Troubleshooting and Parts info for Hydrovac Brakes 1984

[Seon1]

I've had my '84 Chieftain on a P30 chassis with a 454 engine for about a year now.  Thinking that I didn't have power brakes, I need to install a remote power brake booster but was informed that the Chieftain certainly has power brakes.  Can anyone direct me to where I can get info on this Hydrovac system, how to trouble shoot and where to get parts?

[bluebird]

I bought the brake parts for my 80 Itasca from O'Reilys auto parts. They weren't too exspencive either. Not really power brakes like you're used to I bet. They run off of the power steering pump. I replaced both front calipers, pads, rubber lines, and master cyclinder on mine. I was pulling a 4000 lb trailer and wanted no problems. The brakes still wasn't great in my opinion. My challenger has much better brakes, but it has 4 wheel discs.

[DaveVA78Chieftain]

From what I have read, the 76-96 P30 chassis used a Hydroboost system, not a Hydro-Vac system.  The Booster in a Hydroboost system uses the Power steering pump rather than engine vacuum (Hydro-Vac system). One of those emissions controls driven changes.
Hydroboost was an option for 73-76.
I also think 76 and later P30 used 4 wheel disk brakes.
What do you mean by "Remote Power Brake Booster"?

As far as parts, it depends on what you need.  NAPA carries most of the parts. 
P30 1 ton truck chassis - Used for both motorhome and Step-Van (Bread Truck) applications.
You will have to procure a P30 chassis manual from E-Bay etc.  (http://www.classicwinnebagos.com/forum/index.php?topic=4974.0) for more detailed information.  The Bishko CD-ROM version may be your best bet as it would contain all manuals if there are multiple books (later years) http://www.autobooksbishko.com/Items/1984%20Chevytruck%20GMC%20Shop%20Manual/13675.html

Make sure you know what year chassis you have.  Winnebago typically built the current year house on a previous year chassis.  So a 1984 Winnebago would be sitting on a 1983 P30 chassis.

Dave

[bluebird]

Not all 1976 and later chassis had rear disc brakes. My 80 had rear drums, and it was on an 80 chassis.

[DaveVA78Chieftain]

Thanks for that feed back.  Some parts information I was looking at implied they only  4 wheel disk.  Did your 80 have hydroboost? The 84 Service manual I just recieved in the mail shows both vacuum booster and hydroboost versions.

Dave

[Seon1]

I just googled Hydroboost and read the "how to troublingshoot". 
In my case, I don't have a problem with the steering nor braking other than I having to apply more pressure on the pedal when I'm towing my 4K lbs boat.  At times, I'm literally "standing" on the brake pedal when a vehicle pulls in my lane without notice. 
Has anyone ever removed their hydroboost and replaced it with a hydovac?  I'm thinking that'll be the way to go(?) .

[bluebird]

Yea, my 80 had hydroboost brakes on it. It stoped just fine when i wasn't pulling my race car. When I was pulling, I had to stand on the brakes a couple of times. That's why I went through the brakes, although there wasn't much differance when I got done. I just used regular compound pads on the front, if I were to do it again I'd use the best pads I could find. My Challenger stops much better, but it does have matalic pads on the front and they are noisy. Almost sounds like they are worn out, but it's worth the noise.

[RV Mech Tech]

Seon - one thing to keep in mind when diagnosing or troubleshooting brake systems-  if the brake parts at each wheel  (disc pads or drum shoes) are in good condition (meaning that there is at least 25 % (minimum) or more friction surface then whatever boost system you have will do its job and the parts at each wheel  will do there job- you can have a perfectly working boost system but if the pads/shoes or drums/rotors are in poor condition or any part has gone past its minimum service life or specification  ( minimum thickness of pads or shoes or rotors or drums for example ) then you cannot expect the system to work the way it should especially in a towing situation or 'panic' stop - what Dave has mentioned regarding the equipment and braking system on  your motorhome is very important so that you have the correct specs for repair - the theory behind braking systems is that the system converts 'Kinetic' energy (the energy of motion)  into 'Heat' energy (Coefficient of friction) and it must dissipate that heat through the parts of the brake system including all mechanical parts at each wheel disc or drum- if any part cannot dissipate that 'heat energy' because the parts are in poor condition and the operating temperature designed into that specific braking system is exceeded you start to get brake fade or worse decreased brake power and the brake fluid begins to boil - it does not take much especially under today's driving conditions - check the condition of your entire brake system  and if I may suggest your steering system as well - in an emergency situation  especially with a motorhome you want the maximum braking and steering available when confronted with a situation that requires a split second decision in traffic.         

[DaveVA78Chieftain]

Seon,
The 76-81 Dodge M500/M600 chassis also used a hydroboost system (front disc / rear drum).  On the Travco site (http://www.dodgetravcos.com/index.php?p=1_46_Understanding-Dodge-Motorhome-Brakes) there is the statement:

Some of the 1976-1981 Dodge M500 and M600 chassis braking systems required high pedal effort to stop the motorhomes. The “fix” was to install a second vacuum booster in tandem with the existing booster. One source of a kit to correct this condition is Big John’s, 7917 Sev­enth St., Downey, CA 90241; (310) 869-6298.

Not sure if they are still in business or if this could possibly be applied to the Chevy P30 chassis but might be worth checking into.  I have no idea how they would have added a vacuum booster in tandem with a hydraulic based booster (hydroboost).

I have some hydroboost information on my website.  At the bottom of the page there is a link to a pdf file that provides a lot of diagnostic, repair, and adjustment information for both Dodge and Chevrolet Motorhome chassis systems.
http://dave78chieftain.zxq.net/hydroboost_brakes.html

Dave

[angrybreadbox73]

a lot of medium duty chevy izuzu ect chassis box trucks did indeed use a dual booster system if i am not mistaken for both the front and the rear brakes just for the problem you are describing but on the other hand if you are able and can find a 4 piston caliper brake setup on a similar vehicle with the same axles it could be a worthy conversion as in dealing with heavy duty and race vehicles myself alot the bigger brakes you can stuff behind the wheels the more stopping power you have and the more resistance to fade if brakes are properly ventiated now lets say ya dont wanna go that route ok no prob get high perfomance pads and shoes and get more airflow to the braking surfaces thu ductwork drilling holes in non friction areas i hope this helps oh by the way if ya think the brakes are hard now try doing an expiriment in a very wide open area and shut the engine off while slowly rolling you will see a major difference it will feel like there are no brakes at all