Intermittent grinding noise at highway speeds.

[RobertFord]

Hey everyone,

I have a '91 Explorer XLT w/ 4.0 OHV and A4LD engine/trans and lately I've been hearing weird sounds from the engine.

1. At startup you hear a slow grinding sound, this goes away after a minute or so.
2. When the engine is warmed up, and cruising down the highway at 70-75mph, every now and then the grinding noise will reappear. The noise will recede when I let off the gas, but come back when I put my foot down again, at this moment the car also seems to lack power. The noise will then eventually disappear again after a minute or two. (This usually happens once in a 1.5-2hr drive, but it WILL happen)

It's a grinding noise, not too hard but you can sure hear it...

Any thoughts on what this might be? I just bought new rocker arms and pushrods, but havent gotten around to installing them. Would be too bad if I had to junk the truck with those nice parts sitting around...

 

[monsterchuck]

Fan clutch maybe? That's a hard one to guess at without seeing or hearing.

 

[RobertFord]

Tried making a sound clip of it, but it was inaudible. I have recently changed the oil and it seems to be gone for now. I'll make sure to replace the oil again soon as a sort of-mini flush and hope that'll be the end of that.

 

[notaprob]

It wont hurt to check around the pulleys to see if there are any signs of it rubbing something.