Hi there. I have a 1998 F150 4.6l that has seen better days. I left it running with the heater on to dry out the interior due to a leak that I have been troubleshooting. It was running fine for about 2 hours (maybe) and then started to make a scraping/grinding noise in the engine compartment. It sounds almost as if the fans are catching something, but its intermittent, and only lasts maybe a second at a time. I shut the truck off because I had no idea what it was. Checked oil and coolant levels to make sure the engine wasn't needing anything. Let it cool for a little bit then tried to run it again. The noise came back. I tried googling it, couldn't find any videos that duplicated what Im hearing. Anyone have any clues that could point me in the right direction?? TIA.

 

take a good look at the fan for starters. When it is making the noise, shut it down, remove the belt and restart it to see if it still makes the noise. That should tell you if it is one of the accessories pulled by the belt.

 

Yeah. Ill check in the morning. The odd thing is it was just sitting there idling fine and it started making the noise.

 

Update. Started it this morning, and no noise. Ran fine for 20-30 mins then noise started again. Louder on passenger side. It did the squeaky thing a few times then a constant buzzing / spinning noise. I shut it down, then when I put the key back in and turned it to the "run" position the truck started up immediately - without going to the "start" position with the key. The buzzing noise was still there. So. My theory is that when it gets hot something shorts out and is engaging the starter and the grinding I heard was the gears trying to mesh, and the buzzing is the starter spinning when it finally engaged the teeth. My question is - would it be something like a faulty relay is engaging when it gets hot, or does it sound more like the starter solenoid malfunctioning when hot? Basically - should I pull the starter and have it tested, or replace the relay?

 

It could also be the ignition switch.

 

Is there a way to test this?

 

UPDATE:
Replaced the ignition switch, didn't help. Still have power at the solenoid relay on the small wire when the key is in "run" and the starter will still try to engage. Tried shifting to neutral to see if that might be part of it, still trying to engage. It only seems to happen when the truck is warmed up. I also hear a clicking noise that sounds like its coming from somewhere in the middle of the dash right before the starter tries to engage. Is there another relay in the cabin for the starter? Something else that might be shorted? Please help...