please help.. bleeding new brake setup!

[treefingers]

hi everyone

i'm at the brakes stage of my mk2 rocco build, and i am having troubles, I wonder if anyone can help? This is the first time I've done this so really need some help!

I've got all the brakes fitted and I am at the stage of bleeding the fluid through. I am using a pneumatic one man bleeder.

I bled all four corners, and then went to test the brake pedal but it wasn't very hard and as I looked at one side of the front callipers I couldn't even see the callipers move when I pressed the pedal.

So here's the problem.. when I bleed the back brakes not much fluid comes out of the bleed valve, it steadily but very slowly. I am guessing this is because of the rear regulators I have fitted, is this normal?

The front left calliper bleeds very slowly, like there is a massive restriction somewhere. The front right calliper bleeds OK but I can't see it moving when I push the pedal. I had similar problems yesterday so I just tried another new master cylinder in case I had pressed the pedal with no fluid in and damaged the seals. The new cylinder seemed to let the brakes bleed OK but when I checked the pedal there was not nearly the amount of resistance I'd expect.

Any ideas would be appreciated!! What could be causing resistance in the brake system?



For your information I have new copper lines, new braided lines, new drum brakes rear, vauxhall 256mm brakes front, 16v golf servo and 22mm master cylinder. The cylinder is set up with opposite corners and the brake reducer/regulator things on the rears.

[Nate]

When you say pneumatic bleeding, do you mean a gunsons ezbleed or similar?

Go right thru the whole lot and make sure you've not got any slight weeps from any unions and try again.

Personally I favour the old school 2 man bleeding method or failing Guay use a mityvac

[bengould]

Have you adjusted the rear drums correctly. I'm sure I remember reading on here a while ago that spongy feeling brakes can be due to the rear wedge shaped adjusters not being pulled down enough. If you've bled the system twice and checked for leaks everywhere, as suggested above,then I'd try and adjust the rear shoes a bit more.

For bleeding I use a one way valve on a short length of clear hose. You can buy one in the motorbike section of halfords or make one from cheap bits off eBay.

Ben.

[marcus]

If you're bleeding using something which connects to the brake fluid reservoir, make sure the rod linking the pedal to the master cylinder isn't over-adjusted or it could be blocking the outlets in the m/c.

[mark1gls]

I had problems bleeding my brakes after a rebuild and it took ALOT of bleeding to get all the air out. So may be try it again.

[Nate]

Another one that I've heard of but never tried it to open the rear bleed nipples with a pipe on them going to a jar to catch the fluid and then leave them for a few jours, topping up the fluid as required

[treefingers]

i'm using a Sealey pneumatic bleeder..
http://www.ebay.co.uk/itm/like/25143673 ... 0&ff14=108

thanks for the help guys. so i've written a list of things to try this week to get them working..

1. didn't even know about adjusting the rear shoes, don't know how to do this but I will need to!
2. the master cylinder could be sticking, gonna take it out and check if the piston has come back
3. i'm going to do another bleed but in the correct order (was doing RR RL FL FR before)
4. check for leaks throughout the system
5. pushrod length.. could be something to do with this as I had it out when the car was painted. It's adjusted so you have about 10mm of free play in the pedal before you feel the cylinder pushing.

will let you know how i get on!

[marcus]

Re adjusting the rod, it's not the amount of play in the pedal you're interested in, it's the amount of play at the m/c end, it should be barely discernible ie a tiny bit of play, but not none, because if it's none, then the m/c piston could be permanently pushed in a bit, which you don't want.

[Nate]

didn't even know about adjusting the rear shoes, don't know how to do this but I will need to!

with drum on, rotate until you can see the bottom of the wedge through a bolt hole. get someone to stomp on the pedal, and while they do, you need to hook the bottom of the wedge with a pokey thing and shove it downwards as hard as you can, then get them to release the pedal.


is the pedal soggy (indicating air in the system) or does it slowly sink to the floor (indicating a loss of pressure)

[treefingers]

Right still had no luck getting a hard pedal, it's baffling me now! Had a second mechanic come and look at it and we still can't solve it, he says something's not right but we can't find what!!!!!

I still can't get a hard pedal, it's soggy and I can push it all the way to the floor. It seems like air in the system but I've bled and bled the system so it's very strange.

If I sit in the car and pump like mad it doesn't get harder, I don't get any brakes. If I pump about 10 times in a row really fast I get a tiny bit of braking (nothing usable) on the rear but it fades really quickly.

Marcus - I've checked and the pushrod has about 2-3mm of freeplay before it comes into contact with the master cylinder. I thought there wasn't enough pushrod but it's fine here.

Nate - It's soggy and it'll sink to the floor, I can push the pedal all the way down with not much trouble. There's some resistance but it's nothing at all like a firm brake pedal.


So it can't be the master cylinder.. I'm on my second brand new cylinder now. It can't be the servo? It seems like it's a problem at one point in the system as the pedal won't stop any corner. It must be at the master cylinder end? Could it suck in air at the reservoir seals? I've adjusted my rear drums now too so it should be fine there.

I need to double check but I'm pretty sure these are the pipe connections, if anyone could tell me if this is correct that would be great..

[Nate]

My m/c has the 2 reducer valves coming out the bottom and the 2 feeds to the front coming from the side

[bengould]

My m/c has the 2 reducer valves coming out the bottom and the 2 feeds to the front coming from the side

As does mine. I doubt it would matter though as long as you have 1 front and 1 rear brake on each part of the master cylinder. Can't hurt to try and swap them over though.

Ben.

[Chaps]

I know this is a really daft question but, you haven't put the callipers a on upside down have you. I.e brake nipples at the bottom. I made this mistake once when doing a conversion and had the same results

To you gents with the other type of master cylinder, can you post a pic of the setup and brake line connections into what holes on the mc.

[go-for-it1]

Your MC appears to be different from the standard ones fitted to Mk2's unless it is just the way you have drawn it, as Nate and Ben have already said the two rear brakes pipes with the reducers come out of the bottom and fronts come out of the side nearest to the rocker box. However your connections appear to be orientated correctly with front right and left rear in line with each other. Are any of the calipers/drums bleeding correctly or are they all slow? Leaking reservoir seals could draw air in but also leak fluid out which you would see. Have you changed any of the pipes or brake hoses during your build? Collapsed hoses or crimped pipes would create a restriction in fluid flow.
Try bleeding with the 2 man method. Do each brake individually with one person pressing the pedal whilst the other opens the bleed nipple, once the pedal is on the floor tighten the nipple then let the pedal up. Repeat until there is no air coming out and don't assume the first flow with no air in is it, do it a few times to ensure any trapped air is displaced before tightening the bleed nipple whilst the pedal is down. There should be a good flow when doing it this way so if it is a poor flow then your problem is further back from the caliper/drum, e.g.pipes/hoses/reducer. Make sure you don't let the level in the MC drop below minimum during bleeding.
Sorry if it sounds like I am teaching you to suck eggs but a methodical approach will result in success.
The 2 copper pipes in the photo are front brake pipes.

[Tim_R]

Am I right in thinking you went for a 16v servo and MC when rebuilding? So it looks something like this?



My J plate car never had pressure regulators fitted to the original MC so when I fitted the 16v stuff in the picture above I didn't bother hunting any down and no issues with the back end locking up. I think it may have a different design of rear cylinders compared to earlier cars, but I'm not 100% on that.

I'm wondering if the fact that they are now effectively upside down compared to the original position in yours is causing them to trap some air that can't be bled out?

It's worth going through the manual bleed that go-for-it1 has suggested first and possibly even clamping flexi lines to rule out calipers which won't bleed properly.