I Have A 1997 Ford F-150, 4.2 V6. i have had it for 10 years now and it has 196,000 Miles On it. I Haven't Had Much Wrong With It Since I've Had It. The Other Night I Came Home From The Store With No Problems Noted. The Next Morning I Got In It And Started It Up. It Acted Like It Didn't Want To Start But It Fired Up And There Was A Loud Knocking/Tapping Coming From Under The Hood. I Have Had Numerous People Look At It And Got Alot Of Tips As To What It Could Be. Looking For Some Help On Here. Any Ideas??

 

Is the knocking coming from inside the engine? Is it a metallic knock?

Check your coolant level. Is it low?

Check you oil. Any water/coolant in it?

Sounds like maybe lower intake manifold gasket leaked and allowed coolant in one or more cylinders. Damage to rod(s) and/or bearings might have occured during start-up.

 

Ditto what BrianA said. Does it knock? Does it now have an intermittent miss at idle? There was a recall on the 4.2, and FoMoCo paid a lot of $$ to fix them. Check with Ford to see if it is covered (ten years -- hah).
Best bet is to trade it in or replace the engine with a re-man. Boneyard engines, unless they are low mileage, are probably not a good idea with this engine.
You should run a compression test before deciding that it is cooked, but most likely you will find coolant in one cylinder after it cools down. Does the radiator hose get REAL hard, indicating pressurization by engine compression and combustion?
tom

 

Yes It Sounds Like Its Coming From Inside The Engine. Coolant Level Is Good And The Oil Was Just Changed.Never Thought To Check The Radiator Hose And See If It Was Hard. Sounds Like I Might Have To Work On Getting A New Vehicle Soon.

 

Don't right it off yet. Depending on the damage (assuming there is some) you can have the gaskets replaced and some times a damage rod/bearings can be replaced from the bottom end without having to pull the engine.
My guess is you have a bent rod and are hearing rod knock.

If you aren't up to doing it yourself, check with a local shop that you trust.

Aside form the LIM gaskets, the 4.2 motors seem to have a lot of life in them.
My '05 has 112,000 miles on it and it runs perfect. I do check the coolant level just to play it safe. If I ever see it start to drop, I'll immediately get the gaskets replaced. I 'spect the engines are good for 250,000 + miles. 300,000 would not suprise me.

Hey, keep us posted!

Thanks!

 

Its In The Shop Now And The Last I Talked To Them, They Were Still Trying To Pinpoint The Problem. I'll Send Them The Suggestions. Thanks

 

Garage Called Today And Said The Bearings Or Rods Or Both Are Really Bad And They Said The Crank Is Probably Destroyed Also. They Said My Best Bet Was To Contact Local Junkyards And See If i Can Find A Used One With Low Milage. Well Bad News But I've Had Her For A Long Time And She Done Me Good So I Can't Complain Much.