Fig. 40M-Checking Bellows Load
Fig. 42M-Modulator Bellows Good
Holding the modulators in a horizontal position, bring
them slowly together under pressure. The modulator
bellows in question, if defective, will reach the center
line of the comparison gage before the known good
modulator lines up with the outer gage line.
If the modulator bellows in question is good, both modu
lator assemblies will be within the outer gage lines as the
assemblies are slowly brought together.
Vacuum Diaphragm Leak Check.
Turn modulator so vacuum line stem points downward. If
Fig. 41M-Defective Modulator Bellows
IMPORTANT: Gasoline and/or water vapor may settle in
the vacuum side of the modulator. If this is found WITH
OUT the presence of oil the modulator MUST NOT BE
Check solution that comes out of the modulator for evi
dence of lubricity. If the solution does not have the feel of
oiliness, it can be assumed the solution is a mixture of gas
and/or water. The way transmission oil can be on the vacuum
side of the modulator is by a leak in the vacuum diaphragm.
If oil is found, the modulator must be replaced. If oil is
not found in the vacuum side of the modulator but the trans
mission oil level is continually low, and NO external leaks are
found, there is a possibility that a pin hole leak exists in the
diaphragm and the modulator should be replaced.
Inspection for External Damage.
Check for dents or cracks in modulator.
b. Check modulator valve sleeve alignment. Roll modu
lator on a flat surface to determine if the sleeve is
concentric to the modulator can. If the sleeve is bent,
runout will be visible, and modulator must be replaced.
If the modulator passes the above checks, the following
items should be checked as a possible cause of the problem.
Check freeness of modulator valve in modulator.
Check freeness of modulator valve in transmission case.
c. Check the vacuum line from the manifold to modu
lator for holes, cracks or dents. Check the rubber hose