Brake problems - Hot Wheels edition

Stevehose said:
I did a brief test drive yesterday with vacuum s\disconnected and problem did not repeat but will do a longer drive again once the rain stops.
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I could translate Dante's Divine Comedy to another language before our CA rain stops...
 
Drove it 15 miles with the vacuum detached from the booster. No issues. So I'll first yank the master cyl to check the clearance. If that checks out then on to the booster. Fortunately, I did not detect any rotor warpage or other damage from this issue.
 
There is a conclusive test if you are brave. Disconnect the pedal altogether and pull the rod out.
Go for a ride with no brakes, use the parking brake to come to a stop. Do it in a closed track.
 
ATE brakes that don't release are almost always the rubber lines swollen/collapsed internally. They look fine from the outside but restrict fluid from returning. Should go into the FAQ.
 
Ok I wish I had read the section in the manual about how to refit the master cylinder and the clearance needed, figured it was just a bolt back on deal. I read the brake booster section but no mention of that of course. So feelin’ kinda dumb here lol.

Here is the removed tip, obviously sent to me with my choice of 3 different thickness washers to match up with the MC.

So do I do the plastigauge like the manual says or is there a shade tree way to do this? Not sure how plastigauge is going to stay in place in the MC during assembly. But I have some.

The head of the tip is 8mm, the washers are 1mm, .7mm, and .1mm respectively.

IMG_5005.jpeg
 
Doh ... just glad you figured out what the issue was. now its just sorting it out ... you have learned its NOT all 3. i probably would have done the same thing as you.
 
rsporsche said:
Doh ... just glad you figured out what the issue was. now its just sorting it out ... you have learned its NOT all 3. i probably would have done the same thing as you.
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Yeah, let’s hope it’s one of them!

I will use a smear of grease to hold the plastigauge in place for the test.
 
Ok thanks to @Luis A. I have procured China’s finest alignment tool. There are no instructions except for the cryptic ones on Amazon, and the text on the device is confusing, but the blind squirrel has adapted and overcome!

It doesn’t fit over the master cyl (as several in the reviews noted) so I whittled the edges down to clear. I used the rounded end of the rod to measure the distance inside the pipe:

IMG_5013.jpeg


Then put it on the booster to see the clearance with the rod (the tip pulls straight off the rod (does not unscrew)).

IMG_5016.jpeg


Even with all 3 washers off it was still barely touching so I sanded just enough off for .5mm clearance:

IMG_5017.jpeg


So basically the MC was being pushed in by at least 2.5mm over spec. It appears to me that the inside pipe of the MC bottoms out right at the front edge of the booster, so you want the tip of the booster rod to be just under the front edge. I’m hoping this solves the issue and provides insight to those replacing a rebuilt booster in the future. Onward.
 
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