I have a 1986 Freightliner 10 wheel dump truck with a Cat 3406B and 13 speed transmission. I pulled my 20 ton tag trailer up a 6% grade today empty, and it was about 90 degrees outside. I was in 8 low doing 900 on the pyro. Towards the top of the hill, I noticed my water temperature was at 208 or so. (It normally runs about 185-190 when idling or on flat ground) so I backed it down some to keep the temperature from rising any more. I do not have an air fan hub on this truck, just a thermal one. First off, is this normal, second what should I look at first? Thanks in advance, this is my first real truck and I don't know much about them. Keith
When was the last time the core was pressure washed? If it has A/C and Air Charge cooler over time the core will clog with fine dust. Grain trucks I use to work on would need cleaned twice a year sometimes. That viscus fan may not be pulling enough air also.
A viscous fan hub has a life expectancy. The very small amount of fluid eventually disappears and the engine starts to run hotter.
if that fan is working properly you should be able to hear a change when it gets that hot.
Thanks, sounds like it is the fan clutch then, because I hear no change and the temp seems to just keep climbing with no stopping it even if you drop gears.
I made sure the outside of the radiator was clean, is that what you mean? I don't know any of the history on the truck.
NO, the outside can look clean, you can't see the whole outside if there's other coolers in the way, and then you'd have to shine a light from the other side and look through to see how dirty the fins are. One way to check, is to rinse with a garden hose, then spray on some detergent, keep rinsing and repeating. It will run clean for a bit, then you'll hit a dirty spot, and you know it's dirty. Sounds like the clutch though, if it stays cool enough when moving, but overheats going up a grade.
^good stuff Delmer. I ran a 977 raking up roots on a golf course job, very dusty and they blew that out every week or it would climb on up there. I too think it is the fan but a clean rad and CAC would not hurt.
That seems like a high temp for it sitting. Unless my gauge is off mine sits at 170 idling and normal driving if it's not working too hard. I do find on the warmer days like above 85 if it's really working the fan can't keep it cool if pulling up a grade with my 210 on but I am at about 90,000lbs and have to take it easy, seen as high as about 205. I just chalked it up to being older and cooling system not as good as newer stuff, below about 85 it will keep it cool no problem.
To properly clean a radiator core externally, A/C denser and air charge cooler has to be removed. And carefully using a pressure washer {not to close} start at front side and doing your best from back side. Air charge cooler can be washed as well as A/C denser. Normally on a viscus fan hub if it's leaking fluid-dust/oil will collect on the front side, check with mirror.
Thanks, I will make for sure the rad and CAC is clean. Sounds like I need a fan clutch though.
Hi after you have checked all of the above.check to see if the water pump impeller is not turning on the shaft.the impeller is a taper fit on the shaft and if not fitted correctly can come loose. Also there were a batch of water pumps that had a plastic type impeller bonded to a steel hub, when hot the impeller would spin on the hub Mark
Thanks. I cleaned the radiator tonight with my friends home made radiator gun. Will also test fan clutch and inspect water pump.
Removed fan clutch. Should I replace with a Horton air fan clutch? Also I am assuming this flange is part of the clutch itself as there are no fasteners holding it on.
The Horton is a complete unit. You will need a fan solenoid, temp sender, cab switch for manual over ride. Kind of spendy because you will get hit for no core unless you buy new. Personally I would find a replacement viscus fan hub and leave it be.
Could I set up the Horton just to be on / off manually? With no sending unit, just the new clutch hub and a cab switch and small solenoid and an air line? And make sure the right nut is behind the wheel?
You could yes but does this rig have working A/C? I have known a few that have done that and wished they had not later on. Only takes one time on a hot day.
No AC doesn't work
Well no problem there with a A/C pressure switch. I can't tell you what to do but if it was me I would wire it up for automatic and manual over ride.
Interested in the Horton because I am having a tough time finding the thermal clutch which is what I want to do, no part number...
https://kit-masters.com/wp-lib/wp-content/uploads/2017/04/Viscous-ID-Flyer.pdf
Thank you!
I condemned the fan clutch too quickly. Replaced with a new OEM viscous clutch. No difference in temperature. What next? Thermostat, water pump? Pressure test radiator? New core? When I hit the top of the grade in Sedona I was running 210 with no sound of the fan coming on. I have a 6 blade fan currently. Should I replace with an 8 or 9 blade? Was going 40mph towing 22k on the tag trailer running 1750 rpm about 850-900 EGT I recall.
I was watching and was afraid the fan wouldn’t fix the problem. Those engines eat water pumps. So many PSP, PIP campaigns, Service Magazine & Truck Engine News bulletins about those. Many product updates. It could still have original fiber impeller that is known for slipping. You could take some temps, run some numbers, check some delta T’s or just change the water pump, backing plate & T-stats. New coolant. The problem will probably go away. I just changed a water pump on a 3406B with a fiber impeller. That was overheating. Whoduthunk there would still be fiber impeller water pumps left in the wild?
At 1750 your near the bottom of torque range. EGT's will climb.
roll it back to about 1600, TS? Even lower? Enquiring 3406B operators want to know
Drive it how ever you want to, I'm not repairing it or paying the bill.
Jack Crews said “Ain’t Nothing Like a Caterpillar Engine”. I believe him.
This truck doesn't have a pyro or anything so I was just looking for clues. I only have a few grades I pull, none long enough to figure out The best practices.
Old rule of thumb, If your hard on the throttle to maintain speed on a grade or can't gain speed you need to drop one gear. Should maintain speed easily at 65% throttle. If it's a 2100 rpm engine it should be pulling easy at 1900 and running 195* to 200* with fan engaged.
Yeah, uh ha jack crews.
Yea i'm in the same boat. I tend to drop a gear if it hits 1400, and keep it at 1500-1700 for hard pulls. But no long grades here either. I haven't found a grade mine won't hold speed at in 7th even at 90,000lbs.
You can check that pretty easy without swapping parts. Plumb a pressure gauge into the side of the block. Should run around 30 psi steady at speed. Best to be able to watch it while driving. Slipping on shaft can come and go with different temperatures.
Thanks, that is how I drive. if it won't accelerate then back out of that one and go a hole lower. This truck runs 175 and I might get to 190 on my little pulls. It has the air fan. I figure with 325 hp and 1075 torque it is pretty modest fueling, so not too likely that it will cook too hot to need a pyro.
Saw this video yesterday, I assume this is what you mean?
Lock your old viscus clutch, I have had 3,2 Mack’s and1 cummins doing the same thing tried the new clutch with no luck.is it the clock spring type or the flat ,pop spring type?
Clock spring
Mark the little shaft in the center of the spring and heat it with a heat gun to see where it goes when it gets hot and stretch the spring to make it stay in that position when cool .I have had good luck with this,maybe it wil work for you