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Go Back   Madabout Kitcars Forum > Mad Build Area > Marlin Sportster, Cabrio, Berlinetta and Roadster builds

Marlin Sportster, Cabrio, Berlinetta and Roadster builds Enthused or Confused about your vintage Marlin build? Ask away here or show off your build.

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  #501  
Old 10th February 2012, 19:32
denniswpearce denniswpearce is offline
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Default Dual servo

Tried to finish off my servo installation today, but met an unexpected problem. I attached the new feed lines to the remote reservoir then fitted it in place. I have added a couple of pics to this so you can see results. Servo is sandwiched between the battery and pedal box. I then decided to route the feed lines under the new servo then up to the m/c input. A very long route but out of the way I thought. Connected it all up then with my wife sat in the seat to push the pedal we bled the system. Surprisingly after 6/7 pumps per cylinder all the air appeared to be driven out. Then foot on the pedal and it went straight to the floor with not a lot of resistance. Then tried it twice more with small amounts of air being expelled but same result with pedal.
It did not make sense, why do I not have a brake, after all when I tried it with the original lines ( which were too short and via a straight line ) I had a good brake pressure. I then bled them again but this time did approx 20/25 pumps per wheel and got much more air out and at the end there was pressure when I applied the brake.
I took it down our private road and it worked but I would not want to stop in an emergency on the main road. Something still amiss.
Only thing I could think of is that the new lines are much longer ( approx 850mm ) and it dives down under the servo. Have I created an air gap in the lines to the m/c, which are not under pressure, unlike the the copper lines that feed the wheels from the m/c. So is the air staying in the lines and gradually seeping in to the system. I am going to have to bleed them again and I will shorten the lines to a more direct route.
Any suggestions as to what my problem is ?

In the pics you can see my solution to my wing stay issue I had like the rest of you. I intend to add one more U clamp as the plate is big enough. I copied Robins solution with the fibreglass mudguards because of my 18" wheels ie holes through the side.
There is also a pic of my old servo in place.
I will one of these days post a pic of the car when I bought it with all its stickers on ( even under the bonnet as you can see ) and how it looks now.


DSC00350 by denniswpearce, on Flickr


Sportster 019 by denniswpearce, on Flickr


DSC00348 by denniswpearce, on Flickr


DSC00345 by denniswpearce, on Flickr
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  #502  
Old 10th February 2012, 21:27
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Grey V8 Pete Grey V8 Pete is offline
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Hi Dennis.
You need to hold your hydraulic fluid reservoir up above the highest master cylinder inlet boss, so gravity gets all the air bubbles out, before you start bleeding the brakes. This will need a re-route of your pipes to above the M/cyl to allow this.
I made a fancy new bracket to lift my remote reservoir higher only to find it fouled the bonnet, so I had to replace the old lower one. I am hoping that the above technique will work on mine and that no air will "escape" from the brake fluid over time. Peter.
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  #503  
Old 10th February 2012, 21:47
denniswpearce denniswpearce is offline
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Thanks Peter, it makes sense. I have made a natural trap for the air with no escape for it. I will do as you suggest.
Thanks again.
Dennis
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  #504  
Old 11th February 2012, 09:34
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Quote:
Originally Posted by denniswpearce View Post
I took it down our private road and it worked but I would not want to stop in an emergency on the main road. Something still amiss.

Any suggestions as to what my problem is ?


DSC00350 by denniswpearce, on Flickr
Hi Dennis,
I think you must still have air in your brake lines, and I think you may need to rotate your master cylinder by 180 degrees. At the moment, air trapped in the top half of the cylinder has no way of escaping as your exit pipes are at the bottom.

...peter

P.S. The new wing stays look good!
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  #505  
Old 11th February 2012, 14:16
denniswpearce denniswpearce is offline
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Interesting reply Peter. My understanding of m/c, s is, after the post from Grey V8 Pete, that the rubber pipes from the remote servo to the m/c are not under pressure, they are supply pipes, whereas the copper pipes are the pipes that go to the wheels and are under pressure when you apply the brakes, but not the rubber supply pipes. So surely when I bleed the brakes air will be expelled from the copper pipes. Cannot see why it matters if they are on the top or the bottom.
I shortened the rubber supply tubes this morning to a more direct route and before I bled them I held the remote reservoir up in the air well above the m/c. Air did not come out until I tapped the tubes then small air bubbles came out for about five minutes of continuosly tapping the pipes. Eventually the bubbles stopped so I bled the system. Brakes do have a feel to them and the car will stop but I again would not want to take it out on the main road. Pumping the pedal makes the brake marginally better.
Something is still not right.
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  #506  
Old 11th February 2012, 16:24
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Quote:
Originally Posted by denniswpearce View Post
Pumping the pedal makes the brake marginally better.
Something is still not right.
That is the classic symptom of air in the copper brake lines.
Have you bled all four brakes?

What do others think?
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  #507  
Old 11th February 2012, 16:44
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Hi again Dennis. You have most certainly still got air in your system, in particular I suspect you have still air bubbles trapped in your master cylinder itself. I had a similar problem some years ago after I replaced the M/C seals in my 2.0 GL Sierra, which had a similar setup as "our" cars. I eventually cleared the air by using a Gunsons Ezibleed to pressurise the system and then got someone to help me pump the brake pedal for a conventional bleed while the system was pressurised in this way. It also cleared a lot of gunge from the lines so must have been shifting quite a lot of fluid through them. I wouldn't worry about the outlets from the M/C being underneath. The standard Sierra set up had one underneath anyway as the fixed reservoir on the top dictated this. You can also wrap a rag around the M/C outlets and just crack the pipe nuts open to assist priming the M/C. Also only use fresh fluid! Don't be tempted to re-use the old as it will still have microscopic air bubbles in it and being hygroscopic will have picked up lots of water anyway over time. For bleeding a previously empty system I always leave it overnight after the first bleed session and then re-bleed again. This allows any small bubbles to form one big one which is easier to expel. Peter.
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  #508  
Old 11th February 2012, 21:58
denniswpearce denniswpearce is offline
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Answers to both Peters now, I have bled all four wheels several times now at different stages ie when I had new longer rubber supply lines several times plus the new shortened route several times but all with the same result, insufficient pressure. I always do a full bleed, furthest wheel first.

I do know of the pressurised system which uses the pressure from your spare wheel to a bottle full of fluid, then a line from there to your reservoir with a replacement screw cap supplied with the kit. With it all connected you go round each wheel in turn, furthest first and open the bleed nipple with a tube into a jar of fluid and hopefully with the whole system under pressure it should expel the trapped air from each wheel in turn. I believe you don,t need to pump it with this system.
Obviously going to buy one tomorrow morning to try that out.
Never use old fluid only new each time.

Oh, the joys of motoring.

Thanks boys

Last edited by denniswpearce; 11th February 2012 at 22:00.. Reason: Never use..... added
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  #509  
Old 11th February 2012, 22:05
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No in theory you are right and the Ezibleed is designed to be a one man operation but the fluid only trickles out.
However if you do also pump the pedal it really wooshes out so all air is really purged through the lines. Worth topping up the reservoir more frequently as it really shifts some fluid this way.

Just a thought. Is your master cylinder and seals new? If a primary piston seal has gone it is possible that you are pulling air in that way? Peter.
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  #510  
Old 11th February 2012, 22:11
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Another trick is to prise the front brake pads back enough to get a piece of shim in between the pads and the pistons, then bleed as usual. This worked a treat on an old Cortina that I had as it got rid of any air bubbles trapped in the calipers themselves. Worth a try anyway. PS don't forget to remove the shims afterwards! Peter.
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  #511  
Old 12th February 2012, 11:11
denniswpearce denniswpearce is offline
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Thanks for all the advice Peter. which I would use, however, I bought a Gunsons eezibleed this morning and the selection of caps they provide are all the wrong size. So I have a kit I cannot use.

For those of you who have remote servo,s, like the three feed type then the Grunson eezibleed will not fit because your reservoir is a quarter turn twist to lock cap and not a screw cap, so said kit is u/s

Hey ho,
May have to take it to my local garage for assistance.

Last edited by denniswpearce; 12th February 2012 at 14:18..
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  #512  
Old 12th February 2012, 16:13
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I also suspect that the problem is due to the peculiar orientation of the master cylinder causing air traps. Why not swap it for the 22mm Sierra one as Peter (and now me) have purchased. The fluid feed is then on the top and the brake lines on the engine side. Much easier to plumb in without creating air traps. I know it's more money but probably cheaper than a visit to the garage and it looks much more of a "proper job" when the fluid enter and exit ports have the correct orientation.

BTW I used an Easibleed with my remote reservoir when I first bled the brakes (I guess I have a different one) and it worked a treat. One man bleeding and not a lot of fluid wasted.

Cheers, Robin
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  #513  
Old 12th February 2012, 17:10
NigelB NigelB is offline
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Dennis,

At the risk of emberrassing myself (but it was a long time ago now), step back from it for a while and check the obvious..............

Back in the late 8o's, when I built my Marlin Roadster, I refurbed the brake calipers with new seals etc and fitted them to the hubs with the pistons pushed right back in the pots. I bled the brakes, passed MOT and everything was 'hunky dory'.

A couple of years later I needed to change the m/c (can't remember why) and having done so I tried to bleed the brakes once more. 3 months later, with three months of spongy brakes, 3 months of head scratching and a wife with a right leg muscle that Usain Bolt would be proud of I was under the car again and when suddenly I had my Eureka moment.

The beed nipple was on the bottom of the caliper and the fluid supply at the top. So all the air at the top was just stayng and there was nothing but fluid coming out the bottom.

What had happened was that I had fitted the calipers on the wrong sides when I built the car, and I guess that because the pistons were right back in their pots when I first charged the system any air that was in there was forced out before the fluid reached the calipers. Not sure.

But I swapped the calipers over, replaced the pads and all was fine.

Now you cant fit the BMW calipers the wrong way round, but that experience was certainly a good lesson in 'check the bl**ding obvious' first.
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  #514  
Old 12th February 2012, 18:13
AlanHogg AlanHogg is offline
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Hi Dennis
i believe your problem is likely to be the orientation of the master cylinder and the route your supply pipes are taking.I would suggest that you rotate the M/c so that the supply inlet is vertical and that the supply pipes take a more direct route rather than dropping under the servo and then rising again.Its a bit like trying to bleed a caliper with the nipple at the bottom, almost impossible to achieve.
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  #515  
Old 12th February 2012, 20:39
denniswpearce denniswpearce is offline
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Guys thank you so much for all these helpful words.

Robin that is an option I am thinking about.

Nigel bleed nipples are at the top so possibly not the solution.

Alan I have added a pic showing modified supply pipes which are now a much shorter route and not under the new servo. But as explained in a previous post, the reservoir was held vertically well above the m/c after shortening and the pipes were tapped until all no air bubbles came out of the supply pipes. Then a big bleed, 20/25 pumps per wheel, till only fluid came out for another 5/6 pumps.
Unfortunately air is still in the system.

Thanks guys


DSC00363 by denniswpearce, on Flickr
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  #516  
Old 13th February 2012, 08:21
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Quote:
Originally Posted by Mike View Post
Andrew has fitted the Ford 22mm master cylinder, with standard BMW brake components, and piped it up as per his original set up, with only two outlets being used: one to the rear, and on to the front.

Mike
Can I assume then that Andrew blanked off one of the two outlets from the front of the Ford M/C? As I understand it they are siamesed both coming from the front section of the M/C. I was thinking about doing the same as it means I wont have to re-run the brake lines to the front callipers as I have only a single connection with a T-piece at the front.

BTW I have replaced the small threaded adjuster on the M/C side of the servo with a 35mm long cap headed set screw. Fits in the operating rod of the M/C fine and the cap head means you can use an allen key to adjust and tighten it. I re-used the little locking ring from the original adjuster.

I have "reserved" this coming weekend to do the changeover....


Robin
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  #517  
Old 13th February 2012, 10:30
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Quote:
Originally Posted by MartinClan View Post
Can I assume then that Andrew blanked off one of the two outlets from the front of the Ford M/C? As I understand it they are siamesed both coming from the front section of the M/C. I was thinking about doing the same as it means I wont have to re-run the brake lines to the front callipers as I have only a single connection with a T-piece at the front.

BTW I have replaced the small threaded adjuster on the M/C side of the servo with a 35mm long cap headed set screw. Fits in the operating rod of the M/C fine and the cap head means you can use an allen key to adjust and tighten it. I re-used the little locking ring from the original adjuster.

I have "reserved" this coming weekend to do the changeover....


Robin
Hi Robin

Yes, Andrew capped off one of the outlets, repeating the arrangement on the BMW master cylinder. On the Ford MC I am not sure it makes any difference which one is capped is the bore consistent at 22mm?

Do you not think it would be safer to have individual pipe runs to the two front wheels? With only one feed pipe, if you lose one, you lose both - and to quote Martin Brundle " Head off straight to the scene of the accident!!"

Your cap head screw is a very good idea: perfect for its application, and readily available.

Do you have your own private road, or disused airfield to conduct some empirical tests???????

Mike
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  #518  
Old 13th February 2012, 11:20
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Quote:
Originally Posted by denniswpearce View Post
Thanks for all the advice Peter. which I would use, however, I bought a Gunsons eezibleed this morning and the selection of caps they provide are all the wrong size. So I have a kit I cannot use.

For those of you who have remote servo,s, like the three feed type then the Grunson eezibleed will not fit because your reservoir is a quarter turn twist to lock cap and not a screw cap, so said kit is u/s

Hey ho,
May have to take it to my local garage for assistance.
Dennis - do you have an air compressor? If so, I could lend you my pneumatic brake bleeder - it connects to an air line and when you pull the trigger the escaping air creates a vaccuum in the collection pot. You just have to attach the tube to the bleed nipple, crack it open and pull the trigger until all you get out is fluid.
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  #519  
Old 13th February 2012, 12:11
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Quote:
Originally Posted by Mike View Post
Do you not think it would be safer to have individual pipe runs to the two front wheels? With only one feed pipe, if you lose one, you lose both - and to quote Martin Brundle " Head off straight to the scene of the accident!!"
If the ports on the M/C are siamesed it won't matter - if you loose pressure in one you will loose it in the other. If they are not siamesed and run off separate chambers in the M/C I won't be able to block one off anyway 'cause nothing will then work as the fluid has nowhere to go preventing the whole M/C from working.

Quote:
Originally Posted by Mike View Post
Do you have your own private road, or disused airfield to conduct some empirical tests???????
Live in a cul-de-sac. Should be able to sneak out and give it a quick test when there is no-one about...

Cheers, Robin
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  #520  
Old 13th February 2012, 14:23
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Hi Rob

I think it is more a case of failure at the wheel or caliper in one wheel, means you will lose braking to both with a single supply to a T.

But an interesting question about the MC not working and locking solid if one port is closed off.
However, I am sure Andrew has just blanked off one port, just as he had for his BMW.
Mike

Quote:
Originally Posted by MartinClan View Post
If the ports on the M/C are siamesed it won't matter - if you loose pressure in one you will loose it in the other. If they are not siamesed and run off separate chambers in the M/C I won't be able to block one off anyway 'cause nothing will then work as the fluid has nowhere to go preventing the whole M/C from working.


Live in a cul-de-sac. Should be able to sneak out and give it a quick test when there is no-one about...

Cheers, Robin
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