ash_hammond
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| posted on 21/7/06 at 09:09 PM |
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Poor Rear Brake
Hi Chaps
Finally got all the brakes fitted and just got around to bleeding them. The front brakes work fine, however, the back drums are very poor and i can
move the drums by hand when the brake pedal is depressed. All the braking system is new except the master cylinder. There seems to be no air in the
system at all, i have bled them by hand and i have also tried a power bleeder both to no joy. Also did the usual of longest to shortest brake line.
The rear brake setup is shown below, from here it goes to a rear "T" piece and then out to each wheel cylinder via flexi hoses. Also there
is no ovious kinks in the pipe and i seem to get plenty of fluid out of the beed nipples.
Any fruitful suggestions, to aid a successful saturday?
cheers Ash
 
Rescued attachment S4010010.JPG
.: www.mac1motorsports.co.uk | www.m1moc.com :.
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DIY Si
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| posted on 21/7/06 at 09:19 PM |
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Is the black thing a pressure reducing valve? Sounds silly, but have you adjusted the rear drum shoes properly?
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davrus
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| posted on 21/7/06 at 09:25 PM |
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wheel cylinders seized maybe , if fluid is coming out the nipple and the cylinder pistons are not seized then adjustment must be the answer
Good luck
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davrus
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| posted on 21/7/06 at 09:27 PM |
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post a pic of the rear brake set up . might be able to help you more
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ash_hammond
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| posted on 21/7/06 at 09:36 PM |
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Rear Brake Shoes
 
Rescued attachment S4010013.JPG
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DIY Si
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| posted on 21/7/06 at 09:43 PM |
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Blimey davrus, any chance of making that avatar a little smaller?! It's all I can see. Brake shoe adjustment can only be done with the drum on
really. Otherwise all looks good in the pic.
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ash_hammond
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| posted on 21/7/06 at 09:46 PM |
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Will resize it did not know it was that big when i uploaded it 
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davrus
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| posted on 21/7/06 at 09:50 PM |
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is the brake pedel poor or good
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ash_hammond
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| posted on 21/7/06 at 09:54 PM |
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Resized.JPG)
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DIY Si
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| posted on 21/7/06 at 09:55 PM |
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Are the pads different thicknesses or is it just the pic?
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ash_hammond
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| posted on 21/7/06 at 09:56 PM |
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Yes, the brake pedal feels ok, perhaps more adjustment is the answer.
.: www.mac1motorsports.co.uk | www.m1moc.com :.
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ash_hammond
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| posted on 21/7/06 at 09:57 PM |
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yer its just the picture, they are brand new shoes.
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DIY Si
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| posted on 21/7/06 at 10:03 PM |
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Sorry if this sounds condescending, but have you ever set up drums before?
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ash_hammond
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| posted on 21/7/06 at 10:06 PM |
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not condesending at all, any help is welcome, i have never build them from scratch, but have adjusted them before, mostly on VW's.
Why do u spot somthing wrong?
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DIY Si
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| posted on 21/7/06 at 10:14 PM |
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No, they look fine, but these sort (don't know what vw stuff looks like) can only be set up with the drum on. It's really difficult to
explain, but I'll try.
First, since everything's in place, just put the drum on.
Then, on the back of the drum is the adjuster head/screw. Turn this in until the drum starts to stick when turned by hand. Then back off 1/4 turn.
Now spin the drum and listen for it catching/high spots. If none can be heard turn the screw back in slightly.
Turn the drum slowly until it's at the high point. Then, using a SOFT faced hammer, tap the drum top, bottom, left and right. Spin again and
keep going until the high spot goes away.
All being well, if you turn the screw in slightly again it should slow the drum without any obvious high spots. Back the screw off by a slight amount
(ie to where it was a moment ago).
Go for a drive/see how the pedal feels.
Got all that?
[Edited on 21/7/06 by DIY Si]
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ash_hammond
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| posted on 21/7/06 at 10:20 PM |
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yes the logic seems ok, except there is no screw on the back of the drum. i would love to take the car for a spin but its missing one major part.....
the engine and box 
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athoirs
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| posted on 21/7/06 at 10:21 PM |
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May be silly but is there a reason why the the whole brake assy is 90deg out? ie the cylinder should be at the top? the bleed nipple i think may be in
the wrong place if its in this position and some air might still be left... this is a common problem with disk brake set ups
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DIY Si
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| posted on 21/7/06 at 10:24 PM |
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I didn't think you could get these 90º out as the bolt holes are a rectangular shape? Could be 180º though by that thinking.
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ash_hammond
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| posted on 21/7/06 at 10:30 PM |
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Thats correct the holes in the rear uprights only allow the back plate assembly to be fitted in one place also other MAC#1's are fitted in this
way. i have pumped quite alot of fluid though the system so i am thinking that the possibility of air in the system is getting less likely
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athoirs
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| posted on 21/7/06 at 10:34 PM |
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Yup thats right. still think there might be air in the cylinder in that position. you could try taking the two bolts out that hold it on pull forward
rotate so that the nipple is at the top and bleed. just remember to but a g clamp over each piston or they will pop out! then put it back in and try
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DIY Si
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| posted on 21/7/06 at 10:36 PM |
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Bugger beaten to it. As he ^ said. Take it out of the backplate and try bleeding it on the bench, as it were.
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britishtrident
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| posted on 22/7/06 at 06:02 AM |
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Sierra G valve ----- !!!!!!!!!!!!!!!!!!!
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zetec7
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| posted on 22/7/06 at 07:21 AM |
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If there's air in the system, the pedal will feel spongy, and enough air to allow you to hand-turn the drum with the pedal depressed would also
allow the pedal to go to the floor with virtually no resistance. If there's any feel at all to the pedal, then air isn't the problem. I
agree with the out-of-adjustment prognosis. Although it's hard to tell for sure in the photos, it looks like the upper and lower shoes are very
different distances from drum contact. If this amount of throw is more than the wheel cylinder can accomplish, there will never be much braking.
Look for the adjustment problems - the best is to have someone slowly depress the pedal a little, while you watch the shoes for signs of equal
movement.....
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dr-fastlane
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| posted on 22/7/06 at 07:22 AM |
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Yes, throw away that Sierra G-valve. And get a brake reducing valve from an Fiesta or Mondeo. Or fit an adjustable bias valve from an Fiat Uno. Like
most of use do.
------------------------------
I have not failed once. I have successfully found ways that will not work!
https://www.motor-forum.nl/threads/hardtail-dragstyle-project.343482/
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ash_hammond
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| posted on 22/7/06 at 07:35 AM |
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Many thanks to you guys for the posts, i you have just confirmed what i was thinking and the theme through the posts is "check the
adjustment"....... No i am now off the a cuppa and hopefully a fruitfull day in the garage awaits me.
cheers
Ash
.: www.mac1motorsports.co.uk | www.m1moc.com :.
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