Hello all.. Quick question hopefully someone will be able to help out with... I have a 97 F150 with the 5sp 4.2l v6, with 68000 miles.. Occasionally when I turn the truck off after a short trip.. 5 miles or less... I will hear a kinda "clunking" sound.. it almost seems like the engine still wants to run after shut down. I tried to use Valvoline Synpower to try and clean everything out.. but it still makes the sounds.. has anyone ever had this happen? ANd no.. I know about the ticking as the truck cools down.. this is a definite clunking sound.. thanks in advance...

Joe

 

yea thats what i was about to say that it was the truck cooling down or some water or condensation dripping on the exhaust. I usually hear like a loud clunk after i shut it off but i think its just the suspension settling down or something.

 

I wish it was as easy as the suspension settling or water condensing .. but the noise is definately coming from the engine... and only after it is shut down... kinda like it is still trying to fire...

 

oh ok i think i know what you are talking about. Sorry i cant help you i know its some mechanics term but i just cant think of it but ive heard of it and theres someway to fix it.

 

The same thing happens with my truck. Someone told me it was the oil cooling off in the oil pan.

 

I think the term you are looking for is "Dieseling"

I means in a Gas engine the engine still tries to turn after the ignition is switched off. This is caused by heat in the ignition chamber and some remaining fuel igniting.

I dont really know how to fix this problem. I believe it occurred more with Carburated engines than FI engines.

Hope this helps.

 

The correct term for this problem is called pre-ignition. It's problably your spark plugs. Try using a colder plug than what your using now. Just my 2 cents.

 

Originally posted by F1504u2nv
oh ok i think i know what you are talking about. Sorry i cant help you i know its some mechanics term but i just cant think of it but ive heard of it and theres someway to fix it.

LMAO F1504u2nv! Thanks for your help..

 

Hey I do what i can.

 

I've had my truck since October, and it's done this since new. I drove another used truck with about 36K miles and it didn't do it.

The best way I can describe it is that there is kind of a shudder on shutdown. Mine does it all the time, regardless of how warm or cold the engine is.

I asked a tech at the dealership to listen, and he agreed it wasn't normal; almost like one or two cylinders fired an extra time.

The tech told me to bring it in for service, but I haven't had the time. Everthing else seems normal; no other problems.

Mark Salvetti
Saugus, MA
2001 F150 V6 manual

 

I am gonna try a tune up with some better plugs.. although I think I used bosch platinums at 23000 miles.. I now have 68000.. I have also heard the term dieseling.. and I am tempted tobring it in for service as well.. Just sounds like it is gonna be really expensive.... ohh well.. thanks for your input Gus.. I appreciate it...

 

Mine makes a plinking noise after a drive, but mine is coming from the exhaust system, i dont know what your noise is, if it is coming from the engine, but mine is just the different types of metal in the exhaust system cooling and contracting, the same may be true in your engine, different types of metals cool down at different speeds, this could cause pops and clicks. Its probably not dieseling since fuel in the fuel rails is released back into the gas tank upon engine shutdown, and pumped back up to pressure when you turn the key. -Jason

 

more stuff to think about.. but honestly.. I just started hearing this noise about 250 miles ago.. definately a new noise... and I have not made any modifications to the truck that would warrant any new noises from the truck... thanks though.. I appreciate all input..

 

I replaced my plugs and plug wires with Bosch products it is still there.