Lotus Elan and Lotus Elan Plus 2 Forums

1970 Plus 2 with Weber heads, no servo, dual circuit master cylinder (new).
It is a dual circuit master with the line feeds coming out the engine side of the master cylinder. GMC226 is the part number.

Despite bleeding the brakes ad nauseam, I cannot get a decent hard pedal and am concerned that there may be something else to be considered.

I am bleeding using a Mityvac using a compressor and get close to a clean bubble-less stream and have fully run through the system several times. But still don’t get a good hard pedal.

My next attempt at bleeding is going to include trying to stop any air coming in around the bleed tubes, which I think may be my problem.

If that doesn’t work, my only thought is that I have a faulty master cylinder or some invisible leaks in the system - am I missing something obvious?

Given the lack of OEM solutions on the brake cylinder front, I am wondering the benefits of adding a single servo to the system - but assume that one has to get the air out of the system before that would be of any benefit at all.

So - any suggestions of where to look or alternate bleeding approaches - is there a simple way to QC the master cylinder without taking it out of the car?

Thanks in anticipation.

Nick

You need to bleed the master cylinder independently first. Plenty on net on how best to do this.

Starting on the furthest brake, is that the rear left (then RR, FR FL)?. Light tapping on the calliper when the nipple is open.
You can also try lightly feathering the pedal?
I don't think the elan brake circuit it that complex that you need pressure or vacuum. Try the old fashioned clear tube.
Do you suspect you have the original master cylinder, was the original a different size than the not assisted?

Thanks.

The master cylinder is not the original one.

I believe that I can bleed the master cylinder independent of the system by just running a line from the cylinder to a jar and see what happens?

I believe that the GRC226 is dimensionally the same as the original., but I believe that the original had dual servos to help it.

Thanks, I will start next with the master cylinder and see what I find
N

I have put thread sealant on the threads of the bleeders in past but I'm not entirely sure that it did much. If you bleed it into clear tubing and you keep seeing bubbles in there it may be that there is something wrong with the master cylinder. A servo will make your pedal even mushier. With a servo you would usually use a larger bore size master to make the pedal higher. Small bore equals more line pressure for a given pedal pressure (good) but more pedal travel(less good) Large bore equals less line pressure for a similar pedal pressure (not so good, gotta press harder) but less pedal travel(good). The servo deal with large bore master gives you both good things with the only bad thing being another piece of equipment to go bad periodically. It gets the line pressure back up without a penalty in pedal travel

PS if the master is n.o.s.and its been around a while its likely bad. I converted my Elan S2 to twin circuit brakes and put a seal kit in the new but old master. The design is not one of Britain's proudest moments..

Billmack wrote:PS if the master is n.o.s.and its been around a while its likely bad. I converted my Elan S2 to twin circuit brakes and put a seal kit in the new but old master. The design is not one of Britain's proudest moments..

At least they had brakes - unlike American cars of the 50's, 60's and 70's!!

before changing parts, you may first try to make sure that you don't have a bubble somewhere in the system (this may be lengthy, esp. if yo need to take out some parts to bleed them at the proper angle) - then you can find out if you indeed have a leak (if internal, you should be able to see the brake fluid coming back to the tank when pressing the pedal).
One thing I've had with a tandem master cylinder rebuilt by a "professionnal" was a hastily pushed in intermediate piston without brake grease, which resulted in an hairlike piece of rubber torn out from the seal, and which travelled to the rear valve, making in effect an intermittent leak. On the same note, I suppose you inspected and cleaned the master cylinder priori to installation, but if not and internal condition is bad, you would see particles coming back from it to the tank, at which point I would take it out for a good clean (and possilby polish, to restore an adequate sealing surface)

good luck !

I'm not really qualified to comment on aspects that may be specific to the Elan but speaking generally on a couple of points:

1. Did you change the brake pads at the same time as bleeding the brakes? If so you won't get an accurate feel of the brakes until the pads have bedded in. New pads will generally result in a "springy" feeling brake pedal until they have correctly bedded in. Also you can't really properly judge the feel of the pedal with the car stationary. You need to take it for a drive.

2. As someone mentioned previously you do need to bleed the brakes at each wheel in the correct sequence. Sometimes you may need to repeat the bleeding sequence again or three times until all the air is eliminated

As usual , most helpful.
I am going to bench bleed the cylinder first and see where we go from there
Thx much

OK, here's a quick dumb question - on a dual circuit master cylinder which circuit serves front and which back?
Is it logical like the outlet closest the front, serves the front brakes and the rear (ie closest to the steering wheel) does the rear brakes?
Master cylinder bled, no bubbles
and it is moving fluid.
Nick

Is it back in the car hooked up? If pedal is still bad look for flexing of components out at the calipers and wonky flex hoses..

Port nearest the pedal is the primary circuit and is connected to the front brakes.

thank you (: