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Discussion Starter #1
Hi All,

I've finally traced the leak in my breaking system to the righthand rear calliper.

This has taken me ages because it's a tiny leak and only through leaving the car standing for 6 weeks did I at last find the evidence I was after: a couple of drips inside the rim of the wheel!

I've now got it up on stands, wheel off and can see fluid dripping off the wheel side of the "disc shield", so it appears to be coming from the inner faces of the calliper.

Having looked up the £20 worth of seals which I guess will fix it, is there anyone who has done the job who can give me the titbits of information they learned the hard way?

Would you actually recommend just replacing the calliper rather than messing about with it?

Thanks in advance, I've pencilled in next Friday to do the job, so want to get the parts ordered ASAP!

Cheers,

Alex
 

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IMO if you have a leaking caliper one side, the other side may warrant very close inspection. I dont think you can make a decision about repair or replace until the caliper is off. If when it is removed there is no wear or rust in the cylinder then I reckon new seals will be enough.

Over the years the calipers on both sides will have worn equally. If you repair the one you could get some brake pull to the one side, so if I were going to embark on this job I'd be prepared to repair both or replace both, as a pair.
 

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Discussion Starter #3
Thanks for the advice, as far as I know the callipers are only a year old, so I think this is probably a manufacturing/assembly defect and am hopeful the other side will be ok.

This being said, I will check it over thoroughly.

I'll strip the other one out of the car before making any decisions.

Cheers.
 

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Yikes only one year old and they have a leak? thats not good! I've just had my two fronts fully referred as they were sticking...

Thanks for the advice, as far as I know the callipers are only a year old, so I think this is probably a manufacturing/assembly defect and am hopeful the other side will be ok.

This being said, I will check it over thoroughly.

I'll strip the other one out of the car before making any decisions.

Cheers.
 

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Discussion Starter #5
Yikes only one year old and they have a leak? thats not good! I've just had my two fronts fully referred as they were sticking...
They were fitted as part of the re-commissioning work done on the car before I bought it, so I can't be 100% sure of their provenance, however, they look new and all the brake lines and flexis are new, so I believe they were replaced.

Saying that, if I can fix the irritating leak which meant I had to bleed the system every couple of weeks, it will be money well spent as it'll really increase my enjoyment of the car!
 

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Discussion Starter #6
Pah! Stripped off the calliper and it's brand new, no sign of a brake fluid leak on further investigation, it seems to be new oil coming out of the axle dripping into the wheel... That's another issue for another day as it was only a couple of drops.

I invested the rest of the morning crawling through the whole brake system and finally think I've found the issue (again, admittedly!). After reinstalling the calliper and replacing both rear bleed nipples (as some chump had over tightened them, probably me) and pressure bleeding the system I left the pressure on and looked everywhere until I found some fluid which was where it shouldn't.

The servo nearest the front of the car had fluid dripping from the rubber hose, but both fluid lines were tight and not leaking. I'm now suspecting a dying servo.

I've never seen any white smoke and am not losing any fluid (which you can judge from the reservoir), however, the rear brakes keep getting about 4" of air in which ruins the pedal. Does anyone know if this servo is for the rear brakes? If so, it is finally starting to make sense and I'll rebuild the servo, unless anyone has a known good one lying around they want to sell?

Cheers
 

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Maybe check your brake light pressure switches while you're at it. They are of low quality lately and they sometimes start leaking at the top where the wires connect to them.
But most of the time it's a booster if you get air into the system over time.
 

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Discussion Starter #8
Thanks Sling, I finally found a "circuit diagram" of the RHD twin servo set up last night and was surprised to see those switches being in-line.

I'll have a really good look at them, where about on the car are they physically located?

Having read up on the servos/booster it seems that rebuilding a bonaldi unit at home might not be worth trying, so I think I'm going to strip it out at the weekend, take it apart and try to identify what has failed. If it is something big and obvious which I can see comes in the rebuild kit, I'll take a punt, if it seems to be a few things or wear, I'll bite the bullet and get a replacement unit.
 

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Discussion Starter #11
hmitd, the first diagram is really useful! My guess is I've got a couple of problems as fluid appears to be leaking out around the by-pass and air is getting into the "heavier pressure to brakes" chamber and being sent to the back brakes.

Now I can see what the thing is made up of and how it works, tearing it down is a lot less daunting!

Cheers,

Alex
 

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I'll have a really good look at them, where about on the car are they physically located?

My car is a RHD - so the front switch is located just below the rear booster against the firewall. Close to where the exhaust runs down to go underneath the car.

The rear switch is located underneath the car at the rear - on the right hand side - infront of the differential. So basically below the right rear seat area.

This what they look like (SL134SN) - and sometimes leak where the plastic meets the metal :

http://mgaguru.com/mgtech/electric/et119a.htm
 

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The servo nearest the front of the car had fluid dripping from the rubber hose, but both fluid lines were tight and not leaking. I'm now suspecting a dying servo.
I've had one of my boosters leaking fluid from the airvalve area. I just removed the offending booster and connected the two brake lines together with a connector. When I shook the booster you could actually hear fluid inside. I might be wrong but a correct booster should have no fluid inside. I then bled the system again and used the car with only one booster without any air leaking into the system anymore.

Then I saw the price of the rebuild kits :yikes:

So I took my booster to a brake centre and they found a torn seal inside. After their rebuild and fix I refitted my booster - bled again and since then my brakes are 100%

(Well as good as a 40 year old cars brakes can be :biglaugh:)
 

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Discussion Starter #14
Sling, thanks very much, my car is a RHD from SA, so I'll check the switches in the locations you suggest.

Also thanks very much for the advice on the booster, I'll take it out and see where the fluid is where it shouldn't be! Is driving the car with only a front booster ok? I'm assuming it just degrade the effectiveness of the rear circuit a bit?

Depending on what I find I'm in in two minds as to attempt repair or just to bite the bullet and get a new one to solve the problem once and for all, the repair kits are too expensive to take a chance one in my opinion.

I'll let you know how I get on.

Thanks again,

Alex
 

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Is driving the car with only a front booster ok? I'm assuming it just degrade the effectiveness of the rear circuit a bit?
Hi Alex. Driving the car with only one booster is fine. I have driven my car with all combinations during my battles to sort out the brakes.

No boosters, front booster only, rear booster only :biglaugh:
 

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Discussion Starter #16
Hi Alex. Driving the car with only one booster is fine. I have driven my car with all combinations during my battles to sort out the brakes.

No boosters, front booster only, rear booster only :biglaugh:
Thanks, I'll give it a go then, it sounds like you and I have been through pretty much the same issues with air creeping into the brakes but with seemingly no loss of fluid!

Luckily for me, I think your experience is going to help me close this out once and for all...
 

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When I had to do mine (also the rear brake one) it was the seal in the air valve piston that had failed.
The rest of the seals and diaphragm looked OK although I replaced them anyway of course.
Wasn't too difficult to re-build with the classic Alfa kit, you just have to be methodical in noting how it comes apart.
Taking plenty of pictures as you go helps.
 
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