[DeTomaso] Another brake question.
pantdino at aol.com
pantdino at aol.com
Sat Jul 11 17:10:12 EDT 2009
I bought my car with two stock rear calipers on each side. My understanding is that the proportioning valve was removed (and I believe the shuttle valve also) and that was OK because of the 4 rear-caliper situation.
I have been thinking I would like to remove the extra 2 rear calipers because they create more drag on the rear discs and increase the pedal motion.
Just to be certain, I don't need to replace the proportioning valve if I?remove the extra 2 rear calipers?
My experience is that when a car?has a very hard pedal intermittently it is in fact the booster or vacuum problem.
Jim
-----Original Message-----
From: JDeRyke at aol.com
To: wdemelo at cogeco.ca; detomaso at realbig.com
Sent: Thu, Jul 9, 2009 8:54 pm
Subject: Re: [DeTomaso] Poor brakes
In a message dated 7/9/09 5:35:36 PM, wdemelo at cogeco.ca writes:
> It feels like I'm driving a '65 Ford with drum brakes. Every so often
> they work (1 in 20 attempts), otherwise I've got to really step on the pedal.
> I don't think my booster is working. How do I test it?
>
Pull and plug the vacuum hose at either end and try them. There should be a
difference in stopping power. Also, if they're working, there will be an
audible 'hiss' when you step on the pedal or let it off. The true test though
is to add a 0-1500 psi gauge to each circuit and check the pressures.
Without a proportioning valve, you'll be hard-pressed to get 350 psi with the
engine off, but you should see 1200 psi with the engine on and vacuum at the
booster. I've found several Panteras in which the vacuum line was disconnected
for some odd reason....
The shuttle valve under the booster often sticks in internal varnish at one
end or the other of its travel, and it will not reset itself; the only fix
is to take it completely out, remove the end fittings and tap the shuttle
back into the valve center with a nail-set, then replace and carefully
re-bleed the whole system. With the shuttle stuck, you essentally LOSE the
brakes
at that end of the car, which makes for p-poor stopping power. The shuttle
can be safely thrown away and the various lines hooked together. Its only
job is to warn you of worn brake pads, and only if you still have pads with
ground wires embedded.
Finally, if you also throw away the stock non-adjustable proportioning
valve, ALL the brakes will run at full power rather than having the fronts
hamstrung as they are stock. Deleting the prop-valve and the shuttle valve are
often the only brake upgrade most street Panteras need. And its pretty low
cost. Good luck- J Deryke
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