Exhaust temperature variation
Flying my Cessna T210N has been a joy with a few problems alone the way that just seem to always happen with any GA plane. However the last 3 flights have puzzled. First leg in the morning the JPI showed exhaust temperatures all over the place with 100 degrees difference between cylinders, concerning but the engine seemed to run smooth as it always has. I continued to watch it carefully for the next 2 hrs. Arrived at my destination, a few hours latter I headed back home. JPI showed everything normal now with 30 degrees difference as it has for the last year or so. So I thought whatever was clogged cleaned itself out and all better now. Until the next 2 flights, exactly the same scenario. What is going on, is it the engine or the gauge?
anyone else seen anything like this?
Comments
Well my gut thinking is if you've got something in the fuel. Two tens are known to harbor contaminants which is why you should always be rocking the wings for sumping. As a start I would suggest aggressive investigation for contaminants in the fuel system. There's about 50 questions that need to be answered try to do any kind of troubleshooting online but I would definitely start simple. Carl
IA 47yr A&P DAL A/C Inspector 172n
Also a complete and thorough check and analysis of all upper deck reference lines and connections. Carl
IA 47yr A&P DAL A/C Inspector 172n
More importantly, what is the TIT ? Is it varying and is it within the recommended limits. ?
EGTs on a turbocharged aircraft are less important.
The plane is flown just about every week so there isn't any old gas in it and I drain the sumps once a month as well as the tank drains each time I fly.
The TIT is the same in both cases, ussally 1590-1600. Each cylinder when normal is between 335 -365. 2&4 being the hotest and 1&2 being the coolest. 5 is only a little hotter on climb out.
When it messes up 4 shows like 390, 1&2 are 300-310, 5 shows 390 and 6 shows 310.
Flying it for a couple hours, top off the tanks and fly back home its all back to normal till its sits in the hangar over night and then fly it in morning the next day. I haven't figured it out yet.
It may be an induction leak on a couple of cylinders.
But, it sounds like a couple of sticking exhaust valves, which is the dreaded 'morning sickness', and clears up when hot.
A cold compression check may show the problem, but the Lycoming wobble test is better,
you can also remove the valve covers and watch the exhaust valves opening as the prop is rotated. [ easier if the top spark plugs are removed]. the valve my open ok but will not fully close.
Valve sticking normally is not an issue on a big bore Continental. Carl
IA 47yr A&P DAL A/C Inspector 172n
So, why not check ? removing the valve covers is not intrusive or difficult.
BTW, I've have had exhaust valves stick on my TCM GO-300, and the 2nd time I started using Alcor TCP, which scavenges the lead-dibromide from the valve guide and stem...solved the sticking problem. [ it converts the lead stuff to lead phosphate, which is very soft and goes out with the exhaust gas.]