dunc
Active Member
- Joined
- Aug 1, 2016
- Messages
- 255
- Location
- Crawford, CO
- Aircraft
- AR-1C 915is, RAF/SH/SC
- Total Flight Time
- 5000
It's not even summer yet. As I transitioned from learning to fly gyro in the pattern, to short (<50 mile) x-country flights, in my newly purchased used RAF 2000, I noticed that the coolant temperature would run at the 225 redline, and easily approach 250 over longer distances at 4800 RPM, 70 mph cruise. I originally removed and placed the sensor in some boiling water, or about 200 F at this altitude (digitally measured) and saw the RAF gauge measuring 225 F. I figured the sensor was bad, and continued flying assuming indicate 225 was "really" 200 so "no problem".
I bought another sensor and just now replaced the old one. Same in flight measurements were seen. I returned to testing with a pan of boiling water, but this time found the gauge was properly measuring the 200 boiling temp. Both sensors measure about 50 ohms at 200 F, but I can't find what their spec is. I think I was using a battery charger during my earlier test so the battery voltage may have been higher, causing an error in the earlier meter reading of boiling water. In flight my battery voltage is about 13.3 - 13.5 volts.
So I now think I have real problem, not an instrument accuracy problem. I burped the system by squeezing the radiator hoses and no longer see any bubbles raising to the overflow tank. My water pump has the vertically mounted thermostat which I understand is more prone to air issues. The cabin heater works fine. I replaced pump and stat along with oil pump, timing belt and pulleys late last year. I have a single row radiator, and at 75 F today's density altitude was about 8000 MSL, so not a "lot" of airflow. I have not flown at sea level to see if thicker air would make a difference, thus imply a thicker (more core) radiator is needed here at my 6500 MSL home.
Ideas for what next? Any way to insure or test that no air is remaining is the coolant system?
I bought another sensor and just now replaced the old one. Same in flight measurements were seen. I returned to testing with a pan of boiling water, but this time found the gauge was properly measuring the 200 boiling temp. Both sensors measure about 50 ohms at 200 F, but I can't find what their spec is. I think I was using a battery charger during my earlier test so the battery voltage may have been higher, causing an error in the earlier meter reading of boiling water. In flight my battery voltage is about 13.3 - 13.5 volts.
So I now think I have real problem, not an instrument accuracy problem. I burped the system by squeezing the radiator hoses and no longer see any bubbles raising to the overflow tank. My water pump has the vertically mounted thermostat which I understand is more prone to air issues. The cabin heater works fine. I replaced pump and stat along with oil pump, timing belt and pulleys late last year. I have a single row radiator, and at 75 F today's density altitude was about 8000 MSL, so not a "lot" of airflow. I have not flown at sea level to see if thicker air would make a difference, thus imply a thicker (more core) radiator is needed here at my 6500 MSL home.
Ideas for what next? Any way to insure or test that no air is remaining is the coolant system?
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