Lotus Elan

Front brake callipers binding

PostPost by: fireblade » Fri Jun 11, 2021 3:12 pm

Took the Elan for a quickish 15 mile spin yesterday and about a mile from home sensed the brakes were starting to bind and that the free movement on the brake pedal had gone. Lifted the front of the car and could just about turn both front wheels. Centre of front wheels were hot and the rears were normal. On slackening the bleed screw on one of the front calipers I could turn both discs freely. So with the Servo disconnected do I assume the brake master cylinder is the problem and requires an overhaul. On checking it was actually 6 years and about 6-7000 miles ago that I replaced the master cylinder so it didn't last very long. Again thanks guys for all your advice.

Roger.
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PostPost by: LI-599 » Sat Jun 12, 2021 12:37 am

Hi again,
If it is 6 years plus since you replaced the fluid, I still think changing that first is easier than removing the master cylinder.
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PostPost by: mbell » Sat Jun 12, 2021 1:37 am

If it's an issue with the master it's most likely the seal or channel back to the reservoir not allowing fluid back and therefore not fully releasing pressure.

A fluid change might clear it out or a rebuild of the master.

I had a similar problem with lots of rust clogging mine up. I went for a new master as the one fitted was much too large, especially for a car with no boosters.
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PostPost by: 2cams70 » Sat Jun 12, 2021 3:38 am

What type/brand of fluid did you use 6 years ago when you filled the system?
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PostPost by: Donels » Sat Jun 12, 2021 7:44 pm

It sounds like a fluid expansion problem which then binds the callipers creating more heat and expansion. It does point to the master cylinder not allowing the fluid back to the reservoir. While the fluid is old it usually absorbs water reducing the boiling point and causing brake fade, you don't appear to have this problem.
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PostPost by: LI-599 » Sat Jun 12, 2021 10:06 pm

Yes I now agree with Donets, I now recollect that the old fluid in mine caused the pedal to appear become locked solid but the brakes were ineffective. Strange though that the problem is only affecting the front calipers. Time and effort will solve the problem.
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PostPost by: Donels » Sun Jun 13, 2021 7:31 am

It’s probably affecting front and rear, it’s just that the braking force is split something like 70/30 front to rear so the biggest effect is on the front.
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PostPost by: nmauduit » Sun Jun 13, 2021 8:20 am

Donels wrote:It’s probably affecting front and rear, it’s just that the braking force is split something like 70/30 front to rear so the biggest effect is on the front.


or it could be that the rear is frozen solid (circuit blocked or calipers), hard to list all possibilities without testing the car (and inspection, outcome of the purge etc.)
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PostPost by: fireblade » Sun Jun 13, 2021 9:37 am

Again thanks for all your contributions. I think this problem has partly been created by me not changing the brake fluid. Initially I thought the brake fluid looked dirty but on further inspection it doesnt appear to be too bad. I do remember using DOT 4 having researched this at the time and I avoided using synthetic fluid. Even so the fluid has been in the system for over 6 years and should have been changed long ago.
I think Donels diagnosis of the brake master cylinder not allowing fluid back into the reservoir seems to be the answer so I have decided to pull the master cylinder and replace all the seals new brake fluid and bleed the system. I will post an update when completed.

Roger.
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