Hi all,
I have recently had the front calipers from my 1.3 Rallye S rebuilt (stainless sleeves and new seals). Now when I brake, the pedal feels soft and the car pull left quite violently. If I pump the pedal a few times first, the car does pull up straight although the pedal doesn't feel solid - also when then releasing the pedal, the car tends to pull right, although not as badly as when it pulls left. It is almost as if the right caliper is slow to activate and slow to release.
There are no leaks that I can see and the system has been re-bled a number of times.
Any ideas please ?
Thanks
Steve
Car pulling left under braking
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Bart
Re: Car pulling left under braking
You discribe all symptoms of air in the system...
If you remove the assembled cilipers from the disks without undoing the leads, and operate the pedal gently, you should be able to see which piston(s) move instantly, and which might stay a bit behind. These are probably the leads that you have to bleed (again). Be carefull not to press too hard as you push out the pistons...
By the way, after 3 successive vacuum servo's in a year all started leaking, I finally opened one and found the membrane still in excelent condition. Reason of the leak was the seal in the 'inner' chamber. I replaced this with a standard lip seal of 50x38mm (E 2,-), closed the thing again and painted it. Works splendidly and will most likely last for another 35 years. Very satisfactory friday night's job.
Bart
If you remove the assembled cilipers from the disks without undoing the leads, and operate the pedal gently, you should be able to see which piston(s) move instantly, and which might stay a bit behind. These are probably the leads that you have to bleed (again). Be carefull not to press too hard as you push out the pistons...
By the way, after 3 successive vacuum servo's in a year all started leaking, I finally opened one and found the membrane still in excelent condition. Reason of the leak was the seal in the 'inner' chamber. I replaced this with a standard lip seal of 50x38mm (E 2,-), closed the thing again and painted it. Works splendidly and will most likely last for another 35 years. Very satisfactory friday night's job.
Bart
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Huib Geurink
Re: Car pulling left under braking
The problem may be air in the system as Bart describes. Bart has Girling brakes of the S2.
I assume you have the S1 Dunlop system.
For the Dunlop brakes it is often necessary to rebuild the piston and make sure the retraction mechanism inside the piston is set to 0,08 to 0,1 mm. This requires very special tooling. Also there should not be axial play on the pin.
Sleeving the front brakes is dangerous. The wall of the 2 1/8" cilinders is already thin. In fact 2 1/4" cilinders were discontinued in the sixties because they exploded. Machining the walls of the 2 1/8" cilinders to insert sleeves makes them go below safe limits. Things like driving through water with hot brakes and extremely high pressures during a panic stop put very high strain on the metal. You will of course never make a panic stop, but I always figure the car should also be safe to drive for my wife, daughter and son.
The process I have developed for the Dunlop brakes is as follows:
1) grind the cilinders to 0,4 oversize
2) nickle plate the cilinders with an electroless process to ensure uniform thickness
3) zinc plate the cilinders
4) machine new pistons to oversize. Stainless steel with same temp coefficient as cast iron for the front and brass for the rear.
5) rebuild piston while setting retraction to the correct value.
Quite a bit of special tools and grinding stones have to be made. I also wrote the software to calculate the diameters on the various sections of the pistons to make sure the standard seals fit.
What you can do is look at the pads when somebody steps on the pedal. Using a micrometer with magnetic stand to measure the displacement is even better. If you see the pads move it is usually to much.
You may also have play on one of the wheelbearings.
I assume you have the S1 Dunlop system.
For the Dunlop brakes it is often necessary to rebuild the piston and make sure the retraction mechanism inside the piston is set to 0,08 to 0,1 mm. This requires very special tooling. Also there should not be axial play on the pin.
Sleeving the front brakes is dangerous. The wall of the 2 1/8" cilinders is already thin. In fact 2 1/4" cilinders were discontinued in the sixties because they exploded. Machining the walls of the 2 1/8" cilinders to insert sleeves makes them go below safe limits. Things like driving through water with hot brakes and extremely high pressures during a panic stop put very high strain on the metal. You will of course never make a panic stop, but I always figure the car should also be safe to drive for my wife, daughter and son.
The process I have developed for the Dunlop brakes is as follows:
1) grind the cilinders to 0,4 oversize
2) nickle plate the cilinders with an electroless process to ensure uniform thickness
3) zinc plate the cilinders
4) machine new pistons to oversize. Stainless steel with same temp coefficient as cast iron for the front and brass for the rear.
5) rebuild piston while setting retraction to the correct value.
Quite a bit of special tools and grinding stones have to be made. I also wrote the software to calculate the diameters on the various sections of the pistons to make sure the standard seals fit.
What you can do is look at the pads when somebody steps on the pedal. Using a micrometer with magnetic stand to measure the displacement is even better. If you see the pads move it is usually to much.
You may also have play on one of the wheelbearings.