Good afternoon all,
I have a friend who has a 2010 Chrysler 300 with the 3.5L V6 engine in it. We were getting a misfire in Cylinder 5 and after new spark plugs and swapping coils, I did a compression test to find that all other cylinders had 160-170psi and the 5th cylinder had 40psi.
I proceeded to do a leak-down test with about 90psi of pressure on the 1st, 3rd, and 5th cylinders (bank 2). All cylinders had a little air coming from the oil fill cap, as is usually the case, but with the 5th cylinder I heard air coming from the exhaust pipe and it wouldn’t hold pressure at TDC.
I initially thought burnt exhaust valve, but upon pulling the head I noticed the valves didn’t look burnt. Now there was a good amount of carbon build-up, but what concerned me the most was the rocker arm assembly.
All rocker arm and valves seemed to line up except for cylinder 5 exhaust valves. The rocker arm on those valves seems to have literally shaved about 5-6mm of metal away, even going as far as to cutting into the black bolt you see in the pictures. The rocker arm doesn’t fully seat over the exhaust valves. All other rocker arms can be moved and wiggled by hand. The 5th cylinder exhaust rocker arm cannot, and can only be moved with a rubber mallet. What this tells me is that that rocker arm is putting pressure on the valves, while the rest of the rockers aren’t putting any pressure. Since at a resting state the rocker arm seems to be putting pressure, I’m going to still assume that there is an incomplete seal on those exhaust valves.
Would this make sense? I think the car is due for a new rocker arm assembly, about $350 on Amazon, but I’m wondering if this is likely to solve my low compression on that single cylinder problem. Valve issues seem to be common on these engines and the valve clatter was loud when the engine ran. I took the entire cylinder head to a machine shop so I guess we’ll see what happens once we get a report back.
I guess my question is, can this damage lead to an incomplete valve seat, leading to the exhaust leaking the compression? Did I make the right move?
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