Figure 2-189. Trailer brake coupling installed at front of Vehicle

C3, TM 9-2320-211-20

(b) Using feeler gage (fig. 2-190), check clearance of

unloader valves; it should be 0.010 to 0.015-inch. If

clearance is not within these limits, adjust valves as

described in (c) below. If clearance is correct, proceed as

in (d) below.

Figure 2-189. Trailer brake coupling installed at front

of vehicle.

2-199. Air Compressor.

a. Air Leakage Tests. Excessive leakage at

components or at connections in the compressed air

system can be detected by the soupsuds method. With

compressed air system fully charged, coat outside of

components and connections with soapsuds to check for

leakage. A 3-inch bubble formed in three seconds is the

Figure 2-190. Checking and adjusting air

maximum leakage permissible. If excessive leakage is

compressor unloader.

found, tighten the connection or replace the component.

b. Adjust (all models).

(1) Unloader Valve Clearance Adjustment.

(c) Loosen locknut (fig. 2-190) on both adjusting

(a) Remove unloader-valve cover (fig. 2-190)

screws, turn screws until a 0.12-inch clearance is

from compressor cylinder head. Remove cover gasket

obtained, and tighten locknuts.

from cylinder head and discard it.

(d) Position new gasket on compressor cylinder

head, and install unloader-valve cover.