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3406B Running hot?
- Thread starter Keith Merrell
- Start date
Truck Shop
Senior Member
Keith Merrell
Well-Known Member
Thank you!
Keith Merrell
Well-Known Member
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.
Coaldust
Senior Member
- Joined
- May 9, 2011
- Messages
- 3,346
- Location
- North of the 60
- Occupation
- Cargo Tanks, ULSD, RUG, Methanol, LPG
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?
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?
Truck Shop
Senior Member
At 1750 your near the bottom of torque range. EGT's will climb.
skyking1
Senior Member
roll it back to about 1600, TS? Even lower?
Enquiring 3406B operators want to know
Enquiring 3406B operators want to know
Last edited:
Truck Shop
Senior Member
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.
Coaldust
Senior Member
- Joined
- May 9, 2011
- Messages
- 3,346
- Location
- North of the 60
- Occupation
- Cargo Tanks, ULSD, RUG, Methanol, LPG
Jack Crews said “Ain’t Nothing Like a Caterpillar Engine”. I believe him. 
skyking1
Senior Member
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.
Truck Shop
Senior Member
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.
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.
Truck Shop
Senior Member
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.
Tenwheeler
Senior Member
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.
skyking1
Senior Member
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.
Keith Merrell
Well-Known Member
Keith Merrell
Well-Known Member
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