"Forgot to mention this is a very low mile XJ 112,000 miles from a little old lady in Ellensburg WA who drove it to church every Sunday. It has been maintained but not a lot of preventative stuff. I'm assuming the fan clutch is original from 1999 at this point."

The absolute worst thing that can be done to a vehicle is not drive it. The cooling passages in the head and block could be packed with concrete.

 

The stock Cherokee has a trans cooler built into the radiator, and some models have an additional cooler that sits in front of the radiator (I have one on my Country). I don't remember if the additional cooler is plumbed BEFORE or AFTER the radiator.

Here's why it matters: If you are towing, your trans is generating a lot of heat. If that heat goes into the radiator, it puts a load on your engine cooling system. Then you take that cooled trans fluid and run it through an external trans cooler, which drops the temp further and makes your transmission very happy. (In cold climates it can actually be too cold, which, while not catastrophic, shortens the life of your trans. Modern trucks actually have thermostats on the trans cooler system for this reason.)

All of that is normally fine, BUT, you just dumped a bunch of heat into your engine cooling system. If you are already struggling with engine temps, that's not really a great idea.

If you put the trans cooler BEFORE the radiator, you dump heat out of the trans fluid into the air, instead of into your radiator. It's even better if you mount it somewhere other than in front of your radiator.

 

The post above yours says that he already replaced it, and it didn't fix it.

That's because fan clutches have no effect whatsoever on the coolant temperature at highway speed.

 

Also tracking some threads talking about springs in the lower hoses, and the pump sucking the hose closed. I don't recall one in mine but it was last year I replaced it (OEM hose).

 

I think it made it slightly better, but I am still above 210 (slightly) going up hills or if I go faster than 60.

 

Right -- I am looking at the Hayden coolers, do you think a thermal bypass is needed or not? They sell them with and without. Looking at the 677 and 697.

I also did verify there is a spring inside the lower hose.

Of course, I might be panicked over nothing.... maybe it won't ever go above 215/220....

Also thinking of removing the driving lights temporarily -- I have my license plate in front of the winch solenoid so it blocks a bunch of air too.

On the before/after question on trans coolers, Hayden says:

 

Yes, judging by what came out of the heater that's probable.

I just don't have time left before my trip to flush it. I may run some block cleaner stuff (from NAPA) in it before I flush too.

 

B&M plate/fin transmission coolers have an automatic bypass until fluid is 'up to temperature'.
Routing before or after stock heat exchanger in radiator (not a cooler but an exchanger) depends on your climate and use of vehicle. Auxiliary first will dump excess heat into atmosphere, then fluid passes through exchanger and will be additionally cooled OR heated up.
Stock exchanger first will dump excess heat into coolant (which is already working hard at cooling engine).
There are additional factors regarding routing but I am trying to simplify for better understanding.

 

I've been recommending using Amway laundry detergent as a flush. You can put it in there and take a trip, unlike the caustic stuff they sell as block cleaner.

I just got a PM today from cruiser54 who told me he tried TSP, and likes what he sees. You might toss a quarter cup in your radiator before you make your trip, and plan on a flush when you get back.

 

Yah I've seen several threads on Amway laundry detergent. Don't know any Amway people....

I'll probably use the NAPA/MACs cleaner... it did a great job on the heater core.

 

I removed the driving lights that partially block the grille, will see how that goes on the trip.

 

Many updates here:

- big issues on the camping trip/towing: overheated on all 3 passes and the transmission puked fluid everywhere at the same time (white smoke), ambient temps were around 90
- topped it off (lost about half a quart of ATF) and drove home (gently) ok

I just installed a Hayden 698 plate and fin transmission cooler, which has a built in thermal bypass.
http://www.rockauto.com/en/moreinfo....=7669844&jsn=3

A quick test run yesterday @ 86F ambient, not towing, at speeds up to 75 and up hills, showed very stable engine temps (barely above 210). Will hitch the trailer up and hit the pass this week and see how things go. The early evidence suggests it was the heat from the transmission being exchanged into the cooling system (versus the other way around at start up)

I keep the heat exchanger/radiator in series, and put the cooler after it. Considering an inline filter too.

I'm still planning to use some coolant system cleaner and then backflush the block at some point.

 

There is a member on this forum (I don't remember who) who gets really bent out of shape at any suggestion that the trans cooler be put BEFORE the radiator. But I think you've seen the results, and it requires only the most basic understanding of heat exchange to see why it make sense for some cases.

If your problem is the trans is too hot, then you want it AFTER the radiator.

Some people will tell you it's not necessary, and they are correct. It's not necessary. That doesn't mean it's not good. A lot of newer cars have them.

I put one on my family car, and may put one on the Jeep. After a lot of research on flow rates, I decided on a filter base that fits the same oil filter as the engine, and that's what I use for the trans. The tall one - Wix 51515.

Makes it simple to keep the inventory to one filter. That one works for the engines on my family car and my Jeep, and on my family car transmission. I'm considering converting my pickup to the same. Gotta get more info on required flow rates, first, though.

 

What filter base did you use?

Is the flow rate etc ok through that filter? I've seen some people use hydraulic filters from tractors etc.

 

Mark did you mean WIX #51459/NAPA #1459? It's like 1.8" longer than the WIX #51515/NAPA #1515.