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Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3362
Experience:  ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician
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Fe145. Truck coolant temp fluctuates fro 190 to 160 on both

Customer Question

Fe145. Truck coolant temp fluctuates fro 190 to 160 on both the ecm and cluster temp sensors. Wire and sensors have been checked. Changed thermostat and still have same problem. Air lifted system when installed coolant. There is def an pocket of air trapped. Was wondering if there was any places that are common.
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Daniel Wilson replied 1 year ago.

Hi my name is***** will be glad to help. If the thermostat is new but you have poor circulation still the potential causes are waterpump or loose belt, restricted radiator core or oil cooler blocking flow, Head or head gasket problems. Start by flushing the system with "cascade brand" powder dishwashing detergent and water, run to temp for 20 minutes under a load and drain. Repeat as needed and end with a final straight water flush before filling with coolant. To check for a head gasket problem use a block tester from NAPA etc to test for combustion gasses in the radiator, The blue dye will turn green if so. If ok and still a problem after the flush and the radiator and oil cooler are not restricted, replace the water pump. Let me know

Customer: replied 1 year ago.
Water pump and belt are fine. Looking to talk to a Fuso expert tech that knows these motors. I checked all the normal things already. Fuso have a mind of there own
Expert:  Daniel Wilson replied 1 year ago.

I work on these engines and have the manuals. The cooling system is nothing special. 4m50 should be the model in this truck. But sure, I'll opt out so someone else can help from here.

Expert:  Jeremy replied 1 year ago.

My name is ***** ***** I will assist you with your question today.

I'm an independent contractor and I don't get paid until a rating has been made. No rate, site gets it all.

We can go back and forth as needed to help resolve the issue you are having. Follow ups are free after ratings, so rate in confidence!

What year is this one? Do you have the full VIN number?

you're getting fluctuation on both sensors? Are they the same time showing the same temps? What do you mean by fluctuation. Are the temps bouncing up and down or are they slowly changing? Does it happen at acceleration and deceleration?

On the air pockets, I need to know the year so I can give info on that. As example, if newer than 2004, you could have a EGR leak which will cause fluctuation on nearly all the Fuso models. On the older ones, a vacuum pressure gauge is needed to pull the air out because of the crappy head design on the engines. It helps to know what you are working on.


You want a 5 star service and I want to provide a 5 star service. Please consider that I don't know your skill level as well as I can't see,

touch, smell, hear the vehicle/machine in question. Please provide as much detail as possible and I will provide as much back.

Once an answer is provided, you should see a rating screen. Please rate my personal service to you. The ratings are my personal feedback,

they are not the site feedback.

Thank you for allowing me to assist you through Just Answer!


Expert:  Jeremy replied 1 year ago.

I see you viewed this and this is still showing as a open question due to no positive (3 stars or more) rating.

Did you still need assistance with this?