Front brakes not releasing

[Forkie]

Alright lads, no need for the sarcasm here !!!!
As an aside - i never had notification that either of you had replied to my last ' fixed' post - i went on now regarding a notification re the parcel shelf topic - logged on, and these posts just appeared....as if my magic....?
Anyhow. I can only explain it as it is. I personally could not work out why i had the issue. So my guy was happy to investigate, and ok he is not a 'Triumph' guy ( his forte is French stuff ) but an excellent engineer, very methodical in his work, and prides himself in getting the job done, and correctly. I believe he thought pretty basic system, should be fairly easy fault to find. But it wasn't. Going through everything, he also was not really finding fault with anything in particular - aside both ' new' front calipers having excess fitting grease behind all the pistons - he even querried if the 'new' pads were a tad too thick - such was his struggle to find a problem....
But he did finally narrow it down to a M.C. problem, and again, found nothing wrong staring him in the face, which was why he decided to try that washer the other way round. And for whatever reason, the pads now back off as needed. I did ask him that very question, which way round was it / is it - and he replied ' it has been stripped that many times i cannot remember' We also agreed we cannot see why it would matter which way round it should go, as surely the same effect would apply.

[Forkie]

Hi Clifford,
Unfortunately i am unable to view the animation that you have posted, for some reason.
So i take it from your lengthy reply, you believe i may then still have an issue somewhere within the braking system?

[johnnydog]

But it appears to be sorted Nige - that's the main thing!
Perseverance seems to have paid off - well done (to both you and 'your man'!)

[Forkie]

Or is it !!!!! Clifford has made it obvious that it cannot be that washer, as it has never been an issue before in all the production life , or the albut 50 years after. . So that has now thrown doubt in my mind as to whether the issue has been found, or not .

[Clifford Pope]

Sorry about the animation. It worked when I tried it a day after I posted the link, but now for some reason it doesn't.
Anyway, what it showed was the inner side of the groove for each piston at a slant, ie the groove was wider at the opening but was narrower at the bottom. The result was that under pressure the whole seal bowed, but when the pedal was released it tried to return to its rest shape, pulling the piston in a bit.
Imagine pushing a rod through a tight but flexible rubber grommet - when you stop pushing the rod it always tries to pop out a bit - it never stays put because the rubber is distorted. It's a convincing argument in itself, but as the Lotus owner with excessive piston retraction found, is critically dependent on the degree of slipperyness (sp?) of the piston. It seems a tiny and entirely arbitrary variation between shiny, very shiny and highly polished having crucial implications for brake balance.

Also the extent of the retraction would surely depend on the physical properties of the brake fluid? You might expect that a silicone brake fluid would not work in the same way as traditional fluid (think Teflon coated frying pan!)

And of course the contrary evidence in the present example that the shape and orientation of an unrelated and hitherto unknown washer was the real answer all along. Those engineers at Girling must be feeling a bit silly.

[Forkie]

Another person that is feeling silly, apart from the engineers at Girling - is me - ive joined this forum to ask for help to keep one , yes just one of these old girls running. I was 7 years old when these cars went out of production. 7. How, at 7 years old, was i supposed to know everything about this marque? I pays my dues, i ask for help, i do not expect to have the mickey taken. I am trying my best to keep this 49 year old car on the road - and at the same time, trying to keep my 14 year old son interested, to take her on after me. I am struggling to do just that , when we get , shall we say ' less than what was expected' . I think i best leave it there, before im banned, for the first time in my internet life.

[Clifford Pope]

Forkie, there's some misunderstanding here. I'm so sorry if I've offended you - I'm certainly not taking the micky, merely speculating as to how brakes are meant to retract, and why the standard explanations are not completely convincing. But you have it seems made it work by reversing the washer, so that's good, and all you really need to know.
It's like water divining - I don't believe it, but it does appear to work.

[Forkie]

All i was trying to say is what was found, whether wrong, or right. But it appears to have solved the issue. I was merely trying to explain what was found, and how it was found.

[Forkie]

So back here again. So i will carry on my findings from when i replied to Alec earlier regarding releasing bleed nipple had no effect.
N/S/ F - wheel removed, disc was not free to turn easily. Fitting kit removed - outer pad fairly free, barely no dust. Inboard pad solid - no movement at all, fair bit of dust. Lever out. Clean up, deglazed pads. Push pistons back. Pads now fall in, disc now spins freely.
O/S/F - wheel off - this disc seemed freer, although some rub. Fitting kit off - both these pads had a tad of movement, minimal dust. Ditto above refit pads, disc now free.
So i take from this that none of the pistons are fully retracting, with the N/S inboard pad being the worst culprit. So , assuming this brake drag issue was sorted a while ago, it would appear not, and i seem to of been chasing engine power issues that i could not really find
So as is right now all pistons ' home' and discs free. I wil swap that servo valve next before taking up Bills' idea. I assume that the engine needs to be running to test the operation of the servo valve, to create the vacuum, so will more than likely fire her up after swapping that valve, and apply the brake, and see what i get. If that fails, it will be the clean up the pistons approach. I think i have had in my mind it cannot be the calipers/ pistons, as they are all ' new'. All very interesting.....

[johnnydog]

I am replying relative to your last comments that the n/s/f inner pad was tight and took some effort to be removed....
I have read through again (and read again!) all the posts relative to this and the fact that you described in your last post that the inner pad was very tight makes me wonder....you have said in a previous post that there was no corrosion or brake dust build up in the calipers, which themselves have been remanufactured. If I read it right, the pads are now cleaned up and went back in OK.
In the past, when replacing front brake pads (in non Triumph cars) in some instances, the new pads when manufactured had a thick paint coating on the metal back plate and this caused the pads to be tight on assembly. The new pads needed a file running over them to remove the paint coating and also a small amount of the metal to be a good but free fit. This was down to the quality of the replacement pads. I always use old stock Lockheed pads in my Triumphs which fit perfectly with no degree of reprofiling. Could it be that the pads did fit snugly (or possibly too snugly!) when cold but when they warmed up, some expansion caused them to stick (although I appreciate that the reverse should occur as they cooled down).
Could the remanufacturered calipers have a too thick a paint coating where the pads sit? They should be a snug fit, but equally, totally free so that they can be taken in and out by hand.
Just long shot really with a view to your last post, but the ideas and suggestions are quickly running out!!