101 Front brakes retaining pressure

[PeterP]

While waiting down the garage I notice CanDo was no free rolling very well, like the brake were grabbing. On the way home it started to get noticeable taking off at the lights, by the time I got home I had to put it in Lo just to get under cover. The front rims were quite warm compared to the back.
Jacked the front up, no turning wheels so cracked the nut on a brake line at the T-piece on the diff housing and heard the shoes contracting and now have turning wheels again.
I suspect the master cylinder even though the rears seemed OK. I was wondering if anyone has had this happen before?
I tested the servo unit and it has no vacuum leaks and seemed to working fine previously, is there anything I should do to it while its out other than paint it?
Any tips advice appreciated.

As a matter of interest I was wondering if any one had heard the following servo issue -

From email archive - You will not find any on the open market, so don't even look if any people have them they are hanging on to them the same with the vacuum servo unit part number # AAU1277 these are now obsolete same deal none on the open market. DON'T OPERATE THE SERVO UNIT WITHOUT ANY BRAKE FLIUD IN THE SYSTEM AS YOU WILL CRACK THE BRAKALITE INNER'S IN THE SERVO, THUS CAUSING GROWN MAN TO CRY. YOU HAVE BEEN WARNED!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!. You can get a 110 replacement servo unit but there is extra parts required and work. Its not straight forward, this is your only option again you have been warned.

Cheers
Peter

[101 Ron]

Check the pushrod from the brake pedal to the piston on the master cylinder.
That pushrod should have a adjustment nut.
It must have some free play or your brakes will build up.
With the brake pedal at rest the push rod should rattle around abit if you try a move it with your fingers.
The back brakes will not get as hot because of the load proporsioning valve near the back axle.

[Mick_Marsh]

Brake hoses develop a restriction. As was explained to me, it's like cholesterol in your arteries. It allows the brakes to be applied but restricts them from releasing.
This happened to the hybrid and the fintail.
You may wish to change the brake hoses for new ones.

[101RRS]

As Mick said - I would replace the rubber hoses if you have not already done so - can cause symptoms as you suggest - rubber de laminates inside and acts like a one way valve.

If it is not that then I cannot help - except that my booster and master cylinder were rebuilt by my local brake place - so I think the position that there are no parts for them is a bit of a furfy.

Garry

[Scouse]

If both front rims were equally warm, then it's probably not going to be a brake hose issue. Check the master cylinder freeplay first as suggested by 101Ron.


I'm not familiar with the set up of these brakes but I know on some old English cars the master cylinder cap has a breather hole. If this is blocked, it can cause a similar problem.

[101 Ron]

If both front rims were equally worn, then it's probably not going to be a brake hose issue. Check the master cylinder freeplay first as suggested by 101Ron.


I'm not familiar with the set up of these brakes but I know on some old English cars the master cylinder cap has a breather hole. If this is blocked, it can cause a similar problem.

Your right on that one too.

[101RRS]

If both front rims were equally worn, then it's probably not going to be a brake hose issue.

While each of the front brakes has their own rubber pipe, there is one central rubber hose that brings the brake fluid down from the chassis to the front axle where it then branches to go to each brake. If there were problems with this pipe both front brakes could stay on.

This pipe was an issue on my 101 and as result I replaced the lot.

Garry

[PeterP]

While each of the front brakes has their own rubber pipe, there is one central rubber hose that brings the brake fluid down from the chassis to the front axle where it then branches to go to each brake. If there were problems with this pipe both front brakes could stay on. This pipe was an issue on my 101 and as result I replaced the lot.
I think you may be on the money here. I have heard of this problem by thought CanDo was not old enough for blocked arteries but probably is. I'll put three new hoses and a kit in the master cylinder and let you know what I find.
Thanks everyone.
Peter

[101RRS]

When you do the master cylinder be aware that it is basically two master cylinders in one (one for each brake circuit) - there is a small seal (o ring?) on the main shaft that separates the two circuits and this can be easily damaged when the master cylinder is being rebuilt or sometimes it just fails. The result is not a safety issue but if there is higher pressure on one side compared to the other, fluid can leak across to the other brake circuit - this slowly drains one circuit of fluid and puts it in the other with each application of the brakes - maybe less than 1 ml at a time. This shows up as one fluid reservoir going down and the other filling up - as I said not a safety issue as the pressure equalises on both sides when the brakes are on and transfer stops.

It is quite common with 101s and most people just transfer fluid back to the low reservoir when required. Ron fixed his by using silicon fluid in his system and I have a small pipe joining the two reservoirs so the high one just drains back to the low one.

My master cylinder was built OK but started fluid transfer about 10 months later.

Oh - and another thing that could be causing the issue is the brake shuttle valve - has the slide inside moved to close the front brakes off - would stop the fluid releasing the brakes but then you would have no front barkes either and if operational the brake light on the dash should light up.

Garry

[PeterP]

Well Garry your diagnosis was correct, the centre hose is very blocked. I've taken the corresponding hose off the back also and it was OK but I will get them both remade. They are the same threads as the ones going to the front wheels (which I have) but are longer.

I saw your thread about joining the reservoirs and when I looked at mine the clutch went to the single cell reservoir on on the right and both the brake lines go to the dual cell one on the left. Did not see it as a real problem.
https://www.aulro.com/afvb/images/imported/2011/05/1661.jpg

Many thanks,
Peter

[101RRS]

Well Garry your diagnosis was correct, the centre hose is very blocked. I've taken the corresponding hose off the back also and it was OK but I will get them both remade. They are the same threads as the ones going to the front wheels (which I have) but are longer.

I saw your thread about joining the reservoirs and when I looked at mine the clutch went to the single cell reservoir on on the right and both the brake lines go to the dual cell one on the left. Did not see it as a real problem.
https://www.aulro.com/afvb/images/imported/2011/05/1659.jpg

Many thanks,
Peter

That pic of yours is disgusting:o - too clean:D.

I have clutch and rear brakes on one single reservoir and the front brakes on a single reservoir - I do have to correct double reservoir for the clutch and rear brakes but am too lazy to put it in.

If Can Do was mine I would be concerned about your arrangement. I do not feel that the amount of fluid in the clutch pot is enough to feed the brakes - certainly if you develop a small leak. Also you cannot see the level without taking the lid off. I would have a look at changing your arrangement.

On hoses - how are your individual brake hoses for the front brakes.

Garry

[PeterP]

Sorry about the pic, I love my Canon SLR.:D
I hear what you are saying about the reservoirs and I will look at it one day, bit lazy myself at times.
Have not taken the individual hoses off yet.

Whats the go with the silicone fluid? I have heard it does not compress as much as normal fluid. Also that you need to flush the system before putting it in

Peter

[101RRS]

Whats the go with the silicone fluid? I have heard it does not compress as much as normal fluid. Also that you need to flush the system before putting it in

Peter

I will let Ron answer all that as he is the expert :).

Garry

[101 Ron]

Experts can get online fault finding wrong.......:D:D:D:D
I now use in all of my vehicles Russel brand silicone brake fluid.
It is dot 5 rated, by that doesnt mean much these days as better quality normal brake fluid can now be dot 5.
The main reason I use it is because silicone is very slightly thicker and more viscous and it lubricates the seals like oil does.(normal brake fluid has little lubrication effects)
It makes the brake components last longer.
Normal brake fluid is hydrostopic....meaning it adsorbs water and a moisture which is suppose to be safer and the brake fluid usually turns from a blue to a brown colour when it is no good any more and has assorbed to much moisture and must be bleeded out.
I find if you bleed the brake system every 2 years like you are suspose too, the silicone fluid has no issuses.
I find no wheel cylinder corrosion and longer lasting rubbers.
Silicone brake fluid and normal brake fluid can be mixed with no ill effects, but why would you want to.
I just open up the brake bleeders one by one until the fluid changes colour and you then know you have the silicone fluid right though the system.
Another advantage is if it leaks or you spill it there is no effects on paint work.
The disadvantage is trying to find the silicone fluid as no one stocks it and then it is expensive.
There are alot of old stories about silicone fliud........in practice using Russel brand silicone fluid none of them have been true.

[PeterP]

Just about ready to put back together with all new rubber hoses.
https://www.aulro.com/afvb/images/imported/2011/05/320.jpg

Previously when I have done a few braking tests the back wheels always locked up so I have pulled the apportioning valve off. It was not seized and I managed to get all the 'O'rings and seals from the local brake shop.
https://www.aulro.com/afvb/images/imported/2011/05/321.jpg
While trying to establish how it works and if I could test it I started to realise it has probably been plumbed incorrectly.
The line from the front was connected to the left hand connection and the line to the axle jump hose was on the right connection as per pic.
Page 70.25.23 of the service manual shows it the other way round and the arrows seem a very good clue its wrong.:eek:
The pipes do not appear to be bent in anyway though.
I have never played with one of these before so I ask, am I seeing this correctly?:confused:

Thanks Peter

[Mick_Marsh]

From email archive - You will not find any on the open market, so don't even look if any people have them they are hanging on to them the same with the vacuum servo unit part number # AAU1277 these are now obsolete same deal none on the open market. DON'T OPERATE THE SERVO UNIT WITHOUT ANY BRAKE FLIUD IN THE SYSTEM AS YOU WILL CRACK THE BRAKALITE INNER'S IN THE SERVO, THUS CAUSING GROWN MAN TO CRY. YOU HAVE BEEN WARNED!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!. You can get a 110 replacement servo unit but there is extra parts required and work. Its not straight forward, this is your only option again you have been warned.
If it is not advisable to operate this servo without break fluid, how is one meant to bleed the brakes after replacement of the master cylinder?

[Blknight.aus]

If it is not advisable to operate this servo without break fluid, how is one meant to bleed the brakes after replacement of the master cylinder?

Gravity, vac bleeder, pressure bleeder, prelubricate the MC and fill it.

Lots of choices...

Be careful with your choice of brake fluids. Dot 3,4,5 5.1 are not all the same.


Dot # is rarely available any more so skipping that the others are available in synthetic and non synthetic flavors AND they are not always interchangable with a butter consitency goop being the end result. It turns out that this was the nail in the coffin for fozzys brakes with a clot of it holding the fast fill open (single line brakes) so no brake pressure for me with the pedal on the floor as quick as you like. In hind site I should have pulled it down and fixed it when it happened instead of slating him off the road for rebuild.

[Mick_Marsh]

The brake pedal was solid when I got it. I had the master cylinder reco'd because it was dribbling. I suspect the booster is stuffed as well as it hisses when the brakes are applied.
I am using PBR Gold Dot DOT4 brake fluid. Would that be ok or have I made a mistake?

[101 Ron]

Normal dot 4 is not a mistake.
I have always bled the brakes normally by pumping the pedal and never had a problem.
I find the brakes on my 101 bleed well and I dont know why people have so much trouble bleeding them.
The only problem I have found is the fluid transfer from one reservior to the other and the silicon brake fluid fixed that for a very long time and then the fitting of a general purpose Quad ring in the master cylinder during a normal overhaul instead of the one supplied in the overhaul kit.
The 101 will gravity bleed with time too.
Brake shoe adjustments must be carried out regularly on the front brakes if you want a good pedal as the front shoes wear quickly.

[PeterP]

If it is not advisable to operate this servo without break fluid, how is one meant to bleed the brakes after replacement of the master cylinder?
I put 6mm tube on the front bleed valve and got them above the height of the master cylinder and cracked the valves and left it over night.

[101RRS]

Hi Peter,

What is the current state of your 101 - I understood you got it on the road but I believe you wanted to do more too it.

Is it totally finished? Silly question I know as they never get fully finished.

How about putting some more of those great pics you do for us to drool over.

Cheers

Garry

[PeterP]

Been busy doing some travelling, getting the last child married off and working on my golf handicap. As they say 2 out of 3 ain't bad.

My first objective was to get CanDo 100% mechanically sound. After total engine rebuild, new bearings in the gearbox and diffs, different high range gearing and overdrive, total overhaul on hydraulics, tiding up the electrical system and dash I am almost there.

I still have a noise in the rear diff when backing off. This is the only thing I did not do myself and suspect the pinion bearings have not been torqued properly.
Other than that it is like brand new so that leaves the external pretty ups.

The motor with 20 thou oversize high compression piston and bigger valves with the stage 1 heads and fully balanced pulls the taller gearing no problems and it runs ever so sweet.

It drives great. The haystee springs and Michelin tyres are great on the road. Have not done much off road as yet but what I have done it appears unstoppable.

Next up will be sealing and soundproofing the engine cover and then it is onto the body and painting. Rome was not built in day and neither will CanDo, apparently:(.

Overall :D:):D;):D:cool::D
Following some recent pics and CanDo website link

Cheers, Peter

CanDo Diaries (http://users.comcen.com.au/~peterp/101index.html)

https://www.aulro.com/afvb/images/imported/2012/03/88.jpg
https://www.aulro.com/afvb/images/imported/2012/03/89.jpg
https://www.aulro.com/afvb/images/imported/2012/03/90.jpg

[101RRS]

Thanks for the update - those TAC plates look good ;).

Noises can be a bit tough to track down - knowing your attention to detail the final product will be a gem - it is a credit to you.

May sure you let us know when you have painted Can Do all up.

Cheers

Garry