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Old 11-04-2014, 07:10 PM
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Default Disc brake question on the 40

I did the disk brake swap on my 73 40 using the goodies from an 83 80.
New calipers and new pads. I'm having a problem with the front brakes hanging up and not fully releasing. I thought it might be the master cylinder so I replaced it too. Fronts are still hanging. I can 'crack' the line and release the pressure, it just seems to be hanging in normal use. It also seems as though I have to really stand on the pedal to get it to stop, more than I think I should have to. The booster does have a hiss, sometimes worse than others.
Any suggestions on what to check next? Could it be the rod that goes between the booster and master cylinder needs adjustment?
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Old 11-04-2014, 07:32 PM
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I would check the rod between the booster and the master. If it is too long it does not allow the master to fully relieve the pressure and create a condition that is consistent with the symptoms you are experiencing.
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Old 11-04-2014, 08:53 PM
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Remove the check valve to the front brakes. Drums need pressure to keep the pads seated.
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Old 11-04-2014, 09:00 PM
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Quote:
Originally Posted by treerootCO View Post
Remove the check valve to the front brakes. Drums need pressure to keep the pads seated.
x2
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Old 11-04-2014, 11:17 PM
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Thanks fellas! I just went out and pulled the check valve from the front res, will get it bled and test drive tomorrow. Probably picked up a tad more power without the front brakes on too!
I gave the seal on the booster a shot of lube too, maybe quiet the hiss some and soften up that seal.
Thanks again...
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Old 11-05-2014, 10:46 AM
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I wouldn't wait too long on replacing the booster, relative to the hiss. You might also test the booster by running the truck for 60 seconds, shutting it off, and pulling out the check valve from the front of the booster and seeing if the booster has held a vacuum. It should hold a vacuum for at least 5-10 minutes.

You should be able to use a variety of Toyota boosters in your application, as far as replacement.
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Old 11-06-2014, 10:50 PM
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Good tip, Steve. I will do that. It seems like I still need to stand on it to get good braking. I may tear into it again this weekend.
On another note, pulling that check valve was just the ticket!
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