Lotus Elan

So, where's the fluid gone.....?

PostPost by: robertverhey » Sun Oct 27, 2013 12:49 am

Absolutely....will take him all of 5 min to make a u-shaped bridge, and if you ever decide to go booster-less like many have, you're sorted!
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PostPost by: reb53 » Tue Nov 05, 2013 5:57 am

May have an answer to this mystery.

Had a call from the re-builder yesterday who'd received the servo back, re-tested it, and had a brainwave.
A replacement spring they had used was one that they received supplies of a year or so back.
He became suspicious of it, and whether or not it was a true replacement in terms of its strength.

As it is the one that regulates when the servo starts to work its operating characteristics are critical.
He re-fitted the original spring, and the difference was marked, with the servo working with less pressure and no "suddenness".
This huge improvement is also obvious in the car now that I've received it back and re-fitted it.
It's now usable but I'm not 100% convinced yet, as it is different, but I'm attributing that to the overhaul of both the servo and the master cylinder.
I intend to run it for a while to let everything settle down and will probably re-bleed the brakes in a few weeks as well.
Just goes to show what a huge difference small things can make, and how valuable a proper tradesman is who doesn't just say " Oh, they're all like that, no problems with my work.....".

Cheers,
Ralph.
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PostPost by: reb53 » Thu Nov 07, 2013 1:48 am

Another trip today shows the long pedal travel to still be there, but without such a sudden stop when the brakes do finally work.
Also the occasional pulsing back through the pedal.
The brake guy, who as I said is a proper tradesman, has run out of ideas and has offered to give me my money back.
As much as I don't like taking it, and would much rather have a 100% servo, I've accepted his offer and am thinking about getting one of the Lockheed replacements.

Has anyone had experience of these, and am I jumping out of the frying pan into the fire ?
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PostPost by: StressCraxx » Thu Nov 07, 2013 4:33 am

reb53 wrote:Another trip today shows the long pedal travel to still be there, but without such a sudden stop when the brakes do finally work.
Also the occasional pulsing back through the pedal.

Has anyone had experience of these, and am I jumping out of the frying pan into the fire ?


Just a guess. Pulsing back through the pedal may be due to warp of one or more brake rotors. If your wheel bearings have excess play either front or rear, the rotor lateral movement plus the rotor warp above may cause brake pad "knockback". The lateral motion of the rotor pushes the pads and pistons away from the rotor and back into the caliper, leaving excess pad to rotor clearance. The displaced fluid returns to the master cylinder.

The next application of the brake at the master, the piston in the master must transfer more fluid into each caliper just so the caliper pistons can again apply the pad to the rotor. The additional fluid transfer to move the piston the additional distance causes a long pedal.

If you confirm that is the problem, I suggest you explain it to your brake guy when you buy him a pint!

Regards,
Dan
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PostPost by: reb53 » Thu Nov 07, 2013 5:42 am

Thanks Dan,

When I told my brake guy about the pulsing he seemed to know exactly what caused it and said " if you return the servo to me I can fix that, by putting the stronger spring back in........".
i.e. I'd have no pulsing but the brakes would be back to being impossible to use.

There is also the fact that this problem has only appeared since the brake work was done.
When I put the car away for the Winter it was fine, as it was on a couple of runs during the Winter.
Doesn't seem likely that bearing/rotor problems just chose this time to pop up put I will investigate as being a Lotus who knows......

In the meantime I would be really interested in opinions of the Lockheed servo.

Ralph.
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PostPost by: robertverhey » Thu Nov 07, 2013 8:30 am

Before he gives you your money ask him to make you a little bypass tube (as suggested above). You still haven't absolutely, definitely identified the booster as the culprit and the master cylinder was overhauled at the same time.
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PostPost by: billwill » Thu Nov 07, 2013 1:15 pm

robertverhey wrote:Before he gives you your money ask him to make you a little bypass tube (as suggested above). You still haven't absolutely, definitely identified the booster as the culprit and the master cylinder was overhauled at the same time.



I was just about to say that, when you have said it for me. 8)
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PostPost by: billwill » Thu Nov 07, 2013 1:20 pm

Were the calipers and/or disks removed and replaced since the time when they last seemed to work OK.

It could be something as simple as a bit of grit behind one of the disk securing bolts causing it to be out of line & hence wobbling and thus as mentioned above pushing the brake piston back an excessive amount each time you release the brakes.
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PostPost by: rgh0 » Thu Nov 07, 2013 1:33 pm

A long brake pedal travel can also be due to the end seal in the master cylinder back to the master cylinder fluid reservoir needing more pedal travel before it shuts off. if the rebuild was not done well or the seal installation faulty this could be an outcome independent of the booster.

cheers
Rohan
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PostPost by: reb53 » Thu Nov 07, 2013 7:43 pm

Thinking on this over night, and in the early hours, I decided that the next step would be to have a real close look at the master cylinder so I'm thinking along the same lines as Rohan.

I'll start by sealing off the line that enters the servo from the cylinder at which time the pedal should be solid.
If it is I'll bypass the servo and see if it remains solid.

Would be nice to have an answer but bit of a pain if I have to remove the cylinder 'cos it's such a fiddly job.

Thanks for all the suggestions so far.

(The calipers haven't been disturbed).

Ralph.
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PostPost by: reb53 » Fri Nov 08, 2013 3:07 am

Checked out things a bit more today.

With the engine off the pedal has normal travel, no sponginess, no long movement.
( So not pushing fluid up into the reservoir.)

Driving down the road can be semi OK, then suddenly long travel, and at the bottom as the pedal hardens up, it starts to push back against my foot....(!). Can actually see it rising.

I next disconnected the vacuum hose and plugged it.
When driving pedal now OK and able to be modulated. No sudden sinking, but much harder due to lack of servo assist.

So it might be time to leave it disconnected and put some softer pads in. EBC Greenstuff ?
Is the difference that noticeable between "servo", and "no servo but using softer pads" ?

Ralph.
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PostPost by: Galwaylotus » Fri Nov 08, 2013 6:22 am

Noticeable yes; however, I removed my servo and installed Greenstuff pads and am very happy with the result. As someone mentioned on this forum, it isn't the "just breathe on it" feel you get on a modern servo assisted car but it isn't a panic stations situation either - just a minor adjustment in technique in my case. I quite like it.
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PostPost by: UAB807F » Fri Nov 08, 2013 6:31 am

reb53 wrote: (part quote)
So it might be time to leave it disconnected and put some softer pads in. EBC Greenstuff ?
Is the difference that noticeable between "servo", and "no servo but using softer pads" ?

Ralph.


Hi Ralph,

To be honest, yes it is a noticeable difference but nothing like the difference between "servo" & "no servo" using the OEM harder pads. I think it takes a couple of outings to get used to the feel because we all have our own personal views on what's "right", after which it becomes second nature.

I'm an unashamed convert to the no-servo brigade and was so taken with the feel of the brakes that I also converted my Europa to the same system. Both had perfectly functional Lockhead servos on so it wasn't a case of being forced into the move, I could easily have retained the servo assistance simply by reverting to the original pipework.

Given how much time, trouble and no doubt cash you've put in so far, I think I'd splash out on a set of greenstuff pads and give them a whirl. Drive at least far enough to bed the pads in and then you'll know if it's worth pursuing a new servo unit.

Brian
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PostPost by: reb53 » Fri Nov 08, 2013 7:19 am

Thanks a lot for the replies.
Sounds like time to order some pads.

I suspect that the knowledge that the braking will be consistent will outweigh any feelings that the braking isn't strong enough.
When I went for a slow drive around with no servo I at least felt sure that the brakes would work as expected, whereas before it was bit of a lottery as to what was going to happen.
Is "SJ Sportscars" the place to go ? OK to use their on-line ordering, or give them a ring ?

Thanks a lot guys,
Cheers,
Ralph.
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PostPost by: rgh0 » Fri Nov 08, 2013 7:22 am

http://www.head2head.free-online.co.uk/Rover/servo.htm

A write up on the operation of the servo ( a Mark 2A unit in this case but the Mark 2B units works the same just a different vacuum cylinder design)

From that description you can deduce some of the reasons behind them being slow to come on and hard to modulate.

Lots of springs that need to be of the right tension and pistons that need to move freely!

cheers
Rohan
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