Okay, had to replace the factory tranny cooler cuz the fittings on the top interfere with the bottom of the 6.0 intercooler. There is not enough room for both. After trying for several weeks to find a 6.0 tranny cooler on E-bay or in junkyards I stumbled on an article about flex-a-lite tranny coolers. They looked pretty good so I ordered a big one (32K GVW).

Put in the tranny cooler and the intercooler today. Intercooler is fine - EGTs drop quicker after a hard acceleration, stayed very cool on the highway (about 475 at 70 mph - pre-turbo sensor).

But the tranny heats up quicker and doesn't cool off as fast. Went to about 180 and stayed there. Cools off at stops and then heats up when I'm moving in traffic. On the highway set itself at about 175 and never dropped. All that was empty and significantly warmer than the factory tranny cooler which no longer fits. I'm concerned about putting the 5 wheel on and going very far.

So, anybody with experience with these coolers? Any thoughts or suggestions? I sure don't want to take the front end apart again but looks like that is in my immediate future. I would appreciate any experience or suggestions you guys could share.

 

Bypass stuck open?

 

That is a possibility - How do I check? If that is the issue - what's the fix?

BTW - thanks for the response.

 

Did you bypass the cooler in the radiator?

 

Yes, I did bypass the cooler in the radiator some time back. The factory cooler and the Tru Cool kept things cool. Before I bypassed the radiator cooler the tranny would still get warmer than I wanted to run. In Houston we seldom have issues with things being too cool. The tranny was compeletely rebuilt - triple lock TC, clutch packs, valve body, pump, etc. and runs well. Until I took the factory cooler out and put in this other one I've had no temperature issues.

 

May be a flow issue. The larger cooler may be flowing too fast. Fluid coolers need a certain amount of restriction to be effective. Higher backpressure gives the fluid more "loiter" time in the cooler.

The flip side of that is the big cooler may not care if the truck is loaded or not, it's just run 180 all the time. Can you hook the fiver up and drag it around a while to test it?

 

Thanks for the suggestion. Got to pick up the 5er from the shop in the next day or two. Maybe I'll take the long way home and see what happens. Blew a tire in New Mexico and when it went it took out a propane line, the fender well, etc. When it rains, it pours.

Anyway, I had the same thought about the cooler. Its a tube and fin and looks like it may flow a lot. I wondered if the fluid was in the tube long enough to cool off. Guess I'll see. Thanks again.

 

Cookie, I have to disagree with you. Every engineering principle says that the more flow, the more heat transferred. Thats not to say that the outlet temperature from the cooler might not be higher, but the net effect of a higher outlet temperature and the higher volumetric flow rate will be a greater heat removal at the higher flow rate. What will happen is that, at the higher flow rate, the average temperature in the entire system will be lower, the inlet temperature to the coolers will be lower, and since almost all of the fluid is in the transmission, not the coolers, thats a good thing.

I also wondered about bypassing the bottom radiator tank cooler. The water in the bottom tank has to be well below the engine temperature, maybe down around 120-140 degrees. That is well below the temperature of the oil coming out of the tranny, so the bottom tank cooler should reduce the temperature, UNLESS it is seriously plugged, and cutting the flow down to all the coolers in series. I would try to blow out that tank cooler first, before bypassing it.
Finally, someone on another thread reported that the Ford-recommended flow rate through the coolers is minimum 32 oz in 15 seconds. Thats easy to check with a bottle at the end of the return line and a helper in the cab. I'd check that flow with each combination of coolers.
Is it possible that the new cooler he installed has a bypass, which might be defective? That might explain the temperature going up on the road and going down at idle, when there is almost no heat at all generated.
Warren

 

Warren,

There is no bypass in the new cooler - it is a straight tube and fin design and is significantly larger than the OEM cooler. My radiator cooler is not clogged as I did blow it clear. When it is inline with the tranny coolers (at least the factory cooler and the Tru-Cool) my tranny temps ran consistently at 180-200. When I bypassed it they dropped to 140-150.

I currently run 160-180 consistently. That is both in town and highway miles unloaded. I have not had a chance to see what happens with the fifth wheel but will Monday. I am also watching E-Bay for a 6.0 tranny cooler.

Thanks for your input.

 

PS - my transmission pressure is good and the bypass is not stuck open. But the tube on the new cooler is large enough to suspect the cooler fin surface area is not enough that the amount of hot fluid going through it under pressure can shed as much heat as the factory cooler - which puts the fluid through lots of small tubes with a large surface area on each tube, allowing the heat to shed more effectively.

 

Mike, what became of the tru-cool? I just installed a 40,000 gvw Tru-cool on my 02. It is running about 110 - 120 F on the highway unloaded. It wasn't much different than that w/o the Tru-cool; I installed it for upcoming towing.
I feel that the temperatures you are running at unloaded are about 50 degrees too high. Something is amiss. Bypassing the radiator cooler when it is not plugged should not lower the tranny temperature unless the radiator temperature is very hot and therefore not cooling the tranny fluid! Are you sure that your torque converter is locking up? In an older Ford diesel I once had a sensor fail that caused the T/C to never lock. I was towing, and could only go about 20 miles, then had to stop and cool down. went 150 miles that way to get to Portland and a Ford shop, which found and replaced the sensor. To a lesser extent, driving unloaded w/o the T/C locked would run the temperature up - don't know how much. Thats quite a long shot; from your sig and the mods you've made you obviously know your truck.
Do the flow test I mentioned before to verify that there is adequate flow going through and coming back from the coolers.
I hate to see you spend $ for another cooler until you are sure what you have is working properly.
Before it was stolen I had one of those non-contact temperature guages; it was very interesting to point it at a surface and get an instant temperature reading. A good modern radiator shop should have one and could even sell you one. With it in hand you can measure, for example, the temperature of the bottom radiator tank, the temperature of the new cooler that you can see behind the grill, the temperature of the top radiator hose, which should be at about the thermostat temperature, etc. etc.
I'll be very interested to see what happens when you tow.
Good Luck
Warren

 

I certainly agree with the principal, and if I didn't have a job that required me to test fluid coolers on a daily basis I would agree in application....but I see it every day, the coolers that run a marginally higher backpressure are much more effective at keeping the total system temperature down. I know it should be the other way around, but in my experience it isn't.

 

I can't pretend to know what you guys know about the coolers and flow charactaristics.
However........ I am going to hazard a guess that the more surface area of the hot oil gets exposed to the cooling air, it would be a more efficient cooler. The tube and fin design would be much less effective than the kind that has the multiple little flat tubes, similar in design to the AC condenser.

 

I have to agree with Cookie on this one. If the fluid is moving past the cooling area at a fast rate and back to the transmission then it is not recieving the heat transfer that is needed and is returning to the tranny too hot and then it does not bring the heat transfer out of the tranny that is needed. Remember that the cooler is a small area and is the only area providing the cooling and you may be rushing past it. Sounds weird but after working on heat exchanger systems it makes sense.

Kwik,

I also agree with you on the more tubes provide more surface area the better off you are.

Good luck with the cooling issue.

Anthony

 

Warren,
I agree with your perspective about the temps. The only thing that has changed is substituting a tube and fin cooler for the factory cooler. Everything else is the same - tranny has good pressure. T/C is locking up, Tru-cool is still in line with new cooler. I really think the new cooler tubes are too big and short and the fins are not adequate to reduce the heat. Believe me, I've checked all those things you've mentioned.

Also, the temp gauge is an electric gauge in the port over the shifter on the driver's side. It has been reliable up to now. Also, prior to changing the coolers I had taken a long trip and the tranny got hot coming down a mountain pass with the fifth wheel (10K lbs) so I had flushed the tranny and changed the fluid.

Only variable that has changed is this particular cooler. So, that's why I'm leaning that way. I do appreciate your feedback because I could easily have missed some of the things you mentioned.