T6 front brake - backing plate/splash guard replacement

[TTKT]

Hi. Odd problem - horrible noise when angling steering wheel to the left - a rough-road campervan
On inspection, brake backing plate / splash guard front bolt has broken away with part of the plate; middle bolt missing; rear bolt in place, but totally un-done and gouging a groove in the brake disc! Fixed to get home, using cordless drill and fencing wire. (Standard equipment in Australia!)
I have the new backing plate and bolts, and torques from a post by Loz. Thanks!
Just checking - do I really have to replace the the caliper mounting bolts as they are "stretch bolts" or "Torque to yield" fasteners - ??
And, if I do, does the marking on Loz's diagram (see attached) - "150 Nm +90deg" 0- mean: Tighten to 150Nm, then add a half-turn no matter what the torque???
What if it breaks?? I'm new to this concept, info would be appreciated. Thanks!

 

[Skyliner33]

150Nm + 90deg means tighten to 150Nm then 1/4 of a turn. That's why they are bolts that need to be replaced. The bolts are designed to stretch.

 

[TTKT]

Thanks!. Damnit, I meant 1/4 turn, not half. Stupid error. But this clarifies it - new language.

 

[TTKT]

Does anyone know the part number for the "stretch bolt" big-disk brake-caliper-mounting bolts (#19 in the attached diagram from Loz) ?? Thank you~!

 

[phazer]

Part N90685403 £6.42 each

Best off going to a dealer as ebay/other sellers will likely charge more and there's postage too

 

[TTKT]

OK. Finished - for now. I replaced the RHS disc backing plate, and re-used the disc and pads. The gouge in the disc is less than 0.25mm deep and will wear out before the overall wear limit is reached. Used new caliper-mounting bolts with their 180Nm-plus torque. Used some SikaFlex so as to try catching any loosening bolts before they fall out!
I am attaching, if possible, the photo of the old backing plate with its broken-off segment that probably started the whole problem.
I was able to stop the scraping, 1000km from home, with fencing wire and some newly-drilled holes to tie the plate to the wheel-bearing holder. Most of it lasted till home, but somewhere along the way the loose-but-trapped bolt was wedged and came out.
What's new - after the new plate replacement, I decided I should check the Left hand side. Amazingly, it rattled under pressure - the backing plate has broken at exactly the same place - but it has been caught early enough, that neither of the other 2 retaining bolts have loosened.
This suggests to me that there is a design fault, these plates and their double-thickness gussets at top and bottom bolt-holes, are under-engineered - at least for Australian roads.
I have packed the area with SikaFlex so as to dampen vibrations, and tensioned the top of the plate with wire. New backing plate might arrive from Singapore in a month . . . but might suffer the same fate in a few more miles of corrugations!

 

[TTKT]

PS Mine are 308mm discs. The backing plates for the 340mm ones may well be better.

 

[DXX]

Just checking - do I really have to replace the the caliper mounting bolts as they are "stretch bolts" or "Torque to yield" fasteners - ??
And, if I do, does the marking on Loz's diagram (see attached) - "150 Nm +90deg" 0- mean: Tighten to 150Nm, then add a half-turn no matter what the torque???
What if it breaks?? I'm new to this concept, info would be appreciated. Thanks!

Yes replacement required, make sure the wheel is at full lock to get access and the threads are dry.
They won’t break.

 

[4wdMotion]

Well I'll be blowed!!! What a coincidence. early November, my relatively low kms T6.1 LWB 4Motion (also in Perth, WA) suddenly developed a horrible driver side "scream" when turning to the Left! Thought I must have a wheel bearing about to collapse - dry metal on metal horrible screaming noise. A quick roadside check of that, all seemed holding together and no visible signs of anything untoward and as long as I only turned gently and slowly to the left there was little or no noise. Got home gently and set about investigating origin of noise if not wheel bearing and eventually found that one of the small bolts (no.5 on the parts diagram) holding the driver side splash plate had worked itself out, obviously got bent and was grinding itself against the disc rotor (340mm rotors). Long story short - splash plate was fine (not broken or holes oversized like @TTKT ; not easy to find anyone readily available to consider skimming the 340mm rotors (and there was a little lip on outside edge), so replaced both rotors (non-VW), pads were all okay and then checked, torqued and loctited each of the small splash plate retaining bolts on both sides. Will now keep a check on them.

 

[TTKT]

Wow, thanks for that - I'm not the first to think that some bits of the the T6 are a little under-engineered for Australian dirt road conditions. But in general, it is a magnificent machine. Mine has coped with a 100mm suspension lift without need for lowering the rear diff, and the front is good after new shocks and a total 35mm lift.
(The first time I thought it was a bit woeful, was when the power steering hose disconnected itself from the steering rack near Kingoonya in South Aust a few years ago . . . my wife found she could not steer the van without it)
Back to brakes: After the noisy failure I wrote about, I found the same backing-plate cracking problem on the left side of mine, but no bolt-loosening (yet). I still wait till to see if the Sikaflex damps the plate vibrations enough to delay replacement of the plate until the disks / pads are worn out.
NOTE that the professional Eurocar mechanics I use, say that they just re-use the brake caliper mounting bolts, rather than over-torque and discard them later! But as I have now bought new ones in anticipation of a disc change, I guess i might as well use the new ones.

 

[Mr Fi]

Part N90685403 £6.42 each

Best off going to a dealer as ebay/other sellers will likely charge more and there's postage too

@phazer do you know if they are the same part code for the smaller 308mm disc/caliper setup? I'm not sure if it makes any difference but mines a 2020 T6.1.

 

[TTKT]

Hi. The parts I was given for my smaller rotor setup are VW-N90685403.

 

[Mr Fi]

Hi. The parts I was given for my smaller rotor setup are VW-N90685403.

Thanks TTKT, in that case they appear to be the same part code for both size brake systems.

 

[phazer]

Thanks TTKT, in that case they appear to be the same part code for both size brake systems.

Yeah T6.1 seems to be different. T5.1 and T6 are different parts for small/big brakes

 

[Mr Fi]

Yeah T6.1 seems to be different. T5.1 and T6 are different parts for small/big brakes

Any idea where I’d find the correct part code for the smaller T6.1 bolts?

 

[phazer]

Any idea where I’d find the correct part code for the smaller T6.1 bolts?

I'm out of the country but can check when I get back if noone posts before

 

[phazer]

So on the T6.1 (checked MY2023), the carrier and caliper attachment bolts are apparently the same (2E3 16", 2E4 17"), these are the parts:

Carrier bolts N90685403 £6.54 each

1 Set attachment parts 2H0698141 (replaced with WHT010143) £3.12 - part number suggests 4 bolts for £3 which might be a mistake as the original part was £25

 

[DXX]

Wherever you source the bolts make sure they are grade 10.9. ‘10.9’ will be marked on the hex’ head. If they are not marked don’t use them and don’t re-use the old bolts that’s like re-using a condom.