FJ62 Radiator Oil Cooler - PS Air Trap

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Output Shaft

Output Shaft

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Well…
Sorry to start a new thread, but this is kind of a new topic.

After getting all flush & excited about possibly using the FJ62 oil cooler (heat exchanger) built into the bottom of the FJ62 radiator for a power steering cooler on the FJ60, I decided to take a closer look at it. What I discovered did not make me happy. See illustration at bottom of page.

>>>

The oil inlet and outlet ports on the oil cooler of the FJ62 radiator are not located at the highest part of the oil cooler tank. There is about a 3/8" to 1/2" (or more) horizontal air pocket leading up to the heat exchanger surface/roof above.

This distance, between the top of the ports and the bottom of the radiator is a giant air trap. Air trapped in this large horizontal space, spanning the width and thickness of the radiator seems like it would never completely purge.

Perhaps the FJ62 A440F auto tranny could flush the cooler or deal with the bubbles, but we all know very well that PS pumps are not happy when air gets in the system… (or never gets out of the system).
  1. It seems that the air trapped under the upper top recesses of the tank would contaminate the PS fluid with bubbles for a very, very long time…
  2. It seems that bleeding the PS of all air would be impossible.
  3. It seems that bubbles released from the oil cooler would be churned into foam by the PS pump only to be recirculated back into the system and get trapped in the oil cooler upper recesses again.
  4. It seems that bleeding could never really be accomplished with any sort of semi-success without tilting the car at least 30º on the driver's side and downhill while bleeding. Even still not all the air could be purged.

Maybe those who have already installed this system on their 60 and have had good success with it could share their experiences. I would love to hear them.

But the bottom line is: If I don't hear some success stories using the FJ62 oil cooler as a FJ60 PS cooler… I ain't gunna do it. sigh.



(crappy illustrations below not to scale.. for visualization purposes only)
FJ62-oil-cooler-render.webp





FJ62-oil-cooler-air-gap-CL-up.webp
 
What I have read/heard/experienced is that PS pressures are very high and trapped air gets compressed and passes through the system without issue. I have built my own bent-tube PS coolers that should trap a ton of air, and yet they quickly pass the air and the system is quiet. Besides, the cooler is typically mounted on the return side, so air returns to the reservoir (and can leave the oil) before the fluid is re-pressurized in the pump.

I wouldn't overthink this, and it's not that big a deal to hook it up and see what happens. You will not damage your PS system by passing some air bubbles through it, along with the PS fluid. And for the rest of us - how will we learn, if you don't do it? ;)
 
remember that the p/s fluid that is going through the cooler is on the low pressure side. Air pockets are a big deal...the cooler needs to be physically lower than the p/s pump, if thats true then I think generally air pockets would be of less concern. Personally I would rather just have the p/s cooler external to the radiator, not part of it.
 
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but there is something nice and simplistic about seeing just a radiator up front and nothing else. I know.. weird.

Yes - I don't like the 'look' of my trans. cooler in front of my AC condenser on my FJ62, but so be it.

Good for you, for giving it a try. Pitfalls 1 and 3 seem accurate, but fairly unlikely to happen. The bottom of a radiator just doesn't get that hot, unless something is drastically wrong.
 
This is how I did the PS cooler on my 61. After running for a little while, cranking the wheel back and forth, and topping off fluid as necessary, I haven't had any problems with bubbles. Sure the radiator might not keep the fluid as cool as an external line, but it'll keep it from boiling.
 
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