Hey guys, been a lurker on here. Since I have a ford now I Figured I'd join. I bought an 88 f150 xlt lariat with the 302 5.0, 5 speed. Truck and engine has 210,000kms. I bought the truck for $700, it had some bogging issues. I changed the plug, wires, cap and rotor which cleared it up. I noticed there's a humming.sound xcoming from the engine, not a power Steering pump whine, but a somewhat pitched humm sound. I Can't pin point to where it is. Truck can be in neutral, I give it gas and the humm raises with the rpms. It's not loud but it's noticeable to me. Any thoughts of what this could be? I want to take it on a 3000km round trip in a month, seeing If it's a big worry. Any input would be great. Thanks guys!

 

my alternator started doing that when the bearings were going bad in it. might check that? do you still have mechanical fan, if so then it could be from that, i converted mine to the electric fan to take some load off the engine.

 

Hhhmmm. Never Thought of that. I know the alternator is going because with heat on high and No lights on, at idle it's reading around 10v on the gauge

 

if its the orig alternator, then yea, bearings are going bad and thats the humming noise, or it could be the belt driven rad. fan, or both. i had to replace both on mine, and tensioner pulley, and the humm/squeak went away.

 

It's the belt driven fan. Thinking of it, I changed an alt. On a Grandam a month or so ago, it's not a high pitched whine like that. Almost sounds like it's coming from the back of the engine area

 

You can also check the smog pump silencer. It's an actual muffler on the passenger's side fender well that muffles the smog pump. There's a rubber hose attached to it that runs down to the smog pump. They can rust out and get pin holes in them. I built my own replacement from wire mesh, pvc and moved it off of the fender well along with the vacuum chamber and opened up a whole lot of room for a future project. Second battery, under hood air compressor, etc. Not exactly sure about the 88, but it should have that silencer.

https://www.f150forum.com/f10/smog-p...lencer-160471/
I painted my new filter silencer black since this thread. Looks great and works great.

Here's the vacuum canister relocate.
https://www.f150forum.com/f10/vacuum...162114/index2/

 

didnt think of that, that is a possibility too, or maybe even a small exhaust leak near the back of the mani or something. is it affecting driveablilty or performance?

 

I know there's a decent exhaust leak behind the engine because when it's cold out I see smoke coming up from behind engine in the bay. Doesn't seem to affect performance at all. It's Just a mid pitched humming sound which follows with the rpms.

 

this may sound wierd, but it could be electrical interference with your speakers. as the alternator speeds up the humming will speed up, this happened to me when i installed a cb radio in a truck i had...just a thought

 

Negative on the interference good sir. I can hear it when the hoods popped and I'm looking around the engine bay. I havent been outside in a couple weeks due to surgery but I'm saying all based on what I looked at