F150 with a thump/thud

I have a 1997 F150 that has been making an odd noise (something new and different). It seems to be coming from the engine-ish area. It makes a hollow whooshing kind of noise, followed by a thump/thud that I can feel through the accelerator (think frighting off beat base drum living under the hood). It sounds like a very large valve of some kind closing. It does not do this all the time, and both times it has done it have been at low altitudes- might not mean anything but my truck doesn’t seem to like low altitudes- it idles low there. It has done this twice now- once 2 or 3 times in a minute for about 50 miles and then it just stopped miracle!. I added oil in the interim of that and I thought maybe that had helped- it was embarrassingly low- took 4 quarts to get it to read half way up the dipstick. I might have murdered my truck. It did it again when I was on a long trip, coming home. It only did it 4 or 5 times, but it was enough to make me beg my truck to at least make it to Vegas, then realizing I was risking death if I stayed there I begged it to get me to Henderson, then Kingman, then home (Prescott). My truck kindly listened to my desperate plea and hasn’t made a peep since, which means I made it home but now I can’t get my mechanic to have a clue. I tried that the first time and he said “hmm.” That was incredibly helpful. So do I need a new truck? I might be able to afford a 1998 model.

“I added oil in the interim of that and I thought maybe that had helped- it was embarrassingly low- took 4 quarts to get it to read half way up the dipstick.”

Um… so the noise is coming from the “engine-ish” area, huh?

I don’t dare guess. But you may want to start pricing out boneyard replacement engines. This one probably has a spun bearing, and it’s probably going to seize any time soon. If this is your maintenance plan, there’s no sense getting a new vehicle.

I have to agree with mountainbike.
If he sounded frustrated, it is because he (like me) has little tolerance for people who abuse their vehicles, and–based on your own statements–you have surely abused this vehicle.

At this point, you might as well just drive it until it dies, but you have to realize that it could die…
…as you are crossing RR tracks
…while in the midst of 18-wheelers
…while driving through Death Valley
…while driving through a dicey neighborhood
…so you should probably start shopping for the replacement vehicle right away.

Incidentally, the way that you abused your vehicle is–sadly–not unique.
In the automotive forum of City Data, somebody posted a disturbingly similar situation with his/her Corolla:


I’ll bet that mountainbike can pick out my response (under a different screen name, of course) in that thread on City Data!

LOL, thanks VDC. I’ll not post a guess which is yours in deference to your privacy, however I loved that thread.

4 quarts low, that’s not a good thing, but you might get lucky, you caught the oil problem in time, and it’s at least possible what you are hearing is only a minor problem. Don’t assume the worst I guess is what I’m saying.

There’s two things I can think of that might make that kind sound. One is a malfunctioning pcv valve. Another is a stuck thermostat, quickly unsticking. I had a Ford Galaxy one time, and that happened to it. A loud “thunk” sound when the thermostat would unstick and fly to its full open position, then a whooshing sound as the coolant moves through the passages. Test the pcv and thermostat, worth a try anyway.