Bad knock in moter

CHOPPEDSTYLE98

MEMBER
TOYOTA 4RUNNER

I have a 1994 toyota 4runner with 200,000 miles on a V-6 moter. A few months ago I was going down the road and a loud knock started. The entire top end of the moter is brand new so I'm guessing it's comeing from the lower end of the moter. When the idole goes up the knock goes faster, I think I know what it is but I'd like a profesional opinion. Thank you.

1 Reply

MHPAUTOS

MECHANIC
31,937 POSTS

Hi there,

As you can imagine, determining where a knock is coming from with out hearing it is rather tricky, So I will advise the best place to start looking. If the top end has been overhauled this can often put extra pressure on lower end components. Listen carefully to the noise, is it crank shaft speed or slower. Is it a heavy knock or hollow. Start engine and isolate each cylinder one at a time by disconnecting the injector, if the noise diminishes, you would be thinking piston or big end bearing as the load on the piston is reduced with out spark igniting the mixture. Any thing else would probably be a main bearing failure. But the only way to find out for sure is to dismantle and inspect, the longer you run the engine the more damage it will incur,

Mark (mhpautos)