20 replies to this topic

[Scruffs]

Hiya,

I've searched the numerous topics on this, but nothing seems to be working for me on this problem...Not sure if there's anything specific to this setup I'm missing...It's alot spongier than it ever used to be on a standard setup.

SPEC: Yellow band master cylinder, no FAM7821, wilwood prop. valve in rear line (bulkhead), fiesta front calipers (nipples at top), cupronickel and braided pipes throughout.

I can get the pedal to the floor, it takes alot of effort - i.e. two feet, me gritting my teeth and the master cylinder bobbing up and down in front of the scuttle (it is attached, just deflection in the mounts), but it still hits the floor which I don't like one bit... Oh and all the leaks I was posting about earlier have been fixed, the pedal does not creep either..

I have been through 5 litres of fluid trying to bleed this and have finally thrown in the towel! There is NO AIR at all coming through the nipples. Have tried two man method, eezibleed, pushing pistons back into calipers, car nose up, car nose down, dancing in a circle whilst praying to some hydraulic messiah and various combinations of all of the above but IT'S STILL NOT WORKING!!!

I did not bench bleed the master before fitting, sounds messy and I've never had trouble bleeding this in the past. This leads me to believe it's either the proportioning valve or the calipers. If I crack a front caliper and push down so I'm only on the rear circuit, the pedal is very firm. If I crack the rears then the front circuit seems very spongy so I think I have eliminated the prop valve by this method (although the 'out' is lower than the 'in' on the valve, I have not found a single snip on the web about these trapping air in them).

But is the above test doing what I think it is? Am I really isolating the f/r circuits??

Guessworks has said a couple of times about systematically bleeding the system by isolating various parts with a bleed nipple - sounds very logical but how would I do this without making a complete mess though?!

Anyone else with Fiesta calipers and a spongy pedal? I'm concerned I've fitted some orrible flexy, big bore calipers and I'm always going to have to shove a load of fluid about.

I cannot drive the car at the mo so I'm not sure what pedal effort it take to lock the fronts, but I hate spongy brake pedals and I think it's dubious whether it would get through a (strict) MOT.

Cheers for any help you can offer, it's very much appreciated!

al

[Shifty]

Not had any experience with fiesta callipers, however can fit them the wrong way round?

The bleed nipple should be at the top, if its not then the system won't bleed properly

[Ethel]

I'm wondering if the master cylinder is faulty. A poor piston seal could leak back in to the reservoir. You could make up some blind pipe unions to screw in to the master cylinder to test it.

[Scruffs]

Thanks for your replies so far guys

Seamus - You're right they can be fitted the wrong way round, but I have mine correctly fitted, I'm so sure they don't have air in after all this bleeding!...

Ethel - Pedal doesn't creep so I'm pretty sure the master is o.k.? This is the same master I used with a standard setup and it was fine then..
was rebuilt 5k miles ago (although it has sat for a while admittedly)

I will try bleeding it with the pedal depressed tomorrow - as far as I can see there is no easy way to bleed the red areas in the attached picture with the pedal up using eezibleed?

Maybe I should try and clear up my questions, I have a habit of brain-dumping onto forums without making myself too clear

• Am I correct in thinking I can isolate line pressure in the front circuit (and hence gas/sponginess in the front circuit) by cracking a rear bleed nipple? (and vice versa) - If this is true, then I can be pretty sure it's not the Wilwood valve.
• How to systematically bleed the system union-by-union (guessworks' method on a few threads) without making a horrible mess at every component when I fit the nipple/plumb the lines back in? Do I need to drain down after every component?
• Can anyone comment on pedal feel with Fiesta calipers? Can they push the pedal to the floor with two feet and a giant i'm-about-to-crash heave?
• Has anyone had problems with Wilwood valves (http://www.wilwood.c...01-PV/index.asp) mounted with the 'out' lower than 'in'?? This how it sits when mounted upright...(I am bleeding the valve in the 100%/no reduction position)
• Has anyone had to remove Fiesta calipers to bleed them?

Thanks again for taking a look at this, I think I will turn to some hard liquor in the meantime...

.al

EDIT: JUST REALISED THIS PIC ISN'T THE STEPPED BORE YELLOW BAND MASTER (IS IT BLACK/GREEN BAND?)...BUT I GUESS THE THEORY IS STILL THE SAME?

Attached Files

•  YelBrakeMaster.JPG   34.18K   15 downloads

Edited by Scruffs, 05 October 2008 - 09:31 AM.

[dklawson]

I have standard Mini brakes so I cannot comment on any of the special parts that you've installed. However, I have resorted once or twice to cracking the flare joints at the proportioning valve to get fluid to/through the proportioning valve. It is messy but it works when you have trouble bleeding the rear brakes.

It sounds like you have replaced the entire brake system. Is this correct? Does it include the rear shoes? This may sound trivial but it is not. The brake shoes for the Mini have the friction material relieved at one end and this must be positioned correctly. Forgive this grainy picture, it's the best I can offer:
http://home.mindspri...nityBrakes2.jpg

In this picture, focus on the leader lines pointing out the relieved friction material and how/where that area is positioned relative to the direction the wheel is rotating. Left and right sides are the mirror image of each other. In both cases, the relieved friction material area is positioned to contact the inside of the drum "first" in the direction the drum is rotating.

If the shoes are positioned incorrectly you can have a soft pedal that no amount of bleeding will correct.

[Scruffs]

Thanks Doug,

I have not rebuilt the rear brakes on this occasion, but I will check anyway...

Looking at that JPG I posted up I'm pretty sure I've isolated the problem in the front circuit as the rear circuit has a very hard pedal. I'll go through it all again today though. I'll try taking a caliper off aswell.

Just one thing that's bugging me this morning...Top port is front circuit, lower port is rear...correct?!

Cheers

Al

[digitalboy0]

i know it sounds silly but ya 2 centre nuts holding ya disks on just make sure they are nice and tight my mini did the same as ures and it turns out that was the problem !!!

[jonjosar]

It seems like your pretty well clued up as to the do,s and dont,s. I,ve seen it a couple of times on minis and other makes where there were all the symptoms of a hydraulic fault. Through trial and error, they turned out to be mechanical. In the case of the mini, it was caused by a set of rear minifin drums that were worn in such a way that when the shoes contacted the actual drum face, they flexed as the drum face was worn at an angle. The other car i remember was a nissan, spent ages changing master cylinders, load porportioning valves etc. It actually was a seized slide on one of the front calipers and the caliper twisted slightly when pressure was applied.
I cant suggest anything other than have a good close look at the drums and calipers to make sure there is no movement in them. A little movement at this end will give a huge reaction at the pedal end.

[YIANO]

i have had a similar experience in the past with poor brakes in my case one of the calliper pad retaining pins was so kinked it prevented the pad from moving and started chucking fluid out the master cylinder vent hole
just worth mentioning

[Ethel]

Opening a bleed nipple will depressurise one of the circuits - the pedal will travel further but should go as solid as the closed circuit once the open piston bottoms out. To bleed along a line you just need to slacken the pipe unions a bit when pushing the pedal and tighten them before you let the pedal up (same as a bleed screw only messier), put some rag round the union and it's not too bad.

Try blocking off the master cylinder outlets with a bit of crimped and folded pipe in a union if you're in any doubt about its condition.

The lower master cylinder outlet is intended for the rear - the upper is a smaller bore and will give higher line pressure but more travel. You could measure the diameter of the Ford caliper pistons, I've worked out the surface area of the Mini ones to compare.

http://www.brakesint.com/ has some useful data.

[Scruffs]

Hi guys,

Thanks again for all your useful replies.

-Rear shoe on each side was incorectly fitted (by me ), fixed them, but no improvement at all.

-Hub nuts not torqued, so torqued them and again no difference....

-Rear circuit is absolutely solid, I'm convinced it's not in there.

Now - the fiesta calipers....there is between between 0.75 and 1mm piston movement from no pedal effort to a 'large' pedal effort, with 0.5mm of that just taking up the pad-disc clearance (ie 0.25 - 0.5mm of 'spongy' braking movement left). The piston's between 45 and 50mm diameter. That's a conservative guess of 0.8ml of fluid the master's got to move to take up this movement in total. Top bore in master is 17.8mm, meaning it's got to move ~3.2mm by my sums. I don't know what the motion ratio between pedal and master is...could this result in problems?

The thing is, I can't easily see where the deflection is happening that means the piston moves this far...I'm sure it's not the disc or the caliper body...Has anyone had a problem with flexible pad material? Thinking about it, the pads are rubbish. They are the original motaquip fiesta items which I fitted purely so I could bleed the system and pootle about until I decided what pads I want (before MOT). God knows what chemicals they've been in contact with, and they certainly aren't flat....Surely they can't flex that much though?? I think I'll have to step pads up the shopping list to remove these frm the equation.

I have one more bleeding run to do (nose to the sky, pedal held down with eezibleed) and then I have to pack up for the week (away with work), so this topic may resurface then!

Meanwhile if anyone has anything else to chip in, go for it please! anything!

Cheers

Al

[Ethel]

Mini caliper pistons are 2" so the Ford's must be similar enough? Blocking off bits of the system would seem the easiest way to track this down.

[Asphalt]

IMO there's nothing left exept the master cylinder.
I had an similar problem. Was fine 'till I changed brakes (from drum to disc) and bleed.
It turned out to be the master cyl.

You propably could have messed the MC up whilst bleeding.
The bore wears in the area the sealing ring moves in normal conditions of use.
Then, when trying to bleed and pushing the pedal to the floor the sealings travell over a (in most cases invisible) step and get damaged.

I'd suggest you grasp the nettle and buy a new master cylinder (just to be on the safe side )

Edited by Asphalt, 05 October 2008 - 03:33 PM.

[Sammy D]

SAME PROBLEM! Same Fiesta set up.

Totally connfused also. I gave up and started to drive it some of the spongeyness has gone but it's still there.

One thing I did notice is that evey time I bled them I would only get half as much fluid out the nipples as what I was pouring in, even when the fluid was constantly draining out the nipples with no air coming out.

There must be more air in there somewhere! I need some more fluid and I'll try again. Or I might just pay a garrage to do it and let them be confused also.

[Scruffs]

Last bleeding attempt gave nothing new...

I think you're right about how the M/C could get damaged asphalt - but I can't really see how my problem could be M/C seals? The pedal is soft - not creeping...It has to be compressing gas or mechanical movement somewhere, not a leaky seal...?

I've isolated the problem on the front circuit - but that's all I've achieved so far...I will replace the pads with a lump of steel when I get back and see if it's still spongey..

Cheers for the info on your setup sammy, anyone else with fezza calipers, do you have this problem or are you good?? I'm still a bit concerned the Ford calipers are flexible items compared with the Mini standard setup (although I can't see where they would be flexing..)

Ta again

Al