Lancia Motor Club

Model Technical and Interest => Fulvia => Topic started by: mister bridger on 01 March, 2012, 05:26:06 PM



Title: brake bleeding from scratch
Post by: mister bridger on 01 March, 2012, 05:26:06 PM
I've just read through the 4 page thread on brake bleeding and I'm none the wiser as to why I'm getting no "brake pedal". System has all new pipes, hoses and master and slave cylinder seals. I'm using the tyre pressure method of pushing fluid through and getting clear, bubble free fluid through every nipple. There was a comment regarding assembling the master cylinder "wet" to avoid air locks but not sure how you would go about this. Sorry if i'm opening an old can of worms!


Title: Re: brake bleeding from scratch
Post by: Richard Fridd on 01 March, 2012, 05:53:06 PM
I took 'wet' to mean filling the master cylinder with fluid 'on the bench' and making sure it works before reuniting it with the rest of the braking system components best regards richard


Title: Re: brake bleeding from scratch
Post by: andyc on 01 March, 2012, 06:24:08 PM
You could always try slackening the brake pipes(only by one or two flats) at the master cylinder and bleed there then try the same at any brake unions/connections working your way to the brake calipers.


Title: Re: brake bleeding from scratch
Post by: lancialulu on 01 March, 2012, 06:29:43 PM
Not wishing to upset but did you assemble the MC with seals correct way round?

I have never had to prime the MC on the bench but have often had no pedal.

Use gravity and wait. when fluid appears at the rear close the bleed nipples open the front. when fluid appears at the front close the bleed nipples. dont let the fluid go down too far in the MC. It takes time - go and put the kettle on! Do you have a pedal?? if so continue with gentle top pressure to the MC bleeding from the furthest back first etc.

Tim


Title: Re: brake bleeding from scratch
Post by: ColinMarr on 01 March, 2012, 07:22:10 PM
If you are getting fluid from the reservoir through to the bleed nipples on the cylinders, then the master cylinder must we Ďwetí and should produce a pedal when the bleed nipples are closed. I suspect something is wrong with the master cylinder.

If you were bleeding in the more conventional way without a positive pressure on the reservoir, then you might suspect air being drawn back via the bleed nipples (as I have experienced!), but this seems not to be the case.

Good luck,

Colin


Title: Re: brake bleeding from scratch
Post by: Scott on 02 March, 2012, 08:32:53 AM
When I overhauled the brake system on my Fulvia I fortunately didn't have any problems like this (mine were more around seized bleed nipples!) and the Eezibleed system I opted for worked well.
From what you've said it certainly is sounding like a master cylinder issue. If you just do a search engine search for 'testing master cylinder' there are some good articles out there so you could at least start with some basic checks. You'll then know what to kick or swear at.


Title: Re: brake bleeding from scratch
Post by: mister bridger on 02 March, 2012, 05:23:16 PM
Spoken to Robert at Omicron who was very helpful. I've had the master cylinder apart about three times today to check everything is right and that the two parts of the front plunger are free (they weren't, but are now!) Everything is totally air free and, I believe, correctly assembled but there is still far too much movement on the pedal. One thing that seems wrong is that when pumping the pedal, fluid can be seen coming back up into the front part of the reservoir, suggesting that the front plunger is not moving forward as it should, but I can't for the life of me think why. Any helpful suggestions other than posting it off to Omicron for an expensive check over?


Title: Re: brake bleeding from scratch
Post by: lancialulu on 02 March, 2012, 06:36:15 PM
Sent you a PM

Tim


Title: Re: brake bleeding from scratch
Post by: mister bridger on 03 March, 2012, 09:59:17 AM
A friend came round this morning and we bled the brakes the old fashioned way - open nipple, push pedal, close, lift pedal, repeat ad infinitum - and got quite a bit more air out. The pedal feel is greatly improved but still not there, and there is still fluid pushing back up into reservoir at the front. Will try bleeding again in a few days perhaps when fluid has settled, but other than that totally run out of ideas!


Title: Re: brake bleeding from scratch
Post by: ColinMarr on 03 March, 2012, 10:40:30 AM
I donít understand how fluid can come back up into the reservoir. The first millimetre of movement of the pistons in the master-cylinder should close off the hole that feeds fluid between the reservoir and the cylinder.

If your problem is just excessive pedal travel, one possibility might be that the push-rod between pedal and servo is too short. I had trouble with this and had to successively adjust it to increase the length of the rod. Beware, if you set it too long, the pistons in their relaxed position will cover the feed hole and as the brakes get warm they will seize on!

What fun!

Colin   


Title: Re: brake bleeding from scratch
Post by: Richard Fridd on 03 March, 2012, 11:09:30 AM
 I was told in the workshop last week :To detect which corner may be harbouring the suspected air some would iscolate each piston assembly by means of clamping the relavent hose and trying the pedal feel once again.I the feel is still not satisfactory with all hoses clamped the problem is upstream of the hoses.also if a bias valve is fitted this needs to be in a position to allow fluid to pass freely.if adjusting that pushrod which Colin mentions it is worth checking the are sufficient threads to secure the dome nut.best regards richard


Title: Re: brake bleeding from scratch
Post by: ColinMarr on 03 March, 2012, 12:18:05 PM
Just to clarify the point that Richard made about the domed nut. I never needed to adjust that nut on the rod between servo and master cylinder. I adjusted the other end where the push-rod to the servo fits over the ball on the side of the pedal. There's quite a lot of adjustment possible there and can be done standing on your head inside the car!


Title: Re: brake bleeding from scratch
Post by: mister bridger on 04 March, 2012, 09:03:30 AM
I donít understand how fluid can come back up into the reservoir. The first millimetre of movement of the pistons in the master-cylinder should close off the hole that feeds fluid between the reservoir and the cylinder.


This is definitely still happening. I'm unable to do a road test as the car is not much more than a bare shell but I suspect the only braking effort must be coming from the rear plunger. Either the front one is not moving forward, or fluid is escaping past the front seal? Can someone confirm I have the front plunger assembled correctly? The order I have is plunger, cup washer, pierced alu disc, small spring, brass disc, circlip, main spring (shorter of the two).


Title: Re: brake bleeding from scratch
Post by: Davidb on 04 March, 2012, 02:53:38 PM
Just a thought: have you got the cup washer seal on the right way round? Wrong way could account for the bubbles and lack of pedal pessure.
The "open" side should face forward.


Title: Re: brake bleeding from scratch
Post by: Davidb on 04 March, 2012, 03:00:07 PM
To clarify having just read my own posting!: by "bubbles" I meant fluid coming back into the master cylinder.


Title: Re: brake bleeding from scratch
Post by: mister bridger on 04 March, 2012, 03:53:15 PM
I wish the answer was that simple! Definitely on the right way round.


Title: Re: brake bleeding from scratch
Post by: Richard Fridd on 04 March, 2012, 04:05:52 PM
How is the bore condition?


Title: Re: brake bleeding from scratch
Post by: mister bridger on 04 March, 2012, 04:12:13 PM
As far as I could tell it was good. No pitting or scratches.


Title: Re: brake bleeding from scratch
Post by: roddy on 04 March, 2012, 05:23:20 PM
Just a couple of small points :-  you are aware that the piston in the m/c bore has a ring of small holes, which has a smooth steel washer held against the holes by the rubber seal.  This is in effect a one-way valve for the flow of brake fluid.  The washer is there?

Also, it is possible to transpose the rear calipers.  You definitely have the bleed nipples to the inside and to the top side of the caliper?  If the bleed nipples are to the bottom, the circuit won't bleed.

Regards - Roddy


Title: Re: brake bleeding from scratch
Post by: mister bridger on 04 March, 2012, 05:32:11 PM
Just a couple of small points :-  you are aware that the piston in the m/c bore has a ring of small holes, which has a smooth steel washer held against the holes by the rubber seal.  This is in effect a one-way valve for the flow of brake fluid.  The washer is there?



Regards - Roddy
I'll take it apart again tomorrow and examine what's there - I don't remember a smooth washer, so we could be on to something. Rear calipers are fitted correctly (I just went out to the garage and checked!)


Title: Re: brake bleeding from scratch
Post by: Richard Fridd on 04 March, 2012, 06:19:39 PM
I take it the  nipples facing south was a joke! Imagine pumping away in that situation


Title: Re: brake bleeding from scratch
Post by: chugga boom on 04 March, 2012, 09:19:18 PM
I donít understand how fluid can come back up into the reservoir. The first millimetre of movement of the pistons in the master-cylinder should close off the hole that feeds fluid between the reservoir and the cylinder.

If your problem is just excessive pedal travel, one possibility might be that the push-rod between pedal and servo is too short. I had trouble with this and had to successively adjust it to increase the length of the rod. Beware, if you set it too long, the pistons in their relaxed position will cover the feed hole and as the brakes get warm they will seize on!

What fun!

Colin  

 I've litterally just had this problem with my fulvia, basically the futher you went the more the brakes siezed on, when i rebuilt the car the mastercylender was shot, i sourced a better one out of the shed and rebuilt it, stupidly not thinking to check the push rod length i just bolted it on and away to go, today we measured the length of the rod and found it was 3mm to long therfore doing exactly as you said, the other noticable difference now is the pedal travel is correct where as before the brakes were right at the top of the pedal with nearly no travel, anyway alls sorted now MOT this week and ready for use, crazy little fault thats easily missed


Title: Re: brake bleeding from scratch
Post by: mister bridger on 05 March, 2012, 04:48:44 PM
OK, these are the parts of the front piston/plunger, in the order in which they were fitted. Can anyone confirm whether they are right or wrong?


Title: Re: brake bleeding from scratch
Post by: Neil on 05 March, 2012, 05:51:11 PM
I tried to attach a page from the spares book, but after reducing the file size it was still to large (3MB PDF), hopefully this small screen shot will help, I can mail a larger full page copy if required.


Title: Re: brake bleeding from scratch
Post by: ColinMarr on 05 March, 2012, 05:58:46 PM
That looks right to me and they line up with the parts shown on the diagram that I have (the same as Neil has just posted). There should also be a coil spring (number 18 on my diagram) that presses this assembly back down the master-cylinder and there should be another similar spring between this plunger assembly and the rear plunger/ piston. Is it possible that one of these is missing?

Colin


Title: Re: brake bleeding from scratch
Post by: mister bridger on 05 March, 2012, 06:04:50 PM
Damn! All is as it should be then, including the bigger springs, so I'm no nearer solving the problem. ???


Title: Re: brake bleeding from scratch
Post by: lancialulu on 05 March, 2012, 06:09:00 PM
And from the concise repair manual....

Seems strange as you look like to have the right sequence. The front plunger operates the larger of the front caliper pistons. Is it possible you have got the plumbing round the wrong way?

Tim


Title: Re: brake bleeding from scratch
Post by: mister bridger on 05 March, 2012, 06:52:41 PM
And from the concise repair manual....

Seems strange as you look like to have the right sequence. The front plunger operates the larger of the front caliper pistons. Is it possible you have got the plumbing round the wrong way?

Tim
That's the pic I've been working from. Don't think the plumbing is wrong but hard to tell exactly as the pipes do cross over and are hard to see. It will be tomorrow's job to check.


Title: Re: brake bleeding from scratch
Post by: lancialulu on 05 March, 2012, 08:04:00 PM
Could the front stop screw be leaking?


Title: Re: brake bleeding from scratch
Post by: mister bridger on 06 March, 2012, 06:41:04 PM
Taken everything apart and all is as it should be, and pipes to brake calipers are correct. All I have succeeded in doing is getting air back into the system and my mate who helped me with the bleeding is on holiday! Will just have to wait I guess and try again.


Title: Re: brake bleeding from scratch
Post by: nistri on 07 March, 2012, 08:01:01 AM
I guess you have an S2 Fulvia (with 21 mm master cylinder and Girling calipers). Double check the brake pipe connections as I recall that there was even a mistake in one of the official Lancia instructions. From memory I  cannot now tell you the correct fitting, though (sorry).

I also assume you have raised the car (at the back) by fitting axle stands under the rear axle: this allows full opening of the brake limiter valve, otherwise it will not be possible to bleed the system fully.

The length of the servo pushrod is critical for correct operation of the brakes. Did you measure up how much it is on your car?

Difficult bleeding can be greatly helped by using the pressurized system (EezyBleed) with the aid of the spare wheel pressure.

I also guess you have used the correct bleeding sequence starting with the front top nipple of the passenger side.

Good luck, Andrea 


Title: Re: brake bleeding from scratch
Post by: ncundy on 07 March, 2012, 08:06:52 AM
Why would putting axles stands under the rear axle help? Surely you have to jack the body up off the axle as it's the relative height difference between the body and the axle that opens the limiting valve  ???


Title: Re: brake bleeding from scratch
Post by: mister bridger on 07 March, 2012, 08:22:28 AM
Have to agree with ncundy there, though as I'm getting fluid to the back brakes it's probably not part of the problem. I've tried bleeding in every sequence I can think of. What is the accepted "correct" sequence? Brakes are plumbed as per the diagram on p29 of the concise repair shop manual.


Title: Re: brake bleeding from scratch
Post by: chugga boom on 07 March, 2012, 08:32:32 AM
just a thought for you, on my augusta there is pitting right at the end of the master cylinder, when bleading the brakes the seals travel futher than normal travelling accross the pitting and allowing air into the system, to get around this i mearly cracked one blead nipple at a time and let gravity take over , didnt pump the brake pedal at all just let the fluid run through, takes longer but ended up with a solid pedal, with the system blead the seals go no where near the pitting in the master cylinder so is perfectly safe, may be worth a try, i always bleed brakes this way now, when i did the fulvia last week i disconected the load valve lever off the rear axle and pushed it all the way up to give maximum fluid flow, then disconected the brake pipe where it goes onto the n/s rear caliper until fluid came through, reconected pipe then blead caliper, did the same on o/s rear then went to n/s front and just used the bleed nipples then finally os front, whole job took about an hr but pedal was solid 1st time, hope this works for you, james


Title: Re: brake bleeding from scratch
Post by: nistri on 07 March, 2012, 10:50:31 AM
Jacking up the rear axle pushes the arm of the brake limiter valve that in turn pushes the valve arm inside its housing and opens full flow of brake fluid to the rear brakes, ciao,  Andrea


Title: Re: brake bleeding from scratch
Post by: nistri on 07 March, 2012, 10:58:21 AM
Front of the car

Master cylinder (LHD)

Steering wheel (left)

Nipple sequence:
2 (top front)         1 (top front)

4(bottom)            3 (bottom)

6 (rear)               5 (rear)

This is the bleeding sequence recommended by Lancia. For RHD cars just swap sides.
Good luck, Andrea


Title: Re: brake bleeding from scratch
Post by: stanley sweet on 07 March, 2012, 04:49:14 PM
That's exactly how I did mine recently - tops, bottoms, rears with axle on jack - worked perfectly first time. However...........that was after a lot of messing about which sounds very similar to the original problem here. Press the brake pedal and the fuid would bubble in the reservoir. Cylinder rebuilt a couple of times to make sure parts were correct but it turned out to be pitting which I hadn't noticed. Had it refurbished at Omicron and that was the problem solved.


Title: Re: brake bleeding from scratch
Post by: ncundy on 08 March, 2012, 09:52:55 AM
Jacking up the rear axle pushes the arm of the brake limiter valve that in turn pushes the valve arm inside its housing and opens full flow of brake fluid to the rear brakes, ciao,  Andrea

You're correct of course, I need to get into the garage more :)