Eagles International Forum

Well Walter, prepared to be underwhelmed.

First, a very special warning: modifications to air brake systems must be done with every consideration that the modification will not affect the function of either the service brakes or the parking brakes. If a modification is made, the whole braking system must be tested using DOT test procedures. Further, I am not an air system expert and I am only describing what worked for me.

The simple answer that worked for me was to simply remove the service interlock valve from the system. The modification was very simple as shown in the photo below:
The service interlock valve is shown on the right and the simple bypass line is shown on the left.

This essentially connects the PP1 (parking brake valve on dash) directly to the diaphragm which compresses the parking spring (via the normal relay valves).

I made this modification many years ago and it has worked flawlessly since then.

Again, I want to make sure that it is clear that I did a ton of testing before I put the bus back on the road. On paper, it would appear to be a straight forward modification, but air brake system are complicated.

I did not do a good job of documenting the function of the PP1 valve. My best recollection is that I used the original Eagle PP1 valve, but I think I had to remove one air line. Best guess is that it was a small air line to the service interlock valve that provided a signal to move the check valve.

Jim

I'm adequately whelmed. This is a nice elegant, simple solution. When my Model 05 was modified, they ran new lines to the brake chambers. I think I will modify my Model 15 like yours, since it has been acting up from sitting around waiting for me to get things done.

Ok, so where is the valve?

I believe mine has been removed.... what they did to do that I am not sure!

The valve, on my model 10, was in the lower outer compartment below the driver's window. Lots of air components in that compartment.

Jim

Walter, if you do modify your system per my method, will you pay attention to the PP1 valve and if you had to remove a line? My poor old tired brain just can't recall.

Jim

Sure will, if I remember, you only have a couple of years on me.

Attached are pictures of the Service Interlock Valve area in a Model 10 (rust below), and a Model 15, as well as the color page in the manual showing more detail (the pictures can be zoomed). On both, they are located in the bottom of the compartments below the driver's side window. It will be a while before I play with it, but at least it is located easily, and is even labeled.

Walter, thanks for the pictures.

I never thought much about my pdf repair manual, but it is only black and white. When I looked at the page you show (with the color), it really makes a difference.

Jim

There is nothing better than the original manuals. It's not just the color coding, it's the fold-out charts for various things that are much larger than a single page. The earlier manuals that covered the 01 and 05 have very detailed technical drawings that are very good. Pdf's can be handy for searching, but I prefer the feel of a real manual. That said, the current state of digital cameras is very good for bringing the old manuals to life.

Jim,

Sorry for the delayed response.

Thank you so much for your instructions. We apparently need to get our heads examined. We weren't putting the pedal to the metal so to speak.

Thanks for showing us your customization!

God bless and happy Eagle'ing!