4.0 Knocking

[Redranger89]

I have a 1998 ranger. I have noticed a loud knocking sound when at idle. When i start up the truck it sounds ok but then the rpm's drop and there is a loud knocking sound coming from the engine somewhere. Any ideas?

 

[Gabe8810]

Answer it, no sorry could not resist. is there any oil leaking or bad head gaskets?

 

[cr_the_machinist]

Does it like to eat coolant or oil or both? A little more info on the situation would help out. Any past problems before this one surfaced?

 

[Redranger89]

I had just gotten the truck in the past month. I wanted to change the oil and noticed that the dipstick said there was too much oil. It was past the full line. Maybe that had something to do, i dont know. It does not leak or eat any oil or coolant. Truck has no major engine or trans problems except this knocking.

 

[Redranger89]

And i did change the oil. It is now at the correct level. But still making the knocking sound.

 

[Big Jim M]

Red Do you know the difference in a loud knock and a loud "click"? We need to know more about the noise and if it shuts up when the throttle is advanced..also does it shut up after a few minutes of operation..
As for the oil, go ahead and change it and put the prescribed amount in her. Then after running for a few minutes check the level on the stick to see where the level is with the proper amount of oil in there. The last owner might have over filler her OR the stick may have been changed and that level is NORMAL in your vehicle.
Big JIm

 

[Redranger89]

It is more like a loud click. As far as i can tell the noise goes away when the throttle is advanced. It does not shut up after a few minutes. It only starts when the rpm is around 800-900.(idle). When i start up its around 1000-1200rpm,for a few seconds before idle, and does not seem to make the noise.

 

[Big Jim M]

You describe a valve noise. If so it is NOT terminal. Will be easily repared or if left alone could last many tens of thousands without any trouble.
If the rockers are adjustable a small twist on the adjustment will cure the click.. If NOT adjustable a longer pushrod (ford stocks these just for such a noise) will cure the click.
Of course it could be any number of other things but what I have described is by far the most common in most engines.
Big Jim

 

[Redranger89]

thanks, i will check it out

 

[Ranger44]

Have you changed the oil already?

It may be as simple as the engine not liking the oil.

Using a different brand oil can cause it to knock.