| Hydraboost [message #85457] |
Fri, 21 May 2010 00:08  |
Luvn737s
Messages: 1106
Registered: June 2007
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Are there any considerations in driving a GMC with brakes converted to hydraboost, especially in mountainous terrain? Does it have a backup, like a vacuum resevoir in a standard power brake system?
Randy
1973 26' Painted Desert
Ahwatukee (Phoenix) AZ
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| Re: Hydraboost [message #85470 is a reply to message #85457] |
Fri, 21 May 2010 06:43  |
John Sharpe
Messages: 489
Registered: February 2006
Location: Texas
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| Quote: |
Luvn737s
Are there any considerations in driving a GMC with brakes converted to hydraboost, especially in mountainous terrain? Does it have a backup, like a vacuum resevoir in a standard power brake system?
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Randy, The hydra-boost systems have an accumulator that stores pressurized power steering fluid that is available for use in case of loss of power from the hydraulic pump.
John Sharpe
Humble,TX
'78 Eleganza TBI
'89 Spectrum 2000 MPI V-10
'40 Ford Panel Delivery TPI
johnasharpe@gmail.com
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| Re: Hydraboost [message #85475 is a reply to message #85470] |
Fri, 21 May 2010 07:22 |
Luvn737s
Messages: 1106
Registered: June 2007
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Does the accumulator have a diaphram inside that is charged with Nitrogen? If so, does the accumulator need to be checked before driving to verify that it's charged (pressurized), or do you just wait a minute before driving to make sure.
While the vacuum system relies on the engine running for vacuum boost, this system sounds like you're relying on a power steering pump belt. I guess they squeal sometimes before they let go, so there's some warning.
Is it a reliable system, though, in practice?
Randy
1973 26' Painted Desert
Ahwatukee (Phoenix) AZ
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| Re: Hydraboost [message #85486 is a reply to message #85475] |
Fri, 21 May 2010 08:31 |
John Sharpe
Messages: 489
Registered: February 2006
Location: Texas
Karma: 1
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Is it a reliable system, though, in practice?
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I've owned vehicles that had a hydra-boost system and it worked fine. Never noticed any loss of boost. It's capable of providing more boost than the vacuum systems. The system is DOT approved and has been installed on hundreds of thousands of vehicles. Like Cadillacs, Lincolns, and others.
John Sharpe
Humble,TX
'78 Eleganza TBI
'89 Spectrum 2000 MPI V-10
'40 Ford Panel Delivery TPI
johnasharpe@gmail.com
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| Re: Hydraboost [message #85517 is a reply to message #85486] |
Fri, 21 May 2010 12:11 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
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| John Sharpe wrote on Fri, 21 May 2010 08:31 |
| Quote: |
Is it a reliable system, though, in practice?
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I've owned vehicles that had a hydra-boost system and it worked fine. Never noticed any loss of boost. It's capable of providing more boost than the vacuum systems. The system is DOT approved and has been installed on hundreds of thousands of vehicles. Like Cadillacs, Lincolns, and others.
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is it dependent on engine RPM for it's force? i know my power steering doesn't work well at idle.
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: Hydraboost [message #85538 is a reply to message #85457] |
Fri, 21 May 2010 15:45 |
LYNN L
Messages: 140
Registered: March 2005
Location: Pearland TX.
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Fred,If it"s good enough for cadillacs and lincolns along with 1 ton trucks and school buses then it"s good enough for me. At idle (1000 RPM.) my hydroboost puts 2000 psi. on the front calipers and 1900 psi. on the rear with only firm pedal pressure. If you calculate the actual pressure applied across the pad surface to the discs it will blow your mind. Believe me this coach stops like a 3500 van now and the rear bogies work even better since installing Jim K"s. quadrabag system.
Lynn L
76 Eleganza Cad.500
Pearland TX.
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| Re: Hydraboost [message #85570 is a reply to message #85457] |
Fri, 21 May 2010 20:24 |
LYNN L
Messages: 140
Registered: March 2005
Location: Pearland TX.
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Arthur, Bob Drews helped me with finding a custom hydroboost unit. He also has pictures posted of his installation along with mine on the photosite. I am posting his letter sent to me as I could not be any more concise. I hope he doesn"t mind..
Lynn;
The first version of a hydroboost that I installed, I had the same results as you have, good line pressure but needed a heavy leg pressure on the pedal. I talked with Tim Hendersen and sent the unit back and had it rebuilt with the large power piston and, most important, the
.545" input rod (reaction) and the large accumulator. The accumulator does not have any effect on pedal pressure needed, just somewhat of a larger back-up in case of loss of engine power.
After the rebuild with the specified internal parts, I have a much improved foot pressure to have effective braking. The small (.545) input rod and the large diameter power piston (1.56") is what you need to get a nice foot pressure and yet positive braking.
If I read your photo's correctly, you may have lengthend the 'bell-crank' lever that attaches to the MC rod. This in effect will give you a lower pedal ratio, increasing the leg/foot pressure on the pedal. The MH is marginal as is, just slightly over 4 to 1 ratio, most vehicles are 5 to 1 or more. So you may have lost some pedal ratio, and that does not help the heavy foot problem.
Take a look at my photo site http://tinyurl.com/ye6a8t and take a look at the cut-away of the hydroboost. Notice how the pedal rod pushes on the input rod sleeve, Bendix states to keep this angle no more than 3* off center. The angle showing in your photos is way to far out of line, in my opinion. It will have a "wedging" effect on the sleeve, and cause it to jamb. Poor alignment here will also cause leakage, as the sleeve is grooved for an "O" ring, as you can see in the cut-away view.
I do not have any spare mounting plates, Tim sent several with the first version, and I returned the ones I did not need. I would think he could furnish you one of these with a rebuild. The following is some info from my post to the GMCnet.
> Precision Rebuilders in St Clair MO is where I got the booster from. Tim
Hendersen is the tech rep there. 1-800-325-2690
This is what was used to rebuild the second version booster. A booster
housing that will accept the GM master cylinders with the 3-3/8" bolt
pattern, 1-5/8" nose diameter of the MC, nose depth of 9/16"; A four bolt
flat mounting plate, the bolt spacing will fit the vac booster holes; Now
the important internal parts; a .545" diameter input rod (reaction); the
large 1.56" power piston;
the 0.72 to 1 ratio lever; and the large external 3.0 cu. in. accumulator
(usually blue in color, now may have changed to silver)
The stroke of the Bendix booster is 1.66"<
Hope this helps you, I do not mean to be critical, just want to help fellow GMC'ers. Let me know if I can help in any way.
Take care from Bob Drewes in SESD
As you can see Bob made some very knowledgable suggestions and I corected all of them..
Lynn L
76 Eleganza Cad.500
Pearland TX.
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