This just started a couple of weeks ago. My truck makes a strange noise just before coming to a stop. Its kinda hard to explain other than it seems to be a cross between a chirp and a squeek, kind of a "booping" noise. It seems to come from the drivers side of the engine compartment. Its not the brake indicators, I checked that. The noise doesnt increase or decrease with the speed of the tire rotation. I cant get it to happen with the truck sitting and idling or at least I cant hear it. I havent heard it when under acceleration. I have checked all hoses and connections. All seem to be tight with no leaks or cracks that I could find. There is no excessive smoke and the truck runs fine. If the lift pump is bad, would this cause the injection pump to sound different?

 

Try an experiment. Do what you do to make the noise except this time to stop do not use the normal brake. Stop using the emergency brake only. Do this a couple of times and let us know if this makes a difference.