Hi, I'm having some trouble with the brakes on a H reg 1.0 uno, The problem being; sometimes when you brake, the pedal goes straight to the floor and only slows the car marginally if at all. It has had new cylinders on the front and rear, new hoses and pipes all round, has been on a pressure tester overnight, and is not leaking any fluid whatsoever. The problem is sporadic as the car can go for weeks without any failure and when it does play up, pumping the pedal does the trick and the brakes work. Also I think the car has had a new master cylinder, although it may have been second hand.

Welcome to FiatForum

Sounds like you need to bleed the whole brake system to me. May be worth changing the fluid at this point if its very old

welcome, another uno owner :woot: make sure you add your self to thread on how many unos on the road, if you havent already

sounds like air to me aswell

Welcome to the forum

Empty ALL brake fluid and refill with NEW - not drops from several leftovers. Might be air in the system, or water bindings in the brake fluid. It is hygroscopic and binds itself to standard H2O...

Morten.

Thanks guys, but complete system has already been pressure bled, so I'm pretty sure its airless. It's had new fluid too when the pipes were all replaced, along with new discs and pads.

recheck master cylinder,check rear brake compensator,and rear brake shoes maybe they r not holding their adjustment.
good luck

yes, I think it's the master cylinder as well. New seals ('cups') may have been fitted the wrong way around, or I think there is a piston that, if fitted the wrong way around, prevents the correct amount of fluid from being drawn in.

Replace the master cylinder complete if you can, otherwise rebuild with reference to a Haynes manual diagram or similar.

I believe that if the rear shoes are losing their adjustment (fairly common problem that will give this symptom as anton says) you will also have a slack handbrake lever. Perhaps test the handbrake a few times and count the clicks - should be four or five maximum. (EDIT: someone will no doubt point out that the handbrake should only have 3-4 clicks - on the Uno, this will simply make the lever harder to pull up I've found 4-5 works best.)

-Alex

I had a similar problem, where sometimes my brake pedal would need a couple of pushes to go hard, others where it was fine, and others where it almost went down to the floor.

It turned out to be a sticking caliper. What was happening was that both the caliper piston and also one brake pad were sticking, and not retracting fully when the brake pedal was released. When the pad got stuck, it meant that the piston retracted too far, so that at the next push of the brake pedal there wasn't enough travel to take up the space between piston and pad, hence the pedal going down to the floor.

Worth checking that the caliper sliding surfaces and 'wedges' are clean and lightly greased with copper grease. Also make sure that the area in the caliper where the pads move in and out are also clean and free of dirt or corrosion that can cause the pad to catch.

Other than that I agree you should try re-bleeding the brakes. If you still have no joy then it's most probably a master cylinder problem.