mystery tanks/cylinders under chassis?

[The_Handier_Man1]

From: 70winnie  (Original Message)
Sent: 6/22/2005 1:05 PM

I have these... tanks? cylinders?  under my winnie, on the outside of the frame between the battery tray and the waste tank, driver's side:

http://ama3.com/temp/mysterytanks.jpg

I thought they were part of the brake system but now I'm not so sure.  The hose that leads to the top of the photo goes into the side of the battery tray and then STOPS.  it's open to the tray, not plugged or anything.  (I was so confused when I discovered this that I forgot to follow the OTHER hoses/tubes to see where they go!)  Now I'm wondering if that hose is some sort of emergency pressure release.

Anyway, does anyone know what these babies are for?  And whether it's OK for that hose to just dump out into the battery tray?  (I haven't seen anything come out of the hose, but I haven't tested it in any way).



From: Slantsixness
Sent: 6/22/2005 1:19 PM

Andrew,
Hydrovac boosters. (I won't tell anybody here you didn't know they were there...uh oops, I guess I did!)

Denison might know if the hose is actually just a vent, or it actually connects to something. If it's just a vent, nomally there is a little fresh air filter behind the driver's seat that it's connected to (looks like an odd oil filter) I don't think it should just lay in the battery tray though....

Tom



From: denison
Sent: 6/22/2005 4:08 PM

One of the large diameter rubber hoses should connect both boosters to the intake manifold, and should have a one-way check valve in the line between the manifold and the boosters. This is the vacuum TO the boosters. The other large diameter hose is the atmospheric air that is vented into both boosters when you step on the brake. It is normally connected to a small air filter, located somewhere as far as possible from moisture and dirt. At floor level just behind the driver is where many of them appear. I cant tell from the picture which hose goes where though.
In normal ops with the engine running, there is a vacuum pulled on both sides of the rubber diaphram inside the large chambers.
When you step on the pedal, the brake fluid from the master cylinder pushes open the air control valve on each booster, to let outside air into the side of the air chamber furthest from the booster piston - providing the increased brake fluid pressure to stop the RV.
Based on how rusty those boosters look, I would recommend budgeting for getting them rebuilt by Alretta before long. The rubber diaphrams inside can split, the air control valve can get gummy, etc.
I would bet that if you could see inside the boosters it would give you nightmares.



From: ClydesdaleKevin
Sent: 6/22/2005 9:19 PM

Those are your brake boosters.  One hose should go to your intake manifold, and the other hose goes to a small air filter...probably right around where your battery tray is.  It is indeed a crucial part of your braking system!

Kev



From: 70winnie
Sent: 6/22/2005 9:55 PM

Thanks for the replies and explanations.  I should mention the reason I was "poking around down there" is that almost all of the brake fluid has disappeared from my master cylinder.  Needless to say, the brakes don't work.  Fortunately, the vehicle was moving under the engine's idle when I found this out!  There doesn't seem to be any leakage around these boosters but there does appear to be leakage under the engine, forward of the tranny pan.  I didn't have a good light with me so I couldn't investigate further.  Looks like I might be replacing the entire brake system before too long!

I guess I'd better read up on the subject.... anyone have any book or website recommendations on the subject for someone with limited mechanical experience?



From: Slantsixness
Sent: 6/23/2005 7:00 AM

Andrew,
Your proportioning valve is likely right in the frame where you are describing this leak. It looks like a junction block for brake lines. Probably one of these lines let go (rust/corrosion). replacing the line isn't all that hard, but it would be best to invest in a good quality line wrench, rather than trying to remove it with a standard open end wrench.

Line wrenches look like box end or closed end wrenches, but have a slit cut out to enable you to put the wrench on the hydraulic line.
The reason you don't want to use an open end wrench is that it only contacts the fitting in two places, and will usually strip the fitting nut. Plus, these things are really tight, to so sometimes a well placed light tap at the base (head) of the wrench will work it loose. (Naturally, spray P'blaster (best penetrant on Earth) all over the fitting to remove corrosion)

Any Auto parts store will carry these hydraulic lines, but invest in a hinged tubing bender (around $15) and you can make professional looking and reliable replacement brake lines.

But check to see where it's leaking... could be corrosion, kinked or cracked line, loose fitting, but likely one of your lines has given up on you.

Tom



From: denison
Sent: 6/23/2005 8:36 AM

While you are replacing one line, inspect all of the others too. And if you havent replaced the brake hoses, this would be a good time to do that - while you are spending time underneath, soaking all of the fittings with penetrating oil (I still have some of my last gallon of WD-40 left, and would buy PB blaster if I saw it in a gallon). If you can give the brake fittings a few days of being soaked daily with the penetrating oil it will help. I cant recall whether the brake flare nuts on the winny are 5/16th or 3/8th, probably both. As slantsixness says, the flare nut wrenches are vital though. And you want the kind that are 6 point, not the 12 point ones.
I managed to get all of my brake fittings freed up the first year I had mine, and about each 2 or 3 years since I loosen and retighten them, just so they dont become impossible to unscrew. Once you have a nut broken free from the fitting it is in, it still might be rusted onto its brake line, and twist that off. This is a nuisance, and usually means you have to replace the rest of that brake line too.
I wish you luck: in other words, that you get the work done without recourse to vise-grip pliers