Hi, I have a 1990 F150, 2wd with a 4.9 and an E4od transmission. About a month ago I replaced a section of heater core hose above the alternator. The first drive after replacing the hose I went 5 minutes away to the grocery store and when I started it back up it made a new noise which I had never heard before. My first thought was something hitting the fan. That is what the sound reminds me off (its not lifters, I know what those sound like). I opened the hood and checked, everything was clear of the fan no tools or old hose clamps. It makes the noise when accelerating from a stop and is more noticeable under load, it will occasionally do it on startup but I can rev the motor in park with no noise. I have no CEL but do have memory codes 49 and 62 (both transmission codes) I don't think those are related because the noise is present when not moving and is coming from under the hood. The only thing I can think of related to the heater hose is spilt coolant on the Air Bypass Valve. The truck is very original and has all the original EGR components. I also changed the oil and found no metal flakes in the oil or on the magnetic drain plug so the engine itself seems to be in good condition. The truck drives and shifts like normal. It will still make the noise with the serpentine belt removed. I also pulled spark plugs from cylinder 1 and 5 they have less than 10,000 miles on them and appear in decent condition. I have also installed a new O2 sensor about 2 years ago. I have attached videos of it driving with the noise and in park idling. I also attached pictures of the spark plugs, the hose, and bypass valve. Anyone have any ideas?

 

Maybe an engine mount let go? Would explain why you're getting a fan hitting something kinda noise, but only under load. Have someone brakestand it with the hood open and see if the engine makes a bid for freedom.

The uneven crud on the plug looks kinda weird to me, but I'm not trained in the art of reading plugs.

 

Thats a good idea but it doesn't make the noise when you brake stand it. I did have a guy start it while I tried to listen. Found a loose spark plug but nothing else. Tightening it didn't fix anything. It rattles every time you start it now. I'm probably gonna have a local shop look at it at this point. I can't think of any other possible cause.

 

I gave it another look over today and decided to try to take some pictures of the back of the engine to see if anything seemed out of normal there. I ended up with the EGR valve in my face and noticed it has rusted through and has a pin hole in it. Could this be the cause of the noise?

 

Could be. There shouldn't be a hole there, for certain.

 

Wow. Haven't seen that before. Yeah, that would make a hell of a racket. If you want to test it you could slap some JB weld over the hole. Wouldn't hold for long, should be long enough to see if it makes the noise go away though!

 

Figured I would go ahead and update this thread, unfortunately the noise was coming from the bell-housing and not the egr valve. Cracked flexplate