General Disc brakes bleed

[71Fiat500F]

Hi folks. I’ve got a ‘71 500 f
I’ve installed the front discs and braided lines up front from ricambio and also a new single master. I’ve bleed all the lines (starting furthest away and moving towards the master), and get clear, no bubbles fluid. I have no resistance at the pedal, and I’m puzzled. Anyone remedy this issue?
Thanks for your help!

 

[the hobbler]

Hi folks. I’ve got a ‘71 500 f
I’ve installed the front discs and braided lines up front from ricambio and also a new single master. I’ve bleed all the lines (starting furthest away and moving towards the master), and get clear, no bubbles fluid. I have no resistance at the pedal, and I’m puzzled. Anyone remedy this issue?
Thanks for your help!

You will probably find that you have to replace the rear slave cylinders will the smallest available. This is because the calipers take so much more fluid to operate than the old slave cylinders. I had to do this in order to get a good pedal. What 'master-cylinder' have you fitted---is it a standard 500 unit (which will do the job) or a 'servo' version?

 

[71Fiat500F]

You will probably find that you have to replace the rear slave cylinders will the smallest available. This is because the calipers take so much more fluid to operate than the old slave cylinders. I had to do this in order to get a good pedal. What 'master-cylinder' have you fitted---is it a standard 500 unit (which will do the job) or a 'servo' version?

I’ve installed the Miniservo Brake Master Cylinder from Ricambi, which is similar fit to the stock one, but a bit bulkier, and is said to provide 30% more braking power as compared to stock. I did not bench bleed the master, as the service manual I have did not call for it, and all 4 wheels are getting clear fluid With no bubbles…..I just cannot get any sort of pedal feel. It goes straight to the floor without any resistance. I may have to try the slave cylinders replacement, as I am out of ideas.

 

[the hobbler]

I’ve installed the Miniservo Brake Master Cylinder from Ricambi, which is similar fit to the stock one, but a bit bulkier, and is said to provide 30% more braking power as compared to stock. I did not bench bleed the master, as the service manual I have did not call for it, and all 4 wheels are getting clear fluid With no bubbles…..I just cannot get any sort of pedal feel. It goes straight to the floor without any resistance. I may have to try the slave cylinders replacement, as I am out of ideas.

My friend and I bought 4 of these 'mini-servo' master cylinders (from Italy, before they were available in the UK)---every one had to be attended to! Initally we had a LOT of problems with them and no response fro the suppliers in Italy OR the manufacturer. My friend checked them all out (2 were siezed--from new!) and I think that he rebuilt them with a set of Volvo seals; I will try and find out what he did to them to make them work. Since the modification, we have had no problems at all, but I would still reccomend that you fit the smallest (5/8 in) rear wheel cylinders. If you get no joy with the 'servo' master cylinder, the standard 500 master cylinder will do the job.

 

[Goldnrust]

Have you tried 'bench' bleeding the new master cylinder?

In some designs pushing the pedal does not cover all of the available stroke of the master cylinder, so when bleeding a new master from dry you can end up with a trapped air bubble that cannot be bled out, causing the sort of soft pedal issues you have.

By taking the master cylinder out and filling it up off the car you might find that you can push the plunger through it's full stroke and possibly expel that last trapped air bubble. It's a bit of a messy job though!

 

[the hobbler]

Have you tried 'bench' bleeding the new master cylinder?

In some designs pushing the pedal does not cover all of the available stroke of the master cylinder, so when bleeding a new master from dry you can end up with a trapped air bubble that cannot be bled out, causing the sort of soft pedal issues you have.

By taking the master cylinder out and filling it up off the car you might find that you can push the plunger through it's full stroke and possibly expel that last trapped air bubble. It's a bit of a messy job though!

I have contacted my friend to try and find out how he resolved the problem of the non-operating "Servo" master-cylinders. Another thought; how are working the brake-light switch? On the m/cylinders that we had, we had a big problem finding a brake-light switch to fit on the end of the m/cyl. I managed to (so far, very succesfully) modify my brake-pedal but my friend, purely by chance, found that a (I think) Peugeot brake-light switch fitted on the end of the m/cyl. If you would like to contact me direct ([email protected]) I can send you some photoe of how I adapted my brake pedal.

 

[71Fiat500F]

My friend and I bought 4 of these 'mini-servo' master cylinders (from Italy, before they were available in the UK)---every one had to be attended to! Initally we had a LOT of problems with them and no response fro the suppliers in Italy OR the manufacturer. My friend checked them all out (2 were siezed--from new!) and I think that he rebuilt them with a set of Volvo seals; I will try and find out what he did to them to make them work. Since the modification, we have had no problems at all, but I would still reccomend that you fit the smallest (5/8 in) rear wheel cylinders. If you get no joy with the 'servo' master cylinder, the standard 500 master cylinder will do the job.

Ah. Thanks for the reply! I’m going to take that master off and reinstall the stock one, and see what I get. My fingers are crossed! I will prob upgrade to a dual phase master eventually.

 

[71Fiat500F]

Have you tried 'bench' bleeding the new master cylinder?

In some designs pushing the pedal does not cover all of the available stroke of the master cylinder, so when bleeding a new master from dry you can end up with a trapped air bubble that cannot be bled out, causing the sort of soft pedal issues you have.

By taking the master cylinder out and filling it up off the car you might find that you can push the plunger through it's full stroke and possibly expel that last trapped air bubble. It's a bit of a messy job though!

Will give it a go!

 

[the hobbler]

Will give it a go!

If you revert to a 'standard' master cylinder, you will DEFINITELY require the 5/8 rear wheel cylinders (early '594' Mk 1 126)--otherwise you will get a very 'long' brake pedal, because as I said, the calipers use more fluid to operate than the original wheel-cylinders.
When (and if) you decide to fit a 'dual-circuit' master cylinder you will find that they are normally too long to fit within the bodywork. Most systems get round this problem by mounting the master-cylinder on a right-angle bracket--the system is expensive. However, there is a sneaky way of fitting a 'dual circuit' master cylinder WITHOUT using that system. Contact me direct (e-mail address on previous message) I will tell you how to do it

 

[71Fiat500F]

Ok guys, I swapped out the miniservo to the stock master and bled with vacuum hand pump. Was not getting much at the pedal still UNTIL it dawned on me to go take a peak at the brake pedal. To my embarrassment I found that the rod from the pedal to the master had slipped down and been not even been pushing the master. I adjusted it back and viola! I now have a nice solid pedal feel. Thanks again for all the responses. I think the miniservo is defective because I could not get it to bench bleed even.
I’ll use the stock MC for now, and eventually convert it to a dual stage.

 

[the hobbler]

Ok guys, I swapped out the miniservo to the stock master and bled with vacuum hand pump. Was not getting much at the pedal still UNTIL it dawned on me to go take a peak at the brake pedal. To my embarrassment I found that the rod from the pedal to the master had slipped down and been not even been pushing the master. I adjusted it back and viola! I now have a nice solid pedal feel. Thanks again for all the responses. I think the miniservo is defective because I could not get it to bench bleed even.
I’ll use the stock MC for now, and eventually convert it to a dual stage.

Got the answer from my friend that I promised you. It would seem that these "servo" master cylinders suffer from irregular construction in that the bore diameter can fluctuate from what it should be---both 'tight' and 'loose'! He was able to repair mine, and his, by fitting the seals from a "Volvo Repair Seal Kit 200 Series". For what a m/cyl repair kit costs, it might be buying a kit and trying to make it work, but sadly, no guarentee.

 

[71Fiat500F]

Got the answer from my friend that I promised you. It would seem that these "servo" master cylinders suffer from irregular construction in that the bore diameter can fluctuate from what it should be---both 'tight' and 'loose'! He was able to repair mine, and his, by fitting the seals from a "Volvo Repair Seal Kit 200 Series". For what a m/cyl repair kit costs, it might be buying a kit and trying to make it work, but sadly, no guarentee.

Great! I’m going to contact ricambio and see if they’ll take it back, and if not, I will give this a go! Thanks!