Difference in oil temp between sender and ext. t-stat line? (Long)

[deanp]

I recently installed an external t-stat, elephant lines and trombone cooler to my '76 2.7. Once installed I let the car idle for nearly a 1/2 hour in the driveway with ambient temps in the upper 70's. Temp on the gauge got to slightly higher than the 180? mark.

In 85? temps last week on the highway the gauge read just north of 210? after 1/2 hour and a little stop and go traffic.

Wasn't sure if the brand new external t-stat was defective or if it was a gauge problem so I bought a hand held infrared thermostat.

I took the car out Saturday, ambient temps between 80-82? and took some random readings:

Gauge at ~190-195?. Infrared temp @ case around temp sender 172?, oil line from scavenge pump to t-stat 156?, t-stat to tank at tank 152?.

Gauge at 210?. Infrared temp @ case around temp sender 198?-200?, oil line from scavenge pump to t-stat 178?, from t-stat to oil tank at oil tank 175?.

Should there be that big of a difference (25?) between the oil temp at the t-stat and sender? To the best of my knowledge the t-stat hasn't opened yet as numerous checks of the oil lines at the front fender have resulted in lines cool to the touch.

This is my first summer with a 911, am I just being paranoid?

(Edited for typos that were driving me crazy)

[Bill Verburg]

Sounds about right. W/ 2 coolers and 2 t-stats there are 2 plateaus of temp.

the first is reached when the engine mounted cooler alone is sufficient to keep the oil cool enough to prevent the external t-stat form seeing oil hot enough to open.

once the external loop starts functioning then temp will rise to the second plateau where both coolers are fully functioning.

Hopefully that is all you need.

The first plateau is around ~180&degF on the gauge the second closer to ~200&degF on the gauge.

both t-stats have the same opening temp &#177 but the internal one sees the higher temp oil.

Keep in mind the gauge is only measuring a single point in the oil system, there are hotter and cooler points in the system.

[vash]

dean, you are being paranoid like i was. one day when it gets hotter outside you are going to grab your oil lines and burn yourself. (almost, but not really) same scenario on my 75 with new carrera cooler.

[Jim Sims]

My '76 911S with a 2.7 factory oil lines and a trombone cooler plus A/C shows about the same oil temp results as you relate; external thermostat doesn't not open until the oil temps reach 180 to 195 F. 210F is a reasonable running temp; hot enough to boil the water out of the oil Jim

[deanp]

Thanks all!

Jim - The 3 to 1's are working well. I have pulled all the AC components out of my car, so if there is anything you want me to send out as back up components for your car just let me know.