Inspection

CYLINDER HEAD


Inspection


INSPECTION AFTER DISASSEMBLY

Cylinder Head Bolts Outer Diameter





- Cylinder head bolts are tightened by plastic zone tightening method. Whenever the size difference between (B) and (A) exceeds the limit, replace them with new one.










- If reduction of outer diameter appears in a position other than (A), use it as (A) point.

Cylinder Head Distortion

NOTE:
When performing this inspection, cylinder block distortion should be also checked. Inspection.
1. Using a scraper, wipe off oil, scale, gasket, sealant, and carbon deposits from surface of cylinder head.

CAUTION:
Never allow gasket fragments to enter engine oil or engine coolant passages.





2. At each of several locations on bottom surface of cylinder head, measure the distortion in six directions (A), (B), (C), (D), (E), and
(F).





- If it exceeds the limit, replace VVEL ladder assembly & cylinder head assembly.

NOTE:
Cylinder head assembly cannot be replaced as a single part, because it is machined together with VVEL ladder assembly.

Valve Dimensions
- Check the dimensions of each valve. For the dimensions, [1][2]Cylinder Head Assembly.
- If dimensions are out of the standard.
- Replace valve (EXH) and check valve seat contact. Refer to "VALVE SEAT CONTACT". (Exhaust side)
- Replace VVEL ladder assembly & cylinder head assembly. Exploded View. (Intake side)

NOTE:
Since the valve (INT) cannot be replaced by the piece, VVEL ladder assembly & cylinder head assembly replacement are required.

Valve Guide Clearance

Valve Stem Diameter





- Measure the diameter of valve stem with micrometer (A).






Valve Guide Inner Diameter
- Measure the inner diameter of valve guide with bore gauge.






Valve Guide Clearance
- (Valve guide clearance) = (Valve guide inner diameter) - (Valve stem diameter)





- If the calculated value exceeds the limit.
- Replace valve (EXH) and/or valve guide (EXH). Exploded View. (Exhaust side)
- Replace VVEL ladder assembly & cylinder head assembly. Exploded View. (Intake side)

NOTE:
Since the valve (INT) and valve guide (INT) cannot be replaced by the piece, VVEL ladder assembly & cylinder head assembly replacement are required.

Valve Seat Contact
- After confirming that the dimensions of valve guides and valves are within the specifications, perform this procedure.
- Apply prussian blue (or white lead) onto contacting surface of valve seat to check the condition of the valve contact on the surface.





- Check if the contact area band is continuous all around the circumference.





- If not, grind to adjust valve fitting and check again. If the contacting surface still has "NG" conditions (B) even after the recheck, replace valve seat (EXH). Exploded View.
(Exhaust side)
- If not, replace VVEL ladder assembly & cylinder head assembly. Exploded View. (Intake side)

NOTE:
Since the valve seat (INT) cannot be replaced by the piece, VVEL ladder assembly & cylinder head assembly replacement are required.

Valve Spring Squareness





- Set a try square (A) along the side of valve spring and rotate spring. Measure the maximum clearance between the top of spring and try square.











- If it exceeds the limit.
- Replace valve spring (EXH). Exploded View.
(Exhaust side)
- Replace VVEL ladder assembly & cylinder head assembly. Exploded View. (Intake side)

NOTE:
Since the valve spring (INT) cannot be replaced by the piece, VVEL ladder assembly & cylinder head assembly replacement are required.

Valve Spring Dimensions and Valve Spring Pressure Load





- Check the valve spring pressure at specified spring height.






- If the installation load or load with valve open is out of the standard.
- Replace valve spring (EXH). Exploded View.
(Exhaust side)
- Replace VVEL ladder assembly & cylinder head assembly. Exploded View. (Intake side)

NOTE:
Since the valve spring (INT) cannot be replaced by the piece, VVEL ladder assembly & cylinder head assembly replacement are required.

INSPECTION AFTER INSTALLATION

Inspection for Leakage

The following are procedures for checking fluid leakage, lubricant leakage.
- Before starting engine, check oil/fluid levels including engine coolant and engine oil. If any are less than the required quantity, fill them to the specified level.
- Follow the procedure below to check for fuel leakage.
- Turn ignition switch to the "ON" position (with engine stopped). With fuel pressure applied to fuel piping, check for fuel leakage at connection points.
- Start engine. With engine speed increased, check again for fuel leakage at connection points.
- Run engine to check for unusual noise and vibration.

NOTE:
If hydraulic pressure inside chain tensioner drops after removal/installation, slack in guide may generate a pounding noise during and just after the engine start. However, this does not indicate a malfunction. The noise will stop after hydraulic pressure rises.
- Warm up engine thoroughly to check that there is no leakage of fuel, or any oil/fluids including engine oil and engine coolant.
- Bleed air from lines and hoses of applicable lines, such as in cooling system.
- After cooling down engine, again check oil/fluid levels including engine oil and engine coolant. Refill them to the specified level, if necessary.