Question re oil temperature at the sump

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Jim Beam
356 Fan
Posts: 405
Joined: Sat Mar 29, 2008 3:23 pm
Location: Albuquerque, New Mexico

Question re oil temperature at the sump

#1 Post by Jim Beam »

My understanding is that the oil temperature reading taken at the sump does not necessarily indicate accurate oil temperature because the oil at that point has not passed through the oil cooler and the temperature is expected to be higher. Question is at what oil temperature taken at the sump should I become concerned that I may have an oil overheating problem? 250 degrees F? 300 degrees F? Whatever? Thanks. I have read the oil temperature articles but still have this issue.
1963B (T6) Coupe
1987 3.2 Carrera
1985 FJ60 Landcruiser
1993 Miata

Dick Weiss
356 Fan
Posts: 4181
Joined: Sun Apr 20, 2008 12:54 am

Re: Question re oil temperature at the sump

#2 Post by Dick Weiss »

Jim,

Over my 60 years of 356s, I never had any problems w/regular or hi-temp oil temperatures as long as the senders and gages
are reading correctly. There is a difference between the early and late 6V senders and their matched gages.

Back in '86 to attend the WCH in Colorado driving a '65 C cp, we experienced the needle next to the red zone across Nebraska and eastern Colorado but it lessened during lower speeds, After our return home to Cin'ti, OH, the engine was removed for a clutch during which the F/shroud was removed for cleaning off the bottom 1/2 of the oil cooler! The oil pressure still was OK before its removal, but a proposed tear down wasn't necessary and it's still "On the Road Again" since.

Oil temp readings @ the sump will be high due the heat produced after the oil passed thru the engine; Oil temp readings w/the temp sender will be slightly lower before it flows thru the cooler which lowers the oil temp before it flows thru the engine.
Several things should be checked out during any repairs--Oil pump assembly clearances and gear matching the specs + the spacer's OD on the drive shaft (next to the spiral gear) and the pump gear that fits the pump cover bore ID to prevent pitch-line wear on one end of the gear teeth producing an out-of-parallelism to the driven pump gear (on mechanical tach drive pumps) This is really critical w/the small oil pumps to produce oil pressures in the 45-50 PSI @ 3000 RPM. Note: The spacer isn't available for purchase; It has to be made to suit the OD to the ID wear. (approx. 005"-.709" or so) If the pump gears show wear on the pitch line contact,
the gears can be reversed on the shafts for good pitch lines.

Dick
























good unworn pitch lines.

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