Volvo L90F

loader was just bought from a local sawmill and new owners had a complaint of overheating. Went and looked at loader. Was missing the expansion tank cap and oil cooler was starting to leak oil into coolant but I couldn’t get it to overheat. Got a cap and an oil cooler and went back today. Changed cooler and started flushing cooling system. Filled system with water and cascade detergent and got it to overheat within minutes. Figured it was airbound. drained about 4.5 gallons of water out. System typically holds around 8 gallons.took off top hose and refilled with garden hose so I wasn’t positive how much it took but it didn’t take long and it didn’t flow out of top radiator hose. Drove around and it got hot again. Like over 210. But the radiator was cool to the touch. Took off top hose and no water. Removed thermostat and water pump. Pump had a slight play in bearing but not bad.put back together without the t-stat.took off all hoses I could and they were not plugged. Put back together and filled with water. started machine. With machine idling I took off both top and bottom radiator hoses and had almost zero flow. Like maybe an ounce or two a minute out of the engine through the bottom hose. Could it be as simple as a bad water pump or do I have an internal blockage? Seem like if my pump was bad I would still have plenty of water running out of the bottom hose. Am I missing something? Put compressed air through any coolant port when I had it apart and it pushed water and air through anything I tried.

Have you checked the air bleed lines from the head and radiator to the expansion tank? Are the tubes/orifices in the nipples in the tank? Have you reinstalled the thermostat as it will overheat without it in place? Are you sure you have all the contaminated coolant out and flushed the system thoroughly? Most of the ones I have has to deal with the mess is like pudding and has to be steamed out and then several flushes with very hot water and detergent.
Have you checked fan speeds?

Ok so here’s what I did and what I found. I returned with a new water pump and thermostat. I drained all water out. Removed water pump and oil cooler. Blew compressed air through everything, one section at a time. When I removed the hose from the expansion tank to the it had a big bulge in the hose and was rock solid. I cut it apart and found a blockage of sawdust and the cascade detergent that I had put in to flush the system. I would say that the sawdust came from the previous owner (sawmill) who had run it without the expansion cap. I put it back together with the new water pump and t-stat, flushed the system and tested the loader. Machine ran at a temp of around 195.

Continue with BWs advice. In the vent hoses you will find restrictors in the 3/8 hoses, typically near the surge tank. You want to make sure both are present and clear. Additionally, you want to make sure that the trans oil cooler which is in between the radiator and lower hose inlet is clear. It is a labyrinth plate cooler. If somebody used stop leak or as you mentioned sawdust, it could definitely be partially obstructed and could benefit rom back flushing. I realize I'm arriving late to the party, sorry for that. Just something to keep in the back of your mind.

Thanks. I finished the repair last Monday and in the owners words “ the boys ran the **** out of it until Friday morning when they think a hyd hose blew and it caught on fire, burning up some harnesses and who knows what” headed back tomorrow to check it out.

We had an L90F that came from a mill. Came with a fire suppression system. They saw no need for it and took it off when it needed repair. One year later, it caught fire and burned

I put together an estimate for the damage and easily came up with $25k worth of damage on a machine that they have less than $20k invested. I really hope it’s a total loss I hate fixing burnt machinery.