Weird Brake Issue

Mark

FIATFREAK
The brakes on my 850 Spider work great except when i go to park the car. My driveway is steep and I back the car downhill into the garage. I head down the driveway and then swing the car uphill to let it coast backwards into the garage. As I swing it uphill, the brake pedal drops to the floor. It then returns to normal until the next time I go to park it.
Everything's been replaced including a just new master cylinder. I've cycled close to 2 quarts of fluid through the system, so I'm confident there's no air in there. Any ideas?

Mark
 
That sir is a head scratcher. I'll cogitation on it for a bit.

So do you normally have brakes when heading up and or down hill?

It's only this sequence of driving downhill (facing downhill), turning to face uphill and then preparing to roll back (nose up hill) that gives you a no pressure condition?
 
I'm not entirely sure; I need to experiment some more. I first suspected the master, so I replaced it, but the problem persists. I'm wondering if the pressure warning switch could somehow be at fault.

That sir is a head scratcher. I'll cogitation on it for a bit.

So do you normally have brakes when heading up and or down hill?

It's only this sequence of driving downhill (facing downhill), turning to face uphill and then preparing to roll back (nose up hill) that gives you a no pressure condition?
 
brake problem

you sir have a caliper problem I think, or warped rotors.
the caliper as you know slide back and forth, and turning the wheel without Appling the brake can lead to, especially at a sharp turn radius can push the caliper (piston) into the caliper housing and make it a pain to get a pedal. check for fluid at the master res to see if there is a sign of an overflow or check rotors for run out. hope this is helpful
mikemo90*aol.com
 
Interesting.

Wouldn't it take more than just a warped rotor to run the piston in on a stuck caliper?

Following this logic, could one of the front wheel bearings be particularly loose allowing the hub and rotor to rotate relative to the caliper, thus driving in the piston? It wouldn't take a huge amount of runout in the bearings to cause something like this.

Given the mechanical acumen of this particular owner I find it hard to imagine him having reused warped rotors, leaving his bearings so loose, or not noticing either one in his shakedown drives after the restoration.

It is something I can imagine I might have done or failed to do in my rush to complete a long term repair/restoration job :(
 
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Are you loosing fluid?

In order for the brake pedal to go to the floor, the fluid has to go somewhere. :confuse2:

Do you have any leaks?
If not a bad MC, then a caliper with a blow-by issue.
Does your brake system have vacuum assist?
 
Calipers and rotors are fine. The brakes work great under all other circumstances.

you sir have a caliper problem I think, or warped rotors.
the caliper as you know slide back and forth, and turning the wheel without Appling the brake can lead to, especially at a sharp turn radius can push the caliper (piston) into the caliper housing and make it a pain to get a pedal. check for fluid at the master res to see if there is a sign of an overflow or check rotors for run out. hope this is helpful
mikemo90*aol.com
 
No fluid loss. It reminds me of a bad seal in a master, except I just replaced it, it did it with the previous master, and it only does it under the conditions I described. You can push on the brakes as hard as you want and the pedal stays hard, except when I go to park.


In order for the brake pedal to go to the floor, the fluid has to go somewhere. :confuse2:

Do you have any leaks?
If not a bad MC, then a caliper with a blow-by issue.
Does your brake system have vacuum assist?
 
If your 850 has the stock rear drums, I'd look there for something loose or sloppy (not your work, but a hardware issue :) ). Drum brakes can cause a lot of pedal play... and the change from reverse to forward having a pronounced effect leads me to suspect the drum brake cylinders, shoes/adjuster shims, or something related.
 
That's my guess too, although the parking brake works fine. Everything back there was replaced. However, I'm not very adept when it comes to drum brakes.
 
850 brakes

I think budge is on to something. the shoes do arc to the drum, so to speak in relation to the normal rotation(forward). on backing up it might pop or knock the shoe/drum relationship outta wack. i'm trying to remember, and I think that the 850 used the same retention setup as the 128, two fiber washers and a spring and pin to maintain shoe/ drum distance. if they are worn or wet, they might not hold their position
bz good call and the best place to start:thumbsup:
mikemo90*aol.com
 
Yes the rear brakes are functionally identical to a 128's. You can use the same drums on either one as well as all the internal bits.
 
Very strange situation :confused:


  1. Maybe your car needs some fresh brake adjuster fiber washers and make sure the adjusters function properly.They really have a tight bind on the shoe and keep it from moving. You can hardly move them by hand if they are done right.
  2. I have a feeling the shoes are freely moving around since an adjuster washer broke apart or a unknowing mechanic replaced it with a steel washer.
  3. I get complete adjuster assemblies (cup, spring, circlip, washers) off old Yugo's since they are abused less than others models and they are a slightly better design. Most junk Yugo's have never had the rear brakes touched and the adjusters are like new from the factory. Newer material in these washers doesn't shatter as easy as original 850 washers do.
  4. Could also be the wrong shoes. I think 600D shoes might fit on an 850 and look similar, but the actuating ears are all wrong.
  5. Don't know if your car has manual or auto adjust drums. Somewhere around 67 and 68 they switched from manual to auto adjust. So if you have manual adjust, this whole fiber washer idea won't help.
    :confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2::confuse2:
 
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I pulled out the factory manual, pulled the wheels and drums, and even removed all the shoe components. Everything checked out okay.

 
Mark,
If I'm not mistaken, those are completely wrong brake shoe adjusters and/or they are installed backwards. The hole in the cup should fit over a pin on the backing plate and a snap ring should face out.
I don't even know how they fit on now, since the pin would be in the way. I think I see a glimpse of a manual adjuster hiding behind the rear shoe? :confuse2:
Do you need early shoes? :confused:
Maybe you could just swap the shoes from back to front, just flipping the shoes so the adjuster cups fit over the pins on the backing plate and you'll be fine.:)
Is the snapring on the backside of the shoe holding on the spring? :confuse2:
 
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Those are a different design from what was original, I have seen that adjuster type on some newer shoes. The old ones you traded the parts from shoe to shoe, these are riveted on from the looks of it at the factory?

The original style have springs front and back with the snap ring to hold the assembly together on the front side.

Not sure that this is the issue but clearly something that is notably different from OE.

The adjuster pin wouldn't fit into the hole we see here so they can't be flipped.
 
Karl's correct, the adjuster is pressed onto the shoe. I bought these from Greg Schmidt, if any one is old enough to remember who he is/was before he disappeared. I think you can see the 1996 date stamp in the photo. I
I checked the clearances and everything seems fine back there. As I mentioned, the parking brake is adjusted and works great too.



Those are a different design from what was original, I have seen that adjuster type on some newer shoes. The old ones you traded the parts from shoe to shoe, these are riveted on from the looks of it at the factory?

The original style have springs front and back with the snap ring to hold the assembly together on the front side.

Not sure that this is the issue but clearly something that is notably different from OE.

The adjuster pin wouldn't fit into the hole we see here so they can't be flipped.
 
BTW, here's a sectional view from the factory manual. It shows the snap ring style of adjuster
 
Mark,
I'm not even sure if the adjusters are causing the problem and I have never seen adjusters like that before.
I'd like to know what the solution is myself.:confuse2:

If Greg was around, he would at least tell us where he got them from. I've purchased stuff from him before only to find a part that won't fit or won't work. He didn't know himself why things didn't work sometimes, only that his supplier claimed the application as Fiat 850/600.
I had a throwout bearing from Greg that didn't work and looked kinda strange. I had to take the engine out again to return it. Greg just gave me a different one and smiled about it. He was a character, but I wish he was still around. I think he now lives in a tree house on some tropical island.
 
They sell that type of shoe with integral adjuster in Europe now. I was looking at a British site yesterday that offers them. I am sure it is cheaper to do them that way as it only involves a press versus a man with tools and multiple parts.

Never met the man,did buy one of his books from him years ago when I lived in Pasadena. More power to him if he is indeed living in a tree house on an island far far away :)
 
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