06 8600 brake issue

Hello:

We have a 06 Int 8600 day cab. with about 250K on the clock. Last 8 VIN 6J299945. This truck was a 18 wh. tractor and was stretched to a flat bed. We had a brake job done at a dealer. The petal is way too sensitive. The slightest touch and it drops anchor. At first we thought the brakes just need to bed in and all would be well. Then the truck sat for a while and we ran out of time to take it back to the dealer.

I've been told there is no adjustment to the air pressure release and the brakes need adjustment. How is this done?

We are down and out in the oil biz and now find ourselves doing all maintenance, and we are OK with that!!!

 

Thanks!!
What is normal air pressure in the brake system?

 

Howdy!
More info.
Relay valves are clean a whistle.
We have 94 PSI in both air system 1 and air system 2 by the dash gage.
The brake levers on all the wheels look to have at least 1" of swing before the pads contact the drum.
The brake petal rest on the treadle valve with no free play.
It feels like there is only off/on in the treadle valve.

 

Are you thinking we don't have enough main air system pressure for the system to function properly?

 

Thanks everybody!!!
The trailer line is plugged.
We made a gage with the correct metric fitting for the diaphragm fitting and the slightest touch to the brake petal gets you 85 PSI at the wheel.
I have a new petal ( treadle ) valve ( the one the brake petal acts on ) due in today.