High oil temp

[a64pilot]

Do you have the inter-cylinder baffles from the "Summerization" kit? Also, items 41 and 44, and 56 and 57 in figure 37 of the parts catalog. How are the seals around the front, sides and across the top back?

Fig 38 maybe part numbers roughly from 95 to 105 maybe?
https://cessna120140.com/wp-content/upl ... g-140a.pdf

Fig 37 is the cowling?

[6643]

Are we talking about a 140 or a 140A? What year is it?

[a64pilot]

1946 140
I see my mistake, but yes I have the baffles, and a blast tube, I even have the oil tank shield.

I ordered a spring, convinced that’s not it, but too easy and cheap to not try it.

[6643]

I have all those on a C90. I know it's a little warmer where you are, but, I don't think I've ever seen temps over 190. I attribute it to tight baffles and clean living.

[a64pilot]

How your oil pressure though? I’m running 40 until 170 or so then drop to 30 when close to 200, it’s the pressure that’s a concern, and it seems tied to temp.
200 isn’t high for oil, heck the wife’s car has an oil cooler, that’s cooled by the 195 coolant, just normal around town driving it’s over 215 or so.
I know my 140 isn’t a car, but nothing bad happens to oil at 200F.

[6643]

Oil pressure has never given me anything to be concerned about. IIRC, it's always been over 40. But, then, since there's no temp issues I wouldn't expect a pressure problem, either.

[a64pilot]

If you have seen 190, then you have gotten as hot as I have.
I don’t understand my pressure drop. It’s definitely temp related, but I don’t understand what’s making it happen
The link posted earlier had a nearly identical problem, but unfortunately they never posted the resolution.
I got my spring today, tomorrow I’ll pull it and inspect the plunger and seat and replace the spring. I don expect it to do anything, but at least I’ll eliminate it as a possibility.
I think it’s my accy case somehow, and I ought to overhaul the bottom end just so I know where I’m at, but the crank is why I haven’t.

[a64pilot]

Well it WAS the spring. I ordered the spring from Fresno air parts, like $9 for the spring and $12 shipping.
When I removed the spring and looked at the new one I thought no way they sent me the right spring it’s way too short, but after checking it, there was significant compression even with the short spring so I thought may as well run it up and see if I have oil pressure. On run up at 1000 RPM I have 45 PSI, 60W oil cold as in 80F or so.
Takeoff and climb she holds the 45 until about 175 or so when it drops back to 40 ish, I had to hang it on the prop climbing for it to get to 200 where it held 35 to 37, it will hold 30 at 1700 RPM with 200F oil. So I think my problem is fixed, it’s a little over 90F on the ground now and humidity real high as there are popcorn showers all around, so 190 cruise I’d say is normal as it’s 90 at 1,000 MSL.
Pic is of the two springs, long one came out, short one is the correct spring, no shimming on either.
I theorize the long spring didn’t have enough tension and was almost completely stacked up, and with engine running the plunger was off its seat and the spring stacked up, so it would hold enough pressure until it got thin, then pressure would come down. Normally the spring would close the plunger to keep pressure up, but the incorrect spring didn’t have enough tension.
My theory anyway, but the learning point for me is if your having oil pressure problems, try a new spring, they are only $9.

[6643]

My bet is someone thought stretching the spring would make it work better...

[simonlowther]

My bet is someone thought stretching the spring would make it work better...

Careful John, someone will accuse you of being a cynic!