw up the remaining threads lol.

Edit - OK just got the right pitch (tested OK on the last working stud). Still no go, garage time it is.

 

[spleenharvester]

Updating this as I've only just got round to it. I confirmed the original nuts which did the damage were the wrong pitch. In short, an M10 x 1.25mm die made light work of this. One re-threaded straight away. The second - which wouldn't thread at all to begin with - took a bit more work, I had to hammer the die on - then turn - then repeat once it came off - rinse and repeat for quarter of an hour and it eventually cut enough to start a new thread with. All sorted now!

 

[varesecrazy]

Updating this as I've only just got round to it. I confirmed the original nuts which did the damage were the wrong pitch. In short, an M10 x 1.25mm die made light work of this. One re-threaded straight away. The second - which wouldn't thread at all to begin with - took a bit more work, I had to hammer the die on - then turn - then repeat once it came off - rinse and repeat for quarter of an hour and it eventually cut enough to start a new thread with. All sorted now!

Good news

That IS metric fine series M10 x 1.25

Coarse series is 1.5 pitch

 

[GettinBetter]

... I had to hammer the die on...

OMG . Not something I'd ever do, but it never surprises me what some people get away with, great that you got it sorted though.
Desperate situations call for desperate measures.

 

[steveras57]

Yep well done for a cheep and abstract fix ! id have bought new studs myself but whatever floats yer boat!

 

[bugsymike]

I have come to this late, but what I think was the cause , was the nuts on the engine side of the mounting are a different thread to the body/chassis side of the mounting.
Ideally and what OP will probably do from now on, is wind nuts and bolts by hand a short way preferably lubricated before applying tools to them, if they don't run down the threads as easily as they came off something is wrong. Presumably this means the ones on the engine side are now suspect also.

 

[steveras57]

I have come to this late, but what I think was the cause , was the nuts on the engine side of the mounting are a different thread to the body/chassis side of the mounting.
Ideally and what OP will probably do from now on, is wind nuts and bolts by hand a short way preferably lubricated before applying tools to them, if they don't run down the threads as easily as they came off something is wrong. Presumably this means the ones on the engine side are now suspect also.

Hence my comments above!