Bad vernatherm??

pierre smith · #1 02-10-2006, 09:03 AM

Mornin' everybody,
Has anyone on here had to replace a vernatherm? Our 0-360 gets up to 180 deg or so even in cold weather with a firewall mounted 7 row oil cooler and 2" hose from the rear baffling. I've seen other posts where the guys couldn't get the oil over 135 deg on cold days. Do these vernatherms go bad and if so, how do you check them? In boiling water?
Thanks in advance,
Pierre

Allen Barrett · #2 02-10-2006, 09:09 AM

Yes, boiling water works fine. the thermastat should open around 187-189 F.
Use a candy thermometer to measure the water temp.

Allen

mahlon_r · #3 02-10-2006, 09:13 AM

The vernatherm can fail in one of two ways:
stays closed..engine will run too cold

stays open..engine will run hot.

If you have enough heat to make the oil temp go to 180 on a cold day that isn't a function of the vernatherm. If the vermnatherm was stuck open then the oil temp can only get hot enough to get 180 oil temp if the engine cam produce heat for that much temp. The guys that can't get temp in the winter are cold not because of the vernatherm but because they don't make enough heat to even get the vernatherm function o0n cold days.
It sounds as though your nacelle is capable of letting you engine get hot enough to get the oil temp to 180 even on a cold day. That is a good thing. as long as the vernatherm and cooler combination can maintain the oil temp around 180 then you have a very efficient system and don't worry. If the oil temp continued uncontrolled upwards as the weather gets warmer then you could have a good nacelle for winter along with a vernatherm that won't close.
You can check the vernatherm function in hot water. it starts expending at around 160 and should be fully expanded by 180F-185F.
Good Luck,
Mahlon
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gmcjetpilot · #4 02-11-2006, 07:31 AM

It sounds like two question and they are not necessarily related. Cold OT can happen even with a good vernatherm.

Cold oil temps is that fact that it is cold out and the engine is not making enough heat. Oil always "leaks thru" the cooler by design (to keep oil for congealing). The next step is block the cooler and than restricted some inlet air to the cowl.

Mahlon can verify this, but there are some Vernatherm's with AD's or SB's, where the end nut or crimp end can fail or come apart. Not sure of the details, but if you have one of the undesirable parts, you may want to check it out and replace/repair/inspect it per the SB or AD (not sure what one it is). George

Kyle Boatright · #5 02-11-2006, 07:37 AM

What kind of airplane are you flying? RV-4, 6, 7, 8, 9?

Unless you're flying an RV-4, a 2" SCAT tube feeding the oil cooler is grossly inadequate. You probably need a 4" tube minimum. That 2" tube gives you 3.14 square inches of cross section for airflow. A 4" tube will give you at least 4 times the airflow.