2009 Volvo Overheat

The vehicle is a 2009 Volvo D12 dump truck/plow truck. It will over heat going down the road and shut down. The engine fan has been eliminated as problem as I unplugged the electrical plug which locks it solid and the fan can be herd pulling air at all rpm ranges. The fan if it matters is the viscous clutch fan style with the electric control aswell. It still overheats with fan locked on. As soon as you restart and let it idle it will cool back down until you put it into gear and start driving again. If you put in neutral and coast before needle hits 220 it will cool down and then once back in gear will overheat again. I have not used a thermo gun to verify gauge is accurate to engine temp yet thats the morning task. Just wondering what ideas you would have. Myself I'm suspecting a inaccurate temp sensor or thermostats not fully opening.

 

O.k baha kinda confused by your use of question mark? Are you saying you agree with thermo after verifying gauge accuracy. Or do you dissagree with my diagnostic procedure and if so what is your suggestion. Just to ad more forgotten info truck had new rad last year, and new fan hub brg assy at same time.

 

Thanks for reply. I did check for good air flow between rad and cac its clear and pulling alot of air. The water pump is good to know. I put a thermo in it today will fill system tomorrow and road test it. If problem still exists the pump will be the next to go on. Its just kinda strange that it does'nt overheat at idle. But I guess higher rpm = higher heat, and more resistance for pump impellar at higher rpm. I'll post final outcome. To ad a small bit of misinformation it is a D13 not D12 if it makes a differance.

 

Well its looking like your bang on the money with the pump suggestion Mark. Road test this morning turned out to be a VERY COLD ride no cab heat and its -20C which in farenhieght is #### cold. Got back to shop truck still overheating both side windows had frosted and windshield half frosted lol. Let it idle in shop for 10 min temp dropped to 170 lower rad pipe was cold upper rad pipe was mildly hot. Boss was going to pick pump up so it will be sitting there for me at 3:30am in morning (winter shift )

I do have a question have the pumps been updated to correct this issue or will it be the same pump design as what will come off? Again thanks for info keep you posted.

By the way do you hate volvos as much as I do or do you learn to like them? lol

 

Well here is the final update Mark you were right the pump was defective. Took it off and impeller could easily be spun while holding pulley flange. I must give volvo credit it was one of the easiest water pumps to replace. New pump was acting good and the truck was pushing snow by 7:00am this morning. Great advice.