Check For Valve Wear At The Points Shown Here; Valve Stem Tip Wear Patterns - Jeep cherokee 1989 Owner's Manual

Table of Contents

9.12

Check the cylinder head gasket surface for warpage

by trying t o slip a feeler gauge under the straightedge

(see the Specifications for the maximum warpage allowed

and use a feeler gauge of that thickness)

that may have formed in them.

Run an appropriate size tap into each of the threaded holes to

remove corrosion and thread sealant that may be present. If com-

pressed air is available, use it t o clear the holes of debris produced

by this operation. Warning: Wear eye protection when using com-

pressed air!

Clean the rocker arm pivot bolt or stud threads with a wire brush.

Clean the cylinder head with solvent and dry it thoroughly. Com-

pressed air will speed the drying process and ensure that all holes and

recessed areas are clean. Note: Decarbonizing chemicals are available

and may prove very useful when cleaning cylinder heads and valve

train components. They are very caustic and should be used with cau-

tion. Be sure to follow the instructions on the container.

Clean the rocker arms, pivot balls or fulcrums, nuts or bolts and

during the cleaning process). Compressed air will speed the drying pro-

cess and can be used t o clean out the oil passages.

Clean all the valve springs, spring seats, keepers and retainers (or

rotators) with solvent and dry them thoroughly. Do the components

from one valve at a time t o avoid mixing up the parts.

Scrape off any heavy deposits that may have formed on the valves,

then use a motorized wire brush to remove deposits from the valve

heads and stems. Again, make sure the valves don't get mixed up.

Inspection

Note: Be sure to perform all o f the following inspection procedures

before concluding that machine shop work is required. Make a list of

the items that need attention.

Cylinder head

1 1

Inspect the head very carefully for cracks, evidence of coolant

leakage and other damage. If cracks are found, check with an auto-

motive machine shop concerning repair. If repair isn't possible, a new

cylinder head should be obtained.

Using a straightedge and feeler gauge, check the head gasket

mating surface for warpage (see illustration). If the warpage exceeds

the specified limit, it can be resurfaced at an automotive machine shop.

Note: If the V6 engine heads are resurfaced, the intake manifold flanges

will also require machining.

Examine the valve seats in each of the combustion chambers. If

they're pitted, cracked or burned, the head will require valve service

that's beyond the scope of the home mechanic.

Check the valve stem-to-guide clearance by measuring the lateral

movement of the valve stem with a dial indicator attached securely

to the head (see illustration). The valve must be in the guide and approx-

imately

6-inch off the seat. The total valve stem movement indicated

by the gauge needle must be divided by t w o to obtain the actual

clearance. After this is done, if there's still some doubt regarding the

condition of the valve guides they should be checked by an automotive

machine shop (the cost should be minimal).

The Motor Manual Guy

Chapter 2 Part

General engine overhaul procedures

A dial indicator can be used t o determine the valve

9.14

stem-to-guide clearance (move the valve stem as

indicated by the arrows)

Valves

15 Carefully inspect each valve for uneven wear, deformation, cracks,

pits and burned areas (see illustrations). Check the valve stem for

scuffing and galling and the neck for cracks. Rotate the valve and check

for any obvious indication that it's bent. Look for pits and excessive

wear on the end of the stem. The presence of any of these conditio

indicates the need for valve service by an automotive machine sho

NEW VALVE