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[gritsop]

Hi all,

I just wanted to share with you my problem with the 33 brakes. It is almost 1.5 years that the 33 pulls to the left under braking. The pull is evident when braking from high speed (> 100km/h) and it is easy for the vehicle to change lane. In my attempt to solve the problem and eliminate issues like worn suspension bushes and incorrect alignment I put the vehicle in rolling road test and the results are the following:

Left front wheel: 3000 N
Right front wheel: 2500 N
Rear wheels: 1300N

These figures are right before the wheels lock up.

Troubleshooting this issue I have done the following:

Replaced calipers a couple of weeks ago with rebuilt vented ones including new seals, hoses, discs and pads with no results.
Replaced almost a year agao the rear cylinders including new hoses with no results.
Replaced a few days before the master cylinder with a new one again with no results.

I had a brake expert shop look into the issue and instead of giving a solution, it made the problem worse by making this mess.


He eliminated the X braking design and separeted the master cylinder chambers so that each one acts either front or rear. Of course this didnt make any difference but only in creating this mess.

Here is my attempt to restore the pipes in their original position


I have the last resort to replace the bias valve (there is nothing else left anyway) as I have the suspicion that since the right front caliper is connected with the rear bias valve through the T shaped union, brake fluid returns to the master cylinder in case of an internal leak of the bias valve.
Is this possible to happen when the bias valve gives up the ghost? although it gives perfect braking results, it may have an internal leak so that brake fluid returns to the master cylinder.

I should also add that manometers were fitted to the calipers and the left front gave 50 psi and the right front gave again 50 psi but in a decreasing manner as seconds passed.
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop

[RFlower]

My first thought is that if it takes less braking force to lock one wheel than for the other, then the tyre on that side has less adhesion.

I suggest swapping over the front wheels, and see if that makes a difference, before messing with the brake plumbing any more.

Regards, Dick.

Edit: I assume you have the same brand, age, wear, and pressures for both front tyres.
_________________
Dick Flower, Nr. Carcassonne. '94 Trofeo 1.4 ie (F), '93 Imola 1.3/1.4 ie (now for breaking) (F), '91 1.7 ie (GB)(spare car), '86 Sprint 1.5 QV (F). '87 VW Syncro camper (F), '73 NSU Ro80 (F), '99 Fiat Seicento (F)

[gritsop]

Hi Dick,

Just swapped over the front tyres and still the car pulls to the left.

The tyres were replaced all four around at October 2006 and they have around 20.000 kms. Yes, same pressure, same brand (Michelin Energy) and wear.

Any ideas?

Regards,
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop

[lee16v]

Hi Than,
Is it possible there is some dirt/rust in the brake lines? I only say as I did some work on my friends Morris Minor due to uneven braking and the fault was quite alot of deposits in the lines.

[ZeNiTh-PbArM]

hi, looks like the only items you haven't changed are the brake lines and the rear brake bias valve.
the loss of braking force is probably caused by a pressure drop, and likely culprits are :
- clogged brake lines : possible, look for a bent pipe somewhere and blow compressed air to make sure everything works well
- faulty rear brake bias valve : might have an internal leak, be somehow stuck, i've never heard yet of a failure that would cause your symptoms but i've replaced dozens of them on 33s and i know for sure that this device is the source of a lot of trouble.
in you case, diagnosis might be more expensive than replacement, but i sure would have tried to swap rear circuits using two flexible brake hoses, at the master cylinder outlets and at the rear flex hoses. Would have known for sure if the rear was involved in your problem.
This sould have been done by the shop instead of messing with your brake lines.
regards,
zp

[gritsop]

Hi ZP,

You are right. So far the troublshooting has cost me more more than 350 € with no result so far.

My plan is to go to my trusted mechanic who has a rolling road test machine and advise him to remove the input lines of the bias valve and create a bypass before the valve. This way I want to eliminate the bias valve during braking and see if i get the same figures on the front wheels.
I also plan to blow compressed air in the pipes using a small foot pump and not using air compressor so that I dont destroy anything.

Needless to say that the brakes are fanstastic in the feel and are far reliable compared to the solid ones. The pulling is the fact that has pissed me off and I really need to sort it out as MOT time is just around the corner.

Thanks to all so far,
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop

[RFlower]

Hi Thanassis,

If you disconnect the two lines to the rear brakes, at the master cylinder and the tee on the RH front brake line, and close the holes with blank screw plugs, you could make a quick road test with front brakes only, eliminating any effects from the rear system.

Incidentally, you said you tested the lines with 50psi and found a drop in pressure on one side. As brake fluid working pressures are in the region of 1500 to 2000psi, 50psi is not a valid test pressure. If you found a pressure drop at only 50 psi you must have a leak somewhere.

Regards Dick
_________________
Dick Flower, Nr. Carcassonne. '94 Trofeo 1.4 ie (F), '93 Imola 1.3/1.4 ie (now for breaking) (F), '91 1.7 ie (GB)(spare car), '86 Sprint 1.5 QV (F). '87 VW Syncro camper (F), '73 NSU Ro80 (F), '99 Fiat Seicento (F)

[gritsop]

Hi Dick,

I guess I was wrong as far as the scaling of the guages was about. The figures were in Bar and not psi.

Here is a pic of the guages used to test the calipers.



The right caliper was reaching 50 bar - as the left did - but in a declining manner as seconds were passing.

Regards,
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop

[paulhide]

What figures did you get for camber and castor values?
_________________
Owner's Club 33 Registrar. Now from P4 & S2 1.7 QV
http://www.alfa-pages.co.uk/viewtopic.php?t=5188

[gritsop]

Hi,

No interelation between the braking and the alignment.

The vehicle is aligned within specs and the braking force test is done on rolling road meaning that the car is stationary.

The photo of the guages was actually a test to see the pressure built on the calipers. The gauges were mounted to the bleeder nipples and the figures indicated a drop in the pressure at the right front wheel.

Regards,
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop

[ZeNiTh-PbArM]

hi,
with pressure gauges the job gets easier! the gradual pressure drop means something is givin up in the circuits.
possible cause are 1: an element expands under pressure, creating additionnal circuit volume hence pressure drop, and 2: the pressure drop is due to an external or internal leak
for cause 1 culprits are :
- flex brake line : it can "inflate" like a balloon under pressure -> i understand they have all been replaced
- rear brake bias valve, might block or not rear circuit
for cause number 2 :
- external leak : is suppose no amount of fluid drops under the car?
- internal leak : might occur only between high pressure and lower pressure, so culprits might be master cylinder (are you sure it's been replaced?) and rear bias valve
master cylinder : leak between high pressure and the fluid tank
bias pressure : suppose the valve is stuck in the "closed" position and one seal leaks, a leak will develop between front circuit and rear circuit.

regards,
zp

[gritsop]

Hi all,

I just had the bias valve replaced with a new on under BOSCH brand name.



Hooked up all the brake pipes, adjusted the valve with 12.2 kg load but still the car pulls to the left

I then got advice from a mechanic specialising in racing cars who strongly suggests that I should now pay attention on the brake line of the front right wheel; it is likely that dirt/deposits inside the line are blocking proper fluid flow.

So my plan is to remove the respective pipe from the master cylinder and blow compressed air all the way till the flex hose.

I ll keep you posted with the progress within the next days.

Regards,
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop

[gritsop]

Hi all

Solved, solved, solved. Removed the T union and blew compressed air through the pipes; my compressor can build up to 8 bar pressure so I am sure it works fine.

I bought a new pipe for the right front wheel but discovered that the steering rack needs to be dropped so that the pipe can be removed

So back on the first thought to blow air through the pipe. I put a clean rag on the end of the pipe and it showed black stains on it after compressed air was applied. There were no particles but for sure the black stains were many for both pipes.

Did a bleeding all around and now the car stops in a straight manner!

I am now glad that the car stops as it is supposed to and the braking system is virtually new as only the metal pipes are left unchanged

Regards and thank you all for your support.
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop

[BigAl]

sweeeeeettttt
_________________
x2 33 16v
pictures http://www.alfa-pages.co.uk/viewtopic.php?t=5203