Spitfire Brake Issue

[Zadkiel]

I am slowly putting back together a MK3 that I purchased partially re-assembled from the last owner after he had all of the body panel beaten and painted. I have discovered throughout that pretty much everything already done was done wrong, so I am basically going over the whole car trying to piece it together and figure out how things should be done, on my very first Spitfire!

Now I have removed all four wheels to have a look at the brakes and there seems to be a problem. The front brakes are "on" (the pads pushed into the discs) all the time and the rear brakes shoes do not move when the pedal is depressed. I removed one of the front brake calipers from the disc and the pads squeezed together with force and cannot be easily separated.

This leads me to conclude the front calipers are not simply seized, they are being pressed on by hydraulic force even when the pedal is not depressed. Conversely the rear shoes will not move even when the pedal is depressed!

So what is my likely culprit here, faulty master cylinder? Any ideas?

[caziques]

Sounds like a problem with the master cylinder, could easily be assembled incorrectly.

I have a an NZ new late Mk III, and a few years involved with parts.

Give us a call if you want to 0220 HEATPUMP (432878).

PS. I'm in Christchurch

[rallyspit]

The Mk3 should have a single circuit brake master cylinder (one pipe exiting the M/cyl), therefore any pressure in the system should operate both front and rear. Has this been altered to a later Mk4/1500 twin circuit system?

I would first crack a front bleed nipple to release any built-up pressure (watch your eyes for fluid spraying around) and then check if the M/cyl is actually pumping fluid. If so, it's probably the rear slave cylinders seized or the brake pipe flattened at some point under the chassis.

[Zadkiel]

Thanks. I'll have a play around with a few things today and then report back. It has the original 1 pipe master cylinder. I wouldn't surprise me at all if it was assembled incorrectly, I was having clutch trouble and pulled apart the clutch slave cylinder and instead of the proper cup inside for pushing the rod there was an old 1/4 inch drive socket. So poorly done.

[Zadkiel]

So the front brakes seems to be sorted, the master cylinder appears to have been a bit clogged or something and whilst testing and doing some pumping the fronts suddenly came off. So I am stripping the calipers down and tidying them up. Then onto the rears. Will take one of a have a look and see how we go.

[tapkaJohnD]

Replace the flexible brake lines, if you haven't.
Old lines can deteriorate inside, causing a 'flap valve' effect that stops fluid flowing back to the master, locking the pads onto the disc.
John

[//j17]

tapkaJohnD said:

Replace the flexible brake lines, if you haven't.

Probably best to do this as a matter of course as I've had this happen on a pair of braided Goodridge hoses that were less than 10 years old (and so got left to be about the only thing that hadn't been replaced before doing so and fixing the problem).

[cpas]

Are you sure the rear shoes have not been loosened off so that, whilst still moving, they are not moving far enough to contact the inside of the drum. Taking the drum off is the easiest way to tell.

[Zadkiel]

Have stripped and re-built all the brakes now and they are all working which is good . Will be bled and done soon, might replace those lines to to be safe.