Cause of my recent low (190-210*F) CHT's on #4 cylinder, with normal
pre-start readings and normal EGT's and power in flight, was just what one
might suspect before even pulling the cowl - a faulty sensor; in this case,
dangling free of the cylinder head, leaning against the intake manifold
tube.
What's curious is how the twist and lock spring-loaded connector came loose
on this bayonet probe: the tiny spot-welded pin that protrudes radially from
the side of stainless barrel that screws into the cylinder head, which the
probe cap is slotted to lock upon, fell out of its hole. I will find out
soon if I need to buy a whole new sensor or just the mounting assembly.
These probes are 12 years old and have 750 hours on them. I see no way to
anticipate or detect this kind of failure before it happens. Fortunately,
it's not a big safety-of-flight item to suddenly get a low CHT reading if
the engine is still making normal power.
Off to call GRT and see what's available in the way of spare parts...
-Stormy
