I have a 2010, 4X2, 4.0, Auto, Extended Cab Ranger with 1200 miles. From the purchase date I have noticed a thumping/pumping sound at around 12 to 15 MPH after cold startup ( first thing in the morning and when leaving work). The sound comes from directly in front of the driver (under the hood) and does not occur if the engine is warm and is restarted, say, after getting fuel. It's as though something is pumping up.
Any ideas? Thanks, Jasper16

 

when its extremely cold like this its a good idea to let it warm up for at least 5 minutes. you are trying to pump oil, power steering fluid, and tranny fluid that are ICE cold and thick as molasses, plus putting a tremendous load on rotating and reciprocating parts that are designed to work at a proper operating temperature. as metal heats and cools clearances change and parts wear differently. there is alot of controversy on this, but this is my views on it so take it or leave it.

hmm but why dont you just take it into the dealer since you just got it and are probly covered for something like that?