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MG MGF Technical - Fitting AP 4 pot callipers

Can you point me in the direct of any fitting instructions for the AP 4 pot callipers? Specifically tips for bleeding/filling from new.
Steve Ratledge

Steve
Have you got braided hoses?
Andy
AndyG

Yep, Already on the car fitted to the original callipers.
Steve Ratledge

Steve
Done this a few weeks ago- really easy.
I'll assume you've got the discs on and calipers and pads fitted,and hoses connected. Starting with the o/s,bleed the outer nipple first, then the inner one. Same on the n/s- outer first then inner.You hardly lose any fluid when you swap the hoses over,just as well as you can't clamp braided hoses.I bought a set of 'one man' brake bleeding tubes from Halfrauds for about 5, these work brilliantly,5 pumps on each nipple - job done!!!
Hope this makes sense
Andy
AndyG

Thanks Andy, Yours sounds like the most straight forward "normal" approach.

I am sure of have heard of pre-filling callipers. Or bleeding them before bolting in to place (either held up or down - can't remember to help the air out).
Steve Ratledge

Hi Steve,

I filled mine with fluid prior to fitting, saves on the number of refills of the reservoir. As Andy says, bleed outer first then inner, driver side is marginally further from master cylinder so that's where to start. Once bolted in position the nipple is uppermost, can't see any benefit in doing them off the car.

I found some cable ties useful for securing the hoses, although it sounds like you might already have that sorted.

Good luck, will you be unleashing them on us at North Weald?
Mike Hankin

Thanks, No I can not make North Weald I will be looking at new houses as a result of being just about to start a new job up north.

But I will give then a work out at Donny and Silverstone in October. :-)
Steve Ratledge

Andy, What quantity of fluid did you use? I am off to Halfrauds in the morning and I don't want to short or throwing best part of a litre away.

Is it realy worth the extra for DOT 5.1 rather than 4?
Steve Ratledge

I used comfortably less than a litre for a complete fluid change, so it's only a few pounds more for 5.1. As to whether you'll see a benefit, it depends how hard you're planning to push it on track ;o)
Mike Hankin

Steve
I bought Halfrauds Dot4 500mls and used about
half.
Have fun
Andy
AndyG

Hmm' I've got the discs and callipers in place. But when I try and bleed them they are leeking from the calliper/brake hose union. I am going to try new washers and see if that helps - but the Rover place is closed.

Does any one know what thread/diameter the union is?
Steve Ratledge

I had the same problem with leaking on my 4 Pots, the fix was simply to tighten the unions a little more. They did need a little more than I was comfortable with though. Did you get the correct bolts with your calipers as they use different fixing bolts to the original calipers?
Dave

By the way my system took a lot of bleeding (used around 500ml of fluid), bleeding all four wheels, but was worth it as they are better than they have ever been.
Dave

Dave, I am convinced that I am going to over tighten in and strip the threads!

I am going to replay the brass washers and try tighten it up again. I reused the existing union and washers from the original Rover fitting.

What do you mean by correct bolts? I have discarded the 2 small bolts that hold the original calliper together (12/13mm head) but I am reusing the 2 Calliper mounting bolts (15mm head)
Steve Ratledge

You will need to replace the cooper sealing washers Steve - IIRC the tightening torque on the union is only 35Nm.
Rob Bell

Wise caution Steve, I sheared one at fairly modest torque and had to cut down one from the old caliper - same thread, just a bit too long for the AP.

Tried a few motor factors for new copper crush washers without success, tried re-using the old ones and got a good seal - seems I was lucky.
Mike Hankin

That's odd - why should these washers be hard to find? Surely they're just standard Lucas Verity Brake consumables?
Rob Bell

For the archive the new copper crush washers are Rover part No. SYF000080 (Was DJP5822) cost 0.92 + VAT each !

They look to had done the job. So my advice when replacing calipers/hoses is to replace the crush washers.
Steve Ratledge

The washers alone did not solve the leak. So I have now ordered 2 new banjo bolts and an other set of washers. The part no. for the banjo bolt is BNP1243 (was SYG100510) they are about 1.90 + vat each.

So my revised advice when replacing calipers/hoses is to replace the banjo bolts and crush washers.
Steve Ratledge

I'm surprised you needed to replace the Banjo bolts Steve - replacing the cooper washers is usually enough. Worth remembering though!
Rob Bell

About a year ago I had SS hoses fitted and the banjo bolts were re-used then. So it might be possible to get say 1 undo & refit before they leak. When I took then off, I visually inspected them and they looked OK - but when pedal pressure is applied you can see fluid oozing out of a couple of microscopic gaps.
Steve Ratledge

This thread was discussed between 24/08/2005 and 03/09/2005

MG MGF Technical index

This thread is from the archive. The Live MG MGF Technical BBS is active now.