Brakes Locking Up

[Pescado]

Thanks Bryan...So just spoke to the previous owner and he told me the MC came from Vicks. When I mentioned me spacing the MC and booster he said "it's funny that you say that because the mechanic did that to get the bleeding completed" is this a normal procedure?

Perhaps a phone call to Vick's?

Also can you guys refer the best repair manual for 1979...looks like Haynes only goes up to 1978

[18Fiatsandcounting]

So just spoke to the previous owner and he told me the MC came from Vicks. When I mentioned me spacing the MC and booster he said "it's funny that you say that because the mechanic did that to get the bleeding completed" is this a normal procedure?

I would think the MC from Vicks would be fine, but separating the MC from the booster is definitely not part of any bleeding procedure that I've heard of. It sounds like something is either wrong with the brake booster and its plunger, or the acorn nut on the end of that plunger is not adjusted right. Do you know if the booster was replaced? Maybe that's the issue? Certainly can't hurt to call Vicks to see if they have any ideas.

There is a Fiat shop manual for the later cars, so if you search around on the web, you might find it. Most of the mechanicals are pretty similar, with the major changes being that the spider changed to fuel injection in 1980 (1979 in California). So, if your '79 has a carb, it's likely not a CA car.

-Bryan

[DieselSpider]

It may be time to check that its adjusted properly and that the adjuster is locked and not moving. It could be something as simple as too thin a gasket was used between the master cylinder and the booster, the gasket has compressed or perhaps when they initially adjusted things they left it a little long and as things settled in its finally gotten to the point where it has become evident.

[bobplyler]

Also can you guys refer the best repair manual for 1979...looks like Haynes only goes up to 1978

You can get the Shop manual in .pdf from
https://mirafiori.com

In the Library section. You have to register before you can get access.

[Pescado]

thanks for all the help guys...I spoke with Vick's today and explained the situation they instantly mentioned the acorn nut needing adjustment (just like you guys mentioned). This coming weekend I will try and remove the MC, hopefully I don't need to take anything apart that will cause me to remove/add brake fluid. I suspect if there is enough play in the plumbing I can just pull the MC away from the booster ( oh ya no gasket in between the two and Vick's confirmed this being normal ) and make the adjustment. The guy I talked to mentioned using some sort of putty or playdough as a tool to show how close the push rod is to the MC...makes sense. When put back together if the rod is completely piercing the putty this would suggest too long, a thin layer should remain ( hair like thickness ) suggesting a good fit. They did say that this procedure can be a PITA as it is kinda trial and error....i'll be psychologically preparing myself for the next few days and will attempt this on the weekend.

[18Fiatsandcounting]

OK, sounds like progress! The procedure isn't as hard as it seems. One spec that I found was that the end of the acorn nut should protrude 0.050" to 0.073" past the front surface of the booster. That would be a starting point, and then you would adjust the nut to be almost touching the plunger cup in the rear of the MC when installed. Play-D'oh, clay, plumber's putty, your wife's lipstick, all will work. Personally, I'd aim for more than just a hair's thickness of clearance, but certainly no more than a mm or so.

-Bryan

[Pescado]

Hey all,

Sadly I haven’t got to this yet, with the cold weather on its way I shifted focus to my boat and yard. Just curious what’s your guys thoughts on working on these cars over the winter? I would think it makes things more difficult as everything stiffens up and probably increases the risk of breaking things…kinda answering my own question here but still putting it out for thoughts.

[18Fiatsandcounting]

I wouldn't do upholstery work or try to install a new convertible top in the Winter, but as far as mechanical stuff, it depends more on you than it does on the car. The biggest problem I have is my hands get less nimble when they're cold, and whacking your hands or fingers seems to hurt more in the cold.

But I'm probably the last person to ask for advice on this. One of my early engine rebuilds involved the challenge of keeping the blowing snow out of the cylinders as I was reinstalling the cylinder head. No garage, just out in the driveway during a snowstorm. I vaguely remember needing to finish the rebuild during Winter break so I could drive back to college after the break...

-Bryan

[DieselSpider]

I put off a lot of the work for the winter when daytime temps are down into the high 70's to mid 80's which is great weather for working on cars and upholstery without drenching everything with perspiration.

Just getting into our best convertible car and boating weather now.

If your too far up into the Frozen North like where I grew up in New England with its 20 to 30+ degree below zero Fahrenheit winters well even your ears and fingers will be too brittle for working on cars outside or even inside a somewhat heated garage.

[Pescado]

Finally got back around to this...sadly a couple weeks ago we had to put our dog of 14 years down, tough times man. Now I'm dealing with a puppy...wow talk about time consuming.

Anyways...got the MC off and really hoping to do this repair without having to bleed the brakes. I attached a picture of what I have exposed, I presume I'm turning this thing clockwise so that it goes further in to make up for the separation my spacers made. The PLAN...stick some needle nose in there and try turning but wanted to know if it matters which part I grab Position 1 or 2? I'm thinking position 1 as 2 looks like it will go nowhere without nut 1 moving...thoughts?

[Pescado]

Maybe nut one isn't even suppose to be there and that was added for spacing to get a stiffer pedal??

[18Fiatsandcounting]

Nut #1 doesn't look right, like it's too large and is there as a spacer like Pescado suggested.

How it's supposed to work: Nut #2 is actually an "acorn" bolt that screws into the splined shaft that goes into the booster. Nut 1 is just its locknut. You adjust bolt #2 so that there is about 1.1mm of clearance between its tip and the cup recess in the end of the master cylinder. Easiest way to do this is put a dab of clay or the like on the end of the acorn nut, bolt on the MC, take it off again, and see how thick the clay is. Adjust the acorn nut until you get this clearance at 1.1mm or so, then tighten up the locknut #1.

Remove the clay of course!

-Bryan

[Pescado]

So finally got to this and kinda completed but not sure how this will turn out until I test drive it. I was able to shorten the travel distance of the rod by turning the acorn nut however not sure how accurate my measurements are…during the adjustment process I found that there is about a 1/4” of free play on the rod, meaning you can pull/push the rod very easily and these movement may have messed up my measurements. I guess I won’t know until spring as we already have salt on our roads so no test driving allowed. Thanks for helping me get to this point and I’ll report back on this later.

PS…does the steering wheel need to be removed in order to take instrument dash off? Struggling pretty good with getting this thing out and certainly don’t want to crack anything.

Cheers!

[18Fiatsandcounting]

PS…does the steering wheel need to be removed in order to take instrument dash off?

No, but it does make things easier. To remove the gauge cluster without removing the steering wheel: Remove the steering column plastic covers (4 Phillips screws from the bottom). Put all stalk levers in the "down" position. Disconnect the battery. Remove the 4 gauge cluster screws. Bring the dash towards you enough that you can get your hands behind the dash to disconnect all connectors and the speedometer cable. Carefully angle the dash around until you can work it past the steering wheel.

But, come to think of it, I've usually just removed the steering wheel since it does make life easier. The challenge could be that the steering wheel is on the shaft pretty tight if it has never come off before. In my case, the steering wheel has been removed many times so it's not an issue.

-Bryan

[micbrody]

When I replaced my booster, this happened to me.
From an older post of mine:
“
Before mounting it, I adjusted the push rod a low as it would go with included lock nut. It seemed slightly longer than it should be, but I still mounted it. Re-assembled everything (yes, the brake pedal spring took me an hour of contortion and tension to finally hook back up). Under no load, I had wife hit brake pedal off and on when I turned wheels. All seem great. I took for a ride. Seemed to great. Brake feel was much more responsive and firm. However, by end of quick ride, brake pedal was extremely firm. Also, the car would not passively roll backwards on incline of driveway!!!). I jacked up car, and front wheels were locked; and one of rear wheels dragged at lot on pads. I pulled up on brake pedal on inside of car. Even though it did not seem to move, the fronts became free. I theorized that pushrod needed to be shortened (I also, then recalled that when I went to bleed front brakes, the fluid did not easily come out when I first opened screws; only after some intermittent mityvac suction did it start to flow). I was able to easily disconnect only master cylinder and pull out push rod. I removed lock nut, and replace with a lock washer (and I applied some thread lock). I was able to reduce the length of pushrod by 2 mm. Re-assembled; everything works great!

So hopefully this will help people need to replace their booster in future: 1) need to cut down two of the studs 2) do not include locking nut on pushrod”