Lotus Elan

Brake issues

PostPost by: l10tus » Fri Jun 12, 2015 10:42 pm

MOT'd my car today - passed!

Very sympathetic tester though! - Because the brakes are not good !

Your thoughts about the Sprint's braking issues would be appreciated:-


List of items:-

Plus2 Discs and Calipers
Braided Stainless Flexible pipes.
New Dot 4 fluid.
Calipers rebuilt by Classicar
Original Girling Servo - rebuilt by Classicar.
EBC pads.
New 3/4 " Standard master cylinder.
Rear brakes fully overhauled by Classicar.

Operation of Brakes :-

Initially there's a worrying pedal travel distance - (approx. 50% of available travel) - before brakes even start to work !

By then, I'm pressing in fear, as the pedal becomes a little harder, and the brakes dip the nose, pulling up straight and level, without locking up.

I cannot lock any of the wheels.

I've only done 30 miles in total.

When tested on the MOT rollers, brake efficiency was just about sufficient to pass the test, with the rear brakes performing better than the Fronts.

Hand brake was excellent.

I suspect the Servo is not working correctly / at all ?

I will disconnect the servo vacuum pipe next time I drive the car, to eradicate the servo as an issue, but wonder if this is more of a 'bedding-in' issue, a servo problem, master cylinder/ rubber seal issue, or a pad material one?

Servo was overhauled 7 years ago, but kept wet with fluid, all other components new 7 years ago.

Your thoughts from experience would be appreciated, but I would like to keep the servo.

How do you test to see if it's working correctly ??

Regards,

Phil.
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PostPost by: AHM » Fri Jun 12, 2015 11:26 pm

Fantastic news Phil Well done!

The servo provides assistance ie how hard the pedal is. It will only make the travel longer if it is working (or leaking) so I doubt it is that - No need to disconnect it it wont help your symptoms.

Long travel as you describe is most likely air - Run a couple of pints of brake fluid through it.

If that doesn't fix it you may have a sticking piston seal which is pulling the piston back. Or a warped disc - but you don't describe those symptoms.

The brakes on the elan are good without the servo so it is not likely to be that. To test the servo operation gently depress the pedal after a slight increase in pedal pressure you should feel a clonk - it's a remote servo so there is a slight lag - Quite likely it is stuck after 7 years but easy enough to unstick once you take it out - Don't worry about it for now though!
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PostPost by: mbell » Fri Jun 12, 2015 11:40 pm

I believe the master cylinder is 7/10 not 3/4 from the factory but that should just make the pedal firmer and shorter travel.

Did your ebc pads have the bedding in coating on them? If so could be that but I would bleed and test booster as said.
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PostPost by: UAB807F » Sat Jun 13, 2015 6:01 am

I have the same larger front calipers, brake lines, EBC pads, no servo and a 0.7" dual circuit master cylinder. I had previously run with a 0.75" single circuit master cylinder and the pedal was very firm with little travel.

I went to a 0.7" bore to give a bit more feel to the brakes and even now the pedal travel is quite low, I haven't measured it but the theory said around 1.5" for maximum run out at all 4 discs and I'd say it's somewhere like that, or possibly less.

I'll go along with the "air in the brakes" idea, it sounds the most logical to me assuming the linkages from brake pedal to m/cyl actuator are tight with no slop in there.

Thinking about the comment about the fronts being worse than the rears, something is definitely wrong there. Even with the standard set up the fronts will be pulling a far greater percentage of the braking effort than the rears, and now more so with larger front pistons/discs.

I can't recall any problems bleeding the system but I do tend to flush quite a lot of fluid through. Daft question time - are the calipers on the right sides with the nipples at the top ? Servo mounted so as it can't retain an air bubble ? Although I suppose the latter would be on all 4 brakes and it sounds from what you say as if the problem centers on the fronts.

Brian

ps - the other thing about dual circuit is that, apart from being theoretically safer in terms of a system failure, you get a lower percentage pass rate on the handbrake..... just in case it's ever needed :D
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PostPost by: Chancer » Sat Jun 13, 2015 9:01 am

Yes you have not reversed the calipers, the bleed nipples should bat at the top where the air rises to.

I did Wonder if it could be that but I doubt that you would get any pedal at all.

Check the free play on the pedal linkage, try clamping off all the flexible hoses with either hose clamps or G cramps/mole grips with suitable soft packers, if the pedal travel is then normal remove one at a time to see where the air or perhaps excess travel is.

As a last resort you could blank off the master cylinder outlets to test it.
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PostPost by: Galwaylotus » Sat Jun 13, 2015 7:30 pm

mbell wrote:I believe the master cylinder is 7/10 not 3/4 from the factory but that should just make the pedal firmer and shorter travel.

Just to clarify, the effort with a smaller diameter m/c will be less but the travel greater.
Pressure = Force/area so smaller area for a given pressure means the force required is less (0.7<0.75)
Pedal travel is a function of how much fluid moves so a smaller diameter piston requires a longer stroke to achieve the same fluid volume.
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PostPost by: RichardHawkins » Sat Jun 13, 2015 7:57 pm

Phil,

Sometimes, bleeding technique can make a difference. When you have finished bleeding and no more air is being dispelled, push the pedal down hard and fast, some people say "kick the pedal down". This will sometimes displace air that a more conventional gentle technique does not move.

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PostPost by: l10tus » Mon Jun 15, 2015 10:11 pm

Richard,

Point noted thanks!

Q: Whilst on the subject, can anyone recommend the easiest method and components required, to 'bridge out ' the servo hydraulic connections, if I want to remove the servo?

Q: If I use a Female connector, will it seal the two Male ends of the existing pipe ends?

Your thoughts would be appreciated.

Regards,

Phil.
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PostPost by: billwill » Tue Jun 16, 2015 11:16 am

l10tus wrote:Richard,

Point noted thanks!

Q: Whilst on the subject, can anyone recommend the easiest method and components required, to 'bridge out ' the servo hydraulic connections, if I want to remove the servo?

Q: If I use a Female connector, will it seal the two Male ends of the existing pipe ends?

Your thoughts would be appreciated.

Regards,

Phil.


I did this long ago and it seemed easy at the time, so I don't recall the details of how I obtained the bridge pipe, but since then the brake lines have been completely redone in non-servo mode, so I no longer have the bridging pipe.

It is a simple U bend pipe with the appropriate female fittings, The seal from the male end is into the FLARE of the pipe on the female end, not to the brass fitting itself, so yes it will seal.
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PostPost by: 661 » Tue Jun 16, 2015 1:58 pm

I'm assuming you have a single system.,To take out the servo, use a pipe straight from the M/C to the 4 way connector which hides inside the right ( UK offside) front leg of the chassis, near the handbrake adjuster. I'd then tidy things up by getting rid of the extra loop of pipes ( M/C to servo, servo to four way connector).
I made a pipe for the job. I'm sure the usual suspects will supply a pipe at no great expense.
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PostPost by: billwill » Tue Jun 16, 2015 3:23 pm

661 wrote:I'm assuming you have a single system.,To take out the servo, use a pipe straight from the M/C to the 4 way connector which hides inside the right ( UK offside) front leg of the chassis, near the handbrake adjuster. I'd then tidy things up by getting rid of the extra loop of pipes ( M/C to servo, servo to four way connector).
I made a pipe for the job. I'm sure the usual suspects will supply a pipe at no great expense.



Aye, that's how mine is now.

>I'd then tidy things up by getting rid of the extra loop of pipes ( M/C to servo, servo to four way connector

And the redundant vacuum pipe from the inlet manifold.
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PostPost by: l10tus » Tue Jun 16, 2015 4:01 pm

Bill will & 661,

Thanks for the replies.

I was trawling the net trying to find Female connectors in UNF but struggled to find one that accepts the Male 3/16 UNF fitting?

So, my local garage confirmed that it's ok to join Flare no. 1 to Flare no. 2 directly.

Got the pipe made up today, trying to fit it tonight.

I intend to try the system without the servo, but really intend to get the servo working again, if I can sort out the problem?

I'll let you know how I get on !
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PostPost by: Galwaylotus » Tue Jun 16, 2015 4:27 pm

Getting rid of the servo was one of the best changes I made to my car. The brakes are very consistent now with a good, positive pedal. :D
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PostPost by: UAB807F » Tue Jun 16, 2015 4:32 pm

If you do intend to take the servo out, then take it easy for the first few miles. I remember when as a youngster I disconnected mine (leaking) while I nipped over to the nearest scrapyard for another one. The first time applying the brakes was something I didn't forget for a long time....... :shock:

I would honestly change the pads for something with a bit more initial bite if you drive it for any distance. I have Greenstuff without a servo, there are other similar makes/grades about I think.

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PostPost by: Galwaylotus » Tue Jun 16, 2015 6:47 pm

I, too, have GreenStuff pads in front. I also took the opportunity when removing the servo to install a tandem master cylinder and Aeroquip brake lines.
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