Question about 1993 Chevrolet S-10
I have a 1993 chevy s10 4wd.with a 4.3 v6.throttle body injection.It started not running well one day.changed plugs wires the works.Well i found #5 cyl had only about 20 lbs of compression.I put oil in cyl to check for broken ring.Nothing changed.same compression.And it makes a loud whining noise like a vac leak.Could this be a valve leaking.Man im stumpped. The noise seems to be comming from inside the engine.
A leakdown test is where you remove the spark plug from the problematic cylinder,and install an adapter and air hose,shop air,about 90 to 120 psi.You have to be certain both valves are closed on that cylinder,and i do this by removing the valve cover on that bank,rotate the crankshaft and watch the rocker arms work on that cylinder,and watch them close completely.Now,install the shop air,and listen for air hissing in the tailpipe,this checks the exhaust valve,and then the intake manifold,this checks the intake valve.Now,you can also listen in the crankcase,and if you hear hissing in the crankcase,then you have bad rings,or a piston with a hole in it.
Posted on Sep 23, 2008
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