International Lancia Forums

Hello everyone,
I am also rebuilding my master pump (18mm also), in fact I did it twice, just this week end,
i tought i could go out with the car at least, it will be for another day (month ?)
my problem, for you specialists :
I dismantle the master cylinder, take out all the seals to reimplace them (with a akron repair kit if you want to know the details), after a good cleaning, control and greasing (I didn't knew about the finishing paste Paul talked about, but anyway there was no marke inside the cylinder)
I remount the whole cylinder,
empty, it will move with reasonable strengh (i mean with the hands, and not the foot pedal), due to the new seals i supposed, and the grease, and it will come back somehow slowly (strange i thought)
the problem is when charged with lookheed : pushed with the same effort by hand, but nearly stucked in this position (it will come back very slowly, wich gives a system impossible to use like that.
I mounted the system like that on the car, to try a bleeding and see what could occur : nothing, for sure (!) stays the same in the pushed position,comes back too slowly (except with compressed air pushed in the rear left brake caliper to give a little pressure in the circuit)

Are my "new" (I suspect not so new, i won't tell you where do they come from !!) seals reacting badly with the lookheed ?
did I made a mistake in the position of the seals, or the small aluminium washers (are they similar front and rear piston ?) i could have missed a detail, even helped by the precious technical doc (thanks to the CD again)
Can you help again ?
Thank you all for your help and advices,
Thibaut

I forgot a point for Paul : the trick with the wine cork made me laugh a moment (well, it is a professional concern for me, I am in the wine production...), then let me curious : how did you managed to give pressure by this way avoiding a shower of lookheed in your beautifull engine compartment ? I would like to have details (if possible a picture ?)
well, some shops have for sale the pressure (tyre pressure) system bleeding, with cap adaptors for some master cylinder pumps, but when i see the kind of adaptators cap (thin aluminium material, which means with a thread, useless on our pumps) provided, i am not very keen to try (well, you all understood i am now somehaw maniac not to spread a single drop of lookheed on my brand new paint around !!)

You are quite right to be concerned. I tried the system years ago and had brake fluid all over the place.

I was wondering what wine Paul is drinking as I think the average cork is too small for the opening. Or is it?

This operation was carried out in France; a very good place for corks it has to be admitted. The car was a Fanalone that was having a transfusion of higher-grade brake fluid.

I was stumped, but my friend Gianmarco carved the cork with his penknife; we may have sealed it with a little polythene cut from a carrier bag, but I am not sure that we did.

Paul

That's quite a tricky one.

First, are you certain that you put back the springs in their correct places?

I think that I had this problem once; I dismantled the cylinder, cleanit all carefully, lubricated it with fresh fluid, re-assembled and it worked. In fact on the road, you would probably find that the slight pressure on the pads may be sufficient cause the master cylinder pistons to retract.

Paul

hello all,
concerning my master pump : i spent a while trying to understand, with your precious advices (I had a good time learning your friends fanalone used good wine as braking fluid, i have some doubt if I would do the same on mine, even if i have all the amount of wine i would need...!)

I had the same conclusion you had on the last message : a residual pressure would lead to push the pistons, the reason why i tryied to mount and fill the whole system. I noticed that in the vice (yes, with the soft jaws !), i pushed the pistons, with the figers on the outlets, they wont come back. when i take out my fingers, the pistons will come back right, sucking air (instead of lookheed), wich make me think it would work properly all mounted on the car
the result : not so good ! well, after a good \"traditional\" bleeding, good pedal feeling, but pistons not going back (just for some last millimeters...)

i have a last doubt : am i right about the disposition of the seals. It is nearly impossible to explain by writting, in my bad english specially, but let\'s try : i undestood (with the photo on the CDrom) that all the seals must be mounted with their lips directed at the front, in order for them to \"enlarge\" and push the fluid in front, in the circuit when pressure is applyed. Am i right ? in fact i have a doubt on the small seal of the front piston (it would be the third one starting from the pedal) : is it also mounted with \"lips\" at the front, or would it be mounted at the rear, I can\'t see it very well on the drawings of the cd rom.


well, i don\'t discourage at all, i just need some more time and your confirmation i am on the good way.
By the way, is there a way i could find a reimplacement for the aluminium washer wich is behind the pressure contacter (front of the master pump), mine is worn and the pump leakes...

Thibaut

If you promise not to drink brake fluid, I will allow you not to use wine in your brakes.

You are right in being supsicous about the small seal on the front piston which is the piston for the rear brakes. It is all a bit confusing.

It must be mounted in reverse, that is, the lips must open to the rear. Remember that between the two seals on the piston there is no pressure. It is the compensation chamber. In fact there is a small hole between that compensation chamber and the fluid container. That small seal is taking pressure from the first piston.

Some versions have an O ring there. Some versions a seal. In the overhaul kit there are both the O ring and the seal. One of them won't fit, so you use the other.

Best would probably be to have an O ring as well as a seal, but there is no room to machine another groove.