SimpleIsBest
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- Apr 5, 2020
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Hi guys, having some issues with my 126 with brakes. This post ended up being quite long, but the main symptoms right now and questions are listed at the end if you don't want to read through what I've done to lead up to this.
First a bit of background, it's a 1981 Fiat 126 Personal 4 (air-cooled 650cc with the plastic bumpers). There's no Polish badges "officially" on it, but from the number of parts with Polish markings on them I think it's probably a Polish made car sold as a Fiat. I also have a Haynes workshop manual for a Fiat 126 1973-1977, which I thought could cover most of my car but have since discovered a lot of small but important differences.
A while ago I decided to have an inspection of the whole braking system since the car had been sitting for a while before I bought it. There were a couple of stages of what happened, which I'll list below:
Stage 1:
Brake cylinders on the fronts were found to be a bit stuck. I decided to order a whole set of fronts and rears since they seemed to be cheap enough. These ended up coming in as 23.7mm front and 19mm rear diameters. I had them fitted and they worked fine, although I found the brake pedal now had a bit of play at the top. Figured that maybe one of the seals on the master cylinder was going bad (original Fiat stamped part), so ordered and fitted a new one, with no difference.
Stage 2:
Decided it was probably the shoes going out of adjustment. The Haynes manual mentioned that to adjust them one had to reverse and brake suddenly. I tried this but no luck. Tried to squeeze the self-adjustment mechanism spring with a big vice but no luck. Eventually bought a new set of shoes, along with brake springs to refresh the whole system.
Stage 3:
Replaced the shoes and springs. Before this point the braking system seemed to be working with just a bit of play at the top, but after doing this I found that there was no pressure at all within the system, even at the rears which were untouched. Decided that the "new" MC was rubbish and binned it, tried the original Fiat item to find it was leaking through the rear seal into car. Ordered a Akron one which I had heard good things about
Stage 4: Replaced the MC with the Akron unit, rear brakes work great but fronts lack pressure. This is where I currently stand
So right now, the symptoms are:
I went through a measured a bunch of things and found the following weird things:
Cylinder diameter mismatch - the manual states 23.7mm fronts and 15.9mm rears, the ones supplied by the shop are 23.7mm fronts and 19mm rears, the original ones on the car are 19mm all round (???) From what I can tell, the MC size remained identical through the course of production, so would a standard 19mm MC be able to pump enough fluid for all these different combinations?
Brake drum dimensions - manual states 170mm or so, one of the front drums has a stamping that states min diameter of 186mm or so, I measured about 184mm internal diameter with a ruler
I honestly feel lost with a bunch of ideas with regards to what to try next. Does anyone have any advice or clarifications with what I've found so far or what I should do next? I'm at a stage where I feel like I should just buy a full set of shoes, springs, and cylinders again from a more reputable shop and replace everything with the hope that it works out in the end.
First a bit of background, it's a 1981 Fiat 126 Personal 4 (air-cooled 650cc with the plastic bumpers). There's no Polish badges "officially" on it, but from the number of parts with Polish markings on them I think it's probably a Polish made car sold as a Fiat. I also have a Haynes workshop manual for a Fiat 126 1973-1977, which I thought could cover most of my car but have since discovered a lot of small but important differences.
A while ago I decided to have an inspection of the whole braking system since the car had been sitting for a while before I bought it. There were a couple of stages of what happened, which I'll list below:
Stage 1:
Brake cylinders on the fronts were found to be a bit stuck. I decided to order a whole set of fronts and rears since they seemed to be cheap enough. These ended up coming in as 23.7mm front and 19mm rear diameters. I had them fitted and they worked fine, although I found the brake pedal now had a bit of play at the top. Figured that maybe one of the seals on the master cylinder was going bad (original Fiat stamped part), so ordered and fitted a new one, with no difference.
Stage 2:
Decided it was probably the shoes going out of adjustment. The Haynes manual mentioned that to adjust them one had to reverse and brake suddenly. I tried this but no luck. Tried to squeeze the self-adjustment mechanism spring with a big vice but no luck. Eventually bought a new set of shoes, along with brake springs to refresh the whole system.
Stage 3:
Replaced the shoes and springs. Before this point the braking system seemed to be working with just a bit of play at the top, but after doing this I found that there was no pressure at all within the system, even at the rears which were untouched. Decided that the "new" MC was rubbish and binned it, tried the original Fiat item to find it was leaking through the rear seal into car. Ordered a Akron one which I had heard good things about
Stage 4: Replaced the MC with the Akron unit, rear brakes work great but fronts lack pressure. This is where I currently stand
So right now, the symptoms are:
- First half of pedal travel is extremely light (front brakes), second half of travel is completely solid (rear brakes)
- With brake pedal fully depressed and held down, front wheels have small amount of resistance but still turnable with wheel on. Rear wheels are completely locked solid
I went through a measured a bunch of things and found the following weird things:
Cylinder diameter mismatch - the manual states 23.7mm fronts and 15.9mm rears, the ones supplied by the shop are 23.7mm fronts and 19mm rears, the original ones on the car are 19mm all round (???) From what I can tell, the MC size remained identical through the course of production, so would a standard 19mm MC be able to pump enough fluid for all these different combinations?
Brake drum dimensions - manual states 170mm or so, one of the front drums has a stamping that states min diameter of 186mm or so, I measured about 184mm internal diameter with a ruler
I honestly feel lost with a bunch of ideas with regards to what to try next. Does anyone have any advice or clarifications with what I've found so far or what I should do next? I'm at a stage where I feel like I should just buy a full set of shoes, springs, and cylinders again from a more reputable shop and replace everything with the hope that it works out in the end.