rear brake valve renew

deQuincey

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this started some time ago with the dissasembly of this spare that i bought




the rear proportional brake valve



as it was advised use a tool to retain the spring when removing the bolts



i will renew it following the advice of a forum friend

 
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deQuincey

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a lot of preparation work was done, basically keep the external bolt and nut position, remove all the pieces, make a new gasket, chrome the fixing plate, new bolts and washers, and new rubber o-rings



remember, as they are suited for brake fluid use they must be EPDM material












a lot of pressure must be exerted to be able to close and thus do the four bolts, so i used this setup



bolts were finally fixed using loctite too





ready for my future brakes job
 
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Luis A.

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Looks like new DQ; very nice.

Why did you renew it? Could you tell something was wrong with it?
 

David

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You make this look so simple and tempting. But I've fallen for that before. I'd be two weeks into this and well over the cost of a refurb'ed unit.

Very nice, as always.
 

deQuincey

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thanks for the comments
it is nothing wrong with mine, rught now it is working fine in the car,
but it is my usual way to do things in the coupe, first find a spare, learn how to repair, renew it, and then stock it until i do the job in the car
that way it is immediate to go through it, and i do not have to wait once the part is dissasembled, it will be just a swap
for example now i have a pair of spare brake calipers front and rear from a scrapeyard, ready for major surgery, i will analyse the possibility of a complete dissasemble or a partial one, and once the decission is made i will go to the car and renew those ones accordingly
too much work ? probably yes, but it is a hobby, isnt it ?:roll:
 

30csl

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Looks great DQ. Where did you get the seals for it?

Im tempted but probably should just leave it alone :)
 

deQuincey

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Looks great DQ. Where did you get the seals for it?

Im tempted but probably should just leave it alone :)
i have a source for o-ring seals in a specialized harware store in bilbao, they are expensive cos i have to buy 3 of them at a time, i need one more for my actual rear valve, so happy to send the remaining one to you (one small and one big)

remark, it is possible to order more but probably shipping costs will make it all too expensive
 

30csl

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Hi DQ, thats very kind but I think i will leave this part alone for now - sorting the cylinder head is a bigger priority ---- sigh.
 

Luis A.

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Hi DeQ,

I just pulled out my coupe from storage where it has been sitting 6-7 months. The rear right wheel would not turn when backing up and eventually loosened after driving the car forward and backwards a few feet. When driving home it completely locked (tire screeching) 3 times in a 20 minute drive. Now it won't do it again. I need to get to the source of this issue before it does again it when I'm on the highway doing 80.

I rebuilt all the calipers and master brake cylinder 2 years ago but didn't replace the rear hoses as they looked good (I know, silly). I will replace the hoses but I'd like to also open up the proportioning valve and take a look and replace the O-rings, so many thanks for this DIY. Did you document the size of the required o-rings? I'd like to get them prior to opening the valve. Thanks.
 

jmackro

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A bad proportioning valve wouldn't cause one rear wheel to lock up. I'm not telling you not to rebuild your proportioning valve if it hasn't been serviced in recent memory, but I wouldn't expect that to fix this problem.

It could be a bad brake hose. With age, they will swell internally, acting as a one-way valve for brake fluid, and causing the symptom you describe. But I wouldn't expect an internally swollen hose to heal itself (you had written: "Now it won't do it again").

It sounds more like a stuck caliper piston. I know the calipers were rebuilt 2 years ago, but 6 - 7 months of sitting can result in corrosion that causes a piston to stick to its seal. Often this will clear up once the piston has been worked back and forth a few times, abrading off the corrosion.
 
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Luis A.

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Thanks for your reply Jay. I just looked at my photo record and I did replace the hoses 4 years ago.

I'll pull the caliper tomorrow and see what lurks within...
 

deQuincey

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yes, i will check the sizes for you luis,
remember to use EPDM o-rings, BTW the other, central rubber seal is impossible to find so treat it gently
as to the symptoms that you described i agree that they might point to a different cause, stuck piston probably
good luck
 

Cornishman

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Handbrake

Could it be the hand brake that was rubbing, got hot, expanded and Locked up?
Sticking cable, or actual mechanism?
However to be fair, I struggle to get mine to hold when I want it to, so it is more likely the caliper as mentioned earlier.
Good luck
C
 
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