3126 running hot

busco · Aug 16, 2002

I have a 1996 fl70 with a 3126 engine and a 6 speed trans with 255/70r22.5 tires on it. It has a 14 ft rv camper box on it and I pull a 20 ft gooseneck flat bed trailer with a race vechile on it. The problem is that going down the road the engine fan is almost running continuos if you are running 65 mpg in 80-90 degree weather.
I have put in 2 new thermostats, 2 new radiators, new water pump, new fan sensor, new turbo (waste gate froze up on old one), checked shunt hoses, changed coolant mixtures, pulled muffler off and ran a straight pipe ( did not help), pulled wire mesh screen off of frt of a/c condensor, talked to local cat dealer. Freightliner says that fan should come on at about 205 degrees (pretty accurate with temp gun) and hot light comes on at 217 degrees with shut down starting at about 230 degrees. I have not had the light come on or shut down take place. just the fan running continuosly.
If anyone has info on this problem please e-mail me if you have a solution at [email protected]

Weave · Aug 16, 2002

It sounds like you replaced just about everything related to the problem. Believe it or not, most of the time I find the cause of the fan running constantly problem on engines with viscous mechanical fans (what I believe your '96 3126 has) to be blockage of airflow through the A/C condenser and the air-to-air exchanger. Are these two units clean with the condenser free from a lot of dents?
Sometimes to narrow a true overheating problem down to engine or radiator/sensors, I'll pull the thermostats out and run the engine without them to see what happens. With a blockage of airflow or faulty fan, the engine will still continue to run hot. If it runs real cool, there is something up with the engine itself- the computer could be causing the injectors to run lean, or possibly the engine is running with too much boost, or other things. See if this stuff helps-best wishes;-)
-Weave-

ClassicOne · Aug 25, 2002

I'm the owner of a '01 FL80 with the same setup and the same problem. Seems to me that my fan runs all the time when the temp outside is 75 or higher. I have found with the cooler weather that if I'm off the turbo the fan clutch will cool down enough to cut out. But with that first hill I will heat the clutch up and the jet engine sound starts up again. The freightliner dealer I went to couldn't help at all. In fact I used to turn wrenches and I was disgusted with the lack of support from that dealer. Hopefully other dealers are better. With the cooler weather and a larger margin of time so I can slow down some the fan cycles less often. Let me know if you hit on a combo that works as I and my codriver wife go crazy trying to think and talk over the sound of the fan

Weave · Aug 26, 2002

Are you folks running your air conditioners? My friend at Fleet Maintenance in Buffalo seems to think that's what is keeping the fan running with the added heat on the A/C condenser. In that event the fan should be running, and you'll just have to put up with the noise.
-Weave-

busco · Aug 27, 2002

Ref running hot
In my case it does not seam to make any diffrence with the a/c on or off. I have run with the a/c off and it still warms up to the point of running the fan almost continous.
Wayne

louixo · Sep 2, 2002

My last truck was a cat in a "D" unit. Always ran hot. The heavier the load, the hotter it ran. That coupled with other problems indigenous to small cats, made me a cat hater. I´ll never own another kitty.

ClassicOne · Sep 2, 2002

after running this truck for a month.... the a/c does affect my fan. But the biggest help was replacing the air filter and keeping the a/c coils clean. have reduced the temps by 10 degrees. Observation though. Even with the engine temps reduced.. going up hills the turbo boost is highest and the fan will come on strong even though the engine temp lags the temp at the fan is higher and thus activates. I wonder if mounting an air dam similar to the century class might increase air flow through the coolers. What do you think Weave?

Wild Bill · Sep 2, 2002

Wayne,

Just curious. When did you become an expediter? I seen the screen name and thought "There can't be 2 of us from Churubusco...lol Then I looked on your profile and seen your name.

Welcome to the board and expediting

Bill Hosler

busco · Sep 2, 2002

Bill
Stumbled accross this site a few weeks ago. Looked like a good site to see if other people are having problems like I am
Wayne

gingerbreadman · Sep 2, 2002

as i am not a mechanic my thought might be the waste gate on the turbo. I think it is supposed to open when the truck gets warm. If if is not opening and just recirculating the hot air.just a thought

busco · Sep 2, 2002

Believe it or not but I already have put on a new turbo charger. That was also one of my thoughts. It needed one on it any how as the waste gate was froze up and I could not get it broke loose.
Thanks for the idea
Wayne

Weave · Sep 2, 2002

I talked with my friend from Fleet Maintenance again over the weekend as you guys have exhausted my resources. He did mention that the fans do run more frequently with 3126's, they are a little "hot blooded." I'm just wondering why, as I've only heard the fan come on with my Detroit once on the highway, fully loaded up a mountain. If someone figures it out, please post the solution.
-Weave-

Larry · Oct 11, 2002

Busco:

I had a small radiator leak in my 3126 Cat and proceeded to added Bars Leak. The truck has run hot ever since. When I went to the Cat dealer and told him that the truck was running hot (I couldn't even run the AC) and that I had recently added Bars Leak, he said the radiator is probably plugged. (It is the original with over 400,000 miles.)

I spoke with Shane Ferguson of Kool Radiator Service in Southgate, MI. They were recommended by several mechanics, including Catapillar in Novi, MI. During our conversation, Shane started telling me about all the trucks that have come in there with newly replaced radiators that were overheating. He said that the radiator and water pumps on these trucks are matched and that even the dealer service departments sometimes do not check to make sure that the proper replacement is being installed. Putting on the wrong replacement radiator can make a difference of 10 - 15 degrees operating temperature.

Apparently the biggest problem has to do with making sure that a smooth tube or dimpled tube radiator is replaced by the same. Replacing one with the other can result in overheating or not heating enough. He said that the VIN # can be run to determine the proper radiator and that the current radiator can be looked at to determine if it is correct one or not. It may be worth looking into.

By the way, a NEW radiator was $890 plus installation.
Good Luck.

Weave · Oct 12, 2002

It sounds like the hot 3126 problems might be close to getting solved. Coolant leak stoppers are a big no-no in diesels. There is a chart in my DDC 60 manual showing how much of a rise in head temp. there is with leak stoppers in the coolant. You are better off letting a small leak go until you can get it fixed properly than you are by adding leak stoppers.
My buddy at Fleet said is is OK to use cooler thermostats to get the water to the right temp. I think CAT wants the 3126 to run at 190 degrees. If the engine uses two stats, just be sure to replace both with two of the same temp. rating. If it takes 2 170 degree stats to get it to run at 190, you've got it beat. Keep me updated!
-Weave-

geo · Oct 13, 2002

give bill moore a call at tsi, those guy's are the best i know of
and they will be able to help to 800 388 3850 they are cat dealer in north jackson oh by youngstown oh

busco · Oct 15, 2002

I think we have finally gotten to the bottom of my running hot problem. After numerous phone calls to the oem radiator manufacture and frieghtliner tech, and finally a call to kool radiator ( posted by one of you ) we finally have determined that the radiator shop has made me 2 wrong radiators. After talking to kool radiator and then finally the great lakes radiator manufacture( the manufacture of my new cores). We have found out that the core in the replacement radiators are of the smooth tube type. The oem radiators in these trucks are a dimpled tube core. In other words the have small punch type marks in the tubes to help slow down the flow and splash the coolant aginst the dimples and the tube for better heat disipation. Kool radiator claims a 10-15 degree diffrence. I sure hope so because that will put me right in the ballpark.:7 :7
Thanks all for the help.
By the way if anyone wants to see the 5000 HP machine I tow with this rig stop By www.kriderracing.com
Thanks again everyone

Larry · Oct 15, 2002

When I spoke to Shane at Kool Radiator the other day, I kept thinking about your truck. Glad they could help. (I can always use the 2 points - I'm trying to catch a couple of people -- ha ha). By the way, with my new radiator my truck is staying at 180 - 185 and not jumping up over 200 like it was previously.

Drive Safe.

Irishjim · Jan 3, 2003

Wayne, Checked out your rig, now that's an expediter.What do you get 20 Gal. to the mile??? PS. If you need front tires for it I have the same size on the rear of my lawn tractor. Be careful out there. Jim.:+

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