HR discs and booster engine stalls

Finny · Post by **Finny** » Tue Jun 16, 2009 9:31 pm

A couple of questions related to Disc brakes.

Given that different calipers can be used on the HR disc brake front ends, how do you know what is currently on them.

This is what I currently have and I have assumed that it is the original HR discs, however can anyone confirm ????

2nd question is related to boosters.
When I hit the brakes, the engine either dies or retards significantly.

It's obviously related to the draw on the vacuum on the manifold.
But exactly what is it doing and what fault am I looking for.

Devilrod · Post by **Devilrod** » Wed Jun 17, 2009 1:04 pm

Sounds like either a split in the vacuum hose or a hole in the diaphragm of the booster which equates to rebuild or replace the booster/vacuum hose. Block off the vacuum line and try the brake pedal again. See if it stops.

Finny · Post by **Finny** » Wed Aug 19, 2009 10:42 pm

Devilrod wrote:Sounds like either a split in the vacuum hose or a hole in the diaphragm of the booster which equates to rebuild or replace the booster/vacuum hose.

You were right

Stuffed diaphragm, tried to rebuild, then decided to replace.

Devilrod · Post by **Devilrod** » Thu Aug 20, 2009 1:03 pm

My FC did exactly the same thing!

rosco · Post by **rosco** » Thu Aug 20, 2009 3:12 pm

Sorry Finny,
Brett got to you first.....
Yes, they appear to be original calipers (from what I can see, they are Girlock - but I can't be sure..... others may know.....?)
Both original units were "fixed" calipers - they have two pistons in each.
They can be re-conditioned with new pistons. piston seals and boots.
Generally, the calipers themselves do not wear out - any issue is usually in the pistons and piston seals...... but, the piston cylinder walls can become significantly corroded....... unlike wheel cylinders, caliper cylinder walls do not play a significant part in the security of the hydraulic system...... as I believe you can appreciate - it is the walls of the piston which work against the inner surface of the piston seal - not the cylinder....... if the cylinder walls are very badly worn - I suppose it is possible to "lock" them out of alignment...... but I would expect this to be rare.......... any takers on experience in this.....?
It didn't cost an arm or a leg to have these types of caliper re-conditioned - I had mine done a few years back along and they were nickle plated into the deal....... I etched my driver's licence number into the calipers so that they can be identified if my vehicle is ever stolen...... you can't hide this part of the caliper under the car.........and then they were coated....... let me know if you want the contact and prices/pix.....

I purchased new rotors at the same time and had the "devils own" time trying to remove the original rotors from the hubs...... ended up getting a rattle gun and destroyed four sets of Kincrome Phillips head drivers ......
If you do this, don't re-fit the Phillips head ones..... Rare's sell allen key headed studs to refit the rotors......... I used Loctite 262 on the threads of those...... this should assist removal if needed before I fall of the perch.......

I note that you have the "factory" hard pipe fitting from the caliper to the brake hose - this came up some time ago - hopefully, whoever wanted a look at this is watching.......

As I have found in many vehicles I have taken a peek at with these HD/HR discs - people tend not to fit the backing plates - just be careful when you grease your ball joints that you don't over-do it..... there is a pin hole vent in the boot of the ball joint - wipe this clean after lubing and again after a couple of days running.

I had to fabricate new backing plates for mine - the originals were "butchered" - in the belief that they would afford more cooling to the rotors.......
The ones I fabricated are similar in design to those fitted to #%RD - they do not "cover" the ends of the rotor - but shield it - I angled out the plate towards the circumference so that there is a gap of around 3/8" at the rear of the cover - this permits free air to enter through the narrower front and is positively "drawn" out the rear by the greater opening.
The front half of the backing plate runs almost parallel to the rotor thus
keeping most of the "line of fire" debris from the road from entering.....
There is also a very important "seal" in the backing plate - you will find that on the rotor hub, there is a matched face which sits inside this seal - it keeps debris out of the inner wheel bearing.....

You may also wish to fabricate some pad cover plates - the originals are made of thin stainless and shaped to fit under the pad retaining rods - they are also shaped to keep the ends of the split pin away from the piston boots.

You may also wish to fit some bleed nipple covers - you will find that the bleed nipples are shaped perfectly for these to slip over and hold the covers in position............ many places which repair/service/bleed our brake system "forget" to refit them - they serve an important role in keeping anything out of the system.
Some people are of the opinion that fluid will "flush" out any debris - but as you have probably witnessed by watching the PVC tubing when bleeding the lines - fluid can pass back through the nipple if the person assisting releases the brakes before you nip up the valve.........

Booster - seems you licked the problem - I wanted to have my original (from HD prem) "Girlock" booster re-kitted - but was told I couldn't get the parts - apparently the valve chest is the issue......

I do not know if PBR do an overhaul kit - I've had mine apart and taken pix of how it works - just be careful if anyone ever undoes that clamp strap...... there is a blasted great return spring which will send you to the ceiling if you are not ready for it........ you'll know what it's like to be in the ring with Mohammed Ali....... if you aren't ready to dodge.......

If you want the test procedure - let me know and I'll post it..... you should have been supplied one with your new booster.....

Which one did you get - mine was a VH 40 L

I will (one day) fit a master vacuum unit - in lieu of the "servo" one......
Being a "single" line unit - it doesn't leave any hydraulic brakes if any one component/line fails...... including the servo unit...... something to think on next time you have to stand on them......

frats,
Rosco

Finny · Post by **Finny** » Thu Aug 20, 2009 9:43 pm

Thanks Rosco, I thought they were original HR ones.

The brakes are working great now.

Funny you mention etching into the calipers

I actually did permanently mark one side, but now for security reasons, but could be used for that

Didn't know that they had a backing plates on the front.

I didn't get anything, so don;t have a model to make them off.
Probably won't worry now until I need to do further brake repairs.

I did see in teh manual that they had pad cover plates.
I probably should make them up, as they can be easily fitted.

I do have the rubber bleed nipple covers on the rear wheels, and was going to add them on the front.

I didn't get any "Test Procedure" with the booster, not sure what that's used for ?

Yes I also got a VH40L.
Would like to put in a dual system, but found it difficult to fit on a manual car.
Maybe when I get around to upgrade time.

Thanks again.

rosco · Post by **rosco** » Fri Aug 21, 2009 1:23 pm

Sure Finny,
The next time you are at the wreckers - and I'm sure others will follow up on this...... also take a good look at LC LJ and also HK/T/G disc brakes.
You may find a set of backing plates which will at least give you the central piece needed to keep out crap from the inner wheel bearings......

those stainless pad covers are very easy to fabricate - just need some pieces of stainless then cut and bend to shape.

Ummm........ master cylinder - yes, with very much interest I will be watching for a non servo unit to come into production which will lend itself to our application - and yes - that blasted clutch master cyl is just placed spot on to stop one such booster being fitted....... I have seen many attempts at creating extension boxes, clever fulcrums and pivots but yet to find something which almost bolts up and can leave the clutch m/cyl in situ.......

frats,
Rosco

rosco · Post by **rosco** » Fri Aug 21, 2009 5:25 pm

As promised Finny,
this is a pic of the backing plate I fabricated - you can't see the part around the inner bearing, but it does give a clear view of the pad inspection cover and where the backing plate screws onto the caliper.
There is an "L" shaped bracket at the rear which prevents the backing plate moving - I will remove a wheel and take a more recent pic including this bracket....

pic....

frats,
Rosco