So I changed out the oil cooler on my 1984 Fb today and went to go start it up and the oil pressure shot up to Max and just sat, it's not exactly the same oil cooler as the one I took off but it's the one Atkins rotary recommended, just want to see why my oil pressure is wacky

 

Mines did the same I got scared and winded taking it off

 

I think theres a regulator/restrictor in the stock oil cooler.

 

The stock coolers have a thermal bypass that stays open until the oil gets up to temp if I remember right.You don't give us enough info to know for sure what you had and what you put on.

 

It's a gs with the 12 a, the oil cooler taken off was stock and put a slightly smaller one on

 

Drove it around and it seemed to be happy, definitely wasnt making 300+ lbs of oil pressure

 

May i ask why you removed the oe cooler and put a smaller one on,likely with no thermostat?

 

The old one had a crack in one of the waternecks sent it in and they said if they repair it it will likely crack again, didn't know the new one was smaller till I got it

 

You MUST use an original Mazda oil cooler or risk damage to the engine. You can use an SA or a GSL-SE oil cooler or even the beehive style oil cooler. But using an aftermarket oil cooler can cause issues. If Atkins recommend the oil cooler then I'm sure it's likely ok. I'm curious what brand it is and if it as a thermal bypass.

 

Using a properly sized after-market oil cooler is ok as long as you have a good quality external oil temperature thermostat. It will by-pass the cooler until the oil is up to temp. I think the FSM has the specs on oil temp at . I believe the factory FMOC opens at 145 degrees.

 

OP are you talking about the $700 NOS beehive that Atkins lists? Everything I see on their site is OE Mazda, and pricey because Mazda doesnt carry the parts anymore. What did you buy that was smaller?

 

Anybody else pick up on 84 FB with 12A "with factory oil cooler"?
OP,do you still have your cracked oil cooler? I'd be happy to take it off your hands.