The International Cessna 170 Association

Hello All,

Summer has finally arrived in Southern B.C., and temps in the Interior approached 100 deg. F. this past weekend. Departing Vernon (about 1400' ASL) with 1 passenger & some baggage at about 2000 lbs we achieved an initial climb rate of about 300 fpm, and the oil temp quickly rose close to the redline. I have an original oil temp gauge in my 1950 A model / C-145 - it was subjected to the boiling kettle test at annual a couple of weeks ago and was pronounced to be "spot on". Minimum altitude for the latter part of the VFR route back to the coast was 6500', so my plan was to climb until the oil temp redlined & then level off for a while to cool down, then climb some more, etc. The needle just grazed the left edge of the redline for the first time as we leveled off at 6500 from a 50 to 100 fpm r.o.c., and after about 10 minutes of level flight we gained about a 1mm gap between the needle and the redline.

So, after the long winded story, some questions ...

1) Does this kind of performance on a 90 to 100 degree day sound familiar to people flying behind the C-145 or O-300? My 180 lb nephew had asked asked at the last minute to come along and I refused because I was a worried about performance. Glad I did!

2) The engine has an F&M oil filter adapter installed - has anyone tried an Airwolf oil chiller with this setup? I have searched the web for opinions/experiences and haven't found much. The price is right and the thing couldn't be simpler, but the extra weight hanging on the adapter might not be such a good thing.

Experiences, opinions, guesses?

Thanks,
David Blom
1950 170A C-FNIE

Check the engine type sheet....the permissible oil temp is no longer the 225 red line on your
original temp gauge....it is 240 using SAE 50 oil.
Do not concern yourself too much about the oil temp, IMO.
TCM deliberately avoided external oil lines for good
reasons Lycoming has AD notes due to their external lines.
For that reason, I prefer FM filters over Oberg/AirWolf.

Hi David,
My A model does the same thing down here in Atlanta. My home airport is right around 1000 feet MSL and on hot days I have to work on keeping the oil temp down. I do agree with what George has said about what the limit is on the oil temp but I wanted to point out something that you might take a look at.
On your F&M oil filter where do the blast tubes point from your baffling? Mine do not quite point where I would like them to. When the F&M filter was added it moved the oil temp probe aft about 4 inches and away from the cooling air provided by the blast tubes. I may be wrong but it seems to me that the reading of the oil temp with cooling air blowing on it will be different from the oil temp internal to the engine. My guess is that the actual oil temp is much higher that we think it is. This is at least what I tell myself on those 100 plus days when I want to go flying.
This is a long way of saying I wouldn’t worry too much about it just check those blast tubes and keep on flying.

David, your oil temperatures are pretty typical. Yes we have a few anomalies out there with installations that won't rise above 160. I have one of those and if we ever figure out why they run cold we'll be sure to let everyone else know.

Just do what your doing in making sure your gauge and baffling are correct and in the best operating order. And as George pointed out run 50 SAE and know the engine redline is 240 with that grade oil.

Gentlemen,

Thanks for your replies. I hadn't realised that running 50 weight oil increased the redline - that sounds like the simplest solution by far.

Dave

The high oil temp is really not a problem until it gets way high. Low is the enemy as you do not boil out the moisture so it tends to let it corrode the internal steel parts. Bruce you might want to maybe block off your cooler to some extent in the winter. I have not seen a problem with low oil temps even up here. Usually they go to at least 180 which is perfect for oil temp. Yes just like pressure measured at differnt point in the engine temp is different too.

marathonrunner wrote:The high oil temp is really not a problem until it gets way high. Low is the enemy as you do not boil out the moisture so it tends to let it corrode the internal steel parts. Bruce you might want to maybe block off your cooler to some extent in the winter. I have not seen a problem with low oil temps even up here. Usually they go to at least 180 which is perfect for oil temp. Yes just like pressure measured at differnt point in the engine temp is different too.

You are correct I'd like to see at least 180 but do not 3/4 or the year here in PA. In the winter/colder months we do block off the front cowl or we wouldn't see 160. Yes our installation is an unexplained anomaly. We have a member who fly's out of Boulder City NV who also has lower than normal temperatures. Both of our installations have been hashed out and we can not explain why they are running cold.

Yep. Flew this weekend with a student for several hours in the pattern. OAT 85-90, oil temp 145. I have one of the two blast tubes blocked. I cant figure it out.

LBPilot82 wrote:Yep. Flew this weekend with a student for several hours in the pattern. OAT 85-90, oil temp 145. I have one of the two blast tubes blocked. I cant figure it out.

This Sunday here in PA it was 85 OAT and saw about 145 same as you Richard. We've just got COOL '49 A models I guess.

I have a relatively new oil temp indicator with real numbers on it. the whole trip to longmont and back almost regardless of the OAT, the highest temp on climb out never went over 210 DEG F and usually settled out in cruise at 7500-9500 ft at about 185-190 DEG F. This oil temp discussion has gone on for the 42 years we have owned the 170 and probably long before that. I think that if all temp indicators were equal, that is, calibrated accurately to a NIST standard, the differences in oil temps would be related primarly to cylinder blow-by, leaning, mag timing, placement of the blast tubes (which cool the sensor a little) and condition of baffling. No two airplanes are exactly alike even thought they look similar. On a lighter note, my plane is RED so it runs faster and cooler than the GREEN ones.

My GREEN one ran around 210 for most of the trip from TX to CO. Return trip @ 11,500 had 180/190, but it was 40 degrees F at that altitude. Running Aeroshell 100.

I've found that, when the OAT is above 90 degrees, mine won't even start.

It might have something to do with my refusal to leave my air conditioned house tho.

I have been doing some work on the Silicone flaps that seal the baffels to the cowl. O-300D in a 1961 172B I have sealed up all leakage in the back baffel. Plug wire holes- lines, ect.... I also sealed the case to back baffel clearances with silicone. I used Permatax Ultra gray. I bought some sheet silicone rubber and am cutting out wider, better fitting, flaps to seal the cowl to the engine baffels. I'm of the opinion that the top chamber needs to be sealed better to cool the cylinders. If they stay cool the oil that migrates through them will not get as hot. In our race engines the oil temp is directly related to cylinder temps. I question those "blast tubes". One of mine just points to, nothing in the lower cowl area and the one on the left side of the engine points to the area where the temp probe fits in the case. I'm thinking this give a fales oil temp. I might do a little testing by stopping up the blast tubes with rubber stoppers and make a few T&G's and then remove the stoppers. A before and after of the oil temp might be interesting. More info after I finish the job friday night and do a little pattern work on Sunday. Thought.....I've been wondering if one or both of those "Blast Tubes" shouldn't be pointed to the area of the Generator to keep it cool... ???

Sixracer wrote: I question those "blast tubes".

As noted in past responses, and frequently discussed by past club patriarch's, the conclusion has been that the blast tubes main function was to help cool the oil temp sensor.

Both of the oil cooling tubes should be pointed at the area where the temperature probe is; that's where Cessna put them. I think it's a myth that those tubes only cool the probe. All of the oil passes through a narrow place in the wall of the accessory case at that point, and it's an ideal place to put additional cooling. The probe is cooled because the oil around it is being cooled.

My last 170 had two oil temperature probes. One was the original one, and the second was an EI digital gauge with the probe mounted in an Oberg oil filter. They both produced consistent readings, although if they were off by a few degrees I wouldn't have known it because the original gauge doesn't have numbers on it. But judging by the position of the needle with respect to the red line, I'd say any differences were negligible. Those tubes actually help cool the oil, not "just the probe."