4.0 Engine tapping noise


Well-known member
Jun 1, 2009
97 D1 4.0 engine tapping noise when warm? Suspect rocker arms wear. However I engaged the A/C Compressor and tapping sound became louder. Disengage sound is less noisy. Any ideas appreciated.


Well-known member
Sep 14, 2010
Northern Illinois
It's hard to tell sometimes if your loosing oil pressure and that shows itself as valve train noise in its early stages. The valve train needs a lot of oil.
That being said there is one thing that happened to these rocker arms that's worth mentioning. There is a steel insert inside the aluminum rocker arm that would get loose just a little bit and make a lot of noise. It's easy to check with the rocker shaft on the bench. Put a little pocket screwdriver into the lube hole for the pushrod and gently try to turn the insert in the rocker arm. If it's a loose/noisy rocker arm you will be able to turn it.
If you find a loose one, post it. You need to know about left and right rocker arms.


Aug 7, 2010
Salt Lake City, UT
It could be the lifters, or it could be a cylinder sleeve starting to loosen. The lifters make a noise similar to a diesel engine at idle. While this sound might annoy you, the motor can run for a very long time with this occurring.
The louder knocking sound is a cylinder sleeve, and is the beginning of the end for your engine block.