Brakes Sticking on

[RogerFrench]

I have a curious issue with the Elan. Sitting in it's garage, the brakes gradually "self-apply". After 2 or 3 days, the car cannot be pushed around, and there is distinct pressure in the brake lines
I assume it's because the brake fluid expands with heat - we're still getting close to 90deg temperatures here, and that the return valve in the Master cylinder is not letting fluid up into the reservoir. Certainly, stamping on the pedal a couple of times helps.
I'm thinking I need to rebuild the M/C - has anyone else come across this issue, please, or have any comment?

[ardee_selby]

The "stamping on pedal" bit suggests the documented Girling servo problem:

http://www.lotuselan.net/publish/lsb_br ... g_on.shtml

However, here is a quote reference brakes "locking on":

"I had this problem a long time ago, brakes sticking on, only released by letting the pressure of by cracking the m/c outlet. Traced to master cylinder not retacting sufficiently to open lock valve. Cured by putting spacer washers on the m/c mounting"

From: elan-f15/brakes-locking-t23892.html

Unfortunately the exact cause & cure in that instance wasn't fed back into the thread.

Good luck - Richard

[royrender1]

I had the same problem put the car in the garage after a drive and the brakes came on traced it in the end to the valve in the servo fitted a kit and had no trouble since that was two years ago
ROY.

[ricarbo]

It's so long since I had a master cylinder in bits, I'm not sure if I've got this right, but I think there is a small springy curved washer under the three legged valve spacer next to the shoulder of the rod that carries the small seal at the end. It's purpose presumably being to ensure the rubber seal moves a bit relative to the three legged spacer. The initial pressure at the pedal pushes the seal on to the surface, isolating the reservoir, so that further pressure forces the fluid down the brake lines, rather than making the reservoir level rise. If the seal isn't working well you initially find the height of the brake pedal varies each time it is pressed, before the brakes bite. if it completely failed the pedal would just go to the floor.
As i say, it's a long time since i had one apart, but if i am right and that spring has broken, perhaps the seal is stuck in the wrong position and is protruding past the end of the three legged spacer.
Just a thought. This washer is not shown on the diagram in the Lotus manual, in either clutch or brake sections, but is referred to in the text. And my memory could well be at fault. I have no view on whether it might be a servo problem.
regards
Richard

[RogerFrench]

Thanks folks.
I know it's not a servo problem - don't have one of those! I suppose I should have said so.

[AHM]

Roger,

I'm watching with interest as I have a similar problem.

The car is still being run-in so it could be any number of things. My latest thoughts are on friction in the pedal/pushrod/rubber cover, or the heater hose getting in the way.

Will have a look over the weekend.

Simon

[ricarbo]

i forgot to say the other symptom of a poor seal is that if you press lightly on the pedal when the car is stopped, the pedal will slowly sink towards the floor. But leakage past the seal seems the opposite of what you have.
regards
richard

[mini64]

AHM,

Did you also recently rebuild your master cylinder? I once put the big cupped washer that holds in the pushrod the wrong way around to where the piston could not come back far enough to release the pressure relief valve in there. I'd go for a drive and after the 4th or 5th brake application the brakes would be locked on solid!

[RogerFrench]

Mine is really odd. The pressure builds in the brake circuit while the car is sitting idle - enough for the brake lights to come on and flatten the battery if I don't isolate it. Darned Master Cylinder, must be!

[patrics]

Hello Roger,
Is the pedal return spring fitted?

Regards
Steve