Arnie
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| posted on 17/7/23 at 02:53 PM |
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Brake Master Cylinder problem
Hi All,
Been sometime since I have posted on the site so hope all are well.
Looking for your help please.
I was having problems with the brake master cylinder (Sierra type). Brakes did not feel right but stopped the car okay. Tried to bleed the front
brakes (rear were okay) however not a very convincing flow of fluid from either of the front callipers. I decided to recondition the master cylinder
with new seals.
Seals changed (took pictures to ensure put them on the same way). Reinstated master cylinder. Bled rear brakes okay. However have been unable to bleed
front brakes. Tried 2 man method and vacuum pump to no avail.
What I noticed today was depending on how I pushed the brake pedal I could get it to travel further in however did not improve ability to bleed the
callipers.
Has anyone any suggestions as to what maybe causing this or does it look as if I will need to replace the master cylinder.
If master cylinder to be replaced any suggestions as to an alternative as the Sierra one is getting harder to find.
Any help you could give would be appreciated.
Regards,
Arnie.
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adithorp
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| posted on 18/7/23 at 07:55 AM |
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Somehow doubt its the master cylinder/seals. If it was then vac'bleeding is less likely to be effected (assuming you assembled it correctly).
I'd start at the bleed nipple and work back but you could go the other way.
Have you removed the bleed nipples and checked they're clear (both the nipple and the caliper hole) but you'd be unlucky for it to be both
sides (same for flexi pipes).
Are the flexi pipes ok? Check does fluid flow if you open the connection before the flexi.
Is there damage in the brake pipe to the front? Pipes kinked or crushed. Check if fluid flows with the pipe loose in the master'. If not its in
the master.
If none of those helps then it's in the master' or pedal linkage.
Is the pushrod fouling somehow on full stroke on the sides of the cylinder? Not sure how you push it differently.
Have you got full return on the piston/pushrod. There needs to be free play in the rod when returned or the cylinder doesn't open to the
reservoir.
Does the cylinder have a retaining pin to secure the front piston? (I don't recall on the Sierra) I've seen those in the wrong hole causing
issues in the past.
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roadrunner
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| posted on 18/7/23 at 07:58 AM |
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I would replace the master cylinder as you need to be sure all is well when it comes to stopping.
For a replacement I would try MK Sport cars as I believe they have an uprated one.
You could also try Rally Design, Lots of parts on there.
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adithorp
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| posted on 18/7/23 at 09:23 AM |
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If you go the route of changing the master without eliminating everything else you might still have the issue.
It's probably worth looking into fitting a smaller diameter cylinder one, rather than the Sierra nit that's designed to work with a
servo'. I believe people have used early Fiesta non-servo brake ones (same bolt pattern?) or a Fiat one of some description. That'll create
more fluid pressure so more brake power (but at the expense of longer pedsl travel).
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Arnie
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| posted on 18/7/23 at 06:10 PM |
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Guys thanks very much for the quick replies much appreciated.
Will check out the suggestions and see what happens. Will update the thread when I have it fixed.
Once again thanks.
Regards,
Arnie.
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Dingz
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| posted on 20/7/23 at 02:13 PM |
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As a silly thought are the bleed nipples at the top of the callipers? Could they be the wrong war around.
Phoned the local ramblers club today, but the bloke who answered just
went on and on.
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ReMan
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| posted on 20/7/23 at 09:26 PM |
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Having been in exactly the same position with sierra m/c recently I'd lost braking and small seepage of fluid back to pushrod shaft.
My m/c is typically a rare one, there were many different designs on the sierra but I'm not currently in the mood/health to go to the trouble of
changing it for a different fit, which would involve changing much pipework etc
I bought a set of seals from Big Red (about the only place you can get them)
Rebuilt it with new seals and easybleeded it all round, the rear callipers are the ones that need to be rotated to get the bleed nipples to the top
Test drive and found it was worse!
Stripped m/c down again and on close® inspection found the bore to be damaged
Started looking on ebay and found 1 second hand that I took a punt on, it cape with the M/C cap so it was worth it for that as mine was broken.
Stripped down, was very corroded but bore looked ok
Repeated all steps from first rebuild and braking better , but pedal would sink to floor on prolonged pressure, though barely noticeable on a run.
Still nothing on ebay, so was getting a bit desperate, but by a stroke of luck at a local show/jumble, I found a brand new one in its box with the
purchase receipt, ll the factory bungs still on, so I ripped it out of his hands for £20!
I've not had time to inspect and fit it yet, but fingers crossed.
So back top your issue and with my fresh experience, I think that it could be blocked flexi apes, or crud from them that has got to the inlet of the
callipers.
So I'd suggest cracking the joint from the fixed pipe to the flexi pipe and see if you can push fluid out of there?
If you can there re-tighten and the undo the flexi to calliper joint and try again, then your down to the callipers themselves.
Just before posting I re-read your post and the replies, and valid points, I noted the comment on the retaining pin in the master cylinder, yes there
is one and it would be possible to fit it at the wrong point. If recall I pushed in the first piston as far as it would go with a screwdriver and
then located the pin, then fitted the second piston assy, so it may be with a re-check.
Hope this helps some?
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adithorp
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| posted on 21/7/23 at 09:56 AM |
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There is a company that will bore out and sleeve rare but worn master cylinders.
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Arnie
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| posted on 22/7/23 at 03:57 PM |
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Thanks guys for input much appreciated.
Have carried out some further investigations. As it is only the front brakes (bleed nipples at the top) that I am having problems with have checked
that the bleed nipples are clear and that the flexies are clear. Decided to take the master cylinder apart again just in case I had put the seals on
the wrong way. However they are fitted as shown in pictures I had taken before removing the seals. Checked that the holes on the master cylinder are
clear. Bore looks okay. Have now rebuilt the master cylinder and will try re bleeding to see if that has change anything. If not looks like I will
need to buy a replacement cylinder. I had thought of replacing the cylinder with the MK upgrade but this would have involved significant work. So
decided not to go down that road. As ReMan mentions bought the recondition kit from Big Red.
ReMan would be good if you let me know if your replacement master cylinder cured the problem.
As an aside re pin in master cylinder. Workshop manual mentions this pin and to remove before trying to remove the 2nd piston. I could not see any pin
anywhere and was able to remove the piston by taping the cylinder as per other youTube videos. Not sure why this is the case.
Will update with any progress.
Once again thanks for the help much appreciated.
Regards,
Arnie.
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Arnie
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| posted on 29/7/23 at 02:57 PM |
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Hi,
Just an update on this issue.
After trying the suggestions above tracked problem to the brake master cylinder. It would only operate on the rear brakes and when trying to bleed the
front brakes there was no fluid coming out at the brake calipers.
Ordered replacement (https://www.ebay.co.uk/itm/175714107530). Fitted it today and everything functions as it should.
Good service from Purevue on eBay (link to their eBay shop - https://www.ebay.co.uk/str/purevue. )
Once again thanks for all your help much appreciated.
Regards,
Arnie
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