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I replaced my fan clutch about 5-6mo ago. When installed, it seemed to still spin like the old one. Even when the truck is warm to 190* the fan still seems to spin with the same resistance as when cold. The engine temp seems to easily reach 190-200 and in stop/go traffic 200+ with the AC running. Can anybody tell me if their fan clutch does the same thing and not "lock up" when at full temp or hot?
I was under the impression that when the engine is hot... ie 200 deg, the clutch should lock up and work to draw in air, thus keeping things cool.
Any thoughts/help would be appreciated.
The only clutch fan which is proven to withstand the immense 10,000 CFM the engine fan generates is the OEM Mopar clutch fan. Yes they're more expensive but at least they work...
Thanks for the reply. So all the typical auto parts store fan clutches don't work adequately to "lock up" and pull air through to cool things.
I know a lot of parts are being made w/ subpar components and don't last but at least out of the box, one should work as intended.....no?
Can anyone else, please tell me if their fan clutch will lock up when the engine is 190-200*
Thank yoiu
As with most over the counter "lifetime warranty" parts...quality is seemingly low on the product priority list as they prefer repeat customers by virtue of necessity rather than choice. So unfortunately over the counter parts store fan clutches dont hold up so well. In defense though, I'm sure there are some people who've had decent luck with one.....but in general most forums this time of the year will start to talk about their parts store budget fan clutch not working. One way to know if it's working is the clutch becomes fully engaged when the front fan clutch temperature spring reaches 205*. At that point you can not miss the LOUD fan roaring under the hood. If you never hear that roar then either the engine temp is not high enough or its not fully engaging. With a properly working fan clutch and radiator clean and free from excessive debris, the Cummins is capable of towing very heavy in triple digit weather while keeping the engine temp in check.
You can find OEM fan clutches at vendors like Genos Garage.
Thanks for the input.
I guess my concern is that the trans and engine temp will run over 200* and I never hear that "roar" as noted when the fan clutch is fully locked.
I prefer to keep things under 200 as heat will definitely destroy this new trans
What temp do you define as a point of overheating?
Last edited by high bid; 06-01-2019 at 12:19 PM.
Reason: added text
Thanks for the input.
I guess my concern is that the trans and engine temp will run over 200* and I never hear that "roar" as noted when the fan clutch is fully locked.
I prefer to keep things under 200 as heat will definitely destroy this new trans
What temp do you define as a point of overheating?
The radiator temp is not your transmission temp.
Do you have a transmission temp gauge?
If so what does it read? I am guessing higher than 200F when your radiator reads 200F.
If I drove an automatic Cummins truck I would make sure I installed a transmission temp gauge, especially if I towed with that truck.
Yes, trans temp gauge can read 10deg over engine temp at times.
When in stop & go traffic, temps reach 200+
I just don't like the fact that both are reaching temps over 200.
If I knew the fan clutch was locking up, I could look into other alternate methods of cooling but would like to confirm this first.
Normal engine temps during unloaded driving conditions should be around 190-195*.
Transmission temps will typically be slightly higher simply because its temperature is controlled by the heat exchanger. Adding a secondary cooler will help.
Normal engine temps while towing heavy can run between 195-215* depending on load and condition. Anything over 220* is too hot for the engine.
Transmission temperatures are normal in the 175-220* range. Anything over 225* is too hot and if you're running 220* for long periods then you'll want to change the fluid more frequent. Towing heavy and not paying attention making sure the torque converter is locked during hill climbs will both cause transmission temps to run excessively high.
I have a 6 speed manual, so I don't worry too much about trans temp, but I know these can get pretty hot.
As for engine temps boiling is at 212F open. A closed system running coolant rather than plain water can get upwards of that and still be in the safe range. When I first got my truck I pegged the temp gauge after a flush and refill of the radiator, missed getting the air out of the heater core I guess and it made it to the thermostat. I let it idle coast back down the hill to my house and it cooled down pretty fast and burped off the air.
I'm thinking larger aftermarket trans cooler and larger lines maybe in your case.....
Typical auto transmission temps are about 60-80°F over ambient outdoor temperature while in a steady speed going down the road. It will go higher while idling and stopped in D, as well as stop and go driving when the torque converter is unlocked. Trans temp fluctuates regardless of what the engine coolant is doing. From the factory, these trucks came with two transmission coolers. A small air/fluid radiator up front ahead of the Charge Air Cooler, and to the drivers side of the A/C condenser. The second one is a fluid/coolant heat exchanger mounted on the passenger side of the engine underneath the turbo. Both of them together do a real good job keeping the trans temps in check unless you are pulling a heavy load uphill with the torque convertor unlocked.
Your coolant temp should not fluctuate much. Mine is rock steady in nearly all conditions at 190°. Two reasons I can think of for unsteady is a thermostat going bad, or your radiator is partially plugged with oily gunk from the factory engine breather setup. If you change the thermostat, only use a Cummins 190° thermostat, absolutely needs to be from Cummins. Other brands are hit and miss.
JR … thanks for the reply.
Cummins thermostat installed 6mo ago w/a complete antifreeze flush. I even added in "super coolant"
I'll check the radiator and make sure all is clean.
Are you able to check the fan clutch "lock up" and reply back?
thank you
Last edited by high bid; 06-04-2019 at 05:16 PM.
Reason: typo
Trans temps up to 200° are normal, not much to worry about there. Trans fluid is essentially hydraulic fluid. I get concerned when mine gets around 220°, that's roughly where the fluid starts to break down from being too hot. 230° is bad, 250º is horrible. The hotter it gets, it shortens the fluid life faster. Short term heating is easier to deal with than an extended time with the fluid hot. In my case, my temp sensor is in the hot line leaving the transmission to go to the coolers, so I get to see the temp of the hottest fluid.
The fan will spin with some resistance when engine is cold or at normal temp on my truck. It doesn't lock up very often for me, even towing. I've pulled my trailer (29 ft camper) through the Appalachians in Tennessee on the interstate and no lockup in summertime. Pulling a steep grade in second gear caused the fan to lock in Vermont that I recall. I also once left my winter front on in springtime and it got warm enough to engage the fan until I pulled over to remove the winter front. It is very obvious when the fan engages, you'll hear it roar and really move air when above 1500 RPM.
For the radiator blockage, you'll have to look at the FRONT of the radiator. It's hard to see with it in the truck, and you won't see anything from the backside. The cause of this is from the factory location of the breather bottle. Crankcase fumes are vented to atmosphere instead of using a PCV valve setup like gas engines. The crankcase vent for us is up front at the timing case with a tube and catch bottle right behind the fan. The oily fumes gets swirled around by the fan which sticks to the radiator fins which in turn attracts and collects dirt. That will over time plug up the radiator enough to cause overheating issues like you have unless you force enough air through the parts that aren't plugged, like when you are driving.
Here's a picture from when I replaced my original radiator in 2017. I changed it because the plastic side tank cracked and started leaking. I relocated the breather bottle in 2004 at ~70,000 miles. Mine cooled normal, even towing. Here's what it looked like when I pulled it at ~160,000 miles (this is a mild case of blockage). Keep in mind, this is the FRONT of the radiator.
Very instructive pics, JR...I'm reminded that when I worked as a mechanic, and for whatever reason might have had the upper fan shroud out or the upper radiator support off a vehicle for any reason, I always used the shop water hose with nozzle to blow water backwards through the radiator fins...This loosened and washed away a lot of the debris stuck to the front of the radiator...Sometimes the amount of leaves, grass trimmings and birds accumulated there was downright amazing...I also kept a fin comb in the toolbox to straighten bent fins...Thanks for the reminder of those days......Ben
With the 24V breather tube location, I see radiators that look like the 2nd one pretty often on higher mileage Cummins trucks.
I like to extend the breather tube down and into a hole in the frame rail to oil up the frame rather than plug up my radiator myself.
05-30-2019, 09:10 PM
...Ben