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PostPosted: Thu May 10, 2018 10:15 pm 
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4 BBL ''Hyper-Pak''
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Joined: Wed Aug 16, 2017 10:44 pm
Posts: 38
Location: Reading, Pa.
Car Model*: 1982 D150 225, 2bbl., 833 OD
I've been replacing brake components as I get the chance on my '82 d150. I got the rear drums, shoes, wheel cylinders and feed lines last Fall. I just did the front rotors, pads, wheels bearings and calipers a few days ago. At the same time, I've been chasing an illuminated brake warning lamp. I didn't even know that it was triggered until I replaced some burned out cluster bulbs. Today, I bled out the existing master cylinder on the truck and then bled out all 4 corners again. Pedal improved a tad, but still a little soft and low. The truck has had a very slight pull to one side on initial brake use, seems to track straight after the initial bite. This was both before and after the front brakes were done although it's a little less pronounced now. It might be due to the combo valve blocking brakes in some manner. I can't find any signs of a leak anywhere. Braking doesn't seem to be what it should be after new parts.

The next step is replacing the M/C with a Raybestos MC39178 . I also have an aftermarket combination valve I bought that I will replace the old one with if the new M/C doesn't reset the combo valve. My main worry is the best way to remove the old M/C . Being a non power brake truck. I'm assuming that the manual and vacuum chamber M/C's are the same. It's the newer style that has an aluminum body and plastic dual reservoir and matches the one that's there now. I checked an online factory parts fiche for an '84, which seems to be as old as Mopar gets. It shows the pushrod and parts that go with it as used on a manual brake truck. None of them are available anywhere it seems, including NOS parts places. The only M/C I have ever replaced was on a power unit, ages ago.

Hope you're still with me. My FSM says to remove the brake light bracket under the dash, remove ( or loosen?) the M/C attachment bolts under the dash. Then yank up more than 50 lbs. of pressure on the brake pedal. Said to pull the pushrod out of M/C? FSM states that the grommet will be destroyed. One of the parts you can't get. I took a look in Haynes, and they state to pry M/C out from the firewall and it will leave the pushrod. The M/C must have a gasket behind it on the firewall attachment plate. I can't seem to locate a M/C firewall gasket anywhere and I'm guessing it's not the same as a vacuum booster one. Would some sort of silicon fix work if need be? Any sort of illustrations on the manual brake M/C setup seem to not exist.

Any advise is appreciated. Perhaps I'll try to replace the combo valve first. Got that from Carolina trucks. I think it might be a GM application that supposedly fits. I don't know that the M/C is the culprit.

_________________
1982 Dodge D150 ( Ram)
225 with A833OD. 2bbl. Non power brakes


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PostPosted: Fri May 11, 2018 7:22 am 
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Turbo Slant 6
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Joined: Fri Dec 30, 2005 2:49 pm
Posts: 653
Location: Houston, TX
Car Model*:
Any way you do it, replacing the master cylinder is probably going to destroy the pushrod bushing. Doctor Diff sells an adjustable pushrod with the bushing included, so you might be able to get the bushing by itself. Mancini Racing definitely sells them, but they want $5 or so for that little piece of rubber or plastic. You can also make one yourself by cutting a small piece of 1/4" ID fuel line.

As for your brake issues, a master cylinder can leak internally (between reservoirs) and give you weak or inconsistent braking with no apparent external leaks. I've had good luck with Raybestos components so far. I'd even recommend their remanufactured stuff over new parts from Centric or Cardone.

I don't know anything about the combo valve in your truck, but if it's basically a distribution block then that seems a little more likely to be causing the initial pull. I don't see how it could cause overall weak braking performance, though. You may end up replacing both.

_________________
Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing


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PostPosted: Fri May 11, 2018 11:57 pm 
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4 BBL ''Hyper-Pak''
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Joined: Wed Aug 16, 2017 10:44 pm
Posts: 38
Location: Reading, Pa.
Car Model*: 1982 D150 225, 2bbl., 833 OD
SF, Thanks for the insight and tips!

_________________
1982 Dodge D150 ( Ram)
225 with A833OD. 2bbl. Non power brakes


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