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Random Broken CV joint bolt.

davegsm82

Go Kart Newbie
Location
Blyth, Northumberland - England
Car(s)
MK7 Golf and T3 Tdi
Bit of a random one, today I was doing an oil service on my 2013 MK7 GT TDi and also trying to identify which side the failing wheel bearing is on, when I looked at the passenger side inner CV area I noticed there was some CV grease accumulated on the gearbox etc.

When I had a closer look, one of the 6 CV bolts had grease all around it, coming out from under the head. When I pulled the bolt just with greasy fingers, it came out with a little persuasion.
It had snapped about 10mm from the head, leaving the rest of the stud stuck in the driveshaft flange, I had to remove the lower balljoint, unbolt the 5 remaining CV bolts and use a stud/bolt extractor on the remaining thread which was an absolute pig to remove.

I replaced it with an almost identical spare from my junk box, so that's not a problem, however when I looked at the bolt closely it's not stretched, twisted or anything, just snapped clean in two. Furthermore when I put the 5x originals back in, they felt a bit... stretchy, as if they were yielding as I torqued them up. The replacement one came from my old PD150 MK4 and it definitely did NOT yield as I put pressure on it.

Are MK7 CV bolts TTY? Do they have a habit of just randomly snapping?
 

GTI Jake

Autocross Champion
Location
Charlotte, NC
Bit of a random one, today I was doing an oil service on my 2013 MK7 GT TDi and also trying to identify which side the failing wheel bearing is on, when I looked at the passenger side inner CV area I noticed there was some CV grease accumulated on the gearbox etc.

When I had a closer look, one of the 6 CV bolts had grease all around it, coming out from under the head. When I pulled the bolt just with greasy fingers, it came out with a little persuasion.
It had snapped about 10mm from the head, leaving the rest of the stud stuck in the driveshaft flange, I had to remove the lower balljoint, unbolt the 5 remaining CV bolts and use a stud/bolt extractor on the remaining thread which was an absolute pig to remove.

I replaced it with an almost identical spare from my junk box, so that's not a problem, however when I looked at the bolt closely it's not stretched, twisted or anything, just snapped clean in two. Furthermore when I put the 5x originals back in, they felt a bit... stretchy, as if they were yielding as I torqued them up. The replacement one came from my old PD150 MK4 and it definitely did NOT yield as I put pressure on it.

Are MK7 CV bolts TTY? Do they have a habit of just randomly snapping?

They’re not TTY, but I still replace them every time just because those washers that span two bolts can (& have) become a buzz saw if one bolt falls out and centrifugal force takes over.

I’ve seen a few instances of people self inflicting that on these forums.
 

davegsm82

Go Kart Newbie
Location
Blyth, Northumberland - England
Car(s)
MK7 Golf and T3 Tdi
They’re not TTY, but I still replace them every time just because those washers that span two bolts can (& have) become a buzz saw if one bolt falls out and centrifugal force takes over.

I’ve seen a few instances of people self inflicting that on these forums.
That's an interesting take on the washer, hadn't thought of it becoming a blade and mine certainly could have in this instance.

Is there any merit in removing the long washers and fitting standard serrated washers, like VW used to fit years ago? I have those on my T3 camper with TDi conversion, it's very, very heavy and puts down a lot of power (relatively) so the bolts on the tiny 100mm CV's are under a lot of strain and none of them have ever worked loosed with those washers in place.
 

krs

Drag Racing Champion
Location
Idaho
Car(s)
MKVIIS R
They are identified as a bolt to be replaced after removal in the service repair manual, which I'm sure most places don't.
 

GTI Jake

Autocross Champion
Location
Charlotte, NC
That's an interesting take on the washer, hadn't thought of it becoming a blade and mine certainly could have in this instance.

Is there any merit in removing the long washers and fitting standard serrated washers, like VW used to fit years ago? I have those on my T3 camper with TDi conversion, it's very, very heavy and puts down a lot of power (relatively) so the bolts on the tiny 100mm CV's are under a lot of strain and none of them have ever worked loosed with those washers in place.

If you dig around here you’ll find cases where the washer saw thing had happened (twice IIRC).

Id just replace them all, torque to spec and move on. Sounds like a fluke that you were mindful enough to catch early, so it’s highly unlikely you’d have another similar issue.
 

davegsm82

Go Kart Newbie
Location
Blyth, Northumberland - England
Car(s)
MK7 Golf and T3 Tdi
If you dig around here you’ll find cases where the washer saw thing had happened (twice IIRC).

Id just replace them all, torque to spec and move on. Sounds like a fluke that you were mindful enough to catch early, so it’s highly unlikely you’d have another similar issue.

I've had a brief look on the search function but 'CV' is too short of a search term apparently so it severely limits results, either way I believe you wholeheartedly, just not 100% sure what to do about it in the short term. I'm currently recovering from Covid and lifting the tools to do this job damn near killed me, going in again might finish me off. Hopefully it will be ok until I get some strength back.

Cheers.
 

GTI Jake

Autocross Champion
Location
Charlotte, NC
I've had a brief look on the search function but 'CV' is too short of a search term apparently so it severely limits results, either way I believe you wholeheartedly, just not 100% sure what to do about it in the short term. I'm currently recovering from Covid and lifting the tools to do this job damn near killed me, going in again might finish me off. Hopefully it will be ok until I get some strength back.

Cheers.

With you being aware of the situation it’ll be fine. If you pick up a noise or vibration you’ll know exactly where to check first.

Hopefully you’re back to 100% soon, I know I had a bad cough for at least a month post Covid. Definitely can take some time to get back to normal.
 
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