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Post by Deleted on Sept 10, 2006 12:11:30 GMT
in a recent posting I casually mentioned that I needed to replace the seals in my rear brake cylinder. I knew that this had to be done as the rebuild was due for its 35 year service and I had noticed some seepage a year or so back. I spent a very enjoyable afternoon yesterday removing the o/s cylinder and wrestling with the upper 7/16 AF nut on which the flats had almost rusted away. To cut a long painful story short I eventually had to chisel it away bit by bit using all the tricks and knowledge built up over a number of years working on old cars. The cylinder looks in good shape but desperately in need of overhaul.One piston was stuck and the whole assembly had not moved on the backplate since the dawn of time. I have very little knowledge of nuts & bolt sizes and we dont have a supplier near by and I obviously need to replace the old nuts with some new ones.The size is 7/16 AF and it is a nylox nut.This is important as the nut screws up against a spring washer and is then released slightly to allow movement of the cylinder so it has to be a self locking nut.My question is ....what sort of thread is used and is there someone who has some spares or a source.The width of the thread seems to be 1/4" Thanks
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Post by Phil Nottingham on Sept 10, 2006 12:24:29 GMT
Its 1/4" UNF and the spring washers are special double ones. it did buy some once from a nuts and bolts place mail order but cannot find the bill now. I got them for my P2
Any car with mechanical Girling brakes eg Ford Pops will use them so perhaps try those sources
They do readily seize on the backplate and poor handbrake is the usual symptom - standing/disuse makes it worse.
I rerubber cylinders only once as they are usually scored/pitted by then
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Post by Multi-Tech on Sept 10, 2006 16:07:20 GMT
i use a supplier close to me, details are: Margnoe Ltd 01483 536800 www.margnor.co.ukenquiries@margnor.co.uk They are very helpful and my be able to help.
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Post by Deleted on Sept 10, 2006 19:03:21 GMT
Thanks very much for that.Now I know the size I can track some down.The washers are serviceable. I am lucky as the cylinder looks good with no scoring and I had from time to time used brake grease to keep the handbrake mechanism free. Lack of use certainly compounds age related deterioration and one of the pistons obviously hadn't moved for a long time. Funny thing is that readings at MOT have always been ok and so has the handbrake. On the positive side,everything is so robust and big it makes rebuilding a pleasure and the handbrake mechanism is a perfect example of a simple effective way of expanding the brakeshoes without a million stupid little clips and springs!
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Post by Colin McA on Sept 11, 2006 21:17:52 GMT
Maybe off topic but I got a call today from past parts to say my rear cylinders and calipers are ready.
I will post some photos when I get them back either today or tomorrow.
Colin
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Post by dorsetflyer on Sept 12, 2006 23:16:53 GMT
Richard, try 'NAMRICK', for any fastener requirements, they do mail order, and the last time I used them were next day deliveries. They advertise in 'Practical Classics'
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Post by Roy of the Rovers on Sept 13, 2006 9:36:34 GMT
Namrick are just down the road from me, not sure if that helps anyone with anything! Might go to the AGM if you want something picked up...
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Post by Deleted on Sept 13, 2006 19:30:01 GMT
Many thanks for the offers of help but I have now sourced some from a local supplier who actually delivered them to me on his way home from work The rubber seals were in a pitiful state and had disintegrated.I really dont know how I had a brake and I assume it was the debris built up around the piston that was supplying some sort of sealing effect.There was hardly any seepage from the dust covers and one side was bone dry. The cylinder is not scored/pitted but has discoloured in the unswept area behind the piston.I have polished the bores with brasso and I think the unit will be ok. The other side will be attended to before I'm back on the road.
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Post by Deleted on Sept 16, 2006 19:22:00 GMT
First,a bit of background. My car is garaged at my parents house some distance away so I only get to work on it on the occasional Saturday and time is a bit tight sometimes for various reasons. I refitted the rebuilt cylinder and everything was hunky dory with the unit correctly sliding on the anchor plate. I refitted the plungers in the housing and refitted the same shoes as they have plenty of lining left. The problem is I just cannot get the drum back on >:(and then I ran out of time. I am working on the o/s rear. The only thing that could be wrong is the plungers as they seem to be high in the housing but seem correctly fitted and work correctly by the wedge on the adjustment correctly spreading the plungers as it is screwed in. Obviously,the slots are lined up with the slots in the housing but the ends of the shoes hardly recess into the housing slots at all. I can't see how I could have fitted them wrongly as the chamfered edge has to face towards the end of the adjuster screw doesn't it? The edges of the plungers are touching as you look in the housing. I can't see that they could work in any other way. If I have fitted them correctly it could just be that I will have to try to line things up a bit better but that drum is bloody heavy. Who needs the Gym with one of these cars! Any helpful suggestions would be really appreciated. Thanks
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Post by Phil Nottingham on Sept 16, 2006 19:26:59 GMT
Assuming you have put the shoes back on the right way - are you sure the handbrake is fully off? The compenster on the back axle may have partially siezed - try working it to and fro.
Make sure the drum adjuster is fully turned out as if the brakes have been partially siezed the linings would have worn unevenly
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Post by Deleted on Sept 16, 2006 20:02:44 GMT
Thanks Phil but the handbrake mechanism is free and working as it should and the adjuster is fully undone and was free. The linings are evenly worn and have been reassembled as before. I took care to mark positions etc. Looking at page 13 section N of the 3ltr w/m, I am 100% sure my plungers look like the illustration but I' ll have to wait til next Sat to find out Thanks for your help.
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Post by Phil Nottingham on Sept 16, 2006 21:17:57 GMT
It is possible to assemble the "tappets" the wrong way round in the cylinder and also the plungers in the adjuster - they do only work one way
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Post by johnwp5bcoupe on Sept 17, 2006 5:47:25 GMT
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Post by Deleted on Sept 17, 2006 9:51:15 GMT
John,thats absolutely brilliant,just what I need Thanks very much, some great images. I can now recheck my assembly next Sat. The ends of your webs do seem to be sitting in the housing much lower than mine. I assume the double ended spring not shown on your image is clipped into the top and bottom elongated hole so as to run parallel with the side of the cylinder? Thanks to you Phil for your further ideas.The tappet mechanism is working ok.
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Post by johnwp5bcoupe on Sept 17, 2006 16:24:04 GMT
That's correct about the spring you can just see the end on the bottom shoe good luck you will get there Just a silly thought make sure you have the adjusters paired up
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Post by Deleted on Sept 17, 2006 18:33:37 GMT
Thanks, I can just see it although my spring runs from the bigger hole at the top to the bottom hole next to the one your spring is attached too. I wonder if by having the spring at the higher hole I will be making the tension too high? I know this is nothing to do with my other problem but I would be glad of an opinion as to exactly where the cylinder end pull off spring should attach or doesn't it really matter that much?
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Post by Phil Nottingham on Sept 17, 2006 19:16:52 GMT
The springs must attach to the correct holes - if you have over-stretched them they may be useless?
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Post by johnwp5bcoupe on Sept 17, 2006 19:50:33 GMT
The springs are correctly fitted in the picture it's the first hole from the cylinder but looking at my picture I could be a hole out on the adjuster side!! I marked the old shoes with a marker pen! but they still may be a hole out one one side well it was 26 years ago! and the difference between the two holes is not a great deal if one is out! over to you Phil the fountain of knowledge
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Post by Deleted on Sept 17, 2006 19:54:18 GMT
Is Johns cylinder end pull off spring located in the correct holes? My adjuster end pull off spring matches his exactly. I would have to be superman to overstretch the double spring! I am not aware of any drawings giving the exact location of the spring catches and the two oval holes seem to line up best. Sorry to come back but where should the spring be attached?
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Post by Phil Nottingham on Sept 17, 2006 20:26:06 GMT
I cannot remember without looking at mine - it is possible to fit them in the wrong holes and I have come across this a number of times.
We are about to go on holiday - doubt if I will have time now to wip off a wheel and drum to see - can you wait?
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Post by johnwp5bcoupe on Sept 17, 2006 20:54:23 GMT
I doubt if you will get the spring in the other two holes on the cylinder side but "Heh" I am not Superman
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Post by Deleted on Sept 17, 2006 21:27:51 GMT
I did manage to fit the cylinder pull off spring into the oval holes and locate the webs in the cylinder but I will alter the setting when I work on the brakes this Saturday and copy the position of Johns assembly. Thanks for the offer Phil, but I can't honestly see that it is that crucial as long as the spring is not over stretched and pulls the shoes off. Thanks
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Post by johnwp5bcoupe on Sept 18, 2006 6:21:16 GMT
Just to make sure I am correct Crossplies I still have my old shoes which will have the marks from the springs as well as mine so I will check for you
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Post by johnwp5bcoupe on Sept 18, 2006 14:38:04 GMT
I have checked two sets of old shoes Crossplies you can see on the back where the springs have rubbed, the problem is the shoes are different one set has two round holes and the spring was in the first two on the cylinder side the other pair were in the oval holes which are the second pair both the cars were on the road before being dismantled so unless there is a definitive answer mine will stay as they are they work
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Post by Deleted on Sept 18, 2006 16:21:26 GMT
That's good enough for me.Thanks for checking and all your help
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