snapped all strut mount bolts- mystery

[92EcoDiesel Jetta]

I was told the gap between the strut cap and the up and down movement between the cap and strut tower while the wheel is hanging is not normal so I  removed both front struts to investigate. All 4 bottom strut mounting bolts snapped! They all snapped at the same spot, right at the nut. They were not overly corroded and I wire brushed them before putting a liberal amount of good quality penetrating fluid before applying torque to loosen them. It didn't help.

Anyway I saw that the top bolt (at the knuckle) has a smaller shank diameter than the bottom bolt and per the Bently that is to allow adjustment of camber. I measured the holes in the knuckle and the top hole is 9.5 mm while the bottom hole is 12.3 mm

I matched up all 4 snapped bolts to see where they broke and noted the smaller shank upper bolts has the same thread diameter as the lower bolts, which is M12 x 1.5. I tried inserting the broken upper stud with nut still stuck to it (with 1/2 " of tread protruding) into the upper hole and it would not go in! How can that be? How is that possible? How was that assembled in the first place? That upper bolt clearly went through the strut then the knuckle, with a nut securing it, before it snapped off. WTH is going on?

I need to buy new bolts and non of the dealers around here has them in stock. I am not sure that if I order the bolts whether the upper bolt will fit. If it is M12 x 1.5 it definitely will not go in. This has been a very strange ordeal. Can someone shed some light on this?

[R.O.R-2.0]

holy crap, you broke the alignment bolts?

how hard of a pot hole did you hit?

i wrecked a mk2, and the front suspension was still golden..

[vanagonturbo]

got any pics of the offending area?

[92EcoDiesel Jetta]

Here are the broken bolts. On the left are the 2 top camber adjusting bolts with smaller shank.

[92EcoDiesel Jetta]

The broken bolt insertedd into the knuckle top hole (less the strut) and this is the position it was in before it snapped.

[92EcoDiesel Jetta]

When I tried to insert the broken half with the M12 x 1.5 thread into the top knuckle bolt hole, it would not go in! The hole was measured at 9.5 mm but the threaded portion of the broken bolt is 12 mm.
I can't understand how that bolt was put in. It is physically impossible.
I am totally stumped! Someone please help me.

[vanagonturbo]

Oh man, I am so glad I dont live on the East Coast!

Ok, the top bolts are not the correct bolts for the car. They are aftermarket junk. The problem is that rust has filled the area in the top hole making it difficult to install the proper diameter bolt. You may need to drill the rust out of it. The reason they likely broke was because the centers were seized into the spindle.

Either way, get some new OEM bolts and nuts and call it a day.

[R.O.R-2.0]

so, how much air did you catch? ive jumped my mk2s before and never done that..

[rallydiesel]

I think whoever worked on them last overtightened them badly. Probably with an impact wrench.

[vanagonturbo]

Actually, whoever worked on it last used inferior grade bolts that are 2/3 the diameter of the factory bolts. I think that is the biggest factor here.

[mystery3]

so, how much air did you catch? ive jumped my mk2s before and never done that..

I think he broke them during removal not while driving. I don't think you could break all those bolts in a wreck and live.

[92EcoDiesel Jetta]

I have no idea if good or bad quality bolts were used. They were not rusted into hole of the knuckle nor were the thread crusting with rust, just a thin layer. I think being overtorqued is a good explanation of why they all snapped. One strut had a dust boot and the other didn't. The slotted nuts were both a bit chewed up so the person who worked on it last wasn't the most careful IMO.

Does anyone know the part numbers of the strut mounting bolts and nuts? The top bolt (the camber adjusting bolt) is different than the bottom bolt and should have a different part number.

This is what the Bently says about the top bolt:  "ROutine camber adjustment is not normally necessary. If needed, adjustment is possible by replacing the upper strut mounting bolt with a special VW replacement bolt. This bolt, VW part no. N 903 334.01 has a slightly smaller diameter shank. Using the lower strut mounting as a pivot and the new upper bolt with its larger clearance, camber adjustment of approx +/- 1/2 a degree is possible. If greater adjustment is necessary, the smaller shank replacement bolt may also be used in the lower mounting hole, for a total adjustment range of approx +/- 1 degree "


N 903 334.01  is not a good number per dealer so the Bently has a typo in that number?

[vanagonturbo]

cant help on the PN right now, but ONLY use the proper bolt. I use an airgun to install and remove those bolts and have been doing it for 16 years. I have NEVER seen what you have happen with an OEM bolt in that particular location on that particular model. The upper bolts you had were junk. the smaller shank bolt isnt really all that much smaller, but it does help. If the car is bent or other major problem, the OEM camber bolt will not compensate enough.

[fatmobile]

I was told the gap between the strut cap and the up and down movement between the cap and strut tower while the wheel is hanging is not normal

 On a MK2 it's normal.

[vanagonturbo]

I was told the gap between the strut cap and the up and down movement between the cap and strut tower while the wheel is hanging is not normal

 On a MK2 it's normal.

careful what you say. There is a limit and I have seen spring perches destroyed from ignored failing strut bearing/bushings...