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Old 03-10-2016, 04:14 PM   #1
Mini-Skoolie
 
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Hydrualic to Air brake system

I have a 91 b700 with the lucas girling brakes. One of my rear wheel cylinders blew back in November last year (luckily I wasn't on the road when this happened). The repair is going to cost about $500 if both the upper and lower cylinders. HOWEVER I happened to notice that a local junkyard has like an 1985 B700 with air brakes.
So my question is: Would it be possible to do basically swap brake systems?
Or would I be better off repairing my lucas girling brakes and pray to the gods that ANOTHER thing goes bad with the brake system?

TL;DR:
Is it possible to install an air brake system on a hydraulic brake system?
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Old 03-10-2016, 04:53 PM   #2
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If you've got lots of time and willing to do really extensive heavy work to do
the swap. The change over would require changing over the axles both front
and rear plus add a compressor to the engine and all of the plumbing and
valves needed as well. In the end you will feel that $500 is a real cheap price
to pay for brakes that work. On the other hand you need to realize that all
of the hydraulics in the brake system are the same age and generally prone to
failure at the same time. Make sure you test the brake fluid frequently for water
content and change it out when it becomes water logged. Brake fluid is
hygroscopic which means that it attracts moisture. Always use fluid from a
sealed container. Once a container is exposed to air it begins to absorb water
from the air around it. That's why it's a maintenance item on all vehicles with
hydraulic brakes. Recently O'Reillys Auto Parts now carries a synthetic brake
fluid that's supposed to overcome this problem, not sure how well it works but
you might check around with local shops who are using it and see if they have
any stories to tell about its efficacy.
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Old 03-11-2016, 07:52 AM   #3
Mini-Skoolie
 
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Quote:
Originally Posted by Dragonpop View Post
If you've got lots of time and willing to do really extensive heavy work to do
the swap. The change over would require changing over the axles both front
and rear plus add a compressor to the engine and all of the plumbing and
valves needed as well. In the end you will feel that $500 is a real cheap price
to pay for brakes that work. On the other hand you need to realize that all
of the hydraulics in the brake system are the same age and generally prone to
failure at the same time.

That is what I am worried about. I was lucky enough that the wheel cylinder blew when I was not on the road. I cannot say when the other one is going to go bad. This is were I was getting at with my question, if both wheel cylinders turn out to be bad it will cost about a grand (in parts) to get it fixed and then not to mention I am still going to worry about them failing without warning.
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Old 03-11-2016, 11:03 AM   #4
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With enough time and $$$ almost anything can be achieved.

My concern would be what sort of liability you would be taking if the bus should ever get into an accident. I would think finding insurance that would back you up would be very difficult to find. Insurance companies will do anything to get out of paying a claim or reducing the pay out. Since we are talking about a major safety component that was changed 100% from what the bus had from the factory I would not bet on the insurance company backing you.

I know this isn't what you want to hear but I think it might be less expensive and less of a headache to get a different bus and convert it or swap the bus body onto a different chassis.
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Old 03-11-2016, 12:00 PM   #5
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I think it would be wiser to fix bus and then sell it and get one with airbrakes...or go through whole brake system ~$3000 (guessing)
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Old 03-11-2016, 12:20 PM   #6
Mini-Skoolie
 
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Thank you everyone for your input, after thinking about it I think I will just fix it and sell it, then DO RESEARCH on a bus that would work best, AND THEN buy a different bus.
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Old 03-11-2016, 04:34 PM   #7
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Personally, I prefer hydraulic brakes over air. Having owned both, air systems are, to me at least, a lot more maintenance heavy.
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Old 03-11-2016, 06:50 PM   #8
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When I bought my bus, I had the choice between two identical buses, one with Hydraulic brakes and the other with air, I went with Hydraulic because I'm far more familiar with their repair and maintenance.
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Old 03-11-2016, 07:01 PM   #9
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I have owned and driven buses with air brakes and buses with hydraulic brakes.

I like air brakes mostly because they can usually have much more braking surface and have a very positive emergency brake.

The newer all disc electric over hydroboost brakes IHC has been using for about 20+ years are some of the best braking systems out there. They are a HUGE step forward from the drum brakes they used previously. Outside of getting wider the brakes IHC used were essentially the same from the '40's until the discs came into service in the '80's.

The Lucas Girling brakes Ford used were good brakes. But like so much of what Ford used on their school bus chassis, the parts and pieces are made out of unobtanium and are priced accordingly.

The biggest issue I have with wet brakes is the fact brake fluid is hydroscopic--it attracts water. The water can then accumulate in places like wheel cylinders causing them to fail prematurely. Also, the water in the brake fluid can reduce the boiling point of the brake fluid to the point where you can literally boil away our brake fluid on a long down hill grade. And without the benefit of a spring brake emergency brake you can find yourself getting towards the bottom of a hill with nothing more than the driveline brake to get you stopped.
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Old 03-12-2016, 07:37 AM   #10
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Modern air have anti lock brakes, and automatic slack adjusters. The most one has to do today with air is the occasional pull of the tank drain cable. Even then, they have monitors to alert you about most things now days.

The treadle valve location is the key to a pleasant transition from fluid to air. If you go to the old school floor mounted treadle, it will be difficult as the pedal pivot is at your heel. For a long time some manufacturers have gone to putting the treadle on the firewall so the pivot is above your foot just like a pickup or car.

Most cars and pickups from the late 60s or so on have all the pedals pivoting above the feet, under the dash. Throttle, brake and clutch if so equipped. Trucks and buses are late comers to that party, but many have been doing it since the 80s with only a few hold outs like Paccar. And even then, perhaps now they have gone to pivots above the foot. I dont know for sure as I cant afford new, so I have'nt been in anything newer than about a 2007.

But at least with air, if you loose air pressure, the park brake will apply and should get you stopped or so near it that you can ditch the rig with minimal risk of injury. I know, there are park brakes on juice brakes too, but because they are separate from the service brakes, no one seems to maintain them worth a darn. So the oil from the leaky trans seal gets all over the shoes and drum and though it will hold on a level surface, trying to use it to stop is futile and may even cause a fire.

IMO
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