I've got an 2006 F150, auto, 4.2 V6 that sounds like a diesel when I drop it in gear---knocking sound. Keeps knocking until the truck reaches normal operating temperature. 2 different Ford dealers have said they hear it but they can't find anything wrong with it. Both dealers said they compared my truck to all the '07s on the lot with the same engine/auto and they all sound the same. Truck runs fine but I hate the way it sounds. I'm thinking of trying a different oil on the next change to see if it makes a difference. Think it will help? if so, what oil substitute would ya'll recommend? thanks.

 

I've heard a few others mention this issues. I don't remember anyone ever mentioning a specific cause that was identified.
I haven't ever heard one first-hand that sounds like a diesel.
It sure is a puzzler. I'd like to figure it out.

Regarding oil:
If you want to try that, 10W30 is what I'd use.
I ran Havoline and Chevron 10W30 in my previous (2000) 4.2.
But, most any of today's oils should be fine.

Have you ever taken a mechanic's stethascope to it and tried to isolate the sound's area of origin?

Thanks.

 

I haven't used a stethascope. I've mainly been relying on Ford to figure it out b/c its under warranty. the whole thing baffles me though b/c the thing runs fine, just sounds like crap idling in gear until its completely warmed up and then it doesnt make a sound. its probably knocking under acceleration too but i cant hear it then. the 2nd Ford dealer said they put in an oasis request or something like that, basically asking for information from the Ford engineers since all the 4.2s they listened to do it. even if there isnt a problem i'd like to know what the noise is, especially since the motor doesnt make a peep, even when freezing cold, until i drop it in gear. if i get an answer i'll be sure to post it. thanks for the oil info. 10W-30 synthetic blend? also, i've been thinking of trading up to a 4.6 in a reg cab. have you driven a 4.6, auto, reg cab? if so, how does it compare to a 4.2 auto reg cab as far as moving the truck---is the power difference noticeable? the numbers between the trucks arent all that different. if i can barely tell a difference i'm not spending the money on the trade in--even if i hate the way my 4.2 sounds. thanks.

 

How do you know it is the engine? It could be the transmission making the noise. Your 2006 will run for more miles than you will probley put on it using 5w20 oil.

People have to get over the thick oil thing. 5w20 is more stable and robust than current 30 weights. It also has to pass tougher durability tests.

5w20 works and Motorcraft is a great choice.

 

well, i'm not sure its the motor. the fact that i hear nothing until dropping it in gear makes me think its the transmission and not the motor, but then again, i dont know a whole lot about some of this stuff. say it is the transmission, what would cause a knocking sound until reaching normal operating temperature?

 

I would try to get a Ford rep. involved, you might have to contact Ford directly.

 

I've already contacted Ford directly. They contacted the dealers I've taken the truck to and at this point are in agreement with the dealers that its just a normal characteristic of the truck. They tell me that my complaints have been noted and I should continue to monitor the situation. I would trade it in, but thats impossible without getting screwed.

 

That sucks. If I had to guess I would say the torque converter is causing the noise.

 

Torque coverter or the pump. Maybe try synthetic oil in the tranny?

 

I thought Mercon V was synthetic?

 

Sounds like piston slap to me and I dont think thicker oil is going to cure the problem. My '99 F-150's piston slap was louder with thicker oil. Id stick with that grade of oil that Ford recommends. If you use a grade of oil other than what Ford suggest, chances are they will void your warranty if you have problems.

 

i have a freestar with a 4.2l i dont know if its the same as the truck but it has a knocking sound when cold and put in gear till it warms up. it calls for 5w-20

 

I have a 06 F 150 and I have no knocking noise. I use motorcraft 5/20. Wallmart has it in a 5 quart jug for $10.28......So one jug plus one 1-quart bottle= one cheap oil change using a semi-synthetic oil.