Brake Master Cylinder Reservoirs. Which goes to which brakes?

[Oz]

1973/1974 Indian.  RM350 (D23). 

On the brake master cylinder, there are two reservoirs.  The front is large, the rear is small.  Which reservoir goes to the front brakes and which goes to the rear?  My rear one is full, my front one is empty.  I don't want to start bleeding both sytems out if one is good.

[DaveVA78Chieftain]

You say you have an RM350.  Chart on srvice manual page 5-58/59 says you have Hydrovac power Brake system.  There is a picture of your system on page 5-52.

Dave

[Oz]

First 2 digits of VIN are R4 = RM350 for 1973.  Chassis data plate also has model as R40/D23. In '74 it would have been an RM300, one of which I had at the same time as this one and it was identical but it was a D24 model (which is exactly the same length and layout as the D23 of 1973) but the data plate on that one also had the model listed as RM350 rather than RM300 because it was manufactured very early in the year, before the conversion process and included the last of the existing 1973 chassis stock.  It's just in keeping with all the classic Winnebago anomalies.  Looking at my photos, you'd say, "Yup, 1974." as there are very distinct differences in the paint pattern and colors as well as between the style of headlight housings, but, it's a '73, RM350 chassis.

Either way, it's a Hydrovac brake system.

It appears that the front reservoir goes to the front brakes.  It's difficult to discern the line tracing from the pix, but it also appears they run to the front booster, which will need to be bled first.  If that's the case, it shouldn't take long at all to verify.

[ClydesdaleKevin]

The Ark had the same chassis and break system, and it was a BEAR to bleed.  And the brake line routing was confusing.  The way I finally got it to bleed perfectly was with a hand pump vacumm brake bleeder.  Not cheap but was the only way I could get it to work right.

As I recall, when bleeding the Ark brakes, we had to bleed BOTH slave cylinders at each booster first.  Each booster has one.  THEN you bleed the passenger rear wheel cylinder, then the driver's rear wheel cylinder, then the passenger front, then the driver front.

The vacumm pump made it fairly easy.

I'm not sure why the manual said to bleed both slave cylinders at the boosters first.  I don't know which goes to the front and which to the back, or if they cross somehow.  I just did what the manual said and it worked out great.  Patti helped by keeping the master cylinder full the whole time.

Kev

[DaveVA78Chieftain]

Mark,
Here is a link to a better copy of page 5-52: http://i286.photobucket.com/albums/ll120/BaileyDave/Winnebago/GRP-05-PG-52.jpg
You can blow it up easy and see details easier.

Yes, output of Master cylinder is feed to boosters.  Front booster is front brakes. Output of booster goes to one end (forward) of brake warning switch.  For the front brakes, there are 2 outputs (Left and right).  Rear booster goes to other end of brake warning switch.  Only one output to rear wheels from brake warning switch.    Both (front/rear) circuits act on the piston inside brake warning switch.  Requires equal pressure on each side to keep it centered.  If one circuit fails, the good side pushes the piston over causing the switch to close (brake warn light ON).  You equalize the pressure on each side of switch as part of the bleeding process.  You have to bleed your booster cylinders before bleeding  wheel cylinders.

[Oz]

Still don't know which goes to which.  I used the vacuum bleeder but it was just about useless.  Last time I bled them with it, it worked great.  This time, after about 300 pumps and getting almost nowhere, I had Tambra go in the cab and do it the old fashioned way.  The first try got all the air out and I had fluid flowing and instantly had pressure brake pedal pressure.  I had her do it 3 more times just for assurance.  I checked one front wheel and there was no air, so I really don't know which reservoir goes to which.

This topic will remain unsolved until someone figures it out.

[Froggy1936]

The larger reservoir always goes to the front brakes on all makes and models of all vehicles.  Also check for brake fluid in the vacuume hose to ea chamber as any internal leak (inside vacuume unit) will go to the engine and you will never see it  Frank

[Oz]

Thanks, Frank that helps a lot!