oil temperature?

[zed]

After I did some mods on my L18 motor, it ran about 10C / 50F hotter than before. It's running well, but water temp was around 90C / 194F on some mountain passes. So, I fitted a tube type oil cooler - about 15" x 9" x 1.5". In December, for the first time, I fitted an oil temperature gauge, with the sensor in the oil pan drain plug. On my first trip over the mountain I see the oil temp never gets above 65C / 149F. Can this be right? I have read that ideal oil temp is between 180 and 220F. Is the sensor position - in the oil pan - maybe giving a false reading? Any opinions would be appreciated. thanks

[datzenmike]

Pan would almost be the coolest place. The oil in the bottom of the pan could be stagnant and not circulating. Somewhere between cooler and filter perhaps.

[datsunaholic]

I would have installed the gauge first, then the cooler, because now you don't know what the temps were before.

 

Most place the sender between the cooler and filter, or in a sandwich plate between the block and filter on uncooled systems.

[hang_510]

Most place the sender between the cooler and filter

install sender before the cooler... unless you want to know how efficient the cooler is ;)

[ggzilla]

In the eighties oil was formulated for 200 degrees F. That may still be the optimal temperature.

 

Oil temperature is primarily regulated by the coolant temperature, it runs about 20 degree hotter than the coolant on most engines.

 

So use a 180F thermostat.

[RoadRace]

In the eighties oil was formulated for 200 degrees F. That may still be the optimal temperature.

 

Oil temperature is primarily regulated by the coolant temperature, it runs about 20 degree hotter than the coolant on most engines.

 

So use a 180F thermostat.

 

oil and coolant temps are, as stated above, directly related. oil temps are generally higher due to the oil being in direct contact with non-cooled and rotating components of the engine. its not a bad idea to put the lower stat in - being in SA i would think it would already have a 180 stat in it - check it out. i would disconnect the oil cooler - just bypass the heat exchanger and connect the in and out lines together and have a look at the gauge, see what you get. almost everybody puts the temp sensor in the pan, sensor location is not an issue. some will put it at the filter housing, but thats genereally when you have a remote mounted filter, rarely in an OEM set up. the other thing could be the accuracy of the gauge - the gauge - new or otherwise - can be wrong. seen it more times than i'd like to.

 

Honestly - when i read your post, the first 'question mark' that popped up was the very first statement: "After I did some mods on my L18 motor, it ran about 10C / 50F hotter than before"

 

50F! what! why? this lead me to think that the timing is too far advanced, the jetting is lean or both. please address this as well. my L18 with a full race ported head, 14:1, .600 lift cam doesn't run over 190F - so there is something else wrong here. please confirm the manufacturer of the head gasket you are using - could also be an issue with higher than normal temps - if you had the head off, that is.

[ggzilla]

"After I did some mods on my L18 motor, it ran about 10C / 50F hotter than before"

 

50F! what! why?

My first thought was that the gauge or sender was changed at the same time. So of the two readings, one is inaccurate.

[zed]

I'm going to look at the sandwich plate between the filter and block - maybe I can drill and tap it to take the oil temp sensor.

I assume the higher temps are caused by more power: I bored the block to 86mm, put in L28 flat tops, skimmed head .020", decked block .020" - compression is around 11:1. Quench is around .035". From the stock 9:1CR, and quench .060".

I have a VDO water temp gauge in the block water plug - I think it's pretty accurate.

 

thanks for all the posts

[RoadRace]

so you had the head off - did you use a Nissan gasket or aftermarket? temperature issues are not uncommon when using a felpro or other aftermarket gasket.

 

your temp sensor location is Ok. i wouldn't change it. i would bypass the oil cooler and take another reading.

 

the hotter temps are not necessarily a direct result of "more power" - there is a blurry line of assymilation between the 2. of course, more intake fuel to burn and higher revs will create more heat - but this is normally not outside the capacity of the OEM cooling system - when in good working order - especially when you have introduced an external oil cooler to aid its operation.

 

.035" quench height with the gasket? so this is a zero deck height motor with a head gasket compressed thickness of .035"? just curious - as this has nothing to do with the functionality of your cooling system.

[zed]

I believe that a .020" block skim on an L18 will leave the pistons out the block by around .010". Mine measured at about .009".

Please would you explain why non-OEM gaskets cause overheating? I used a Payen gasket - about the best avilable here other than OEM.

[hang_510]

Please would you explain why non-OEM gaskets cause overheating? I used a Payen gasket - about the best avilable here other than OEM.

blocked/missing/smaller water passages in the HG.

[datzenmike]

I believe that a .020" block skim on an L18 will leave the pistons out the block by around .010". Mine measured at about .009".

Please would you explain why non-OEM gaskets cause overheating? I used a Payen gasket - about the best avilable here other than OEM.

 

Stock L18s had a -.55mm or -0.021 deck height so milling 0.020" off effectively makes it a zero deck height motor. Crushed gasket thickness is usually accepted as 1.2mm or 0.047" so the space between the piston top and the head surface in the quench area would be basically the gasket thickness... 0.04895"

 

If your pistons were 0.009" above the deck they cut too much. L28 flattops have the same piston pin height as the L18 pistons. Again, to generalize, 0.3mm of positive deck height is considered maximum to prevent the piston and head meeting during high rev rod stretch. 0.009" is .2286mm so you're still good.

[ggzilla]

"More power" is not going to raise the water temp 50 degrees. Not even if you doubled the HP. If your radiator is bad it could happen.