Front brakes dragging

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Front brakes dragging

Postby mattdovey » Wed 09.10.2019, 18:32

Evening all, I have a 91 Elan which I purchased earlier this year. When I went to pick it up the seller informed me that the R/H front brake sometimes sticks. The seller seemed to think the callipers needed a strip and clean. Well they drag all the time.
It has Hi-Spec callipers and discs fitted to it and braided hoses.
So ordered new seals and pistons for both sides. Got my local garage to change the seals and pistons for me as I didn't have time. Didn't make any difference. They had another look for me. They though it could be a bad brake hose. But after inspecting the hoses they think they are ok. They now think that the brake master cylinder may be bad. Before I replace the master cylinder has anyone else had a similar problem?
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Re: Front brakes dragging

Postby lotusflasherman » Thu 10.10.2019, 00:13

No, but I have HiSpec Calipers all round.
It's either a physical binding or hydraulic lock problem.

If new seals and pistons have been fitted it should not be physical binding but check how easy pistons are pushed away from discs with bleed nipples open.

So hydraulic lock ... Check the braided hoses for signs that some idiot has used a hose clamp on them - it can leave a permanent deformation in braided hoses which restricts flow.


Push the brake pedal hard to create the binding and check each bleed nipple in turn by opening and see if fluid squirts out under pressure.

Hose connects to inboard half of caliper and the upper alloy spacer has a drilling and O rings to supply fluid to outboard half of caliper. If you have pressure only from outboard nipple I'd be checking the drilling and O rings that may be restricting fluid returning. Drilling may be partially blocked or O rings out of place.

If you find pressure in both nipples I would consider replacing the braided hose before the mastercylinder. Remember dual circuits connect NSF to OSR and OSF to NSR so if the mastercylinder is playing silly games with O/S Front the N/S Rear should also be affected. (The rear Brake Pressure Limiting Valves should not be interfering for low pressure operation).

Also inspect brake pipes to check none have been flattened anywhere. They can act like valves when high pedal pressure forces fluid through but it has difficulty coming back.

Good luck.

By the way ... it helps if you put your locality on your info'. You may have a helpful member in the locality.
Phil

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Cars: Subaru Forester 2.5XTN, Eclat Riviera, brace of Pacific Blue SE's, Collapso SE, Elan+S.... and now an Evora
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