Daveinet
il
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Joined: 10/29/2003
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I have a GM type hydroboost brake set up on my coach. The problem is the if the motor dies, you only get about two pumps on the brake and then you have very little brakes. I know the the new Workhorse stuff still uses hydroboost, but has an electric helper pump that kicks in on an as needed basis. Trying to figure out how complicated it would be to retrofit the additional electric pump. On the pressure side of the power steering, does the fluid continuously circulate, or does it only flow when the brakes are used? Does the electric pump just "T" into the pressure side with a check valve and a pressure switch, or is it much more complicated than that? How much pressure does it run?
Dave
FMCA F298817
'83 Revcon Prince 31' FWD
502 w/Thorley's & Magnaflows,
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itsalleasy
USA
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Joined: 07/20/2007
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Hydroboost operation.
What's wrong, you got everything hooked back up and getting bored?
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50pascals
rochester, ny
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Joined: 01/10/2008
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The hydroboost system you mention is used on medium duty trucks for quite some time. My business has a Ford F-800 with 190hp 5.9 cummins with the same system.
Now I must mention, the reason I know so much about it is because it is defective and the booster pump goes off when not needed. I have spent over $1500 trying to get the dealer to fix it, and it still doesn't work. As a result, we just put the relay in for the inspection, and pull it when we leave.
With that said...
The electronics are pretty straightforward - provided you do not integrate them into a factory harness, and across 3 controllers or modules, and integrate lights, buzzers, and an engine kill system!
The simplest explanation is that there is a flow switch in the hydraulic circuit (not the brake circuit) of the hydromax unit that is in series with a line from the brakelight switch. If there is no flow, the switch gets closed. Now, if you hit the brakes, the circuit is complete and the pump gets kicked on (until you take your foot back off the brake pedal). It works great and has the same amount of stopping power as the regular circuit. The pump is integrated right into the "master cylinder" assembly attached to the brake pedal. I'll bet the unit is physically interchangeable with a non-backup hydromax.
My plan is to basically wire my own stand-alone circuit for this system. I'll abandon the old wires in place. I also will be losing integration into he engine kill module and the light in the dash, but it's worth it to have the backup brakes. BTW - You don't need the light - it is VERY obvious if the pump is running because it is noisy.
I actually plan to do this twice - once for the work truck, and once for the MH.
I'd suggest getting a unit from a junk yard - then you can see how it works.
The relay for the pump motor is a regular issue Bosch relay. Ford make a "module" that will completely control the unit, with extra functionality for my truck - which you wouldn't want in your MH.
-Rob
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Mike Hohnstein
Germantown, Wi
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Joined: 01/04/2004
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I think the idea is for the engine to keep running. Excessive re-engineering of the hydro-boost calls into question the validity of the state of engine tune.
I have over 250k miles with big block powered hydro-boost equipped vehicles and never had a problem related to engine quitting. I would recommend the modification of the brake pedal to allow both feet to apply the brakes, even with the engine running and booster fully energized, two feet on the brakes stops better in a serious situation. I think them old GM brakes work pretty good as produced.
Saved my butt with a Chevy C-30 crew cab with camper in Chicago, and with type C motor home in Indy, towing race car trailer both times, major tire smoking stops, but it stopped.
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Daveinet
il
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Joined: 10/29/2003
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As I started reading the 50pascals, I'm thinking to my self, why have it automatic? If the engine were to ever cut out, flipping a latching relay/switch on the dash that powers the motor should work just fine. Just find a pump from a bone yard and add it in. Since the boost reserve still works, that will give me reserve until the pump builds pressure. Assuming it has enough flow, I think I'd plum it in before the power steering so I wouldn't loose that either.
Per having the engine staying running, I've only had it happen once, but a wire came off the rotor once and by the time I stopped, I had lost all brakes. It didn't matter because I was only stopping on the side of the road, but I didn't like the idea of loosing brakes. The other situation would be when running out of gas on reserve before flipping to the main tank. Sometimes it takes a awhile before the engine catches again. My new engine is computer controlled, so I don't expect it to die, but anything can go wrong unexpectedly.
Thanks to al for all the info.
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bill h
el segundo
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Joined: 08/02/2001
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Mike Hohnstein wrote: I would recommend the modification of the brake pedal to allow both feet to apply the brakes, even with the engine running and booster fully energized, two feet on the brakes stops better in a serious situation.
Not much room for that on a P30. Steering column is in the way. Maybe I need to get smaller shoes.
Bill and Susan
84 Barth 30 tag powered by ht502/Thorley, Gear Vendors OD
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