I just installed an airwolf oil filter on my M4-220C. It seems that the oil temps are running about 20-25 degress hotter now. To install we had to drop the oil cooler and change out some fittings. Now at the same time I installed 31 inch bushwheels and tail wheel. This reduced cruise speed by about 8-9 mph. The temps are running about 220 F at 23 inches MP and 2300 rpm indicating 116 mph at 2000msl OAT 65 F. Now the questiion is this rise normal because of the changing to the bushwheels or have others noticed a differnce after an airwolf installation. Or did we possibly knock somhing loose in the oil cooler when we had it off. I know the cooler was overhauled in 1999. The oil temp gauge is the original Maule temp gauge. I appreciate any advice.

Flyfish1, I think you outlined the answers.
Easy way to tell if tyre drag did it. Change back to previous tyres.
Check temp sending unit in boiling water.
Moving an old established oil cooler may have dislodged gunk and partially blocked flow.
There was an STC to fit a second oil cooler for those that ran too hot.

Is that STC for Franklins only?

Yes second oil cooler for 220 Franklins was done by Seaplanes Inc , now out of business.

Second oil cooler could also be installed on a field approval.. Just a matter of documenting temps... Would also suggest installing shut off valve on second unit to allow for cooler outside air temps in winter time.

Was there any such issues for the IO-540 on the M7-235B? I'm moving down to Idaho and last time I was down there my oil temp ran on the high limit pretty much the whole time if it was warm outside at all.
I've boiled the gauge and it's right on.
The baffling is sound.
any additives that I could run through the engine to clean the oil cooler? (trying to avoid removing it, obviously)

Akloon, when're you moving to Idaho. I'll be there this weekend.
There is a cooling air egress lip extension you can add of about 2-3" which causes more of a venturi effect to drag more air through the engine.
Sometimes I find scat hose has been routed under the cylinders above the intake tubes and that restricts flow.
There is often a lot of cooling air leakage on old tired baffling at sides and across back of engine and of course the vernatherm can be adjusted.

I usually see loose cowling, poor baffling, seal material hard and otherwise no longer soft and pliable, also quite often baffle seals not flipped to upward position, seals not sealed to baffles, intercylinder baffles completely shot or missing completely? Then the extension of lower cowl as Jeremy stated, this mod will help, but only if baffling is good and effective... It's been 90F-95F up here past week, extended climbout on floats at gross I never see above 340-350F? This is warm, but loaded hot day, high density altitude, slower climb speeds, not unusual. Cruz will drop it down to about 315F in this WX...

Jeremy (and Christie),
Nice meeting you two in Johnson Creek. We briefly discussed high oil temps on my M7-235C. I made sure the front baffles are pointed up and have the small cooling extension below the cowling. The oil temp remains high.
Have yet to check probe with boiling water and of course the vernatherm could be off. Any other ideas?
Link is photo. OAT 28 C in cruise at 21/21
http://dblranch.webs.com/apps/photos/ph ... =181633186

Dave, the oil temp gauge is so often the culprit, so now the front baffles are correct, the unquestionable first move is to ascertain the gauge and sending unit are accurate.
Sending unit in boiling water should raise the needle to 212deg.
There are two posts on back of gauge , with master switch on and a resistance of 200 ohms between post and ground, needle should indicate 140F and with resistance of 34 ohms needle should indicate 250F.
CHT gauge can be checked similarly as 34 ohms should show Cht needle at 500f while 785 ohms should show 200F.

OK. I've checked using resistors as you suggested. I find the gauge is reading about 20 deg too hot when I put the 200 ohm resistor between the post and ground. So makes me feel a bit better.

But I have some questions........

How does the resistance in the sending unit affect the reading? With the 200 ohm resistor between post and ground, the sending unit must also be connected in there with some resistance in parallel. Shouldn't that be compensated for? However when I put an ohm meter between post and ground (master switch off), I can't get a good reading of the sending unit's resistance from either terminal.

I presume the temperature gauge is linear so I can interpolate between the resistance and temperature reading (200 ohms:140 deg as 34 ohms:250 deg).

The next time I have the cowling off, I will check the sending unit with boiling water. But that may be awhile away

The only thought I might add to this is that I'm pretty sure a Franklin 6A-350 has an oil bypass that may open if your new filter setup is causing any flow restriction, thus alowing un-cooled, un-filtered oil to recirculate in your engine. This could raise oil temps, so maybe do a little research on this.

I have since fixed the problem. It was the bypass plate on the franklin which has two bypass springs. The forward is for the oil cooler. I pulled the spring out, stretched it 3/8th of an inch and added one thick AN washer. The addition of the oil filter and line increased the back pressure the same as cold oil would act on the system. The engine bypasses this oil back to the engine without going to the cooler. The increased spring tension requires higher oil pressures to bypass therefore pushing oil to the cooler. Thanks for all the helpful advice.

Glad you found it! Sorry for the slow response, I'm new here