brake bleedingHi

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stu60
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brake bleedingHi

Post by stu60 »

Hi this may be a dumb question but...

standard hawk set up princess calipers at front MGB rear drum brakes and 2 brake master cylinders.

I am changing seized rear cylinder in n/s drum and need to bleed brakes afterwards . I had assumed the brakes circuits are split diagonally side to side but think they may be split front to back?

Questions:-
1. are they split front and back?
2. is there a convention for which master cylinder does which wheels? i assume i will know which cylinder because i will lose some fluid when i take old wheel cylinder out but i then want to know which other wheel to bleed?
3. I might change fluid in front brakes anyway but I have heard somewhere that bleeding the front Princess calipers can be "difficult"; are there any top tips?

thanks Stuart
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clive
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Re: brake bleedingHi

Post by clive »

If it is the standard Hawk setup then the brakes are split front and rear and I would think the front brake reservoir will be for the front brakes and the rear for the rear. If you are only changing one slave cylinder then you can clamp the flexible hose if it isn't braided so there will be minimal fluid loss, however it would probably be a good opportunity to replace the fluid. I have never had any problem bleeding my Princess Four Pots using a simple home bleed kit.
Cheers, Clive.

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peterc
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Re: brake bleedingHi

Post by peterc »

Before starting you can remove the respective reservoir lld and place a piece of plastic over the reservoir and then replace the lid. This stops the draining down of the reservoir fluid in case you don’t possess a proper hose clamp. Do not use mole grips on the flexible.
You should be able to follow the brake pipe routes to see which goes to the rear.
Personally I always bleed the shortest route first but once you have the system bled of air it must be a good idea to pump enough fluid through to change out the old fluid. To speed up that process you could remove the old fluid from the reservoir and refill with new before continuing the bleed process.
I prefer not to empty the system completely as it usually involves more bleeding as air tends to hang up in the system somewhere and need extra bleeding to remove it.
Peter C
stu60
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Re: brake bleedingHi

Post by stu60 »

thanks for prompt replies, split front and rear makes life easier.... Now to do battle with re-fitting that circlip!
Stuart
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StewbieC
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Re: brake bleedingHi

Post by StewbieC »

As already confirmed,
Bias split front to back.
Which master cylinder depends upon who built the car, but if you follow the pipes from the two brake masters you should quickly see which goes to the front and to the back.
It cannot be stressed enough that brakes are an important safety feature of a car and they need to be done correctly. If you are not entirely sure then get some advice or someone to do it who knows what they are doing or at least get them properly checked on a brake machine in a very local garage (Anyone that does MOT's has one of these).
Brakes set up incorrectly can prove lethal. If a back brake locks up at speed then you can easily pirouette into on coming traffic with disastrous results. There is plenty of info available on MGB rear brakes, but please ensure it is right.
Not trying to teach you to suck eggs but it is technical advice that needs to be offered if the question is posed, as a duty of care.
________________________________________________
Stu
Hawk 289, 66 Mustang Fastback with a 289 maximum smiles per mile..
stu60
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Re: brake bleedingHi

Post by stu60 »

hi
Thanks. I am pretty comfortable doing job but question as not done on dual master cylinders before plus not looking at car when i asked question late last night.

Nevertheless, sage words on safety and car will be off to rolling road and MoT check afterwards.
thanks again
Stuart
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clive
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Re: brake bleedingHi

Post by clive »

Just an observation. If you have the Hawk supplied reservoirs with the built in fluid level sensor, it might be difficult to place plastic over the opening and then replace the cap. You might be better putting polythene over the opening and then use a rubber band or similar to make an air tight seal. (Like granny did when making jam!)
Cheers, Clive.

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peterc
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Re: brake bleedingHi

Post by peterc »

Clive, you are of course correct which goes to show I obviously haven’t used that method on the Cobra.
Thankfully I haven’t needed to undertake repairs and have only needed to remove the reservoir contents re fill with fresh at the start of bleeding through new fluid to change the entire contents.
Peter C
stu60
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Re: brake bleedingHi

Post by stu60 »

Hi
All successfully completed. Strangely the new cylinder from MGB hive has different size bleed nipple (7mm) to old cylinder. It's the correct cylinder as casting number is same. Also the tip I found on line to use locking pliers/mole grip to hold cylinder in place whilst installing the circlip made life easier.
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