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 unvovered 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