PNM engineering rear brake calipers

[Rambo]

Rambo is one of the top 5

[Rice crispy]

[Rice crispy]

So a quick look underneath and no obvious leaks will have to take it to my mates and get under it on the ramp to see where it's leaking

[John_W]

My leak was very slow, and I only spotted it because I have vinyl sheet on the garage floor. The clue that something was wrong was having to top up the brake fluid.

When I removed the wheel the outside face of the disc and caliper looked OK, however when I had a look round the back there was congealed oily crud on and around the brake pad and traces of the clean leaking fluid. I haven’t found exactly where the leak is from, as I packed it all up and sent it to PNM for them to do that.

John

[Rice crispy]

John thanks need to get under to double check it. Last time it was running down the wheel but I do suspect it's the same caliper as it looked damp around there and the wheel

[John_W]

Yup, the fluid ran down the caliper, dripped onto the rear right wheel and ran down the tyre on the side facing the centre of the car to form a small pool in the slight indentation made by the tyre on the garage floor covering. It’s not much volume, but any leak of brake fluid is too much.

[GeoffSmith]

The rear RHS caliper leak seems to be a TADTS.

[John_W]

Geoff,
Thanks I found that reference which seems to correspond exactly with the failure on my RHS rear caliper (which has done under 15,000 miles - edited to say that it’s actually less than 6,000 miles!). However I cannot find any primary reference to corroborate the most pertinent statements:
“ ... that is leaking from the piston seal, the right hand rear caliper of the PQ35 platform is extremely prone to this ...
- ... they seem to fail 5 times more on the divers side than the passengers ...
- ... DO NOT fit an exchange recon caliper, VW specifically state that these calipers must not be refurbished so the only way to get a new one is genuine VW or TRW new units BUT not their exchange unit which has an E after the part number...

I would like to find the primary reference for when PNM suggest rebuilding the caliper instead of supplying a new one.

John

ps what’s tadts?

[Rice crispy]

Likewise as if it is on closer inspection then it's my third failure in 4 years

[Brit-Car-Nut]

ps what’s tadts?

They All Do That Sir!

[Saltire]

, apologies

John, as a matter f interest, where did you get your garage floor covering? Considering something similar once I’ve put the insulation in this spring.

[John_W]

TADTS - thanks John.

Jonathan,
Costco flooring.
It’s been down on my garage floor for six years and is very tough, easily being able to withstand a trolley jack.The only problem is that it is a fixed size, so I used their garage floor tiles to go round the edge, which is quite a good solution as they are softer to walk on or stand on, and obviously more flexible as to the shape.

John

[John_W]

An update as promised:

I called PNM today and they said that they have rebuilt my caliper. The guy I talked to was very helpful and informative. He said he has put in a new piston, seal and rubber cover, and cleaned up the pads which are salvageable. Cost (including new copper banjo washers) was a reasonable £55 (however carriage charges and VAT make it a less reasonable £95). I fitted the caliper in 2015, and it lasted less than 6,000 miles and just over two years before leaking. He said if the kit had been bought recently they would have fixed the faulty caliper for free.

He said there seemed to be nothing wrong with the caliper apart from a small wear mark on the old piston which looked insignificant but might have been the cause of the leak; the rubber seals were fine, but were replaced anyway. He said the mark was definitely a wear mark and might have been caused by a slightly wobbly disc, so to check the disc for run-out (I 'll also check again that the bearing isn't loose, but it seemed OK). He suggested that the disc might need a skim, but I doubt it as I replaced the rear discs (with new standard Lotus ones) and they haven't done many miles.

Interestingly, he said they can skim old discs for £25 each + VAT + carriage, as their kit allows for brake disc thickness down to 8mm (the Elan's rear disc is 12mm). I might just get my old rear discs sent down to PNM for a skim to keep as spares.

I'll post again when I receive the rebuilt caliper and get it fitted.

John

[Fredjohn]

Interestingly, he said they can skim old discs for £25 each + VAT + carriage, as their kit allows for brake disc thickness down to 8mm (the Elan's rear disc is 12mm). I might just get my old rear discs sent down to PNM for a skim to keep as spares.

I'll post again when I receive the rebuilt caliper and get it fitted.

John

For OEM disc/caliper, the minimum wear thickness is 10.9mm. Original new 12.7mm. Min thickness for regrind 11.5mm. I always thought min disc thickness was related to it's ability to disperse heat rather than piston/caliper movement. Any (plain English) clarification?

As an aside have they "sorted" fitment of non OEM discs on the separate hub/disc conversion? I had to get my discs skimmed on one side to fit properly.

EDITED TO REFLECT VARIOUS CORRECT DISC THICKNESSES.

[Saltire]

TADTS - thanks John.

Jonathan,
Costco flooring.
It’s been down on my garage floor for six years and is very tough, easily being able to withstand a trolley jack.The only problem is that it is a fixed size, so I used their garage floor tiles to go round the edge, which is quite a good solution as they are softer to walk on or stand on, and obviously more flexible as to the shape.

John

Thanks, John, will definitely be following up on this. Much cheaper than the tiles.

[John_W]

OK the refurbished caliper is on. What a sod of a job! It took me most of today (allowing for 10am start because I'm retired, tea and biscuits at 11:00, lunch at 1pm, but no afternoon tea). The caliper replacement was easy enough, but the brake bleeding was very awkward because I had removed the caliper in my garage without consideration of how I would jack up and remove all four wheels and bleed all four corners when there was all sorts of crap in the garage around them. I have discovered that I am neither as flexible nor as strong as I used to be.

The caliper arrived the day after I paid for it (UPS service is much better than the Post Office), and PNM had cleaned it and the old pads up nicely and provided new copper banjo washers, so good service from PNM. I used over a litre of brake fluid to bleed all four corners and flush out the system using a Gunson's EasiBleed (which worked really well). Some bubbles came out, followed by slightly cloudy old brake fluid and a few lumps (OK, very fine grained specks of particulate matter). The pedal is nice and firm.

Now I just need the salt to disappear from the roads to road test it. Let's say in March. Hopefully March 2018. Where is Global Warming when you need it? Then we'll see if the refurbished caliper lasts longer than the 6000 miles the original one lasted.

John

PS: there was no run-out on the disc and the bearing was fine, so why the piston showed wear marking, goodness knows.

[Rambo]

Glad your sorted now John

PS as an ex geologist you'll know that "global warming" is complete government bullshit and hyperbole

[Rice crispy]

So finally got mine over to my mates to check and it's weeping from where the handbrake mechanism comes out of the caliper. Spoke to Peter at PNM and apparently no one else has ever suffered like me he was quick to say I would have to pay this time which isn't a problem but wanted the caliper to look at first so he could get the right replacement as apparently there are 3 different types now. I sent him the pictures from dec16 and will call tomorrow for an update. Disappointed that it will be a 3Rd caliper in 4 years and 6K miles.

On a good note it's ready to pass it's Mot when the caliper is sorted.

[John_W]

My car got its first outing with the new rear caliper last weekend (the Jim Clark memorial weekend in Duns), and the salt is still on the roads! It works fine; let’s hope it lasts longer than the last one.
But I can’t say I’m impressed that it leaked at all. How did VW get a reputation for reliability and good engineering? Maybe that’s just their advertising agency, or maybe that was before the accountants took over.
MOT is tomorrow.

[Scott J]

How did VW get a reputation for reliability and good engineering? Maybe that’s just their advertising agency, or maybe that was before the accountants took over.
MOT is tomorrow.

they haven't, its an old wifes tale. Go on forums for mark V and mark VI GTIs, cambelts, timing chains, premature rust, brakes, etc etc etc , they sell overpriced junk to the uneducated masses .