Brake bleeding after MC replacement - Conflicting procedures

[HFStuart]

Given the bodges you found elsewhere has the PO tried to refurbish the front calipers and cocked it up?  I think I'd focus on them  - not least as it's the only part you haven't replaced!

One very stupid question  - you do have all four calipers mounted with the bleed screws at the top? People occasionally mix them side to side and you end up with the nipples at the bottom.

[JASPER_40]

Given the bodges you found elsewhere has the PO tried to refurbish the front calipers and cocked it up?  I think I'd focus on them  - not least as it's the only part you haven't replaced!

One very stupid question  - you do have all four calipers mounted with the bleed screws at the top? People occasionally mix them side to side and you end up with the nipples at the bottom.

First things first...... I can confirm that all the calipers are mounted correctly with the bleed screws at the top (refer to included pic).

You are so right about all the other awful, awful bodges and yes, the calipers themselves are the only bits I havent replaced so far. I did note when I got the car that the front calipers were quite clean, indicating that someone had maybe done something with them but the piston dust seals didnt look very new and so I just assumed someone had just cleaned the calipers. Maybe there is something worth investigating there to pull them apart to see if anything is untoward.
The symptoms of long pedal travel and spongy brakes could also be indicative of air stuck in the caliper somehow. However, there are no leaks in either front calipers and all bleed screws seem to bleed normally.....

As per Peters post, the simplest thing to do would be to isolate both front calipers by capping off the 4x flexi lines and seeing what happens. this would determine if the problem was with the MC or at the calipers. My only issue with this capping thing is being able to get all the air out of the line in the absence of being able to bleed the brakes. I think that this may not be such an issue if I let the brake fluid run out under gravity and then apply the cap.

Added a pic of the front caliper for no real reason other than to liven up the thread which is mostly text...we all like a pic eh

[HFStuart]

You can get remote brake bleed nipples for not much but I agree you can just most likley gravity bleed them.

Stupid question No.2  - Are the front hoses connected the right way around? The two piston diameters in the caliper are quite differnent with one designed to work at lower pressure.

[Nigel]

Another diagnostic method which takes me back to the 80's.....

Clamp all the hoses shut using either the correct tool or vice grips
and see if anything changes. If the pedal is still spongy you'll know it's the MC.
 There after, remove clamps in turn until
the problem appears.
 
I acknowledge that you have braided hoses but doing this carefully shouldn't
cause any damage.

Nigel

[JASPER_40]

You can get remote brake bleed nipples for not much but I agree you can just most likley gravity bleed them.

Stupid question No.2  - Are the front hoses connected the right way around? The two piston diameters in the caliper are quite differnent with one designed to work at lower pressure.

Nope...Not a stupid question at all but I checked this was all connected correctly already.

On the bleed screw front, I didnt know there was such a thing as a remote bleeder but google came to the rescue. Wonder if I will find one with M10 X1.25 connection though. I had previously made 4x "Heath Robinson" capping mechanisms to isolate the banjo ends of the pipe connections to the calipers...will take a pic once attached.

Another recollection I had was I remeber finding the odd small "blue crumbs"" in the brake fluid when bleeding at first and I thought that this might be thread locker that a PO had applied to the bleed screw threads to stop them drawing air when bleeding. I found myself that vacuum bleeding did seem to draw air past the threads even with the smallest opening of the screw.....I abandoned this method in favour of the pressure bleeder, or the reverse bleeder or the tried and tested 2 man approach.

I paid such a stupidly high price for this car thinking I would be getting a well maintained example in good order......closer inspection, which isnt really permissible when buying, has uncovered loads of astonishing hidden  horrors......buyer beware. However, I am 95% there in recovering this thing but for this one last brake issue that is preventing me getting a road worthiness certificate (or MOT for you guys on the UK)

Doh....soooo close, surely !...Keep the ideas coming please

[JASPER_40]

Another diagnostic method which takes me back to the 80's.....

Clamp all the hoses shut using either the correct tool or vice grips
and see if anything changes. If the pedal is still spongy you'll know it's the MC.
 There after, remove clamps in turn until
the problem appears.
 
I acknowledge that you have braided hoses but doing this carefully shouldn't
cause any damage.

Nigel

Hi Nigel,  The braided lines cannot be crimped without damaging them as far as I am aware. I could I suppose re-install the original rubber hoses which I now know to be OK as the new braided ones didnt solve my problem or make any difference .

Isolating the front caliper is probably the only cost effective way to check the integrity of the MC installation. I will also cap off the single rear pipe where it attaches to the brake force distributor

Cheers,

[JASPER_40]

I'm sure this isn't your problem but I seem to recall my retaining clips for the wedges were at the back of the caliper not the front. ie you pull on them to slide them out, so your clips at the front aren't holding them....

Of course it could be just another curiosity of my car..

I think you are quite right that logially the clip should be on the back of the caliper as the braking action would naturally draw the caliper block inward. I will change this round as you say when I next take the calipers off.

I will say though that the calipers slide as smooth as a buttered dolphin as all the surfaces have been cleaned and polished and then well lubricated with copper slip.

Cheers

[Neil-yaj396]

I'm sure this isn't your problem but I seem to recall my retaining clips for the wedges were at the back of the caliper not the front. ie you pull on them to slide them out, so your clips at the front aren't holding them....

Of course it could be just another curiosity of my car..

I think you are quite right that logially the clip should be on the back of the caliper as the braking action would naturally draw the caliper block inward. I will change this round as you say when I next take the calipers off.

I will say though that the calipers slide as smooth as a buttered dolphin as all the surfaces have been cleaned and polished and then well lubricated with copper slip.

Cheers

From your picture the wedges and clips look correct to me. Much easier to pull out the pin at the front, not the back. The 'spring' keeps the wedge in place more than the clip. Either way this wouldn't impact air in the system....

[peteracs]

Hi

I agree with Nigel, all the caliper wedges I have removed have the spring on the outside, then if the wedges are stiff on removing you can easily knock them out.

Personally not a great fan of distorting flexible brake lines using pinch clamps, I would always worry if any damage has been made to them, not something I want to worry about….. Coolant hoses I would worry about less!

Peter

[Nigel]

Clamping hoses to service the calipers was an accepted method
back in the day and very little squeeze is required to close the relatively small
inside diameter.
Jasper has a 'long'
problem needing, perhaps, old-school methods.

As he said, fitting the old flex lines and doing this check may well isolate
the issue he's having.

Good luck Jasper!

Nigel

[Ferrit]

Morning from the UK, I guess this answers my question 'did you ever fix the spongy brakes?'  I was reading your three page saga last night and noticed your new thread on a similar subject.

I had good brakes on my SA import, nice and hard.  I had to replace the hoses (all six were shot), and did rear wheel bearings, front discs and pads, a new rear compensator, and one very short run of tubing down to the ns front caliper/front circuit. 

First go bleed using a new pressurised kit MC to calipers.  Did front circuit closest first.  Lots of s##t came out and I ran through a litre of dot4.  All good.  Bottom line the brakes work, pull up straight but are really spongy and lots of travel, almost to the floor.

I am going to get another litre today and try again tomorrow evening.  I might go back to my old way of furthest first.  I have read everything here and checked.  I will report back

[JASPER_40]

Hi Mark,

I am embarrassed to say that my saga with spongy brakes and excessive travel is still ongoing. I have found many problems with the braking system during the course of trying to solve my problem and have replaced just about everything. (brake pedal spongy and goes half way down before I get resistance)

Despite all the things I have found, I am now convinced it is simply air stuck in the system around the main 3 way union at the Master cylinder that serves the Mixed circuit. I need to bleed these connections at the MC itself. Just not got round to doing it yet as there are several other jobs on the car that have been distracting me. I am working on the principle that it may have just fixed itself by the time I get back to it !!

As concerning the correct bleeding sequence, everyone seems to have a different answer. Even ChatGPT isn't definitive.

As best I know to-date, Bleed the Front circuit first and then bleed the mixed circuit in the traditional way (furthest from the MC to the nearest)

I just cant find out if there is a specific bleeding procedure following the replacement of the MC other than bench bleed the MC first.

All my problems with brakes seem to stem from the replacement of the MC and the purging of air as a consequence (I am now on my second brand new MC)

Let me know how you go.

Also, I have been using DOT3 as this is what it says on the reservoir cap. I think the only difference between DOT 3 & 4 is the boiling point ?

Cheers,

Steve



 

[kbetas]

Hi Steve, reading with interest your brake woes..... I bought an HPE a couple of years ago and had similar issues with a very spongy brake pedal which didnt inspire confidence. I replaced some of the hoses and brake fluid etc. which didnt make any difference. So we changed the front brake pads to green stuff racing pads and they totally transformed braking performance. Now when i press the pedal its solid and car stops like a modern one. I've also got a 1975 coupe which had them fitted when i bought it so i thought the good brakes were normal!. They've lasted well too. I've done approx 9000 miles in the Hpe and pads are still good.

[Ferrit]

Greenstuff pads on the front fitted this week with new discs

No bled it all again tonight after rebuilding my os rear caliper that I found leaking and one other weeping connection to a hose.  I checked all the other connections, bleed it with another litre of fluid and on stands it does feel pretty good.  I will report back tomorrow pm.

this is the kit I used to bleed, someone here or possibly the VW T4 or T6 forum recommended it.  It seems to work really well.

[Ferrit]

Much better, but having tried a Beta peddle today at Brooklands I think I can do better.  I will try again in a week or two.  Maybe I will try bleeding up?

[Ferrit]

After the car has sat for a week, it actually feels pretty good.

[Ferrit]

bleeding again when the rain stops.  I found the other rear caliper seized, well pretty much, piston would come out but I couldnt get it back in.  So all rebuilt now.

Hopefully last bleed

[JASPER_40]

Right then Betaboyz....following a 2 month break from my brake saga .... I am ready to get back to it and some judicial use of IA has turned up the following information about how Beta brakes feel and operate.

Can anyone confirm or deny the following ?

Cheers,

Steve

[Neil-yaj396]

I disagree. When the brakes are on form on the Beta the pedal is hard and they perform noticeably better than the brakes on my 2004 MGTF, which has a similar set up - discs all round and caliper operated rear handbrake.

[Ferrit]

Like a lot of cars i have found.  Engine off nice and firm, start the engine and the pedal will drop and the brake pedal now feels less firm.  This is defo normal operating stds on my VW t5.1, but is this correct for a Beta.  Servo hose could be suspect?

Every Beta owner I meet I ask to try their peddle but not had my car alongside to do a Pepsi Challenge

When my car is up and running I will really give is a go and report back