Spongey brakes & Servos!

[galaxie390]

Hi Folks,

Recently put my 1968 2 door back on the road after doing the usual rust. Also completely re-fitted the brake system apart from the shoes which were fine.
I used lockheed wheel cylinders, master cylinder & a new servo kit from one of the moggy centres.

Everything was mounted and assembled as per instructions, but I still find that the first push goes almost to the floor and the second push gives me great pedal. This happens wether the engine is running or not. Occasionally, the pedal stays great but returns to its former self after a short while.

Ive bled the system many many times trying the usual method (furthest away, pumping, letting it settle, pump again) I'm using new DOT 4.

All the shoes are well adjusted and there aren't any leaks.

The brakes otherwise work very well, not withstanding the first push.

I'm starting to get really frustrated with it..................help!!!!!

Any suggestions are greatfully received. Anyway, I 've got to get them working well just to prove the guy from the local motor factors wrong that old cars are a waste of space!! (He also has a very annoying habit of rubbing his hands together in a very 'how can I get more cash from this unfortunate, misguided one' type of way.


All the best,

Rich

[Jefftav]

Rich,

I had a similar problem and a tip I picked up was to have the front of the car jacked higer than the front (supported on proper stands offcourse). The reason it works is that any air rises to the hihest point but you still have to go round all 4 cylinders/calipers to bleed each one properly.

Also is you servo mounted at a slight angle, I can't remember waht the angle is 30/45 degrees?

Hope this Helps, Jeff

[newagetraveller]

have the front of the car jacked higer than the front

Something wrong here I think.

[galaxie390]

Hi Jeff,

I mounted the servo angled upwards at around 40 deg, and the airvalve pointing downwards at around 30 deg as per instructions. I spoke to Delphi Automotive who manufacture the servos under the Lockheed name and they couldn't shed any light on it.

Although I fitted a new genuine Lockheed master cylinder is there any possibility one of the cup seals isn't pressurising? Would that cause this?

Will try jacking the front of the car up as you suggest.

Ta,


Rich

[rayofleamington]

is there any possibility one of the cup seals isn't pressurising?

Anything is possible but that 'should' be very unlikely and I would hope that it isn't the reason! The seal is a tooled part so unlikely that the seal diameter is evenly undersize, howevery the bore could be oversize

[Robins]

Rich
I recon it's your hand brake is adjusted wrong. I had a similer problem myself. Basically your handbrake adjustment was tightened a bit much when fitted and so when you adjusted the shoes in the drum everything seemed ok but when you first press the pedal it puts the tension on the cable and then feels ok unless left which gives the cable chance relax. Not sure if that made sence but I know what I ment, I think.

The way to solve it: Jack up the rear end and take the wheels off. Disconect the handbrake cables from the cylinders.
Adjust the shoe inside the drum through the hole.
Then reconect the handbrake cable to cylinders and adjust that (from inside the car). That should solve your problem.
Let us know if it works mate.
cheers, Daniel

[brixtonmorris]

is it common to fit a servo with standard brakes?
whever i have fitted a servo for people i have always fitted discs brakes.

[Peetee]

is it common to fit a servo with standard brakes

i've seen it specified on a number of cars. I would guess people feel the need to improve the brakes and start with a servo, shying away from the disc option because of the extra cost "I think I'll try the servo first and see how I get on thankyou..."

Moving on a bit, I have often heard that servo's on thier own shouldn't be fitted to Minors because of a risk of brakes locking on (not skidding, something to do with the snail cam I believe). Is there any truth to this rumour? I mean the minor shares most, if not all its brake componants with other BMC vehicles and there is nothing particularly unusual about its set up. There are many, many other vehicles of the period with standard fitment servos and I'm sure thier brakes aren't designed deadly. Perhaps it's a sales pitch to get you to buy the discs as well. Locking brakes just sounds like poor maintenance to me.

[brixtonmorris]

theres a return spring on the shoes with standard brakes.
disc calipers dont have a return the just release and sit in a self compansating position.
does this effect the servo?

[Willie]

I have fitted a servo to my normal Minor brakes and it works on the
front brakes only! I suspected,rightly or wrongly, that there would
be excessive weight transfer towards the front of the car in an
emergency braking situation which would allow the rear brakes to
lock up prematurely which, of course, would create a dangerous
instability. I have had occasion to save a dogs life recently by
stamping on the pedal as hard as I could and the braking was
magnificent. Please don't tell me that a servo doesn't improve
the braking but only makes it easier because if it makes it easier
then that IS an improvement in my book.

[brixtonmorris]

ive seen it fitted only on the front on other minors before willie.
is there a reason for that or is it just lazyness about running pipes around.

[Willie]

No Mark it wasn't being lazy, just a theory, I didn't want to get
in to the realms of fitting a pressure release system on the rear
brakes. I am happy with how it works so it stays. Re do the
late Minis have the peak in the combustion chamber, I don't know
but plenty of people will!.

[grainger]

my servo is only on the front brakes too, i think its quite normal. it makes a big difference compared to the other 2 servoless moggies ive had. speaking to the guy at staffs minors last year he said the only thing to watch for is that it stresses the rubber pipes a bit more than normal

mine gets a bit spongy now and then, but like has already been said, if you keep the brake pads adjusted up its not a problem.

cheers
grainger

[Willie]

Grainger.....Most people with servos will have them working on
all four brakes so it is us who are 'unusual'. I would agree that the
various rubber bushes in the front suspension may be under a bit
more stress with servoed brakes especially the Tie-Rod items but
have had no problems with the actual brake hoses. You could always
fit the armoured type in the event of trouble.

[Wal]

Hi,
I would just like to add that I have recently removed the servo from my Morris, and good riddance to it forever, because ever since it's been in it has been a real pain. I added a servo to my Moggy because I was uprating the engine and thought it would be a useful addition. I've now been through various engine types and brake set ups from drums to discs. The whole time I was having problems with the brakes - sometimes spongy, sometimes excellent and occassionally jam the brakes on hard just for a laugh. Having changed just about every item - pipes, shoes, master cylinder etc. I eventually decided to disconnect the servo and see. Well what a revelation the brakes were perfect and not only that they operated in the same manner everytime. Since then my servo has been disconnected, but only now have I actaully managed to remove it completely because it was located under my carbs. I have also noticed that I have removed about 6 feet of extra pipework with it.

Before anyone asks - yes the servo was new and from a well known manufacturer and installed exactly as specified (between 25-45 degrees from upright and 30 degrees from horizontal for the slave inlet) but it still never worked properly.

So I would add a note of caution on servos as they can be a pain if they go wrong. Also I find, even with an uprated Moggy, that my brake set up doesn't need a servo it's excellent without it (admittedly with discs up front).

Regards,
Wal

[Peetee]

doesn't need a servo it's excellent without it (admittedly with discs up front).

I'm sorry to hear that and, at the risk of rubbing it in, I have to add that a servo'd + discs Minor can have excellent brakes too. I would imagine that it will never have the precision feel of a modern car because of the inherant design of a Minor suspension and steering componants. They were never designed to be put through the sort of loading that can be applied through modern Ford discs and poor roads. Nevertheless that can be very reliable and feel familiar to anyone used to driving contempory cars. As someone who, daily, swaped from driving two 90's cars to a 1960 Minor I was much happier with the disc and servo set up. In operation it's braking action was much more linear that the drum set-up and driving in urba traffic was much easier.

[galaxie390]

Hmmm, a few differing opinions.!!!

Personally, I'd be wary of power assisting the front brakes only from the point of view of poss excessive weight transfer. This would undoubtedly contribute to rear end skidding.

As I see it, servo-assistance on all four wheels doesn't alter the front-rear pressure/ weight distribution only the pedal effort required to operate the system. I suppose the only concern is that is it possible to 'overpower' the system? Does this cause the 'locking on' when the snail cam is at its maximum adjustment and the linings are low?

Its an interesting point about the number of servos fitted that never seem to work well and give varying pedal characteristics. Its also interesting to note that this system has been factory fiited on a number of vehicles over the years, apparently without problem.

Maybe its blind faith, but I would have thought that if there ever a serious concern over the comptability of the moggy brake system and servos would a number of large and established/ reputable suppliers continue to sell the entire kit with instructions??

Yours braking very gently,

Rich

[Pyoor_Kate]

I have to be on the servo support team, I've driven a completely standard minor and my marina disks at the front standard drum rear set up / servo set up was definately my preferred choice. I've not had problems with locking on, strange pedal pressure things, or anything like that....

And to be honest the brakes are quite 'feely' enough for me - and my mum can drive my car....albeit with a cushion

[grainger]

yeah all moggy brakes are 'feely' ... i thouht thats how they are sposed to be ?

sometimes they work sharp and other times not so sharp but they always do the job, and thats part of the reason its best to keep yr speed down and let people go past you .... servo on the front just gives you that touch more control

going down long hills 'fast' is always going to be fun .. servo or not

grainger