Newest trouble to roll into the door. A 2006 Chevy Colorado with an intermittant check engine light. This vehicle shows random misfires at idle only on cylinders #2 and #5. This is sometimes enough to turn on CEL but not always right away. This is typical of a problem with these inline 5 cylinder heads where the valve seats aren't hardenened enough and fail early. Ruling out an ignition or fuel system misfire, an engine leakdown test is performed on this warm engine. This test fills each cylinder with air when it is at top dead center with both valves closed. If there is a significant difference between the air that goes in the cylinders and air that leaks out of the cylinders, the test indicates mechanical issues with cylinder sealing. In these cases, there is usually a major difference between cylinders five or two from the rest of them. Sure enough, most cylinders are below 15% and cylinder five is at 85% leakdown.

The only problem with these is that when you use the Kent-Moore special tool to hold the timing chain in the lower end, it either slips off the guide from being too loose or hammers the tensioner in causing it to stick in, from being too tight. Adding to this is the fact that the guide that the tool is pushing against to hold the chain, has to be unbolted from the top to remove the head. If it moves at all, the tensioner will ratchet out. In either situation the oil pan and front cover have to be removed to retime engine causing an extra 12 hours or so to be added to the repair. On an average only about 25 % of these head repairs can be done without having to pull the lower end. This particular job, the tool was inserted as according to directions but movement of the left side guide on head removal caused tensioner to extend and tool to be useless causing more work. In this one, the front axle also has to be repositioned as it interferes with the oil pan removal (4WD).

Axle rotated, oil pan removed to remove sump tube from front cover

Parts and stuff take up three benches!

Engine with no cylinder head, front cover or oil pan

New cylinder head, new gaskets

New head on engine

Cam and Sprockets installed, all timed up

Timing cover and oil pan installed

Almost all the way together minus fan and shroud