OK so ive been having this problem for quite some time, i have the 4.7 and when i start it up i have a really bad tapping sound, but once it has been started and warmed for like 3 minutes the sound goes away, ive had a rod knock on a previous vehicle before and this sounds nothing like it, im just wondering if anyone had had a problem like this before or maybe knows whats wrong.

thanks for all feedback in advance

 

exhaust leak when it warms up metal expands seals leak

 

Heres a trick, take a long 18" + screwdriver and use it like a sound carrier, put your ear on the handle, make sure they are solid hard plastic or wood, soft grip ones dont work. Places to check : Waterpump, AC, alternator, valve covers.

Also you dont have to worry about a rod knock on the 4.7 overhead cam engines dont have rods.

 

Actually Greg, you do.

A rod knock is caused by the connecting rods, crankshaft to piston, not the pushrods.

 

OK so a few guys i know have told me the exhaust but where would that leak be?

 

MIne was rear of the exhaust manifold drivers side, exhaust manifold gaskets are known to leak on these..bad news is exhaust manifold warpage is sometimes the culprit

 

Learn something new every day

 

You’re absolutely right

 

Good on you for letting him know. He's been waiting since 2012.