Hello All
Would anyone have a service manual that shows a circuit drawing for the late model 944 brake air system? My manual has brake info that was issued in 1960 and 1963 and shows the later style air over hydraulic system but not the split system used in the final version of the 944 effective with serial 43A5043.
Also need any info about how the chamber and cylinder assembly were mounted. Photos would be very helpful.

Thanks in advance

Phil

"PhilC" wrote:

Hello All
Would anyone have a service manual that shows a circuit drawing for the late model 944 brake air system? My manual has brake info that was issued in 1960 and 1963 and shows the later style air over hydraulic system but not the split system used in the final version of the 944 effective with serial 43A5043.
Also need any info about how the chamber and cylinder assembly were mounted. Photos would be very helpful.

Thanks in advance

Phil

Here are some scans from a last of series 88J 922B parts book. The brake system layout would be identical to a later 944.

Another couple of pages; couldn't get them to attach to the original post for some reason.

Hello Rusted
Thanks for the info. Unfortunately I already have the same info from the later model 944 parts book. What I am trying to work out is the porting for the manifold which is part number 5K5306. I might have to give Tillys a call and see if they have one. Was going to make one.
Looking at the pages you posted it looks like the 944's layout is quite different but the actual lines from the pedals are the same or similar.

Regards

Phil

5k5306 manifold must be on the air side?.... OK I found it in the diagram......looks complicated!

It probably does more than this, but reduced to essentials, there’s a connection from the left brake (“clutch”) pedal output port to the transmission to “neutralize” it and also a connection (apparently through a check valve) to the output of the right brake pedal valve, feeding the air chambers. Check valve prevents the right brake pedal from throwing the transmission into neutral but allows both neutralizing and braking with left pedal.

I just realized there’s more to that explanation than I’ve thought of.....how does the air from left pedal to brake chambers not just vent out of right brake valve? If you put a check valve in the line between brake chambers and right pedal valve then how does it release the brakes ?

I’ll go look at my old 922b which I’m sure doesn’t have that complicated valve.........back later!

Ok
Supply in on bottom of left pedal valve and back out to bottom of right valve

Out of top of left valve to two things
1 through a check valve ?? to a shuttle valve?? and then to brake chamber
2 to transmission neutralizer

Right pedal valve has one in on bottom from left pedal valve (supply) and one out of top to same shuttle valve as left side and then on to brake chamber ....no check valves in the line

Sorry I don’t have a parts book to get a number for the check valve or shuttle valve. Not really sure about either of them without disassembly. Just looking at where they are and what needs to happen at that location. I think a “quick exhaust” shuttle valve is what you would need. Left brake to PRESSURE IN, brake chamber connects to CYL, and right pedal to EXHAUST. Might not even need the check valve.

Only question I have is when you apply the left brake and air fills brake chamber up to system pressure, when you release the pedal with a check valve preventing the air flowing back to the left valve, will the quick exhaust poppet cycle to dump air to the exhaust port (through right pedal valve)? Might have to NOT have a check valve in that line so pressure would drop in the supply line and allow the poppet to shift to exhaust when pedal is released.

When right pedal is actuated, the quick exhaust valve should act as a shuttle valve and sent it all to the CYL port (brake chamber)? Then you wouldn’t need the check valve. Quick exhaust shuttle valves are readily available on eBay etc.

Link to catalog page of a typical quick exhaust valve
www.asco.com/ASCO%20Asset%20Library/asco...-exhaust-catalog.pdf

Hi Team,
just found a Product Bulletin, Dated- May 02-1963, and another for--May 06 1965 that have some brake improvement detail for the 922B----the later 944 should be similar if not the same.
Last scan has a circuit diagram at least, so I hope that may help you.
Sorry about the bound book mounting of these PB's blurring the inner edges.
Cheers,
Eddie B

Looks like there is a change from the 88b to the 94a going from separate front and rear braking systems to separate left and right.

My 59a 922b has the single chamber air actuated brakes. Originally it had 4 wheel brakes on the single chamber master cylinder, but I’m down to front brakes only and glad to have them! It had not had brakes in a very long time before I got it, but I’ve gone through all 4 wheels stopping oil leaks and finally got things dried up enough that the brake shoes have a chance to stay dry. I cleaned the brakes thoroughly before reassembly and am hoping they’ll get better as time goes by and I get the chance to readjust the clearance a time or two. Rear brake hardware was torn up enough that I just took it all out and stored the remaining parts for “someday”.

I’m almost certain my brake “treadle” valves do not operate the same as the later versions shown in that schematic. They seem to be a simple valve that opens between bottom gang of 4 ports and top gang of 4 ports. Mine have supply in at bottom and deliver air out at the top when the pedal is depressed.

Hello All
Thank you very much for your help. I have been unable to source a manifold so I will have to make one. Now I have a better idea of how the system functions I can work out the porting for the manifold.

Regards

Phil