Chevrolet DB90 Series, Руководство по обслуживанию

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Sec. 6C-78
53 AND 71 SERIES DIESEL ENGINES
c. Cylinder Head and Gasket Leaks are check-
ed by rem oving head from cylinder block. Inspect
a ll synthetic rubber se a l rings around w ater and
o il p a ssa g e s. The cylinder head can be checked for
leak s as follow s:
(1) Seal off w ater h oles in the head. This is
done by s te e l p la tes and rubber gaskets
clam ped in p lace by b olts. D rill and tap a
suitable hole in one of the p la tes to in stall
an a ir h ose connection. Install scrap or
dummy in jecto rs to insure seating of in­
jector hole tubes. Tighten injector clam ps
to 20-25 foot-pounds torque.
(2) Apply 80 to 100 p si of a ir p r e ssu r e and
im m erse in tank of water heated to 180 F .,
for about fifteen to twenty m inutes. A ir
bubbles w ill indicate leak s.
d. A ir C om pressor Check. On w ater-co o led
a ir co m p resso r, the w ater sy ste m should be p r e s ­
su r iz e d by using the procedure p rev io u sly d e s­
cribed under injector tube te s t. Whenever p ra c tica l,
rem ove crankcase bottom cover, turn engine over
manually and o b serve crankcase for water leakage.
If th is is not p ra ctica l, it w ill be n e c e ssa r y to r e ­
m ove the unit.
e. Cylinder B lock may be cracked causing
w ater in engine o il. This m aybe checked a s follow s:
(1) Using p la te s and suitable rubber gask ets,
se a l off in let and outlet h oles a ir -tig h t.
One inlet or outlet plate should be drilled
and tapped for fitting. Attach tee to fitting
with p rovision for a ir and water inlet.
(2) Adapter fitting should be equipped with
sh u t-off valve and regulated a ir .
(3) R em ove hand hole cover so as to observe
any w ater in p a ssa g e s (p orts).
(4) F ill block with hot water and p r e ssu r iz e
block with 20 pounds of a ir p r e s s u r e . Turn
engine over m anually, observing s le e v e s
and leakage of w ater into a ir p a ssa g e . Drain
engine oil and rem ove o il pan. O bserve
s le e v e s and block for cr a ck s. Turn engine
over manually again w hile inspecting bot­
tom of block.
2. Engine O il in W ater
a. Engine Oil C ooler defect is one of the m ost
com m on c a u ses fo r o il in the w ater. R em ove en­
gine o il co o ler and p r e ssu r e te s t a s previou sly
d escrib ed in "Water in Oil" procedure.
b. Cylinder Head S eals may cau se o il in w ater.
T his frequently o ccu rs at p r e ssu r iz e d v ertica l o il
p a ssa g e that su p p lies o il to the cylinder head. One
is located at the rea r of the block on the right bank
cylin d er head. Inspect th is area carefully when r e ­
m oving cylinder heads for leakage.
c . C ylinder Head may be checked a s p re v i­
ou sly-d escrib ed .
d. Engine B lock may cau se leakage of o il in
w ater if cracked betw een p r e ssu r iz e d o il p a ssa g e
and w ater jacket. Engine block te st has been p r e ­
viously d iscu ssed .
3. Fuel O il in Engine Oil
T his condition w ill usually be noticed by the
in c r e a se in o il le v e l when m easured with dipstick.
T his w ill warrant further in vestigation into the
con sisten cy of the o il (thinning).
a. Fuel Injector C ro ss-O v er P ip e s may be
sp lit at fla re or nuts of line m ayb e sp lit. Retighten
lin e if leaking only to sp ecified torque of 12-15
foot-pounds. If leak does not stop, rem ove and
exam ine. R em em ber, m ost fuel lin e lea k s are
caused by over-torquing and tw isting of lin e s.
b. Injector Body S e a ls leaking may be o b ser v ­
ed by running engine. A m irror is helpful in ob­
serv in g injector s e a ls of right bank, or rem oval
of com partm ent panel under re a r se a t.
c. Injector Dribbling may occur when the in ­
jector valve is not properly seated . T his w ill cause
p r e-ig n itio n . T his cannot be checked u n le ss put
on a testin g stand and tim ed to testin g sp e c ific a ­
tion. A drop or two of fuel at spray tip is only an
indication of fuel trapped in the spray tip and is not
detrim ental a s long a s the p r e ssu r e drop is within
testin g sp ecifica tio n s.
If fuel leak s externally from the body of the
in jector, it should be changed.
Fuel sy ste m may be checked by connecting
p r e ssu r iz e d (40 p si) fuel to outlet of the secondary
filte r and observing injector lin e s .
4. C onverter O il in Water
This is caused by the tr a n sm issio n heat e x ­
changer (converter o il cooler) leaking. To check,
rem ove tra n sm issio n heat exchanger. U sing su it­
able adapter p la te s and rubber g a sk ets, apply r e g ­
ulated a ir p r e ssu r e of 40 to 50 pounds to o il inlet
(plugging outlet). Subm erge in w ater heated to 180°F.
A ir bubbles w ill indicate leakage.
GASKET INSTALLATION
Recom m endations covering the in stallation of
g a sk ets a re provided in the follow ing sev en step s:
1. Clean a ll gasket mating su rfa ce s com p lete­
ly of old gasket m aterial. The p r e se n c e of old g a s ­
ket m aterial im p o se s an irreg u la rity betw een the
mating su r fa ces that can cau se breakage of engine
ca stin g s an d /or lea k s.
2. Check for old gasket m aterial or ra ised
m etal by sliding the sharp edge of a putty knife
lightly a c r o s s a ll gasket su r fa c e s. R em ove any
r a ised m etal with a file to en su re a proper s e a l.
B e su re a ll foreign m aterial is rem oved from
around the studs.
CHEVROLET SERIES 70*90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT