knocking in motor

[ericnj75]

i have a 99 expedition xlt 4.6L and i have a knocking sound in the motor on driverside . it does it when idling and when i give it gas it gets louder what could this be thank for your help.

 

[mustangrfast88]

it could be a blown exhaust gasket, a bad rod bearning but i would say it would be a exhaust gasket

 

[ericnj75]

how do u change that gasket.and how hard is it to do that.

 

[ericnj75]

i just put 93 octain in the truck and the knocking itsnt as loud as it was before

 

[green03]

it shouldn't knock at idle even if it has a performance program. If it is a spark knock at idle then something is wrong. Does it do it worse when it the engine is cold?

Matt R

 

[ericnj75]

yes when i start it up in the morning

 

[green03]

look up "Piston Slap" this is very common. It could also be an exhaust leak that closes up once the parts get hot. Take a good quality audio recording inside and outside and post it for us to hear...

Matt R

 

[ericnj75]

this weekend i was doing a tune-up and i found where the knocking was coming from it is a exhaust leak one of the bolts is snapped off this should be a fun job.thanks for all your help guys.

 

[AvroAero]

Is it a knocking sound only? Are you sure your not talking about an exhaust leak?

I have the same year and engine and I had that problem, turned out for me a exhaust lug blew out on the rearmost side of the manifold. Take a flashlight and check the exhaust manifolds from the wheel wells. If you look in there (you might have to lift the deflectors a little bit) you can see the manifold, take a look along the edges and there will bolts holding it down, check to see there not broken.

Its not really an easy fix. The headers have to be removed and replaced and the broken bolt has to be removed which can be hard depending. I used the opportunity to install headers and the headers ran for 500 USD and can cost somewhere close to that to install (I had mine installed with a few other things and my total bill was 800 CAD).

Or it could be something in the EGR system if not that but its still an exhaust leak.