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MGF Rear Calipers
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Author:  RaymondH [ Sun Apr 07, 2013 8:23 pm ]
Post subject:  Re: MGF Rear Calipers
I tried loosening the caliper bolts today and it made no difference :( The pedal still goes to the floor with the first push and then goes down about a quarter of the way - it doesn't pump up any further at all. I carefully checked the pads against the discs and three of them are sitting fine, I can't get a feeler gauge between them and the disc but the wheel still turns freely. The fourth pad which is an outside one on the opposite side from the piston is slightly off - it sits against the outer edge of the disc but there is a 0.4mm gap at the inner edge of the pad so a litle bedding in is needed there.

I have also tried this with the calipers removed and with a piece of wood fiting neatly in the caliper but it's just the same. Boogah.
Author:  littlearmy1987 [ Wed Apr 10, 2013 1:59 pm ]
Post subject:  Re: MGF Rear Calipers
right if you have try everything else try bedding pads in down road otherwise i dont think your matercylinder is right.
where are you from raymond? laters alex.
Author:  RaymondH [ Wed Apr 10, 2013 10:10 pm ]
Post subject:  Re: MGF Rear Calipers
Hi Alex. I took it that the master cylinder is ok because I got a perfect pedal when I disconnected the rear brake pipe before the bias valve so still pressurising the master cyl without the valve or the rear calipers affecting the issue, my conclusion then being that the calipers were the problem or am I missing something here? Also, the pedal was fine with the drum brakes fitted.

I do agree that it would be helpful to get the pads bedded in and it would be even more helpful to get the engine running! Apart from refitting the starter motor and dizzy I still have the timing cover to change which should be good fun :roll:

My next tack is to disconnect the rear hoses at the calipers one at a time and fit a connector with a bleed nipple to the banjo bolts. That way I can see if it is only one caliper that is at fault. After that I've run out of ideas!!

I'm from Dumfries in SW Scotland.
Author:  West [ Thu Apr 11, 2013 10:38 am ]
Post subject:  Re: MGF Rear Calipers
could you be running out of mastercylinder volume on the rear circuit?

Neil
Author:  RaymondH [ Thu Apr 11, 2013 8:46 pm ]
Post subject:  Re: MGF Rear Calipers
I wondered about that but the master cyl outlet that I used for the rear is the one that originally provided backup for the 4 pots on the front so I think it should be ok. Similarly, what is now the front circuit was originally for all 4 wheels.

I spent some more time on it today and first of all shimmed the calipers to get them central on the discs so the greatest discrepancy is less than 1mm and that will do for me. As expected, this made no difference to the pedal problem but at least it's not now in the back of my mind.... Then I took the rear LH caliper off and blanked off the flexi hose by screwing the banjo bolt into a connector with a bleed nipple on the other end. After bleeding the pedal was much better and, although not at the top, had that pads-needing-bedded-in feel to it. I then removed the other caliper in the same way and the pedal remained exactly the same so I'm now wondering if my LH one is wonky. That is also the caliper whose piston won't screw fully back as in this photo where they are left and right as on the car

Image

Maybe somebody has been playing with the handbrake mechanism before I bought it (used from ebay) which you're not supposed to do and I'm getting air trapped behind the piston. Tomorrow I'll refit the LH first and if the pedal goes down then the problem is on that corner. That will mean a new caliper, if possible, which will be expensive but I had my fill of reconditioned ones when I was doing the front 4 pots... Fingers crossed :roll:
Author:  RaymondH [ Sun Apr 14, 2013 9:25 pm ]
Post subject:  Re: MGF Rear Calipers
Sorted :mrgreen: And a bit embarrassing too :oops: :oops: In short - LH caliper back on. pedal expected to go to floor and didn't. RH caliper back on, pedal expected to be OK and went to floor :? Much cursing later (which didn't help at all) and on the point of ordering a pair of new calipers I had the Eezibleed on with a bleed nipple open, picked up a caliper, moved it around and a whole lot of air bubbles came out :roll: Basically, I had been bleeding the calipers with the nipple pointing upwards in the way that I thought it would be if the caliper was the right way up on the car but I must have got it wrong and air was still trapped in it. The change in angle was very small but enough. Now that both sides are done the pedal still has a bit of travel which I think will go away when the pads are bedded in (you can see the caliper moving as the pads flatten against the disc).

Three weeks and nearly three litres of brake fluid later I can put this down to experience and hope that anybody else who comes across this problem reads this first! Thanks to everybody who posted and tried to help - it's much appreciated.

I hope the servo works now...
Author:  West [ Mon Apr 15, 2013 8:36 am ]
Post subject:  Re: MGF Rear Calipers
Good to hear its sorted!

Neil
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