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

Is the black thing a pressure reducing valve? Sounds silly, but have you adjusted the rear drum shoes properly?

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

post a pic of the rear brake set up . might be able to help you more

Rear Brake Shoes
Rescued attachment S4010013.JPG

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.

Will resize it did not know it was that big when i uploaded it

is the brake pedel poor or good

Resized

Are the pads different thicknesses or is it just the pic?

Yes, the brake pedal feels ok, perhaps more adjustment is the answer.

yer its just the picture, they are brand new shoes.

Sorry if this sounds condescending, but have you ever set up drums before?

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?

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]

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

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

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.

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

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

Bugger beaten to it. As he ^ said. Take it out of the backplate and try bleeding it on the bench, as it were.

Sierra G valve ----- !!!!!!!!!!!!!!!!!!!

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.....

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.

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

That will teach me to write a post pre 9am in the morning with reading it back to my self... so here is what i really wanted to say..

Many thanks for the posts, you have just confirmed what i was thinking and the theme throughout the post is "check the adjustment"....... i am now off for a cuppa and hopefully a fruitfull day in the garage awaits me.

cheers

Ash

I havent been able to see the pics yet as my 56k connection takes too long to wait

Lessons learnt from my brake bleeding times were

1. Make sure the bias valve is round the right way. I assume this has been done as youre getting fluid out of the rear cylinders.
2. Make sure the bleed nipple/valve on the cylinder is at the highest point on the backplate. As previously noticed, we ZR owners dont like our cylinders at 12 oclock and like to have them at either 3 or 9 oclock. whichever it is (3 or 9) make sure the brake hose flexi goes into the bottom of the cylinder (without chaffing the suspension arms (add a bit of a twist which will sort it out if they do)) and that the bleed nipple is at the top, otherwise youll turn up to sva like i did and nearly have a prohibition noticed served on you. Not good.
3. Make sure the front hose flexis are connected to the calipers
4. (assuming your setup is the same as mine) start on the back left, then the back right, then the front left and lastly the front right wheel (bleed sequence) but it sounds as though youve done this so i'll keep thinking about your prob and try to look at your pics on a bb connection.

Mark & Colin probably have some time on their hands and as your local they might have withdrawl symptoms and be able to help in person. I hear theyll do anything for a cappocino with chocolate sprinkles

I suspect it is the G valve.

You will not find an adjuster screw on the backplate as these are self adjusting.

It will not be air as you would have a very spongy pedal.

Before you adjust them make sure all adjustment is off the handbrake cable. Adjust the brakes and then the handbrake.

The adjustment works from the toothed wheels on the metal bar connecting the two shoes near the top. These commonly sieze but can be adjusted manually by levering one shoe out from centre with a screwdriver. Do small bits a a time and keep retrying the drum to ensure you do not overdo it.

When you have fully adjusted them and they still don't work, have a beer and then change the valve.

Jos, spoke to Mark this morning, he had seen the thread and gave same advice. As posted ^ , i have adjusted the shoes using the self adjusting mechanism, the shoes now fit nice and snugg inside the drum. With the drum off someone pressed the brake pedal while i watched the cylinder (which is brand new one) and there is very little movement in the cylinder at all, 2mm at the most the cylinder is not moving out to the shoes. Which says to me the system still has some air playing hide and seek.

before you change the g valve ( which are crap) try giving my suggestion a go it wont take long..

dont you just love drum brakes... NOT

most of them look like they have been designed by a five year old...

Whilst having another go a bleeding the brakes i have found a leaking "T" piece, the one which the brake switch goes into, only a small leek, so refitted that "T" peice and we will have another go after lunch. Await results of round 59.

ash

Doh! That'll probably solve your problems once bled fully.