Engine Cylinder Leakage Testing - Task No 1 - Monday 9th March 2015

Plan:

Gather all tools, equipment and retrieve vehicle information.  Inspect vehicle and check fluid levels prior to conducting a start to ensure correct prior operation.

• Conduct Cylinder Leakage Test and Report.
• Check Valves and Pistons for wear and Report.
• Check Cylinder Head for distortion and Report.
• Demonstrate correct assembly and Valve Timing of Cylinder Head and Report.
• Check Cylinder Bores for Taper & Ovality & Report.
• Complete Knowledge Questions (Within Portfolio).
• Complete Blog.
• Report to Assessor after each section with Analysis and Diagnosis.

Vehicle Checks - Analysis

Engine Oil
Discolouration &
Odour

Healthy Battery

Upon checking oil it appeared discoloured (approaching emulsified), and smelt distinctly of fuel.  Initial indications thus far suggest an issue with Piston Rings/Oil Control Ring.  Header Tank was also below the minimum level required.

Diagnosis:

Investigate Oil issue further and undertake Cylinder Leakage Test.  Upon conclusion of all further tests, also top up the Header Tank to the correct level with a 50/50 mix of anti-freeze (sample of current type in use to be extracted from system at suitable access point).

Task Progression

Remove HT Leads, Spark Plugs, Header Tank Cap, Dipstick and Cam Cover.

Analysis Spark Plugs:

All Spark Plugs were already loose.  Manufacturer's Data specifies a Spark Plug Gap of between 1 - 1.1 mm  and a Torque of 17 nm.

Plug Cylinder       Measured Gap      Condition

            1                     0.95 mm                    Clean

            2                     1.15 mm                     Heavily Sooted

            3                     1.00 mm                    Heavily Sooted

            4                     1.04 mm                    Heavily Sooted

Diagnosis Spark Plugs:

Plug 1 was relatively clean whilst Plugs 2-4 were heavily sooted.  Initial indications were a lean burn in Cylinder 1 and a rich burn in Cylinders 2-4.  However upon further interrogation of the customer, it became apparent that the plug on Cylinder 1 had been more recently replaced due to a cracked ceramic.  Due to the condition of the remaining 3 spark plugs, I would recommend replacement with 4 new spark plugs gapped accordingly.

Analysis Cylinder Leakage Test:

Reading Cylinder 1

I connected the Cylinder Leakage Test Equipment to each of the 4 Cylinders (with piston TDC in each), in sequence of the firing order (1, 2, 4, 3) and recorded the following results:

Cylinder 1 - 45% - Evidence of air escaping Dipstick Tube.

Cylinder 2 - 40% - As above.

Cylinder 4 - 35% - As above.

Cylinder 3 - 37% - As above.

Diagnosis:

In light of the evidence of fuel in the oil, and with the levels of air escaping from Dipstick Tube, I would recommend further investigation by removal of the Cylinder Head in order to examine more closely the Piston Rings.

Removal of Valve,
Collets & Spring

Analysis of Valves (Cylinder Head Removed):

Using a spring compressor, valves were removed and laid out in sequence.  Checks undertaken were as follows:

• Stem Straightness.
• Visual Examination for pitting or gouging.
• Check of Valve Stem to Guide Clearance (Manufacturer's Data 0.015-0.042 mm).

Diagnosis of Valves:

Valve, Spring &
Collets

Checking Valve
Stem to Guide
Clearances

Stem straightness's were confirmed as serviceable by rolling on a flat surface.  Using a steel straight edge as a base for the DTI Gauge (Alluminium Head), the Valve Stem to Guide Clearances were confirmed at 0.016 mm, which is within Manufacturer's tolerances.  Visual inspection revealed pitting and other surface markings, which would require the re-lapping of all valves accordingly.

Analysis Cylinder Head & Block Distortion:

Manufacturer's Data specifies distortion allowance at 0.025 mm.  The finest feeler blade available at the time of examination was 0.05 mm.  Using this gauge blade my diagnosis is as follows:

Diagnosis Cylinder Head & Block Distortion:

Straight Edge &
Feeler Blades

Highlighted Areas are Points Measured
in excess of 0.05 mm

Until such time a finer feeler blade can be acquired, I would recommend the re-skimming of both the cylinder head and block accordingly.  A suitably over-sized Head Gasket would also need to be provided in order to maintain recommended compression ratio's, volumetric efficiency and piston clearances.

Analysis Valve Clearances:

Manufacturer's Data recommends that the Valve Clearances be as follows:

Inlet: 0.20 mm (cold)  Exhaust: 0.30 mm (cold)

Measuring Valve
Clearance

Results were as follows:

Cylinder 1  Inlet: 0.432 mm  Exhaust: 0.356 mm
Cylinder 2  Inlet: 0.535 mm  Exhaust: 0.356 mm
Cylinder 3  Inlet: 0.432 mm  Exhaust: 0.406 mm
Cylinder 4  Inlet: 0.432 mm  Exhaust: 0.483 mm

Diagnosis:  New shims would be required in order to meet Manufacturer's specifications.  Removal of Camshaft and old shims recommended in order to calculate correct sizes.





Analysis Camshaft & Bearing Caps

Sheared No 4 Bearing Cap

Upon removal of the Camshaft it became apparent that the No 4 Camshaft Bearing Cap was sheared and therefore un-serviceable.

Diagnosis:

It may be possible to purchase an individual Bearing Cap, as this is a cast iron Cylinder Head and block.  Alternatively a new Camshaft with 5 Bearing Caps would need to be provided. 

Analysis and Measurement of Shims:

Measuring Shims

Shims were measured with a micrometer and the measurements recorded as follows:

Cylinder 1  Inlet:  3.19 mm  Exhaust:  3.74 mm
Cylinder 2  Inlet:  3.93 mm  Exhaust:  3.74 mm
Cylinder 3  Inlet:  3.77 mm  Exhaust:  3.83 mm
Cylinder 4  Inlet:  3.84 mm  Exhaust:  3.75 mm

Detailed calculations and method used can be found within my Portfolio. I have provided below an image of the respective piece of work :

Shim to Valve Clearance Re-sizing Calculations

Diagnosis

New shims to be provided accordingly.







Analysis of Cylinder Taper & Ovality:

Taper & Ovality
Measurements

Manufacturer's Data recommends a Cylinder Bore size of 79.50 mm.  Measurements were recorded using a Telescopic Bore Gauge and Micrometer.

Diagnosis of Cylinder Taper & Ovality:

All measurements were within a maximum 1 mm tolerance. Maximum Taper is in Cylinder No 3 (0.54 mm) and maximum Ovality was recorded in Cylinder No 1 (0.60 mm).










Overall Diagnosis for Customer

Replacement  8 Piston Rings and 4 Oil Control Rings.

Replacement and gapping of 4 Spark Plugs.

Re-lapping of all valves and seats.  

Cylinder Head to be skimmed and suitably oversized Head Gasket to be purchased. New shims to be ordered and replaced as follows:

Cylinder 1  Inlet:  3.19 mm  Exhaust:  3.74 mm
Cylinder 2  Inlet:  3.93 mm  Exhaust:  3.74 mm
Cylinder 3  Inlet:  3.77 mm  Exhaust:  3.83 mm
Cylinder 4  Inlet:  3.84 mm  Exhaust:  3.75 mm

Replacement of a Camshaft Bearing Cap No 4 or, alternatively replacement of Camshaft and 5 corresponding Bearing Caps.

Replacement of Manufacturer's specified quantity and grade engine oil.

Replacement of Manufacturer's specified quantity coolant mixture (50/50).