My 1991 Explorer has a random light tap between 800 - 1,100 RPMs, under light load in drive or reverse. Seems to be most noticeable when the engine is warm - hot. First noticed at an ATM drive-thru, as I sat in drive at idle. I can't seem to isolate the sound. In park it is not detectable.
Auto transmission rebuilt 7K miles ago. Made sound before and after. In addition, the bottom of my engine is constantly wet with oil. Looks like the oil filter adapter at the engine may be leaking. Ever seen this?
The tap is more of a "thum thum thum thum thum" sound and is constant only when the engine is in gear (under load) at 850 - 1,100 RPMs or so. In neutral, it appears to be gone. Noticed more when going up a hill or "power braking" at 850 - 1,100 RPMs. Can't be heard from inside vehicle, unless windows are down and next to an item to reflect the sound into the window.
I feel confidant that it is not the heat shields. I believe that the sound is coming from the passenger side front area of the compartment.
I guess I need to do the old long extension to the ear test, to isolate more.
My '92 does the same thing. It's piston slap. One of the piston skirts is wearing down a bit, and making a little noise. Mine has gone 40,000 miles with the noise, with no ill effects, 209,000 miles total. 15w40 oil makes it quieter. I isolated the noise to #1 cylinder. When I get the money I'll rebuild it, but until then, I'm not going to worry about it. As long as it doesn't make noise going down the road and you've got oil pressure, then you probably dont need to worry too much about it either.
Piston slap makes sense. I paid close attention today and noticed that it did NOT do it when the engine was cold. When warmed up, it did it just as I described. I have changed the oil & filter regularly every 3K-5K miles. The bad thing is in the last five years, I have only driven it 3K-5K per year. I may consider 1 court of synthetic oil the next change. I run full synthetic in my other vehicle. I have always hesitated full synthetic in this OLDER high mileage vehicle.
This vehicle is getting ready to be my daily driver. 15K per year. It is going to be an interesting year.
Well, assuming it's not a loose heat shield (that really does happen), then noise from the lower end is usually a bit of wrist pin slop and if it's upper end it's usually valve train issues. Some 4.0's had tolerances that allowed a bit of wrist pin slop to be heard. Ford issued a TSB on the subject and consideres it normal. I'd encourage running the oil weight specified by Ford and live with a slight amount of noise.
For what it is worth I have a 93 Aerostar Ext with a 4.0 L. I bought it from the original owner at 133,000 and now have 178,000 18 mo later. As soon as I got it home I switched to Castrol 20W 50. It has worked great ever since. I always run 20W 50 even in a new engine as it is generally a very HD oil. Never any problems and on high milage engines it quiets noisy push rods etc. I live in CA and it easily pased tough emmisions 2 mo. ago so it seems my engine likes it! I have used 20W 50 in a 3.0, 351, 400 and 460 with excellent results!
OK. Well that's what's was spilling all over the floor, 20W50. so long as you keep your O2 sensor in good shape and take care of any codes that come up, you'll pass emmisions no matter how old the motor is. By the way, have you cleaned your MAF sensor?
Join Our Site - Its free, quick and easy!
