The Capri failed the MOT today

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sheff
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The Capri failed the MOT today

Postby sheff » Sat Sep 22, 2018 10:32 am

Not a big surprise to me, but the Capri failed its MOT today.

I've had an issue with the brakes this year where the the brake pedal starts going spongey after a few weeks of the car standing around idle. Thought I'd sorted the problem recently when I changed both rear wheel cylinders that looked like they were past their best and after bleeding the system the brakes worked really well. Got in the car this morning and noticed the pedal had gone soft again :banghead:
Another thing I had my concerns about was the rear brake bias valve. Whilst changing the rear cylinders I decided to remove the bias valve and bypass it with a short pipe connecting the inlet to the outlet pipes. The brakes worked really well after doing this, so I thought I'd sorted the issue.

Whilst the car was up in the air today I had a good look around at the brake pipes thinking I might have a leaking pipe, but all looked okay. The mechanic thought it could be a problem with the master cylinder, but I changed that just over a year ago. Guess I'll have to change it again, as I can't think what else it could be.

One other thing I've noticed..... When bleeding the rear brakes, which is where the issue is. I start with the usual large bubbles coming through, when these disappear the pedal feels good. If I keep bleeding them I get really fine bubbles coming through, which won't go no matter how long I keep bleeding them. Is this a symptom of an air drawing in through the master cylinder? Its a new one on me. Anyone had anything like this before?

All the best
Neil

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Re: The Capri failed the MOT today

Postby Andrew 2.8i » Sat Sep 22, 2018 1:01 pm

sheff wrote:Not a big surprise to me, but the Capri failed its MOT today.

Sorry to hear that Neil.
I haven't had this issue before, but if air is getting into the system and you don't have any leaks, I would have thought that it must be the master cylinder that is to blame.
Was the replacement master cylinder a secondhand one?
In case you didn't know, Martin can now supply MCs that are reconditioned to a very high standard.

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Re: The Capri failed the MOT today

Postby Paul G » Sat Sep 22, 2018 2:13 pm

I'd go along with the diagnosis of the master cylinder too.

When bleeding the brakes if you jack the front of the car a bit higher than the rear this should allow the bias valve to open the flow to the rear a bit more than in the level or nose down position.

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Re: The Capri failed the MOT today

Postby Peter-S » Sat Sep 22, 2018 4:07 pm

If I recall you fitted a new Granny cylinder same as me. Wouldn't expect it to fail that quickly but I'm wondering about the seals between the cylinder and reservoir. Could they be at fault?
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Re: The Capri failed the MOT today

Postby sheff » Sat Sep 22, 2018 8:19 pm

Andrew 2.8i wrote:
sheff wrote:Not a big surprise to me, but the Capri failed its MOT today.

Sorry to hear that Neil.
I haven't had this issue before, but if air is getting into the system and you don't have any leaks, I would have thought that it must be the master cylinder that is to blame.
Was the replacement master cylinder a secondhand one?
In case you didn't know, Martin can now supply MCs that are reconditioned to a very high standard.

Andrew.


Hi Andrew,
The master cylinder was a new one which I replaced when I uprated the front discs and calipers. I also think it could be the master cylinder, but its frustrating me that its not that old and they are not cheap to replace. I'm probably going to take it off the road for the winter now and might try to rebuild it myself as the seal kits are not too expensive so nothing to lose.

All the best
Neil

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Re: The Capri failed the MOT today

Postby sheff » Sat Sep 22, 2018 8:23 pm

Paul G wrote:I'd go along with the diagnosis of the master cylinder too.

When bleeding the brakes if you jack the front of the car a bit higher than the rear this should allow the bias valve to open the flow to the rear a bit more than in the level or nose down position.


Cheers for your thoughts on this Paul, looks like its the master cylinder I'm going to be tackling first.

All the best
Neil

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Re: The Capri failed the MOT today

Postby sheff » Sat Sep 22, 2018 8:41 pm

Peter-S wrote:If I recall you fitted a new Granny cylinder same as me. Wouldn't expect it to fail that quickly but I'm wondering about the seals between the cylinder and reservoir. Could they be at fault?


Yes Peter it was the the Granny one. I'm not sure why its failed after not much more than a year and probably no more than a few hundred miles. Makes me wonder what are we buying nowadays, is it just a cheaply made Chinese copy??
Theres no evidence of brake fluid leakage from those seals, so not sure if that's the problem. I'll strip the master cylinder down in the next few weeks and possibly I'll see what is causing the problem. I'm hoping its just a damaged seal from being poorly assembled.

All the best
Neil

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Re: The Capri failed the MOT today

Postby Fordoholic Nick » Sat Sep 22, 2018 10:04 pm

Sorry to hear this too Neil. Hope you get to the bottom of it mate. Yep its a worry if it is the master cylinder which you have not had on all that long. Good luck with rebuilding it mate. If it is down to the quality of assemble it is a worry as you say, but hope it sorts the problem. All the best now.
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Re: The Capri failed the MOT today

Postby Caprifan Rob » Sun Sep 23, 2018 9:35 am

I had an issue with spongy brakes last year & fitted one of Martins refurbished master cylinders. Haven’t had an issue since, so I would echo the others on this being the issue.
Good luck with the seal kit replacement, has to be worth a try.

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Re: The Capri failed the MOT today

Postby Caprigear » Sun Sep 23, 2018 10:33 am

Caprifan Rob wrote:I had an issue with spongy brakes last year & fitted one of Martins refurbished master cylinders. Haven’t had an issue since, so I would echo the others on this being the issue.
Good luck with the seal kit replacement, has to be worth a try.


I have another batch of the 2.8i master cylinders due back from the refurbishers very soon.
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Re: The Capri failed the MOT today

Postby sheff » Mon Sep 24, 2018 11:34 am

Fordoholic Nick wrote:Sorry to hear this too Neil. Hope you get to the bottom of it mate. Yep its a worry if it is the master cylinder which you have not had on all that long. Good luck with rebuilding it mate. If it is down to the quality of assemble it is a worry as you say, but hope it sorts the problem. All the best now.


Cheers Nick... I'm sure I'll get it fixed eventually. These old cars are certainly challenging!

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Re: The Capri failed the MOT today

Postby sheff » Mon Sep 24, 2018 12:02 pm

Caprifan Rob wrote:I had an issue with spongy brakes last year & fitted one of Martins refurbished master cylinders. Haven’t had an issue since, so I would echo the others on this being the issue.
Good luck with the seal kit replacement, has to be worth a try.


Cheers Rob.... Looks like everyone is thinking the same with the master cylinder. I'm hoping I find a damaged seal in there when I strip it down. At least then I will get a warm feeling that I've resolved the problem.

All the best
Neil

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Re: The Capri failed the MOT today

Postby sheff » Mon Sep 24, 2018 12:05 pm

Caprigear wrote:
Caprifan Rob wrote:I had an issue with spongy brakes last year & fitted one of Martins refurbished master cylinders. Haven’t had an issue since, so I would echo the others on this being the issue.
Good luck with the seal kit replacement, has to be worth a try.


I have another batch of the 2.8i master cylinders due back from the refurbishers very soon.


Thanks Martin, I'll bear you in mind if I don't sort this with replacement seals. Do you have any Granada master cylinders? Or could you get mine refurbished?

All the best
Neil

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Re: The Capri failed the MOT today

Postby ollyw » Wed Sep 26, 2018 5:27 am

I’m going to buck the trend here.

Why the master cylinder over the wheel cylinders?
There’s a lot of poorly made aftermarket examples out there.

If it is the master cylinder based on what you’ve described I’d expect the inside of the servo to be wet with brake fluid.

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Re: The Capri failed the MOT today

Postby Paul G » Wed Sep 26, 2018 8:44 am

I found this interesting you-tube film about how they repair master (and wheel) cylinders for old vehicles where new cylinders are not an option. I would guess this is the process that Martin has done to his recon cylinders.

We'll all have to have this done one day when new cylinders of decent quality are no longer available and repair kits alone no longer work.

https://www.youtube.com/watch?v=X36_uEwgjSI

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Re: The Capri failed the MOT today

Postby sheff » Thu Sep 27, 2018 5:19 am

ollyw wrote:I’m going to buck the trend here.

Why the master cylinder over the wheel cylinders?
There’s a lot of poorly made aftermarket examples out there.

If it is the master cylinder based on what you’ve described I’d expect the inside of the servo to be wet with brake fluid.

Olly W


Hi Olly,
I originally thought it was wheel cylinders which I replaced with a pair of Borg & Beck ones. The old ones were rusty and showing signs that they were starting to leak. It is possible that I bought a bad set but seems strange I have the same problem.
If I bleed the brakes it takes a long time to get air out so I think it is related to an issue nearer the front of the car.

All the best
Neil

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Re: The Capri failed the MOT today

Postby sheff » Thu Sep 27, 2018 5:21 am

Paul G wrote:I found this interesting you-tube film about how they repair master (and wheel) cylinders for old vehicles where new cylinders are not an option. I would guess this is the process that Martin has done to his recon cylinders.

We'll all have to have this done one day when new cylinders of decent quality are no longer available and repair kits alone no longer work.

https://www.youtube.com/watch?v=X36_uEwgjSI


Interesting video Paul.... Looks a good engineering solution.

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Re: The Capri failed the MOT today

Postby sheff » Fri Oct 26, 2018 2:58 pm

I pulled the master cylinder apart at work today and it looks like it has some pitting in the bore when viewed under a powerful microscope.
I've greased the old seals up with some red grease and thinking of refitting it but blanking off the rear port with a bleed nipple to confirm this is the issue. If I can achieve a firm pedal I'll leave it for a few weeks and see if its goes spongy again. If so I'm thinking either a refurb or replacement.

I would'nt recommend buying a new master cylinder off ebay. Judging by mine the quality is not as good as the original fitment. Probably better getting an original refurbished!