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Ford Ranger coolant thumping

I had my 94 Ford Ranger recently repaired, new water pump and coolant. Seems to run okay, but after 10 minute drive, the coolant system loudly thumps and visibly pulses as if there is steam or huge bubbles in the hoses. They are timed irregularly, but about once every 2 seconds and they quickly go away after a minute after shutting off the engin. Water temp is showing normal on the idiot gauge. This is making me very nervous as it’s my only vehicle. Thanks for any ideas…

There’s most likely air trapped in the cooling system. This can easily happen when the cooling system is opened up when replacing parts.

To remove the air from the cooling system, get the engine up to operating temperature. With the engine idling, loosen the upper radiator hose clamp and slip a small flat bladed screwdriver between the upper radiator hose and the radiator hose neck. Allow the engine to continue to idle until all the air is purged out thru the upper radiator hose and nothing but coolant comes out. Pull the screwdriver out from the upper radiator hose and retighten the hose clamp. Check the coolant level after the engine cools down.


Thanks for the quick answer! I’ll give it a try tonight and see if that’s the case. Sounds pretty reasonable to me.