91 with engine knock

[DryDog]

It sounds like someone beating on an aluminum pot with a wrench.
Last winter the waterpump gasket started leaking. It was 5 degrees. I let it drain and figured I'd fix it in the Spring. A couple months later I had to move it and it had a noticable knock but not bad. I last started it in May and it was a very loud knock. A bit hard to start and the noise was in sync with the RPMs. I heard it on the right head area but didn't let it run long out of shear fear.

I was just following a search for "knock", someone suggested bad gas. Could it be that simple???

Matt

 

[DryDog]

After I posted I went out and started it, and let it run about 40 min. It sounds mechanical. I don't have a stethoscope or a real long screwdriver. Sounds like it is between the valvecovers, deep. ??? It idles right and is responsive. we're at 198K nothing major yet except heads and tranny.

 

[mr.steve]

did you ever change the water pump? that impeller could be beating on the inside of the timing chain cover. check your oil and your water circulation next.

 

[wood1]

does the sound of the knock change other than get faster when you goose the throttle?

C.

 

[DryDog]

I had replaced the waterpump in Sep. A couple months later when we had some good freezes the gasket started leaking. When I moved the truck the coolant level had drained to the point it was no longer leaking. I ran it for maybe 2 minutes but that is when I first heard it as a faint knock. I believe I replace the w.pump gasket before I moved it again, and then it was the aluminum pot noise. So many months ago hard to say for sure.

The noise is loudest at idle. By 2500 rpm engine noise almost drowns out the knock. I don't know about oil flow but water must be moving because the temp stayed around the R in normal. A little high from where it usually runs but I didn't burp it after the w.pump because of the knock. I bought a stethoscope. I will get at it again tomorrow after work, see if I can pinpoint it.

 

[DryDog]

I listened to a post that had audio of timing chain slap. This isn't my noise.
It all sounds about the same in the stethoscope, a loud CLICK,CLICK,CLICK,CLICK. Maybe louder under the valve covers.

 

[wood1]

Do you have the ability to post an audio recording? I am leaning towards a possible lifter or worn rocker...

Any decent mechanic would be able to tell you if that is the case I would think.

The 4.0 is known for worn rockers, also a lifter that isn't pumping up will tick as well... you may be able to run an engine flush prior to your next oil change and it could help the tick...

Alternatively, you may have a rod bearing going south... (hope not)

C.

 

[DryDog]

Resolved engine knock.

The noise started when I ran it when it was low on coolant. It must have damaged the water pump. I put another water pump on, no more bad noise. Thanks for your suggestions!