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Originally Posted by bbolander
The FSM for my 98 XJ shows the transmission out line going to the top of the radiator cooler, from the bottom of the radiator cooler to the factory aux cooler and returning from the aux cooler to the transmission return line (AW4 trans).
Even tho I showed the diagram to my dealer and his parts department computer has the same diagram, they insist that the transmission out line goes first to the aux cooler, then to the upper radiator cooler and out the bottom of the radiator cooler to the transmission return line.
I want the OEM routing for my aux cooler. Can someone tell me how it came from the factory.
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The FSM diagram is horrible in this section and lends more confusion than any kind of help. I bought an aftermarket "factory" cooler for my '00 XJ. The only logical way I could see it plumbed was to connect the cooler into the line that runs to the top of the radiator; there is a "quick disconnect" connection where the hard line from the radiator meets the rubber hose. Break that connection (using the special tool to seperate the two lines) and plumb your cooler in there. Everything I've ever read regarding trans coolers says they should be placed in the return line *after* the integral radiator cooler. The reasoning for this is to allow the trans fluid to reach operating temp quickly and, to a lesser extent, warm up the coolant in the radiator (again to get things up to normal ops temp).
On a side note, the FSM labels the top line in the radiator the feed line (from the output of the tranny) and the bottom line as the return; I believe this is backwards. I changed all the tranny fluid in my XJ (and flushed the integral radiator cooler) by disconnecting the return line and letting it dump into a container (You fill the tranny, disconnect return line and use a rubber hose to direct flow into a bucket, run engine for a few "alligator" counts, shut it down, fill the tranny and go again. You keep doing this until the fluid changes color or you've put in a couple more quarts than the tranny holds).... the "return" line I disconnected was the line coming from the *top* of the radiator...the same one the FSM says is the feed line and the same one I plumbed my cooler into...Had this really been the feed line (from the output of the tranny) like the book says, then no fluid would have come out the hardline from the radiator top connection... instead it would have flowed out from the other half of the line connected to the transmission. If you think about it, having the fluid enter the bottom of the radiator and flow up against gravity means there's less chance of cavitation or air pockets.... not so if the flow is as the book says.
With regard to this cooler plumbing and line flow thing, all I know is what I've seen with my own two eyes....
mike
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01-23-2006, 10:20 PM
