Brake dragging and troubleshooting

[Alastair B]

I need some advice for troubleshooting some brake problems on my ’99 de-dion car. My rear brakes both sides drag and my offside front brake the same, but not my nearside front, this spins freely when rotated. I have checked the offside front brake and can only remove the brake pad from one side the other is in tight against the piston.

So I suspect the rear pistons / sliders and the front offside brake are getting stiction. But I was trying to understand if it could be the master cylinder, but the fact that the near side front behaves normally has cast some doubt on that.

Is there a good way to troubleshoot and eliminate the master cylinder? How much free play should there be on the master cylinder when brake not depressed? What adjustment could I do to see if this is the problem? Is brake caliper rebuild with new seals a recommended way forward or refurbished calipers better?

Thanks

[Myles]

Has the car been standing long? Dragging brakes suggest to me that something is gunged up - the mc is unlikely to act as a non-return valve to that extent.

So, I' m not sure I'd be looking at the MC yet - I would persuade the front pad(s) out, clean, check for corrosion, possibly chock/block/reinsert all bar one piston and carefully check that it moves (making sure you don't stomp on the pedal and pop the whole thing out), put them all back in...

...move to the back, remove the yokes, clean/check etc., try a little handbrake to check for piston movement (I'm assuming standard single-piston Sierra calipers here), use a wind-back tool to retract the piston...

And then mebbe flush through some new fluid. Then, once you are fairly sure that all the moving bits are in good condition - then I might start to wonder if the mc might be at fault.

Its been a long time since I documented brake fettling - but these pages on my site might be of some use (especially bearing in mind that I documented this work as a http://alcester-racing-sevens.com/brake_maintenance.htm

[DJ.]

To be honest, assuming the brakes are original, I'd take all four callipers off and either rebuild them with new seals or swap them for reconditioned ones. Once they start playing up they can't be trusted.

 

Duncan

[martyn]

Would be awesome to get that brake bleeding article finished off with some useful tips.  Especially as I'm battling with that at the moment.  Might start another topic on that though to prevent this one going off topic.

[Paul Deslandes]

Not that it would affect the front but check that the handbrake linkage is free and not holding on the rears.  Give the cables either side a good tug and see that they free off okay.

[Alastair B]

 

Thanks for all your responses, I didn’t realise you all had posted until today as the replies to my posting was showing zero, even when there were 4 posts….down to the progress and the new site I guess

Myles – thanks, have seen your Alcester Sevens pages, very useful they are. The car sits in a dry garage with brakes not applied and is not used much from November to March, but has been the case for the last 7 years of my ownership and corrosion can build. I will have a go at the clean/check for corrosion at the front as you state. At the back yes standard Sierra calipers, I will will try the handbrake check as well.

DJ – I think they are original calipers and I appreciate this will be a longer term fix. If I’m working on 3 of them it makes sense to do all 4 properly

Paul – Will check handbrake – but to be honest this is something I never really have to use until MOT time

I will try and find sometime in the next week or so and have a go at some of these ideas and will post back with results.

[Nigel Riches]

Slightly off topic, but related, check the brake pedal return spring is pulling the pedal fully back. 

This caused my cousin grief with his old Daimler V8. 

Nigel. 

 

[Alastair B]

 

In the interests of updating this archive, this is where I’ve got to….

I have established that my offside front does have an inboard sticking piston and so I will be replacing both fronts as a pair with refurbished calipers, pads are OK. My rears, I am not now convinced have a problem. Handbrake might have been a bit tight so loosened off a touch. The rear pistons move and relaxes slightly when pressure applied and released to brakes, sliders were lubricated, pads OK and so cleaned up/re-greased and reassembled. The rear wheels will come to a stop after hand turning after about 1/8th of a turn as the pads are in light contact with the disc and I think this is normal as I can’t seem to find anything wrong. Does this amount of friction on the rears seem normal?