Vernatherm tech questions
 

Ive had a sudden increase in oil temps. I want to eliminate the vernatherm from the troubleshooting process, ive checked it and it extends at 185 degree as it should however it only extends 1/8 inch (.125) and everything ive read says it should extend at least .160 inches
Also the part number has a suffix of A and I dont see that anywhere in parts manual.

Any info out there?

Cm
Ps ive searched the forum already

Fully retracted at 155F, 0.160" extension by 185F, per the Rosta drawing.

May be related to the addition of a crimp to the retaining nut on the sealing tip. There was a factory directive, IIRC.

Thanks
 

I was able to speak to an engineer and .160 was the figure he gave. The nut is crimped. Im hoping the difference between .125 and .160 fixes the issue.
I was seeing a 10 to 15 degree increase in oil temp. A new vernatherm is on its way.

Thanks for the info
Cm

I have always been curious as to the failure mode of Vernatherm valves. It is just a bimetallic spring, but they fail often enough to be one of the first troubleshooting items. Does the bimetallic junction fail somehow?

Ok so I just did some research and discovered it is not a Bimetal spring. This link goes to an explanation on the operation of the thermal actuator. https://www.vernatherm.com/docs/rost...rm_catalog.pdf

Still not sure about the failure mode.

Failure mode
 

I had not seen a jump in oil temps until the weather warmed up and after I removed the winter tape covering the oil cooler duct. The vernatherm could have been slowly failing since last fall. To complicate things I broke the oil temp probe in november and the first replacement sent the gage to the highside peg and the second one checked accurate but then I started seeing higher temps so I was skeptical about it too. I hope the new vernatherm puts the temps back to what I consider normal

Cm

I believe it's a wax pellet encapsulated in the plunger. Sometimes it fails and sometimes the valve top gets a ring cut into it and won't seal. The seat should also be inspected. The way engine shops test Vernatherms, they install them in an oil filter adapter (same as we use on our engine's), toss them in hot water and test the seal.

Don't forget that oil coolers are heat exchanger's. They basically can only remove a percentage of heat in ambient temps. EX: If they can remove 50 degrees at a given airflow this is the same at an ambient temp of 65 degrees OR 100 degrees. When you get the end of the systems ability to remove heat that's your oil temp vs. ambient air temp. And.. The hotter your engine is running, from higher ambient temps, the more heat gets into the oil since these engines are internally cooled by the oil.

Cooler
 

I checked the sealing surface on the adapter and it looks ok
The sealing surface of the valve looks like it was making uniform contact
If my math is correct valve was leaving a .035 gap

Last summer
On an 80F day temps 180
90F day temps 190
100F day 200-210 max

Recently.

80F. Oil temp 200
90f. 210
90+. 210-215

I know there are variables I guess we will see if that .035 gap equates to about 10 deg difference.

If the plunger moves 78% of its travel how would that effect the fliw of oil to the cooler? I would be nteresting to model the flow

Cm