Engine Performance problem
1998 Dodge Ram V8 Four Wheel Drive Automatic 160 miles
I recently replaced the heads on my 2500 because it had a hole burnt thru the exhaust valve # 8 cylinder. The truck ran really great for 1000 miles and then the CEL came on and the codes were for misfire detected on cylinders # 5 and 6, I was baffled because the engine was running really awesome at the time except a very little stammering at idle that it has had since it was new. As time progressed a noise was noticeable while accelerating under load that was similar to a exhaust leak, every time I have tried to locate the source I cannot here the noise in the engine compartment or from below. It also seems I need to drive a bit before I can hear it. It has gotten worse with time and I have stopped driving the truck except for times of dire need for fear something is going to be damaged badly.
I have checked the compression on # 6 cylinder and it is 135, however with a leak down test I couldn’t get it to hold air until I loosened the rocker arms no matter how I bumped the engine there seemed to be no spot that both valves were completely closed is this normal or is a possible problem in the camshaft and or valve train? Sometimes when I am driving the noise sounds like it may be a lifter or something like that. I can repair any thing that the problem may be but would like to know what it is before I start blindly taking stabs it. I used Felpro gaskets and replaced the head bolts with new Felpro bolt so I can’t hardly believe I have a blown gasket but that is the most likely candidate for a culprit I can come up with. In the mean time the idle has gotten a little rougher but my battery went dead a few times and the light resets when this happens it takes a while to come on again I will run a tank or more of gas before the light comes back on.
If you backed the rocker arms off enough that there was slack in th evalve lash and it still wouldnt hold air, need to find out where it is going, out the exhaust, up through the intake or into the crankcase. Apply air to the cylinder and open the throttle, listen at the tail pipe or pull the oil filler cap and see what you come up with
June, 12, 2008 AT 4:52 PM
I am sorry but I believe you misunderstood, I said it did not hold air UNTIL I backed off the rockers before I did that air always came out either thru the intake or exhaust no matter where I bumped the engine to. I tried at least 4 different spots in the compression stroke for that cylinder and air would leak but once I backed off the rockers it held and did not leak air to exhaust, intake, or block. I take this to mean that with the rockers torque down the valves are never closed completely at the same time. But once there is slack in valve train everything is ok. Is it possible for the lifters to get pumped up too high and not collapse back down like normal?
June, 13, 2008 AT 7:35 AM
My bad, Did you have a valve job done when the heads were off? If so the installed height might be too tall thus the valves are held open all the time. If not, it is possible for the lifters to not bleed down, causing the same problem, unusual for it to be both on one cylinder