I have similar problems with my 2001 ej25 . My conversion project started spring 2022 so i am still trying to solve problems.

So i have the SCP setup with the heater return loop on the reversed manifold.

During summer months (temp up to 100)? i was running with 180to 190 after the first 10min of drive when the coolant circuit reached max pressure. Rad fan on when stoped.

Now we are on winter with temp below 50 and? when starting with cold engine and out on the motorway i have 205!! with steady 3000rpm rad fan always off.

If i start with cold engine and the van in parking i have a peak at 195 and then rad fan is on/off properly.

I use the original subaru Tstat of 188F water pump with 2 nipples and brand new OEM plastic expansion tank water pump with 2 nipples rad brand new with proper in hot? and out cold installed.

Was thinking to go with RMW TAMA Tstat of 172 F and run a pipe from my heater pipe with a T join directly to my 2nd nipple (Its just blocked now) on the water pump where my Tstat is.

Think i may blow head gaskets if running my van with 205.

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I have a ‘74 Bay with a 1993 ej22. The rad is in the belly and has a scoop. I have the Tom Sheils t stat. Heater up front is Vintage Air and also have a heater under rear seat.?
Before adding the scoop my coolant temps would run 188-196 degrees and fans cycling. This is on the freeway and city driving. I added the scoop and now average around 172 degrees on the freeway and city as well. No fan cycling. If I’m in a parade or slow traffic temps will reach 198 degrees and fans cycle.?

It’s interesting to read others are having the same sort of low coolant temps. I’m now wondering if it’s worthwhile to check the oem t stat, but that’ll be my next step. It’s weird though the low coolant temp issue started after I installed the rad scoop.?

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