Engine temp did not rise?

RyanB

RyanB

Super Administrator
Management Council Member
PoA Supporter
Joined
Jul 21, 2010
Messages
16,258
Location
Chattanooga, TN
Display Name
Display name:
Ryan
Oil temp did not rise?

I was planning to take a school friend up flying in a 172 this evening. During preflight i checked the oil it was a little low so i filled it up where it needed to be, continued, went to runup area and did runup, oil pressure rose and was basically at max and the oil temp gauge was not reading at all, i quit the flight and went back to add more oil and noticed very little bubbles on the dip stick and seemed to be filled with plenty of oil. Any idea as to this? The plane had just been flown a few hours prior
 
Last edited:
Ryanb said:
Thats definitely possible, just strange it was flown earlier, and i assume no issues.
Click to expand...

NEVER assume.....:no::no:.

People will return planes with obvious issues and not tell a soul...:(
 
Guess the gauge is broken,can't trust the pilot that had it before you. Some pilots couldn't be bothered,or never checked the gauge.
 
N801BH said:
NEVER assume.....:no::no:.

People will return planes with obvious issues and not tell a soul...:(
Click to expand...

That is so true, as soon as i noticed, "hey the oil temp isnt reading" i taxied back onto the ramp and shut her down. I looked at the dipstick and it seemed like it needed more oil so i added some, it looked like it was over the minimum mark as normal, tried starting again and still no reading. I am going to either call or text a cfi in the morning to see what was up, its always a disappointment for the passenger that is excited about going and i hate to say "looks like we cant go today" but it all has to be right.
 
Our school had a Skyhawk that you sometimes had to tap the gauge to get it to work. Not very reassuring
 
How long was the engine running for? It does take a little time for everything to get up to temp, and many gauges dont read anything until over a certain temp.
 
Two same model Cessna 172s that I've flown recently (both 172N from consecutive production years) exhibited quite different oil temperature behaviors.

One would have the gauge start indicating a rise shortly after start and continue to gradually rise to within operating range so that it was indicating normal during runup.

The other one would show the needle pinned to the lower end and wouldn't budge from there until takeoff. First time I flew that one I sat in the runup area on a warm summer day for 10 minutes waiting for it to indicate a reasonable rise until the guy sitting right seat (who flies it regularly) said "you'll sit here all day waiting for that needle". Sure enough, after taking off the temperature indicated normally.

The two aircraft seem to have different indicator characteristics - one has a more linear indication the other one has a narrower range and higher sensitivity.
 
Don't add oil right after running the engine unless you know you are still a quart or so low. it takes time for oil to drain back.. I've seen about a 1/2 qt rise in oil on the stick by letting the plane sit for a few hours.

More oil = more coolant in the thing so the temp will take longer (although not much longer).

I typically don't see much temp till take off, (C172) Usually the gauge will come off the bottom stop at take off time, and at 500AGL it will be registering. I don't like heating the engine that fast, but as the OAT drops, there isn't much I can do without spending 10 minutes in run-up.
 
mattg said:
Don't add oil right after running the engine unless you know you are still a quart or so low. it takes time for oil to drain back.. I've seen about a 1/2 qt rise in oil on the stick by letting the plane sit for a few hours.

More oil = more coolant in the thing so the temp will take longer (although not much longer).

I typically don't see much temp till take off, (C172) Usually the gauge will come off the bottom stop at take off time, and at 500AGL it will be registering. I don't like heating the engine that fast, but as the OAT drops, there isn't much I can do without spending 10 minutes in run-up.
Click to expand...

I second this. My 182 takes up to 9 qts, usually I put in 8. After running the engine the dipstick will read 6 because a lot of the oil is coating engine parts. I actually find that the most accurate reading for my (owned and one-pilot) plane is the first time I pull the dipstick out. After that the tube gets boogered with oil and the reading becomes unclear.

In the OP it does sound like the temp gauge is broken. I have fuel gauges that require me to tap on them to get them to come off zero sometimes. Once they unpeg themselves they seem to read just fine. Maybe the gauge was stuck?
 
Talked with a CFI today and said being that the engine was cold and weather was cool, the gauge reads slowly. He said the gauge was reading today, so next time i will wait longer to see if it rises.
Question: even this oil temp guage will read in the green even if it hasnt rose, so as long as it doesnt show its past all the green is it still safe to fly. If the gauge hasnt rose, but is still in the green?
 
Frequently you will get no indication at all on the temp guage for the oil until you're in the air and climbing. The oil isn't like a cylinder head which warms up quick when running. As others noted adding more oil only increases the amount which must be heated in order to get a reading. Most of the guages don't start reading til they get to near 100 deg F. So with all that I'd suggest that you don't worry about no temp indication until you've got a bit more runtime and more under real power at that. Ground runs don't make a lot of heat and with the slow transfer of this heat to the oil you could be waiting a while.

Frank
 
For some perspective, this is from a 1978 Cessna 172N POH:

8ynyhy3e.jpg


I experienced this in Michigan during our very cold winter. I have never experienced this with an OAT above 25 degrees F or so.
 
^^^

I was going to mention this, but mid-60's is not cold weather ops.
 
Yes, this was in low to mid 60's and engine was cool to the touch as i remember. Said the gauge rises slowly being that it was cooler outside
 
You must log in or register to reply here.
Back
Top