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Wish I had left it alone 😒


cliff.b
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Decided that, as recently suggested, one of the squeaky noises was coming from a disk and on inspection found one piston on near side stuck. So pads out, expanders in and press the pedal. Still didn't move. So pressed very hard and success. Wound the pistons back in but didn't open the bleed nipple as I normally would while doing so.

Repeated several times until happy it was now free, reassembled and out for a test.

Then 😱, pedal incredibly hard and if applying superhuman force, a little braking.

Brought it home, pressing brake pedal with bleed nipple open was firmer than I would expect but still went to floor. Tested again and now pedal still very hard but on pressing moderately it feels like there is a momentary delay and then the brakes are on too hard, locking the front wheels if I'm not careful. I got the hang of them eventually and they seem to have improved but what have I done?

Has forcing the fluid back into the master cylinder when I wound the pistons on damaged it?

As I said, I wish I hadn't bothered looking at it 🥺

 

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sounds like the wavy washer and or the end little seal is not allowing recouperation freely back to the reservoir 

so its looking like a master cyl strip down   do make sure the pedal is fully returning to the stop/switch stop and the pedal pivot is not seized 

as thats a good way to get a pressure build up  with foot off there must be some free play/rattling good fit   on the push rod

if its not free the pedal its holding down 

Pete

 

 

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16 minutes ago, Pete Lewis said:

sounds like the wavy washer and or the end little seal is not allowing recouperation freely back to the reservoir 

so its looking like a master cyl strip down   do make sure the pedal is fully returning to the stop/switch stop and the pedal pivot is not seized 

as thats a good way to get a pressure build up  with foot off there must be some free play/rattling good fit   on the push rod

if its not free the pedal its holding down 

Pete

 

 

Ok, that makes sense. Many thanks 

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1 hour ago, Pete Lewis said:

sounds like the wavy washer and or the end little seal is not allowing recouperation freely back to the reservoir 

so its looking like a master cyl strip down   do make sure the pedal is fully returning to the stop/switch stop and the pedal pivot is not seized 

as thats a good way to get a pressure build up  with foot off there must be some free play/rattling good fit   on the push rod

if its not free the pedal its holding down 

Pete

 

 

Ok, had another quick look and confirmed the pedal is returning fully, doesn't appear to be binding and there is some slack in the linkage to the cylinder. Doesn't mean though that this was the case before I fiddled with it after the first road test.

Roads a bit too busy now for brake investigations so I will take her out again tomorrow to see if I can get any more clues as to what is going on.

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38 minutes ago, cliff.b said:

Roads a bit too busy now for brake investigations

The best time to do a brake test is when the roads ARE busy. You stamp on the brakes and the cars behind all benefit and get to test theirs as well. You are performing a public service. 🙄

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8 minutes ago, Chris A said:

The best time to do a brake test is when the roads ARE busy. You stamp on the brakes and the cars behind all benefit and get to test theirs as well. You are performing a public service. 🙄

Hmm, I could do with learning some more modern swear words 🤔

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Sounds the same problem I had on my Spit. Brakes locked on. Released pressure on one nipple to release but as soon as I applied brakes they locked on. Had to release the pressure again and drive home on handbrake.  Result was a new master cylinder. 

Danny

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Forced myself to go out for further test drive in the sun this morning and decided firstly that the brakes aren't binding in any way.

The pedal still feels hard compared to what it was like before I messed with it, but with a firm prod, the brakes are actually working well, possibly better than they were before. I suppose that as I had a sticking piston they may well be more effective now.

So having confidence now that the brakes work, the issue is how they feel and after driving around for half an hour, I am getting used to them.

On my first test, I definitely had a problem, but I think I resolved that and I am wondering if now it is the way it should have been all along 🤔

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I would touch the calipers and drums after a drive to see if any are warmer than expected. This is a possibility with new calipers because, as you might have read on here, some repro replacements dont allow the pistons to retract properly so the pads rub and give a firmer pedal....

Certainly finding a sticking piston on new calipers is a bit worrying☹️

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23 minutes ago, Pete Lewis said:

so youre just winding us up then    Ha !!

so is the question why was it lighter before whatever or  Not  

dont get your shreaded wheat from a discount store   only use the original  

Pete

Yes. Previously I suppose they were possibly a bit spongy but they worked ok and there was a lot of feel and sensitivity.

I think that's what has changed, for whatever reason. Far less pedal movement required. 

I will get used to it and at least the squeak seems to have gone 👍

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Just now, johny said:

I would touch the calipers and drums after a drive to see if any are warmer than expected. This is a possibility with new calipers because, as you might have read on here, some repro replacements dont allow the pistons to retract properly so the pads rub and give a firmer pedal....

Certainly finding a sticking piston on new calipers is a bit worrying☹️

They were new last year when I first got the car. The RHS one stuck after a few weeks and was not firmly pushing one pad against the disk, causing an annoying noise until the brakes were touched.

I did what I have just done to this LHS one, since which it has been fine.

Seeing if the caliper is warm is a good idea. The piston may still be sticking but holding the pad against the disk, I suppose.

I think I might just dismantle it again anyway and make sure everything is still free.

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1 hour ago, johny said:

Something could have changed as on our cars, even with the brake system in perfect condition, the pedal will not be particularly solid...

 

1 hour ago, johny said:

Something could have changed as on our cars, even with the brake system in perfect condition, the pedal will not be particularly solid...

Decided to have another look before taking car out again. Found disk could be turned by hand but rubbing and the pads took quite a pull to remove. 

Decided to redo yesterday's work. Put spreader in place and pushed brake pedal down 2 and a bit times before it was solid again. Checked pistons and both looked evenly extended. Wound pistons back in, but this time opening bleed nipple, replaced pads and pressed pedal again to seat. Both pistons against pads and disk spins freely when turned.

Out for a test and pedal no longer hard. Braking not perfect but seems to be improving. Maybe I inadvertently  swapped the pads & they need to bed in again.

Test cut short as my low brake fluid light came on and I thought I had a leak. Drove home gingerly and found lever only slightly low and that was due to me forgetting to top it up again after bleeding some off 🙄

I will test further but discovered another problem now which I will post in the appropriate section.

Many thanks all for help 👍

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  • 1 month later...

Just to follow up on this issue, I have recently started experiencing one of the original problems again where initially it feels like the brakes are barely working but on pressing harder they grab too hard, sometimes to the point of locking the driver's side front wheel.

Today I decided to look at the n/s caliper, removed one pad and pushed the pedal to move that piston. But it took a great deal of effort to move it and then to push it back in again. After trying several times it gradually freed up so I put the pad back in and repeated for the other piston, which moved easily right away.

Reassembled and road tested, found the brakes are now fine, so appears to be further sticking piston issues in the OEM calipers I fitted last year.

 

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