Technical problem with the brakes on the seicento sx

[ccavalles]

Hi, I have a problem with the brakes on the seicento sx. There is no way to bleed it and have the pedal stay hard and not go all the way down. It all came from changing the brake fluid. I did it myself and when bleeding, nothing... pedal to the bottom. I took it to the workshop to see if they could clean it up, but it has been bled several times in the workshop, no bubbles come out... Two new brake master cylinders have been tried and nothing. Taking advantage of it, he has put a complete rear kit of shoes and bowlers due to wear. The tested system has been purging the furthest wheel first and so on until the last.
thanks and regards

 

[bugsymike]

Hi, I have a problem with the brakes on the seicento sx. There is no way to bleed it and have the pedal stay hard and not go all the way down. It all came from changing the brake fluid. I did it myself and when bleeding, nothing... pedal to the bottom. I took it to the workshop to see if they could clean it up, but it has been bled several times in the workshop, no bubbles come out... Two new brake master cylinders have been tried and nothing. Taking advantage of it, he has put a complete rear kit of shoes and bowlers due to wear. The tested system has been purging the furthest wheel first and so on until the last.
thanks and regards

Some cars can be harder to bleed than others , but in fairness I wouldn't have thought it beyond the capabilities of a reasonable competent garage/workshop to find the solution.
I assume it was genuine good quality brake fluid you used first time, the reason I ask is many years ago we had a customer top up his brake fluid reservoir with engine oil, destroying all the hydraulic seals in the system!!!
Sometimes an old master cylinder will fail when bleeding, but unless all your replacement master cylinders were dodgy that shouldn't be the answer.
Using brake pipe clamps, has anyone tried clamping all four rubber brake hoses at the same time to see if you can get a pedal then, to locate fault.
A badly worn front wheel bearing can allow the brake disc to move giving excessive pedal travel, but not as bad as you describe and I would have thought your mechanic would have noticed that.
With the compression spring/friction pad type adjusters that can give a sloppy pedal if cheap brake shoes, but unlikely to give no pedal at all.

 

[ccavalles]

Some cars can be harder to bleed than others , but in fairness I wouldn't have thought it beyond the capabilities of a reasonable competent garage/workshop to find the solution.
I assume it was genuine good quality brake fluid you used first time, the reason I ask is many years ago we had a customer top up his brake fluid reservoir with engine oil, destroying all the hydraulic seals in the system!!!
Sometimes an old master cylinder will fail when bleeding, but unless all your replacement master cylinders were dodgy that shouldn't be the answer.
Using brake pipe clamps, has anyone tried clamping all four rubber brake hoses at the same time to see if you can get a pedal then, to locate fault.
A badly worn front wheel bearing can allow the brake disc to move giving excessive pedal travel, but not as bad as you describe and I would have thought your mechanic would have noticed that.
With the compression spring/friction pad type adjusters that can give a sloppy pedal if cheap brake shoes, but unlikely to give no pedal at all.

Thanks for the reply. It is a car with few km, the mechanic has tried it several times. Asking in a classics forum, I have been told to try gravity purging.
The pipes have been checked and they are ok.
The brake fluid is correct.
As I have already mentioned, everything happened when changing the fluid for a new one. Air entered and once bled the pedal no longer had hardness.

 

[bugsymike]

Thanks for the reply. It is a car with few km, the mechanic has tried it several times. Asking in a classics forum, I have been told to try gravity purging.
The pipes have been checked and they are ok.
The brake fluid is correct.
As I have already mentioned, everything happened when changing the fluid for a new one. Air entered and once bled the pedal no longer had hardness.

Gravity purging is usually only necessary when you have a weak master cylinder and according to your thread you are on your third one including two new ones, also you say the vehicle has been bled several times with no bubbles coming out, so if there is no air in the system that would indicate loss is at the wheels which is why I suggested trying four brake hose clamps to see if that give a good pedal and to track were the problem is located.

 

[ccavalles]

Good morning. A 4 bosch master cylinder has been tested but the car does not brake at all and the pedal continues down. Hoses and others have been reviewed. Nothing is clogged, the wheels brake... We'll try a new brake booster to see what it does. I couldn't be that complicated.

 

[bugsymike]

Sorry it is hard to add any more without being by the car.

 

[ccavalles]

Thank you, nothing happens, one day we will find the error if we change everything and with patience.

 

[ccavalles]

Good morning, time passes and the car is still stopped. Servo empty tube checked. It is not the solution. We need to change the servo, although I don't think the problem is there.

 

[bugsymike]

Generally I would diagnose a faulty master cylinder if.
1\ No loss of fluid.
2\ Brake pedal creeps down.
3\ If brake pedal is pressed hard quickly the pedal feels good, but if you relax pedal pressure slightly then it creeps down. Usually if that is the case and you are watching the fluid in the reservoir it may appear to drop a little and then refill as fluid bypasses faulty pressure seals in master cylinder.
Generally speaking any pedal total loss outside of the master cylinder is accompanied by a large loss of brake fluid.

 

[patobravo]

I've also experienced some troubles doing it after changing the master cylinder, but the solution was to insist. Starting by the rear do it like 20 times each wheel, then move to the front and do the same, than back to the rear. after some hardship it worked and bleeded properly.

Also you may have a problem in the servo pin that goes in the master cylinder. som have an adjustable screw tip and it may be unwind and dont allow your master cylinder to return all the way back to fill with oil. To diagnose this undo the master cylinder bolts about 2 turns and try to bleed that way, even with it a bit loose.

 

[bugsymike]

Also you may have a problem in the servo pin that goes in the master cylinder. som have an adjustable screw tip and it may be unwind and dont allow your master cylinder to return all the way back to fill with oil. To diagnose this undo the master cylinder bolts about 2 turns and try to bleed that way, even with it a bit loose.

The original posting was some time ago, so I trust it has been cured/fixed, but always good to know what the fault was.
Not always, but generally if no free play at the master cylinder when pedal released, it can result in a pedal going solid and the brakes locking on after driving for a few miles, until a brake pipe is slackened to relieve pressure in the system until you get home to fix the issue.
It can even be caused by something simple like a brake pedal switch not fitted correctly or a piece of wiring getting in the way preventing full return of the pedal.

 

[patobravo]

It can even be caused by something simple like a brake pedal switch not fitted correctly or a piece of wiring getting in the way preventing full return of the pedal.

That sounds more likely.

I was suggesting to undo slightly the master cylinder as a troubleshotting. You cannot drive the car like that as the servo wont be air-tigh: 1rst no servo assitance 2nd: and the engine will suck air trough it and run very very lean.

 

[bugsymike]

I was referring to brake master cylinders in general, presumably if the adjuster rod was at the wrong length that would be due to someone replacing the servo unit or master cylinder incorrectly rather than a fault developing.
I suspect the OP was on a learning curve from what was mentioned.

 

[ccavalles]

greetings.
The car is still sitting still after months in the workshop. We put another servo with a pump and no pressure, therefore it is not a problem with the pump (3 units) and two servos tested.
I have told the mechanic to try to bleed the pump (I have seen videos that they do it in different cars) there are no other things to change. I think it is an air problem in the circuit.

Thanks for the advice, I'll pass it on to the mechanic. Now the car doesn't slow down at all. Desperate mechanic, never happened to him.
Greetings and I will add news.

 

[bugsymike]

Is the air in the ABS system if fitted?
Is it possible for your mechanic to make up some blank brake pipe unions to fir to master cylinder to prove / disprove where fault is?
Also by use of flexible hose clamps it may be possible to identify which circuit is the problem.

 

[ccavalles]

Is the air in the ABS system if fitted?
Is it possible for your mechanic to make up some blank brake pipe unions to fir to master cylinder to prove / disprove where fault is?
Also by use of flexible hose clamps it may be possible to identify which circuit is the problem.

the car has no abs. It is a 2001 but without system.
What you say is exactly what I told him to try.

 

[bugsymike]

If he has done everything he can think of to repair your car maybe it is time another mechanic had a look with a fresh set of eyes.

 

[ccavalles]

If he has done everything he can think of to repair your car maybe it is time another mechanic had a look with a fresh set of eyes.

It's been like this for 4 months.
This Saturday I will go to bleed the pump to see if that is the problem.

 

[ccavalles]

Good morning.
Found new fiat linea abarth perforated leather steering wheel. I didn't know it existed. I knew other models online accessories.

 

[purf]

Any luck with the brake system? Sounds very strange? Nice steeeing wheel !