Oil Temp Sender Plumbing (again)
 

I have done a bunch of searches looking to see if the location I have my temp sender plumbed to is seeing oil after the cooler or before. I have it plumbed into the 3/8 NPT hole directly above the filter pad on the block. By above I mean with the engine in the boat. I am seeing rather high temps after running hard and it takes me quite a while at cruising to see them come down. Also my oil pressure drops when coming to an idle. This is the break-in oil and it will be changed before next time out. I was using 20/50 Castrol and will be putting Valvoline VR1 40 wt. next.

I take mine from the pan:cool: you did not say how high they were:confused:

I do not have the option of putting mine in the pan at this time. After a hard run it goes to 260 and has a hard time coming back down unless I almost come to an idle. I believe having it plumbed in this port is cooled oil so the temp is a concern. I will be putting a new cooler on before next time out ,but I need to know for sure, if anyone can tell me, what this port is seeing, cooled oil or hot oil before the cooler.

Cooled Oil.

That is if the oil is going thru the cooler. If gen V or VI block make sure you have 30 psi bypass valve installed in hole on oil filter pad. The oil filter pad has 3 holes. Center one is oil going back into engine, this one can have a bypass valve in it way up in hole, but is not needed. On the side of filter pad are 2 holes, 1 round & one oblong. Oblong one is passage from oil pump. Round one on side of oil filter pad is one that need the 30 PSI bypass valve or plugged. If there is no bypass valve in that hole the oil is going to bypass the cooler since bypassing is the path of least resistance.

Turbojack is correct. Oil at that plug or the one up higher on the bell housing boss is after the filter and cooler. The 30 psi bypass valve in the filter pad is a good idea. The part # is 25161284. Cost is $4.95. You can order it at any GM dealer. The stock valve is 11 psi. If you are going to a larger cooler anyway, I would just see if that works to get your oil temp down before changing the bypass valve. You may not need it.

I run a very large oil cooler for a natural 632 and I thought I was having temp problems last yr...260+ indicated after cruising at 4000 rpm then 30 seconds at 6000 rpm. I really couldn't believe the oil was getting that hot when I could grab ahold of the earls line going to the cooler:rolleyes: Anyway, last fall I went out with my engine builder and he brought along one of those "drag racing" infrared temperature meters ran the motor until it read 260 and stopped....the oil temps were 155 in the pan and in the line to the cooler...coming out read 140 degrees. Obviously I don't run an oil thermostat. Put in new sender and new gauge...its still doing it, next step is to move probe from pan to a "T" in the line coming from the engine to the cooler. ;) Moral of this one is...Gaffrigs (in my case) aren't necessarily accurate. :eek:

Thanks to all for the responses. I checked with my engine builder today and was told he only puts the high pressure bypass in for the mentioned reasons. I will replace the cooler, change the oil and put a better oil filter on before next time out. My stock car buddies all run the new K&N oil filters. They like them because they run with the bypass plugged and the K&N is a higher flowing unit with better burst and crumple protection. Also there is an anti-siphon valve for better oil at start-up.

Those infrared temp readers are a good thing. I use one to verify my oil and water temp gauge readings. I have been surprised to find that the gauges are very accurate in my case. I check the water temp at the base of the thermostat housing. The gauge reads the same as the infrared. My oil temp sender is in the remote oil filter housing, opposite the the hose bringing the hot oil from the engine. I check the housing temp to verify the gauge.

Alot of guys have different plumbing. However, the best way to plumb your oil lines and cooler set up is:

Oil comes from the pump to the filter set up on the block. The PRESSURE sender should be there.

If you have a remote filter set up, the oil should leave the block to the cooler.

From the cooler to the remote filter assembly where, if able, the TEMP sender should be located.
The Temp sender should be after the cooler.

From there, the oil travels back to the block to the main oil galley that runs along the cam and crank shaft (priorty oiling) and to their bearings.

The oil temp is most critical at the bearings!!!!!!
Oil temp senders are not very helpful in the pan, because you have no idea the temp at the bearing.

You need to know the temp going to the bearing. PERIOD!!!!

The biggest reason is for viscocity.
If the oil is too cold, it will not flow well in the small clearance it needs to.
If it's too hot, it wont take away the heat necessary to lubricate. In extreme cases, with natural oil, at around 285-290* or so, it will start to turn to a solid, called coke.

Minimum oil temp, should be 212
Perfect oil temp is 220
Too hot is 270

DAVE

Dave, Measuring the temp of the oil going to the bearings makes sense. That would explain why the Merc Race motors have the sender in the 3/8 NPT hole in the block just in front of the filter boss. That is cooled oil. I will relocate my sender and see what the readings are compared to where it is now. Thanks.