B

beech19pilot

Member
Hey guys,

I got a problem with the oil temps. Replace the cooler with a new SW, replaced the vernatherm and the temps are still high. Temps are about 180 in cruise as long as the OAT is less than 85 F. When I land and taxi in the temps will top 230 in a hurry, so needless to say I have getting it parked pretty quick. In AZ this is a problen since the OAT is almost always over 85 F. Anyone got any tips.

thanx,
Mark
520-249-1524
 
Heat mass

Mark,
Your engine is a 300lb lump of hot metal when you descend into the circuit and then all the cooling dissappears when you land. Subsequently the hot parts of the engine (Cylinder heads) conduct their heat throughout the engine and into the oil. You might try a low power descent to get the 300lb of metal cool before you enter the circuit and loose the cooling. I would be interested to hear if this solves the problem. I will find out soon enough, as I should haver my RV-7 flying next month and summer is approaching here in Australia.
Incidentally, a similar temperature increase occurs on jet engines when you reduce power for descent as the fuel is used to cool the oil and when the fuel flow reduces the temperatures rise. Of course it is not a problem as long as you don't exceed the Oil Temperature Limits.

good luck,
Pete
 
Bigger cooler?

I'm based at DVT. I'm flying a -9 with and O-320 with a Positech oil cooler for an O-320/O-360 mounted on the aft baffle and I have not experienced any problems. My cooler is pretty large and it took some engineering to fit it in, but I wouldn't think you should have any problems taxing in with the cooler you have. The RV boys out here told me to put the bigger cooler on so I wouldn't have to step climb.

Where is your cooler mounted, Baffle or firewall? If on the fire wall maybe you need a larger duct to it.

Here's some pics of my cooler mount. You might have to go there.

I'll be on my cell today if you would like to call.


623 910-1939

Roger

080320050034wi.jpg


080320050071dz.jpg


080320050082iu.jpg
 
No matter where you mounted it, it's possible you should create a low pressure area on the aft side of the cooler to keep a positive airflow through it at low airspeeds. You can make up a plentum on the aft side of it going to louvers (sp?) on the cowl.

Many of the experimental guys here in Socal mount the cooler directly to the louvers on the cowl (Fiberglass a bracket into the cowl itself) and simply run a pressure duct either from the baffles or from a seperate ram air scoop. Seems to work fine for them. I wouldn't worry about the oil temp being that high for a short period of time, although it's doesn't happen to other aircraft, I don't think it will damage anything. What are the CHT's like though?
 
Hey guys,

Thanx for the input so far. The cooler itself is mounted on the aft baffle behind the no.3 cyl. The eng is a Lyc O-360-A1A. I would love to see some pics of the install that you are taling about on the cowl. Currently the baffling on the engine is a pressure Plenum, and we were wondering if anyone else has experienced problems with that. We are thinking of adding a second oil cooler or changing the baffling, or both. I agree the high oil temps are not a problem for short periods, but, after all it is a RV. Everybody know we do not just fly these things straight and level were things will stay cool. Every now and again you gotta go out and play. If out just messin around with all the climbs and vertical stuff the oil gets pretty hot pretty quick.

Any more help would be greatly appreciated.

Thanx,
Mark
 
It'd be a week or more until I can get pictures for you. Mostly because I have to get access to one of the airplanes that has this done. I'll try to get some next week, but no promises.
 
High Oil Temps

Make sure the oil temp gauge is accurate.
verify with appropriate thermometer.
Check engine timing
Check for proper oil supply or low oil pressure.
Combustion gases leaking past the piston rings.
Combustion blowby blackens the oil; Do compression check.
Engine baffling not sealing
Baffling should seal the top from the bottom of the engine.
The oil cooler might be somewhat blocked, the oil cooler flange might
be warped.
Is the oil hot, but the cooler isn't??
Air can be trapped in the cooler with low mounted oil coolers.
Was the cooler new? if not, had it been properly flushed? (prob. not your problem)
Is the vernatherm valve defective?
77C valves should move at least 0.090 inch as the temperature rises
from 120 to 170 F. 173 degree marked valves should move at least .16 inch
while temperature rises from 135 to 173 F.
Do you have worn vernatherm seats? Look at the seat in the housing.
Look at the vernatherm where it seats. Try to determine if there is good
contact.
There is a lycoming tool for refacing the housing seats.
.010 of an inch is the maximum allowed to remove when refacing.
Also, if your vernathem screws into your oil filter adapter, your housing
is probably replaceable. (easier,cheaper)

---------------------------------------------------------------------------
the above information is paraphrased from:
Engine Troubleshooting Module
John Schwaner, Sacramento Sky Ranch
His book and software are very useful and I highly recommend them for
Lyc,Cont owners.
---------------------------------------------------------------------------

I suspect you have one of those problems, as it doesn't sound normal to me.
But if you high OAT folks have worked all that out and still want more cooling
but not the weight of a second cooler/lines, another option is an "oil filter"
cooler which I believe were used on Piper Tomahawks. Somewhat longer job of
changing the oil filter,more difficult safety wiring etc, extra scat
hose/drag, but you could probably get 10-15 degrees out of it.
---------------------------------------------------------------------------
 
How big is the baffle opening which feeds air to your oil cooler?

My experience is/was that you need to make that opening as large as possible, which is somewhat larger than what was called out in the baffle plans.
 
You must log in or register to reply here.