14 replies to this topic

[rocoloco]

Hey there,

So I was working on my front rubber cones on my Innocenti Mini Cooper 1300 Export with Cooper S type brake servo and front discs, and when I finally managed to finish the job and I went for a short test drive on my block, the brakes had almost no stopping power and pedal is still very easy to compress, it builds no pressure.

Did I mess up something while Working on my front suspension? I was moving the servo a bit in order to gain access to top arm axle screws and nuts... And the car Was on front stands for about 3 weeks. Before that the brakes were fine.

I don't know where to start, and new brake servo is quite costly. I've also read that when servo fails brak pedal becomes stiff?

Thanks for any info.

Greetings from Slovenia.

[Ethel]

Is it single or dual circuit? Has the fluid level dropped?

[rocoloco]

Fluid level is very very low yes, but I don't know how it was before that.

I think it is dual circuit. I've attached a diagram for my car.

Cheers

Attached Files

•  Screenshot_20230521_105145_Samsung Notes.jpg   45.95K   3 downloads

Edited by rocoloco, 21 May 2023 - 08:54 AM.

[Ethel]

Look for a leak. Rear wheel cylinders are most common, but also the master cylinder from above the brake pedal. Though anywhere is possible if pipes or hoses are damaged. It's also possible the pads & shoes are just heavily worn allowing the master to pump air, especially if the car was at an angle.

[Lplus]

Hmm, dual circuit with servo on one side only - I didn't think that set up existed outside of diy modificattions.

 

Have you tried bleeding the brake system at all?  Since the fluid is now low, and presuming there's no puddles under or inside the car it does suggest a leak into the servo.

Edited by Lplus, 21 May 2023 - 09:48 AM.

[Ethel]

It is the original Innocenti set up - the servo is on the front of a front/rear split.

 

Yes, a leak in to servo is a definate possibility - other leaks will be easier to spot though.

[rocoloco]

Ok, I will search for a leak.

So it can leak to the inside of the car? Where exactly?

Cheers

[viz139]

If the brakes worked fine before this job it is unlikly to be an internal leak in the servo. You jacked up the car to work on suspension so have you damaged a brake pipe under the car?  You moved the servo so have you damaged a pipe there?  Fill the reservoir with fluid and have somebody press the pedal while you check to see where the fluid is coming out. 

[MatthewsDad]

You say you moved the servo around and that the brakes were working well before you started working on the suspension. I'd check all the brake line connections in that area.

I had a problem in the past (MG not a mini) where air was getting into a brake line connector without any fluid escaping. it took ages to trace the problem. Sorted by nipping up a bit. Perhaps you have slightly dislodged a connector?

[slidehammer]

In my opinion you need to take a good look at all the things you either disturbed or might have damaged whilst working on the cones, so any pipe work near them. Have a look up under the pedals the car to see if you can see any sign of brake fluid which would indicate a faulty master cylinder. My guess is you damaged something like a pipe whilst getting the cones in and out. 

[rocoloco]

Thanks everyone, will be tackling it with all of yours suggestions. Awesome forum!

I jacked the car up on the front subframe rails on each side, I am always careful... And I was moving the servo just a bit, did not force it too much. Really weird. Will see.

Edit: I've topped up the fluid and checked for leaks while someone else pumping the brakes, no leaks anywhere. Maybe it should be done with engine running? 🤔 Also fluid level stayed the same, full.

Next up bleeding the brakes.

Edited by rocoloco, 21 May 2023 - 06:16 PM.

[rocoloco]

it was air in the master cylinder. bleeding the brakes at the wheels did nothing, there was no air.

probably because the brake fluid reservoir was very low on fluid, the air got inside while the car was on front jackstands for few weeks. idk 🤔

[MatthewsDad]

Good to know you got it sorted.

[rocoloco]

Good to know you got it sorted.

Thanks!

[rolf]

it was air in the master cylinder. bleeding the brakes at the wheels did nothing, there was no air.

probably because the brake fluid reservoir was very low on fluid, the air got inside while the car was on front jackstands for few weeks. idk

Hello, it seems that I hae the same problem. I tried twice to bleed the brakes at the wheels with no result.
How do we take out the air from the master cylinder?

Edited by rolf, 25 June 2023 - 08:15 PM.