Jeep Cherokee 1999 Electronic Service Manual page 1125

9 - 12 ENGINE
SERV I CE PROCEDU RES
VALVE SERVICE
Th is pr ocedu r e is don e wit h t h e en gin e cylin der
h ea d r em oved fr om t h e block.
DISASSEMBL Y
(1) Rem ove t h e en gin e cylin der h ea d fr om t h e cyl-
in der block. Refer t o cylin der h ea d r em ova l a n d
in st a lla t ion in t h is sect ion .
(2) Use Va lve Spr in g Com pr essor Tool a n d com -
pr ess ea ch va lve spr in g.
(3) Rem ove t h e va lve locks, r et a in er s, a n d spr in gs.
(4) Use a n Ar ka n sa s sm oot h st on e or a jeweler s
file t o r em ove a n y bu r r s on t h e t op of t h e va lve st em ,
especia lly a r ou n d t h e gr oove for t h e locks.
(5) Rem ove t h e va lves, a n d pla ce t h em in a r a ck in
t h e sa m e or der a s r em oved.
VALVE CLEANING
(1) Clea n a ll ca r bon deposit s fr om t h e com bu st ion
ch a m ber s, va lve por t s, va lve st em s, va lve st em
gu ides a n d h ea d.
(2) Clea n a ll gr im e a n d ga sket m a t er ia l fr om t h e
en gin e cylin der h ea d m a ch in ed ga sket su r fa ce.
INSPECTION
(1) In spect for cr a cks in t h e com bu st ion ch a m ber s
a n d va lve por t s.
(2) In spect for cr a cks on t h e exh a u st sea t .
(3) In spect for cr a cks in t h e ga sket su r fa ce a t ea ch
coola n t pa ssa ge.
(4) In spect va lves for bu r n ed, cr a cked or wa r ped
h ea ds.
(5) In spect for scu ffed or ben t va lve st em s.
(6) Repla ce va lves displa yin g a n y da m a ge.
(7) Ch eck va lve spr in g h eigh t (F ig. 2).
VALVE REFACING
(1) Use a va lve r efa cin g m a ch in e t o r efa ce t h e
in t a ke a n d exh a u st va lves t o t h e specified a n gle.
(2) Aft er r efa cin g, a m a r gin of a t lea st 4.52-4.49
m m (.178-.177 in ch ) m u st r em a in (F ig. 3). If t h e m a r-
gin is less t h a n 4.49 m m (.177 in ch ), t h e va lve m u st
be r epla ced.
VALVE SEA T REFACING
(1) In st a ll a pilot of t h e cor r ect size in t h e va lve
gu ide bor e. Refa ce t h e va lve sea t t o t h e specified
a n gle wit h a good dr essin g st on e. Rem ove on ly
en ou gh m et a l t o pr ovide a sm oot h fin ish .
(2) Use t a per ed st on es t o obt a in t h e specified sea t
widt h wh en r equ ir ed.
Fig. 2 Valve Spring Chart
VALVE STAND DOWN
Va lve st a n d down is t o m a in t a in t h e a dequ a t e com -
pr ession r a t io.
(1) In ver t cylin der h ea d.
(2) F it ea ch va lve t o it s r espect ive va lve gu ide.
(3) Usin g a st r a igh t edge a n d feeler ga u ge (F ig. 4),
ch eck va lve h ea d st a n d down : In let va lve h ea d st a n d
down .80 t o 1.2 m m (.031 t o .047 in .) a n d exh a u st
va lve st a n d down .79 t o 1.19 m m (.031 t o .047 in ).
(4) If va lve h ea d st a n d down is n ot in a ccor da n ce
wit h a bove, disca r d or igin a l va lves, ch eck st a n d down
wit h n ew va lves a n d r ecu t va lve sea t in ser t s t o
obt a in cor r ect st a n d down .
VALVE GUIDES
(1) Va lve Gu ides h eigh t r equ ir em en t .
(2) Mea su r em en t A (F ig. 5): 13.50 - 14.00 m m .
VALVE STEM-TO-GUIDE CLEARANCE
MEASUREMENT
(1) Mea su r e a n d r ecor d in t er n a l dia m et er of va lve
gu ides. Va lve gu ide in t er n a l dia m et er is 8.0 t o 8.015
m m (.3149 t o .3155 in s.).
(2) Mea su r e va lve st em s a n d r ecor d dia m et er s.
In t a ke va lve st em dia m et er 7.94 t o 7.96 m m (.3125 t o
.3133 in ). E xh a u st va lve st em dia m et er 7.92 t o 7.94
m m (.3118 t o .31215 in ).
(3) Su bt r a ct dia m et er of va lve st em fr om in t er n a l
dia m et er of it s r espect ive va lve gu ide t o obt a in va lve
st em clea r a n ce in va lve gu ide. Clea r a n ce of in let
va lve st em in va lve gu ide is .040 t o .075 m m (.0015
t o .0029 in ). Clea r a n ce of exh a u st va lve st em in va lve
gu ide is .060 t o .095 m m (.0023 t o .0037 in ).
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