Long, soft brake pedal

[prezoom]

I am running a dual .7 master cylinder on my Plus2, no booster, without a long pedal. The route of the brake lines, both front and back, on my Plus2 are well above the master. I also had problems moving the air beyond the high spot. I wound up taking an old male fitting and a sort piece of metal brake line, with a flare, putting it in place of the caliper bleed screw. Attached a piece of plastic tubing to the metal line and then to a home made reservoir that I mounted a coupe of feet above the master cylinder. Filled the new reservoir with brake fluid and let gravity do its work, forcing the fluid backwards, from the caliper to the brake master. It pushed all the air back out of the system. Pinched off the plastic line close to the caliper when the brake master approached full. Lost a little bit of fluid in the transfer period from the old line/male fitting back to the bleed screw, but not enough to affect the level in the master. Problem solved.

[alan.barker]

On my 1972 Elan Sprint i upgraded to 16P Calipers and +2 Discs and i kept the Original Master Cylinder.
No problem at all and you don't need to change the Master Cylinder.
Imho it's air in the Circuit and you need to check the free play between Cylinder and Pedal.
Alan

[Mazzini]

I put the Plus 2 set up on the front of my Elan S2, I ended up with superb brakes, the car would stop in remarkably short distances, but I had a long soft pedal. My S2 didn't have a servo so the MC would have been different to a car with a servo. There is a thread, possibly several, on the forum about which MC is needed for this set up to give a firmer pedal with more feel. Vaughn in Australia and Steve at Lotus Marques, both whom have experience of this issue recommended a Datsun tandem MC. I've decided to return my S2 to original (right down to the Rotoflex couplings) and I will fit the Plus 2 brakes and Datsun MC to my Sprint, I haven't done it yet...it's on the list of 'things to do this winter'.

[gjz30075]

^^ ^^^ That's what I plan to do, ie, go back to stock setup, if I can't get this resolved. At this point, I've got
to believe it's an 'air' issue. The 180 degree loop may or may not be exacerbating the problem.

[promotor]

If there isn't another issue presenting itself here, a 3/4" master cylinder will make a shorter, firmer pedal as you will be able to move more fluid per unit of distance travelled when compared with a smaller M/C.

[gjz30075]

Thanks Al. A good solution to the GT6 brake conundrum. However, I think I'm making progress.
Per some previous suggestions, I jammed a board against pedal and seat frame and let it sit overnight.
Before removing the board this morning, I decided to crack a rear bleeder. I couldn't tell if air came out
but, WOW, a nice improvement to the brake pedal feel. I had to cut the board back another 1" to get
it jammed in again and I'll let it sit for maybe, another 8 hours or so and crack the other rear bleeder.

Fingers crossed. And many thanks for all the suggestions.

[alan.barker]

This time crack the fitting where it comes out the Master Cylinder
Alan

[Elan45]

OK, Hi Greg. The body shell went to the paint shop this morning. Gotta head back in a moment.

The high spot you've mentioned shouldn't be a problem. MG TD had the master cyl mounted on the frame, under the floor. So did many other cars, my father's Ford T roadster (40's/50's flatheaad hotrod) for instance. I bleed brakes w/ a clear tube and jar and its not unusual to see 3-4 inches of go down the tube on one pump.

Are you sure you don't have a caliper upside down or maybe if you can wiggle the pads, then I wonder if you've got a problem w/ the seals not in right. Did you clean out the seal groove in the caliper bodies real good? I'e got a special tool I made to do this job. I should take a pic and post it for the whole forum. Call me if you wish.

Roger

[gjz30075]

Roger, I'd love a pic of that tool. I did what I could to clean out the seal grooves but maybe it wasn't
enough. I understang why that could cause problems.

Alan, I'm wondering why cracking open the line at the master would fix this? Shouldn't I be further
downstream to catch the air?

[alan.barker]

I find there is sometmes an air bubble.
Try it anyway it only takes 5 minutes with the pedal blocked down.
It can't do any harm
Alan

[paddy]

I use one of these for bleeding the brakes:

https://www.amazon.co.uk/Sealey-VS820-C ... FJHMCATVD9

It forces the fluid out under continuous pressure which, in my experience at least, overcomes issues with high spots because air bubbles have no opportunity to rise up again as they do after each pedal stroke with the traditional approach. I've used it on a range of cars and never had an issue with residual air.

The upsides are that you can do it reliably single-handedly; you don't have to top up the master cylinder; after setting it up it's very quick to go round all 4 wheels and you spend literally a minute at each wheel; you don't have to worry about the possible ingress of air through the bleed nipple threads or anywhere else.

The downsides are:

- you can get through a lot of fluid, which means it's not a cheap method, and you can quickly get through half a litre of fluid thinking that you'll just let it run for a little bit longer "to be sure". The catch bottle also fills up quickly;

- you have to have a perfect seal where the filler cap/valve fits on the master cylinder. If that's not completely airtight then you get fluid leaking out there and into the engine bay below;

- on a RHD Elan you have to remove the carbs to fit the cap onto the master cylinder.

Despite the downsides, I would still use it every time because of the certainty of knowing that you do it once, and it's done.

Paddy

[pharriso]

Paddy, I have a similar Motive Power "Power Bleeder" great on all of my cars apart from the Elan, on my Federal Sprint with the Sovy the seal between the Master cylinder & the Sovy Can cannot seem to hold any significant pressure

[ecamiel]

I have the same setup - GT 3 calipers and original MC.
My brakes are firm with reasonable travel.

The issue is somewhere else.

Eric
64 S1 Hart

[mbell]

I run a single circuit 5/8" master on my +2 (no servos) with rebuilt calipers, new flex pipes and similar loop on exit of master.

There is some pedal travel before the brakes engage, but they engage around level with the accelerator pedal. Once engaged they have plenty of power (lock wheels) and good modulation/feel. So I don't think the master size is a major factor. The issue is more likely one of the other thing mentioned.