brake failure on open road - help

Big lumps of metals and spanners.

Moderators: Moderators, User administrators

User avatar
AdrianC
Posts: 2975
Joined: 29 Dec 2010, 21:57
80-90 Mem No: 9144
Location: Living in Hay whilst the Sun pours down.
Contact:

Re: brake failure on open road - help

Post by AdrianC »

Shaundon wrote:Now just need to know if i should replace the brake master cylinder too ?

I don't think so. The state of the old calipers and bleed nipples says a lot about how long the brakes have been neglected, so helps support the water-in-fluid theory.

You might find that you've started a bit of a jam-and-butter cycle on the brakes, though. If you're replacing the calipers, might as well replace the flexis. Which come as a set of four, so might as well fit the rears, in which case why not new cylinders too? Which only leaves the master as ancient... plus the clutch hydraulics. And then that'll all bring you into close contact with the crusty metal pipework...

It's always the same - a lack of regular maintenance might save a little bit of cost in the short term, but it saves up and adds into a huge bill and job all at once...
A year and a half living in a Westy hightop... http://www.WhereverTheRoadGoes.com" onclick="window.open(this.href);return false;

Shaundon
Posts: 239
Joined: 10 Sep 2010, 18:33
80-90 Mem No: 9386
Location: Surrey

Re: brake failure on open road - help

Post by Shaundon »

I think your right there - ended up replacing the 2 front calipers, master cylinder, rear cylinders, all 4 hoses, and several of the pipes that were corroded, along with a complete flush and change of fluid. Hopefully that will be enough to keep me safe for a while... !

Might have gotten away with less but its just not worth the risk when it comes to brakes.
1984 1.9 petrol wbx DH with a pierburg carb , LHD westfalia club joker.

ben50
Posts: 77
Joined: 23 Jun 2006, 12:35
80-90 Mem No: 5298
Location: Bristol

Re: brake failure on open road - help

Post by ben50 »

HI,

Did you manage to narrow down the problem at all?

I've got a similar issue but it's intermitant - some of the time the brakes are working fine, but then the brake pedal will go all the way to the floor with next to no resistance until I pump it, then get a 'normal' pedal feel for a while, until it does the same again.

My mechanic has changed the master cylinder, bled the system multiple times, checked ove the calipers, reset and checkt he rear brakes any wheel cylinders, checked over the flexi hoses etc, but this hasn't changed the fault.

Any ideas out there?

We're meant to be off to France for two weeks in the van on wednesday it's not looking good at the moment ;o(

Cheers,

Ben
RHD German import 2L CU microbus, slowly becoming a not so rusty camper with a GTI engine

User avatar
marlinowner
Posts: 1528
Joined: 28 Jan 2014, 12:02
80-90 Mem No: 13646
Location: Scottish Borders

Re: brake failure on open road - help

Post by marlinowner »

Sounds like the servo is the only thing left...
1993 SA VW T25/T3 2.5i Microbus/homebrew camper
1981/1968 Marlin Kitcar TR6 Engine

ben50
Posts: 77
Joined: 23 Jun 2006, 12:35
80-90 Mem No: 5298
Location: Bristol

Re: brake failure on open road - help

Post by ben50 »

Hi,

thanks for the reply, my mechanic thinks it won't be the servo, as it would display the opposite symptoms - really hard to press the pedal down and non effective brakes rather than really easy to press the pedal down and no effective brakes?

Cheers,

Ben
RHD German import 2L CU microbus, slowly becoming a not so rusty camper with a GTI engine

User avatar
marlinowner
Posts: 1528
Joined: 28 Jan 2014, 12:02
80-90 Mem No: 13646
Location: Scottish Borders

Re: brake failure on open road - help

Post by marlinowner »

That's what would happen with a vacuum fault, but wondering what would happen if one of the parts in the servo which transmits the pedal movement through to the master cylinder was failing?
Just been trying to understand servo operation with the help of my charity shop bargain purchase, Fundamentals of Motor Vehicle Technology 4th edition (1991).
1993 SA VW T25/T3 2.5i Microbus/homebrew camper
1981/1968 Marlin Kitcar TR6 Engine

Shaundon
Posts: 239
Joined: 10 Sep 2010, 18:33
80-90 Mem No: 9386
Location: Surrey

Re: brake failure on open road - help

Post by Shaundon »

Since replacing calipers , master cylinder etc the problem hasn't recurred on mine (touching wood as I speak), just done 4200km down to Rome and had to brake hard from 65/70mph after two Italian drivers decided to stop dead on two lanes of the motorway in front of me to have an argument through their windows! Luckily the brakes held, as well as the brakes of the truck behind me!

Are you loosing any brake fluid when this happens?
Could be brake fluid boiling, have you changed the whole fluid all the way back to the rear cylinders with new Dot4?.
1984 1.9 petrol wbx DH with a pierburg carb , LHD westfalia club joker.

ben50
Posts: 77
Joined: 23 Jun 2006, 12:35
80-90 Mem No: 5298
Location: Bristol

Re: brake failure on open road - help

Post by ben50 »

Hi thanks for the reply,

My mechanic seems to have sorted it for now...

he recently fitted new front bearing and notice the disks had seen better days so replaced them too -the new ones were a couple of mm thicker. it seems that after all the checking cross checking, replacing the master cylinder, freeing off the calipers checking through all the flexy hoses etc, putting the old disks back has solved it!

Still need new disks soon but i now have working brakes ready for heading off to France tomorrow!!

we'll tackle the disks when i get back.

Cheers,

Ben
RHD German import 2L CU microbus, slowly becoming a not so rusty camper with a GTI engine

User avatar
AdrianC
Posts: 2975
Joined: 29 Dec 2010, 21:57
80-90 Mem No: 9144
Location: Living in Hay whilst the Sun pours down.
Contact:

Re: brake failure on open road - help

Post by AdrianC »

So if the thicker new discs caused an issue, and putting the old worn - which, after all, is why he replaced them - ones back on resolves it... the calipers aren't retracting far enough. The discs that are now thin and knackered were once thick and new.
A year and a half living in a Westy hightop... http://www.WhereverTheRoadGoes.com" onclick="window.open(this.href);return false;

California Dreamin
Posts: 2672
Joined: 03 Apr 2007, 12:54
80-90 Mem No: 8386
Location: Nottingham

Re: brake failure on open road - help

Post by California Dreamin »

This does remind me of several occasions in the past, when brand new (but not genuine) brake pads wouldn't fit into the calipers despite the pistons being fully retracted. They were perhaps a couple of millimeters too thick and the only resolution was to rub them down using course piece of emery cloth on a flat surface (basically taking the 2mm off).

Pads should be completely free and with a little clearance.

Martin
1989 California 2.1MV

Locked