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To hot to handle


coppermack
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I've got a 94 ch613 with a mack 350. Truck ran hot on last trip (hauling grain 25 miles) and then all of the sudden ran cool and wouldn't even get above 120 or so. I assumed it was a sticky thermostat replaced thermostat. Next trip out this afternoon loaded truck (ran app. 1 hr before I hit the road) temp was around 130-150. Made it less than 5 miles and gauge was about to bump into the red. Pulled over, cooled off and came back to shop. Now I'm guessing water pump or maybe an air lock? Pretty terrible as a mechanic so any help appreciated. Thanks

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without being there to look at it I would say find the highest point on the water manifold or the temp. sender and remove the sender or a plug from the manifold and burp it. you may want to drain about 3 gallons first then with plug or sender removed slowly fill the rad. until coolant comes out sender or plug hole then reinstall sender or plug and then finish filling rad. ( make sure the front of the eng. is slightly higher than the rear of the eng. this should remove all trapped air)

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When I fill with antifreeze I always remove the heater hose that goes into the shutoff valve at the manifold. When a/f comes out of there I close the valve and put heater hose back on. Then open valve and refill. Been working good since I did it that way and haven't airlocked since. 2 guys works better for this if you got because usually I'm on top of the tire

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Also with a heat problem that has had most of the major parts checked or replaced and still heats the water pump pressure needs checked.You may have a new pump on it and with out rereading to check a water pump the water pump pressure should be checked before replacing it thinking its bad.To do so use a 50 psi gauge and connct into the coolant system anywere before or below the thermostat.With full engine speed the pressure should be around 18psi and I am guessing with out looking in the manual.I know on one of my engines it was about that.If its lower than that look for a belt slipping due to bad pulleys or belt or a bad pump.The engine does not have to be cold or hot and the thermostat be closed or open changes things very little.The rad cap can be on or off also.

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glenn akers

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  • 4 weeks later...

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