vacuum brakes 1977 landyacht

[acme]

I have a 1977 31' landyacht , very good original condition, and am now going to get it back on the road. The Brakes are vacuum which I understand can be very good and I would like to keep them. When I first moved it to storage I tried hooking them up using vacuum from tow rigs brake assist. I seemed to have good vacuum to the trailer and the brake controler seemed wired corectly. All that happened was release of air from the cotroler on the trailer and no brake action. It has been in storage in AZ for at least 10 years. I guess I am hoping there are bad seals or bleading problems. I am going to work on it in a couple of weeks. Anyone have any Ideas or know of availability of parts? Any advise would be greatly apeciated. I am really looking forward to restoring this dream.

Tim

[davidz71]

Tim,
I have the same brake system on my '77 Excella 500. I will pull my service manual out tomorrow evening and see if we can troubleshoot your system.

[acme]

Craig

Thank you any help I can get. I will be in transit the next couple of weeks. On my way to the trailer in Scottsdale comming from the cold of Minnesota. Very much looking forward to the Sun and the fun of seeing the Airstream after 1.5 years. Time flys.
Thanks Tim

[davidz71]

Tim,
Vacuum to the power booster on the front behind the propane tanks usually comes off the manifold of the gas engine or tee'd into the brake booster. If the tow vehicle is a diesel then another source of vacuum must be provided. I am guessing that it is a gas engine in this case. What kind of hose did you run to the rear of the tow vehicle? I found that air compressor hose would collapse so I used 3/8 airbrake hose. What kind of female vacuum supply hose coupling did you use, 1/2" industrial or 3/8"? I used the 1/2" industrial but had to order it from Gordon Air Compressor Co. out of Memphis, TN. because I couldn't find it anywhere around here.

OK, you should have a constant flow of air (vacuum) at the rear bumper of the tow vehicle. Once connected to the trailer vacuum supply hose, it will provide vacuum through the power brake actuator. If you step on the brake, an electrical signal is sent from the brake controller to the synchronizing valve which opens an inlet port and closes the vacuum inlet port. Atmospheric pressure pushes on the diaphragm in the power brake booster and hydraulic pressure is applied in the trailer brake lines closing the brake caliphers. Are you sure that the brake controller is wired correctly and matches the trailer connector?

Here are some ideas from my manual:

PROBABLE CAUSE: REMEDY

Hydraulic fluid leakage or low fluid level in trailer brake actuator: Repair leak in system, refill, fluid level in trailer brake actuator bleed system. Check power booster stroke.

No vacuum in trailer brake actuator: Connect supply hose. Inspect supply vac. check valve on tow vehicle for proper orientation of flow.

Inoperative brake controller: Check and correct wiring. Check vehicle stop light switch.

Inoperative synchronizing valve: Check wiring. Clean filter. Check and replace valve if necessary.

Inoperative trailer power brake booster: Check booster and replace if necessary.

Brake-away check valve installed backwards: Check flow of air so that check valve is oriented correctly.
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Andy at Inland RV in CA. has parts for your brake system. He was instrumental in getting me setup for my trip to AZ. to pick up my trailer. Having a Service manual helped me understand the system and I don't know what I would have done without it. If you tell me what kind of vehicle you are towing with and what kind of controller we could start from there. If you need schematic drawings, I could xerox them and mail them to you if you want.

[acme]

I am thinking it is a hyrolic problem. But what do I know. The truck is a 1975 chev 350 v8 three quarter ton. I will try to check my e mail on the way if not thanks again and I will be in touch in a couple of weeks.
Tim

[davidz71]

Tim,
This is how I set up my vacuum source off the manifold of my '01 8.1 litre engine.

[davidz71]

Check valve in line: vacuum flow is right to left into manifold.

[davidz71]

Down to frame rail. By the way, 3/8 airbrake hose is covered by plastic wire loom to prevent chafing.

[davidz71]

At the rear bumper I fabricated a bracket made of tin and used a 3/8" hose barb screwed into the 1/2" female coupling. The 1/2" male plug was then capped with a brass cap and then dipped into that liquid rubber stuff you use for plier handles. The plug keeps the female connector clean when not towing.

[davidz71]

Plug pulled out and ready for insertion of male unit from trailer.

[davidz71]

Brake controller under dash.

[davidz71]

Two 15 or 20 amp circuit breakers on two of the elec. wires. I'd have to see which circuits were wired according to directions but it should be universal for all controllers.

[Inland RV Center, In]

Circuit breakers should "NEVER" be used in a trailer electric brake line.

The "oval" magnets used today, draw 3.5 amperes each at 13 volts DC. Therefore a maximum draw for a tandem axle trailer is 14 amps.

The theory of "NO" circuit breaker, is that should a partial short occur, such as with a badly worn magnet, some braking power will still exist.

If you use a circuit breaker, or a fuse, in the brake line, it will open, which will eliminate "ANY" possibilty of brakes.

Stopping a 5000 to 6000 pound or more trailer, requires brakes.

Without brakes, you will need to carry several bibles, rabbit feet, and extra toilet paper.

Don't take the risk.

Safety should never be compromised, "EVER."

Andy
inlandrv.com
airstreamparts.com
airstreamcandy.com

[acme]

Craig

Thanks for the great photos. I Have the same fittings I believe. Purchased from Oasis RV in Tucson. I am anxious to see it again!!!!

Tim