Front brakes not releasing

[Forkie]

So i know ive another test drive etc to do but - re the undercut section of the caliper piston - has been touched on before - ive been wanting to check they are in the correct position before going any further. Am i correct with interpreting the manual - as i see it, with caliper on the car, pads removed, the undercut section is at the bottom of the caliper - in other words the larger, protruding section is at the top, viewed through a horizontal plain. The only other reference i can find - i.e. a decent picture - is from a well known supplier of parts - which shows this undercut a complete opposite axis.....i.e in a vertical plain....

[johnnydog]

That certainly has opened the proverbial can of worms!
I have never rebuilt a set of Triumph 2000 calipers ( never had the need to), but I have a couple of sets of replacement pistons, and they have no cut outs / notches, as per the originals.
However a quick Google shows that different manufacturers of calipers (different car makes etc) state the cut out should be placed in different positions, which doesn't help very much.
Here are CW's remanufactured calipers....

Yet here are another suppliers remanufactured Triumph 2000 calipers..

And here is another piece of reasoning about how they should be fitted...

I'd personally go with the official Triumph workshop manual. There's obviously a reason for the notch /cut out but there are various reasons for its purpose and position, none of which are particularly conclusive. Positioning with the cut out towards the hub seems logical, but maybe speaking to the respected brake caliper refurbishers Big Red may shed some light on it, although their pistons for the 2000 seem to be as original (flat).
I've never had any issue with the standard pistons on my cars, so when the time comes, I think I'll stick with the original design!
This doesn't really definitively answer your question, but gives food for thought!

[Forkie]

I somehow knew i was not going to get a ' certain' reply !!!! C.W. pics are a little difficult to see, but appear to be the same orientation as mine, and mine are, after all, a C.W. rebuilt pair. I know since the seals have been changed for clarity/ peace of mind , and i am fairly sure the chap would of sorted one first , leaving the other as a reference for putting back together, then vice versa. Interesting you say you have ' new ' pistons ready , but are flat - C.W. new pistons do have the cut out. And yes it does confuse when another supplier appears to fit them on the other axis
Well i think for now - unless someone comes up with a more difinative answer, as mine seem to be orientated as C.W. picture shows, which is the same as the manual - i will have to assume they are correctly fitted......

[Forkie]

So a further day of thoughts continue...and i must reiterate i have never, ever had so much hassle with ' simply renewing front brake pads' - although, conversely, i have ' never ever replaced calipers at the same time' either - i have sat this eve and read, read again regarding the braking system re Triumph Repair Operation Manual - ( Blue cover version) - to see if i can pick out anything. I did so that - to do with the M.C. , and Servo - concerning ' brake drag' - but that would concern the hydraulic side.
Can you just confirm, that when i undone the bleed nipple, there was no relief from the pad grip - that my issue is NOT hydraulic - so NOT servo or M.C. - therefore it MUST be mechanical - i e. - to do with the calipers. I really need to narrow this down!!!

[Forkie]

Which way to bleed the brakes - the Haynes says ' furthest to nearest' ( to the M.C. - which is the way i was always taught from a young age ).
HOWEVER - the Triumph Workshop manual states the opposite - nearest to furthest.
More confusion. Did trawl back through the forum this evening but nothing conclusive found. Am doing this tommorrow ( Sunday) regardless so will do as the Workshop manual states - nearest to furthest.

[johnnydog]

Hi Nige,
Having bled a good few Triumph brakes over the years following a m/c change or rebuild, I have always done it by the 2 person method, and f/o/s first, then f/n/s, r/o/s and finally r/n/s, never with any problem relative to the order of bleeding.
With a single system, I don't think it matters particularly whether it is done furthest away first or nearest.
I try to put some form of pad or a small block of wood at the base of the pedal to stop it going all the way to the extent of its travel, especially with a rebuilt m/c or one that was on the car previously, just to avoid the seals moving over areas of the bore that they dont usually travel over. It takes a couple of extra pumps, which is minimal in the overall scheme of things, but I think it is better for the seals on a previously used m/c.
(Have you ever found the front brakes binding slightly on any car immediately after an MOT where the tester has applied the brakes very firmly, probably with much more pressure than with normal braking? This is usually because the pistons have been pushed out a fraction more than normal and have then not released fully due to either dirt, crud or rust on the exposed part of the pistons....obviously time to consider a brake overhaul at this point, but the point is the same I think with bleeding the original master cylinder on the Triumph). It also is important apparantly on some modern cars to avoid any chance of the seals lipping over if the brake pedal is fully depressed during the bleeding procedure.
I have always bled the Triumphs brakes as the official workshop manual states, so I would try that first - if successful great, if not you could always try the furthest first, but I doubt you'll have a problem anyway.

[Forkie]

I'm back !!!!! So the brake bleed did not happen last Sunday as i had a sudden plumbing issue that took priority - that was great fun but will not bore you with that episode
So - today nothing was getting in the way of the old girl so out we went. No test drive or start up today - just was adamant to get them bled so it is ready to take out when an opportune chance arises.
Firstly - and for me with this ongoing issue - most important - is this normal.....so took the advice with the block of wood under pedal. Also decided to take second piece of advice and bleed nearest to furthest, as was suggested above. So starting at O.S.F - wheel was free once jacked up. Once bled, wheel / disc now back tight again. Exactly the same occured on N.S.F. - wheel initially free. Once bled, now tight again. Now i find that extremely odd . We did the two person way - one in car, one on the wheel - one way tube submersed in jar of fluid - undo nipple - foot down - tighten nipple - foot up - and repeat until just fluid for at least 3 times.So with the system in effect open - the bleed nipple - how was it possible for the pads to move, on both front wheels , when there should be no pressure at the calipers, for them to start grabbing the disc again.....? I can only assume that is what occured, to give the scenario of ' wheel free before bleeding, wheel dragging after bleeding. And M.C. topped up after every wheel bleed.
Secondly - i got lucky ( i.m.o. ) in the last 10 days - managed to source a set of N.O.S. Unipart front disc pads, and also a contact that breaks these cars and have ordered front calipers, PAS rack, servo and master cylinder. I know it might sound a little desperate but im up for anything right now - worse case scenario at least i could send away those parts for refurb, retaining my own parts. At least it gives me a few more options is how i see it.

[johnnydog]

I know this is probably very frustrating - I have read all the posts over and over for fear of stating a previously discussed aspect, so if I do repeat anything, I apologise....
You seem happy that the master cylinder is working correctly, as are the calipers. The pads aren't binding on initial fitment....
There are no crushed metal brake pipes...
You say you replaced the hoses with braided versions - if this was my problem I'd be looking at the replacement hoses for the issue as in post #4, or the servo itself as Alec outlined (being sticky).
I am fortunate that I have spares of these 'in stock' so there would be no additional expense if they rectify the problem or not.
The concensus of the braided hoses is that they perform better with a firmer pedal, but are the ones you fitted actually performing correctly? For the cost of two new front hoses and some extra brake fluid, then I would definitely be looking there.
I would also be changing the servo for a known good one.
What else could it be with the symptoms you describe and the parts you've already changed?
I've got a bald patch with all the head scratching....

[Alec]

Hello Forkie,

it is worth checking the push rod setting on the servo, if it is too long it may inhibit the return of the fluid to the reservoir? It should be 0.70" (A shade under 3/4") from the front face of the servo where the master cylinder bolts on.
Possibly slackening the master from the servo would be a simple check?

Alec

[Forkie]

John you are lucky to have just scratched a patch - ive none left at all - anyone would think i am 17 and never done anything to a car in my life. My father in law is 74 and has ALWAYS done all his own maintenance - he loves this car and has always been a great source of help all the way through - i even rang him yesterday afternoon with ' the above' and even he is stumped, completely.
So John - regarding the front hoses - re post #4 - to be fair what you said in that post makes absolute perfect sense - if they were rubber. But they are the Goodrich braided type - on all 4 corners - but i did purchase them as a N.O.S. item a good while ago. They were an un-used item, in a sealed packet. I naturally assumed they would be fine.....what is the actual make up of them ? Do they still have an inner liner, which can still implode? I purchased them after being led to believe they are ' fit and forget'.
Servo - i was on the understanding that the ' general test ' for correct operation was on a non running engine - pump pedal until hard to expel any residue in the system - whilst keeping foot pressure on the brake pedal - start the engine. If the pedal sinks somewhat - which mine does - the servo is functioning.
Alec - someone has recently mentioned ' brake pedal travel' when cold - i assume this is different to what you are suggesting? - i did check that , at the pedal - cold engine / non running - i had a small movement down of slack ( using fingers) maybe 3/4 of an inch, then from that, a further similar distance - but under slight pressure until i felt solid. I assume to check the rod distance by removal of the M/C will require the front pipe off - a total bleed down again.
My own thoughts are this - im not doing anymore until i give it a start and short run, just for my own sanity, just to see where i am , before i start clawing out my chest hair as well.
I just want to reiterate the findings yesterday - front brake pipes, servos, Master Cylinders all aside - when i jacked up each front wheel, seperately, each said front wheel/ disc was free. All we did was set ourselves up for a bleed. After bleeding ,the pads were dragging the discs again - both sides. With the bleed nipple open , on each side but seperately, i assume there was no fluid able to get to the calipers, to operate the pads. But after bleeding, the pads were dragging on the discs again. THATS the bit i dont understand.