Oil cooler is not cooling my oil

[citymunky]

As the new owner of 923/2000, I notice my oil temps from my Autometer gauge range from 200 to 220 degrees without driving hard. This seems a bit high to me. My stock coolant gauge sits above halfway while I'm moving, but if I sit in traffic for over a half a hour, the coolant temps start rasing. I checked to see how hot my oil cooler was a few times after driving and it's always been cold which means to me no oil is flowing to the cooler. I have a FC RX7 Oil cooler running -8 AN SS lines mounted between the headlights behind my grill (so I know I have good airflow), with a 1990 oil filter housing. I know the 1990 oil filter housing allows for some oil to bypass the cooler, but in my case it seems like all the oil is bypassing. Has this happen to anybody else? I searched back to 2006 and found two useful theads about the housing and RX7 Oil cooler, but nothing to help me.

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[Barnes]

What temperatures are you driving in? Sounds like the thermostat is stuck shut.

 

[citymunky]

Temps here in VA have been high 60's to high 80's. You mean the thermostat in the 1990 oil housing is stuck, (item 4 in the pic?). If you remove #4, there is a long probe with a spring. I was thinking about just cutting off the probe, but I'm not sure if I want to do that yet.

 

[Barnes]

Yes, item 4. You could probably just remove the thermostat and plug the hole. You would get full flow to the oil cooler, so it would take some time to get up to temp. But at least you could see if that's why your oil cooler isn't getting hot. I would like to get a second opinion on these before you actually try it. I'm 95% sure it wont' cause any issues, but the last thing I want to do is seize your motor because I made a bad suggestion.

In the high 80's you *should* be getting plenty hot enough for the thermostat to open.

 

You mentioned 200-220 degree oil temps without driving hard, what are the temps under some good hard driving?

IMO, 200-220 degree oil temps aren't anything to be concerned about. 230+ would be concerning for me.

 

[citymunky]

I'm petty sure I can hit 230+ if I wanted to.

 

200-230 is optimal oil temp especially with todays advanced oils. Water vapor is produced in the combustion process and due to blowby some of it will end up in the crankcase. You want that oil hot enough to keep the water vapor from condensing in the oil pan and exit out the PCV or Breather.

 

[citymunky]

That makes sense. Oil temps in my other car range from 195 to 210. 210 is hard driving.

 

[alansupra94]

This was a good thread to read. I was tempted to do the same thing to my 90 OFH but now I know better.

 

[citymunky]

Well I'm petty sure my thermostat in my OFH is most likey non-functioning because it's old. I will plan on buying a new housing soon, it not a big deal for my now because its getting colder outside.

 

This might not really be relevant, but the cummins in my volvo big truck won't throw on the warning light until the oil reaches 251 degrees. It runs between 225-240 on average, and its got over 585k on the ticker.

 

[citymunky]

I think I know what is wrong with my RX7 oil cooler. Today while I was looking under the engine bay I notice that pressure port from the OFH is going to the bottom port of the oil cooler. The return port on the OFH is connected to the top port on my oil cooler. So it would seem to me that oil can't flow within my oil cooler because the oil coming from the pressure port would have to full the cooler from the bottom to top where it would then get sucked down the return port. I going to have to wait until next oil change to swap hoses. I just changed my oil last weeked.

 

[ApexHunter]

If i understand correctly, you are worried that the direction of flow in relation to the way the cooler is mounted could be affecting performance. This would not be a problem as the system is under pressure.

Thorough discussion here

 

[ApexHunter]

I remember watching a Best Motoring enduro challenge where they ran an E46 M3 CSL, NSX-R (NA2), 04-05 STi, Evo 8, DC5-R, s2k, and RX8 at Tsukuba in summer heat. Water and oil temp limits were set at 110* C and 140* C respectively (230*F & 284* F), except the STi which was given a 138*C (280*F) limit. Once the limit was reached the car was required to slow until temps decreased. The results were interesting.

youtube

 

[Barnes]

Quoting citymunky:
I think I know what is wrong with my RX7 oil cooler. Today while I was looking under the engine bay I notice that pressure port from the OFH is going to the bottom port of the oil cooler. The return port on the OFH is connected to the top port on my oil cooler. So it would seem to me that oil can't flow within my oil cooler because the oil coming from the pressure port would have to full the cooler from the bottom to top where it would then get sucked down the return port. I going to have to wait until next oil change to swap hoses. I just changed my oil last weeked.



This should not make a difference. The oil should flow through.

 

[AWDnot2]

Unscrew your thermostat and inspect it. Make sure it's not seized. If it is you can send it to me and I can disassemble it and clean it for you. You can also test by placing it in boiling water. The temp should be marked on the cap in *C. (some aren't) It should be fully open at the temp specified. Ideal oil temp is just hot enough to burn off moisture.