Technical Back brakes - valves -99 punto

[roundeyefat]

hi folks,

Hopefully someone can help.
I'm trying to pass a Nct (mot equivalent).
99 Punto, 1.2 petrol, old model.

Rear brakes not strong enough, on one side.
New shoes fitted last december - already bedded-in by now.
Cylinder must be okay - not leaking and pistons will move side to side freely.
Drums are fine, and even interchanged with opposite side, in case.
Adjusters seem fine, and adjusted.
Handbrake is holding to test limits.
By pressing the footbrake, one can turn the "bad" wheel, by hand, and with effort; not so for the "good side".

An experienced mechanic (not fiat specific, though), can find nothing wrong. I can't find anything wrong either, but am a mere mech. fitter (experienced in general hydraulic systems.
"we" wonder, if there is a pressure splitter or equaliser or whatever, in action.
On the rear axle, each side, there is a steel connector for the steel pipes as they wind across the car. This connector, to me, is hardly an "equaliser" as such, and just has a pipe in and pipe out. It does seem a little on the large side, physically, to be a simple steel pipe connector -

is this some sort of check valve or could it effect the system at all?
If this is a simple connector, is there any other valve along the system which might direct pressure more to one side, than the other?
Anyone got any ideas?

Thanks.

 

[s and b]

i would suspect a collapsed brake hose internally especially at this age

 

[roundeyefat]

Hi s and b,

Thanks, but could a collapsed pipe, reduce pressure?
and how
The brakes physically move when the pedal is pressed.

 

[s and b]

think about it if its collapsed it might only allow a trickle through
easiest way is to see if the cylinder bleeds easy
if it doesnt then try bleeding from the pipe before the hose by opening up the union

 

[roundeyefat]

Yes, it bleeds at the cylinder.
We bled it again this morning, to be sure there is no air either.

One test was last night, another this afternoon.

Unless there is a valve seperating left from right, we are confused.
Is there a valve anywhere?

And thanks, by the way. Everything is on the table.

 

[roundeyefat]

You see, there is another variable which doesn't make sense;

Both left and right hand side, brake shoes were changed together, last christmas. They came as a pair, assuming friction material to be equal.
The car passed the test for brakes, last march (but failed on other issues) - suggesting that they were bedded in sufficiently, and that the usual other stuff was okay.

Now though, you can notice that the good side is wearing more than the bad side - as if, its not getting enough clamping force???

These brakes have be adjusted to the upper maximum limit, successfully. On the tight side, maybe with regard to fuel eff..

 

[Ziggy122]

There is going to be 1 of a few things

As S&B said, there is probably a collapsed pipe, or a flexi pipe thats expanding reducing cylinder pressure

There Master cylinder (as the mk2 is very much alike the mk1) is failing? and as a result causing this issue

A blocked pipe, somehow something has been allowed to enter/ and therefore isn't allowing the correct function

Also with the drums off - can you easily see the shoes moving when the footbrake is pressed?
It could be a seized cylinder..... which can happen

Ziggy

 

[roundeyefat]

Hi Ziggy,

I like your expanding pipe theory.

The pistons, both, are free. We checked with the drum off.
I'm having difficulty with a blocked or partially blocked pipe - the oil go through a hole, probably less than 0.1mms - there would be oil both sides of the blockage and the volume wouldn't matter so much where there wouldn't be a time restriction.

She bleeds at the cylinder just fine.

Master Cylinder - don't know much about this only that she has four lines out. Is it conceivable that the pressure wouldn't go down one line with sufficient pressure?

Perhaps, I should think about lining up a pressure gauge, and checking left and right hand sides, for comparison. Anyone know offhand, what thread goes into the cylinder, or have a photo as well, so I know what to make? I'd have to make sure I can bleed whatever setup - messy, if theres no need though.

 

[s and b]

with drum off hold shoes with 2 screwdrivers and get a mate to push foot pedal,he should be able to move your scredrivers as he pushes brake pedal down tell him to go carefully so he dont pop the cylinders out
this will rule out blockages
im not aware of restricting valves in the rear lines but then ive never had to change front to back pipes on a mk2 punto either so it might be worth considering

 

[dave]

there is a BRAKE COMPENSATOR on each side of a mk1
http://eper.fiatforum.com/eper/navi...=3&WINDOW_ID=1&SGRP_COD=2&SGS_COD=1&DRW_NUM=3

 

[roundeyefat]

@ s and d;
We did a visual only, and the shoes moved. As above, the brakes work but not with enough force (seemingly) - they bleed, pistons move and can be seen to move.
My buddy tries to turn the wheel on, and could with force, turn the "bad" side . No budge with the good side

@ dave;
We couldn't see the compensators (6 and 7) yesterday. They don't appear to be directly in the circuit, per the diagram. Where would you say they are positioned?

 

[roundeyefat]

@ dave,

I took out what looks like a union, but is a valve. It doesn't look the BRAKE COMPENSATORS in the link, and looks exactly like an oversized union. To look at either end, it looks likes a 2mm hole thought it. Looking closer, you can see that one end is crimped; explaining how the valve was assembled.
To clarify for anyone else;
One pipe in
One pipe out
Looks like a union/connector for a steel pipe.
99 punto, 1.2, fixed beam back axle.
This is not what some call a proportional valve- it is not physically linked to anything which might detect the load on the back of the car.
Its not a non-return valve, in the strictest of senses.
There is a valve.

SOLVED

 

[roundeyefat]

To clarify further, this valve is on the steel pipe line, fixed to the round pipe/axle, and before the flexible pipe to the wheels - one for each side; left and right.

 

[roundeyefat]

Re: Back brakes - valves -99 punto - bosch 2530 3308b

For the benefit of anyone else:

This valve, one of two, is marked as a 2530 3308b

Bosch agents don't stock these, and in this case, they are made for Fiat only - and must be bought from a main Dealer.

Cost over 70 euros, and clearly a rip-off.

There is nothing in google or yahoo for this part number, surprisingly. So, there soon will be.

But one does have a choice, you know. I'll bet that if both valves are removed, then there will be no imbalance, and the staff at the test centre will hardly know that they are missing - use ordinary unions (note, I'm not suggesting that anyone else should do this, just thinking aloud).

When I get the new one, I'll dissect the old one, and report the physical contents of this valve.
I presume that its purpose, is to direct the majority of the pressure to the front, by closing (or partially closing) pressure access to the back brakes - as if the back brakes would lock anyway.

You could get "caught out" though, by changing (and dissecting) the wrong valve. One must not presume that the wheel with the poor kilonewton returned rating, is the side with the non-functioning valve. It could be the other way around.

You'd either have to know what the required torque is, or test it with the tool that I've proposed at https://www.fiatforum.com/tech-talk/306076-testing-brakes-before-test.html

 

[flisko]

hi folks,

Hopefully someone can help.
I'm trying to pass a Nct (mot equivalent).
99 Punto, 1.2 petrol, old model.

Rear brakes not strong enough, on one side.
New shoes fitted last december - already bedded-in by now.
Cylinder must be okay - not leaking and pistons will move side to side freely.
Drums are fine, and even interchanged with opposite side, in case.
Adjusters seem fine, and adjusted.
Handbrake is holding to test limits.
By pressing the footbrake, one can turn the "bad" wheel, by hand, and with effort; not so for the "good side".

An experienced mechanic (not fiat specific, though), can find nothing wrong. I can't find anything wrong either, but am a mere mech. fitter (experienced in general hydraulic systems.
"we" wonder, if there is a pressure splitter or equaliser or whatever, in action.
On the rear axle, each side, there is a steel connector for the steel pipes as they wind across the car. This connector, to me, is hardly an "equaliser" as such, and just has a pipe in and pipe out. It does seem a little on the large side, physically, to be a simple steel pipe connector -

is this some sort of check valve or could it effect the system at all?
If this is a simple connector, is there any other valve along the system which might direct pressure more to one side, than the other?
Anyone got any ideas?

Thanks.

so u had a faulty brake compensator on the bad wheel side or the other one?

 

[fingers99]

Give Big Mick a ring at eurocarcare.net or try the Poles at unto.pl. Either will be a lot cheaper than FIAT. Mention the forum and you may even get a discount!

 

[blu73]

eurocarcare have official forum discount now - have a look in members offers section for how to get your discount

 

[fingers99]

Awesome