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MG TD TF 1500 - Brake bleeding problem

Okay, I've installed all new wheel cylinders and new flexible hoses where required. I then proceeded to bleed the brakes. After doing all four wheels I still had no resistance on the pedal. On my other TD there was no problem with this procedure and the brake pedal came right up as I progressed along with the various wheels. Prior to changing the cylinders I had good pedal pressure until one cylinder started leaking which caused me to replace all of the cylinders since they were at least 20 years old and the condition was unknown to me when I bought the car a while back. The car had silicone fluid and I am going back with the same type.
This would be no problem to fix cause I could use the archives. It turned out that the generally accepted solution to this problem is to individually fill each cylinder with a syringe after removing the lines. I did this hooked up the lines again and I still have no brake pedal pressure. If I pump the pedal about 10 times the resistance will rise but then fades to nothing.
I'm stumped. This shouldn't too big a problem. I've bled lots of systems over the years and have never had this sort of issue. I've chaecked all of the fittings and none are leaking. Any ideas?

Mark
Mark Strang

Only thing I can think of is that master cylinder has bad cups. You may need to rebuild and bench bleed it before putting it in the car.
David Werblow

Make sure shoes are adjusted. How old is the MC? If old and corroded, the additional stroke when bleeding could have wiped the seals out. Either that or somehow a lot of air still in the system.
George Butz

George,

The MC is about 20 years old and was good, I guess, prior to changing the wheel cylinders. I bled the old cylinders, just to change the fluid, shortly before one of the cylinders failed and I had good pedal pressure at that point. Everything seems to lead to the new cylinders not getting fliud into them and hence air in the cylinders. The shoes are adjusted. I even went so far as to try bleeding the system one time with the shoes completely tight up to the drums with no change.

Mark
Mark Strang

If you stayed with Silicon, and the MC was working prior to the wheel cylinder failing, it is less likely that the MC has failed.

Have you tried a vacuum system to pull fluid through the system? I find bleeding with a vaccum pump (i use a hand pump system) is the best way to get the initial bleeding done. With silicon, I typically rebleed after a few days to let all the air settle that the fluid may have gotten while pouring it.

If that does not fix it, and you have no fluid leaking at the wheel cylinders, then pulling the MC will probably be in order.
Bruce Cunha

Mark; Try to bleed just the MC. You can do this in the car. Just use the fitting on the cylinder as you would a bleed screw. Its a bit messy but you might be able to get trapped air out of the MC from that point. If you get improvment then bleed as normal. If not you may have to service the MC.
C.R. Tyrell

Thanks,

I'll try some of the above ideas and if they don't work, then I'll go the rebuild or replacement route.

Mark
Mark Strang

This thread was discussed between 17/09/2012 and 18/09/2012

MG TD TF 1500 index

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