1980's brake system disc/drum

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gregcon

gregcon

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The aluminum master cylinder from the late 70's onward is used on lots of older Mopars.

In looking at the factory manual (1983 Chrysler), the brake system (disc/drum) uses a single proportioning valve/distribution block/hold-off valve assembly as pictured.

So here's my question....where is the residual pressure valve? Since the drum brakes in the rear need to have some pressure held in the line, traditionally the master cylinder has the residual valve (RV) behind the brass tube seat. But, the famous aluminum MC does not have an RV. Neither does the prop valve assembly. So how is this function being accomplished?

Aluminum MC.jpg


Prop valve.jpg
 
No. Cylinders are regular.

My guess is the slop-mess of valves and pistons in the prop valve are enough to provide residual pressure...but that's not founded in anything.
 
Actually that would be exactly my guess--the prop valve
 
My understanding is that the need for a residual pressure valve was to keep the wheel cylinders from leaking. The later cars had a better seal design and thus don't need a residual pressure valve and so it was deleted.

Unfortunately, I don't remember where I heard this so I can't say it isn't just an internet myth. I think it is right, but I can't point to any proof.
 
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