oil temperature too warm ? or normal Z51 RPO

[Mike_88z51]

I believe that the fan activation temps for your 86 Z51 are the same as for my 88 Z51. Factory Shop manual specifies 226F for the main fan and 228 for the aux. fan. Since GM didn't think it was necessay to turn on any fans until you hit 226F, I'd have to say that 220F is in the "normal" range. Even so, I usually do not see that high a temp in my 88 when at 50mph. As already mentioned, at 50mph the system should be at maximum cooling capacity with respect to engine heat produced. I replaced the stock 195 thermostat with a 180 thermostat and it runs just over 180F at 50mph. Ta 50mph you should see coolant temps near the thermostat temp used. If yoiu have a stock replacement thermostat, I'd expect to see it a few degrees above 195F at 50 mph on a 70~80F day. A little higher if the outside temps are higher.

I agree with the other posts that you might want to consider purchasing a replacement aux. fan switch. It is an easy 2 minute job to replace the original 228F switch with an aftermarket one that comes on at 205F and off at 190F.

Just about as important as finding a coolant leak is to make sure that the radiator cap is holding pressure. If not, then the coolant can boil in the system and create air pockets or cause the overflow resevoir to overflow losing coolant and eventually contributing to overheating.

If you didn't install a new radiator when you installed the new engine, you might want to pull and really clean the radiator. Checking for debris in front of the radiator is good, but externally cleaning the radiator itself is much better. Make sure all the little fins are straightened and the fin area washed with a good non-caustic cleaner. Road grime can build up on the fins over time and decrease their efficiency quite a bit. I pulled, cleaned, and straightend my radiator fins all in one morning 5 years ago. It has run much cooler ever since.

 

[John Robinson]

What Oil is in your engine?

My 93 LT1 on a trip last week was running 237 Oil 225 Coolant with 97 degrees outside. If the engine is not running a full synthetic such as Mobil 1 it will run much hotter by about 30 to 50 degrees. That is why the General says to use it because he knew there was a problem with excessive heat from dyno oil or dyno blend oil. Some people when they rebuild an engine think it will not break in unless they put dyno oil in it for the first oil change. These cars came with new engines that had Mobil 1 in them from the factory so it seems that it does not hold true that it won't break in with syn oil. If you have dyno in now change to full syn and see what the temp are then and let us know.

 

[Ken]

There is nothing at all wrong with the temperature reading of your oil. Remember, your oil needs a higher operating temperature than the coolant in order to prevent condensation from forming in the engine.