knocking after rebuild

Trent and his Rover

Well-known member
Jun 25, 2006
124
1
She's knocking and it sounds as if it is coming from the Sump area.
I rebuilt her with:
  • New rings
  • New timing chain and gears
  • Main and rod bearings
  • New flowmaster and back exhaust
All her lifters looked good.

Anyone any idea why she might be knocking? Happens after she warms up only. If oil pump was bad I think she'd knock at starting. Her Oil pickup is clean.

Thanks.
 

Swedjen2

Well-known member
Sep 12, 2018
556
113
California
Could be a lot of things. Sound travels in mysterious ways thru running engines. Get an engine stethoscope and locate it. Cracked flex plates can sound like a bad rod or main bearing. A broken CAT can sound like a cracked flex plate....(at least it did to me)
And don't chinse out and use a stick or screwdriver between the engine and your ear.
 

Trent and his Rover

Well-known member
Jun 25, 2006
124
1
Yes the knocking seems to diminish with rpm. I do own a stethoscope yet like you've pointed out, sound travels in mysterious ways. Sounds as if a con rod bearing crapped out but that isn't the case. If the fly wheel is cracked as you have suggested, then I should be able to see that by inspecting as the cranck gets turned. But I don't thibk that is the case as the knocking happens only after warming. If its a cat, I can read its temp before and after the cat with a thermo gun......maybe?
 

Trent and his Rover

Well-known member
Jun 25, 2006
124
1
I removed both manifolds to install new exhaust gaskets at the head and to the pipes in hope that my problem was due to leakage - It isn't. Took 15 mins at idle for the knocking returned. Could the cats cause the knocking? Temp wise they read very close to our other Rover and even if they were toast wouldn't that only effect the smog out reading? If a cats gone bad doesn't the honeycomb just get blown to the muffler anyhow? And the knocking doesn't seem to be coming from there anyhow. Previously I suspected the knocking could be due to exhaust backup, so I went ahead a replaced the muffler and removed the silencer.