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Re: Ford A426C brake vacuum pump, your opinion please? [message #327596 is a reply to message #327535] Sat, 30 December 2017 08:21 Go to previous messageGo to previous message
RF_Burns is currently offline  RF_Burns   Canada
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
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Senior Member
Just my farm-boy mechanic thoughts on vacuum pumps and reservoirs.

In my opinion, both are a great idea. I do have an opinion (or idea) on how they should be plumbed and why. The engine has a huge capacity to draw down vacuum (hoping that is proper terminology), as compared to an electric pump. I currently have a JC4 pump which is plumbed in series between the vacuum booster and the engine, in other words the engine vacuum flows through the pump. My idea is the system should be plumbed in the following order.

Vacuum booster ->check valve --> vacuum pump ---> vacuum reservoir ->check valve ---> engine.

My reasoning is the engine's vacuum capacity will draw down the reservoir and booster almost immediately and the check valves will keep the system at maximum vacuum (or minimum depending on your point of view). If the engine quits, and say you were going down a hill which required multiple brake applications, the vacuum reservoir would provide a source of vacuum for a short while. Once the reservoir vacuum went below the pump setting, then the pump would start.

Now this is point where my configuration come into play. With the pump in-line right at the booster, there is only the booster reservoir to pump down, so the pump should be able to do that fairly quickly to regain power in the brakes. If the pump had to draw down the reservoir as well, it would take much longer to do so and in the meantime your booster brake assist would be very poor.

Does this make sense? I haven't seen where this has been written-up in the past. Or maybe my assumptions are all wrong here.

Comments or ideas?

Thanks

Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

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