engine knock 88 240 non turbo

160k mi. Knocks loud at start up. You can here it destinctively from 30 feet away. Gets lower about twenty minutes at highway speed (55-60). Is suttle but present at idle, after an hour of driving. On start up with loud knock I can quiet it by pulling the number 2 plug wire only. Should I be worried about throwing a rod. I have been running thin oil in it for winter. I read about the piston slap and do not think this is it.
Reply to
jacktheboy
Loading thread data ...

It is not knock if it is at idle. You have a leaky exhaust manifold gasket. The reason it is louder at startup is because the manifold has not expanded to partially seal the leak. You should be able to see carbon deposits around the leak. Replace all four exhaust gaskets.

Regards,

Boris Mohar

Got Knock? - see: Viatrack Printed Circuit Designs (among other things)

formatting link

void _-void-_ in the obvious place

Reply to
Boris Mohar

Maybe, or maybe it's piston slap. Well known phenomenon in B230 engines. Not familiar with it myseslf, but it's said to be worst when cold, and diminishes as the engine warms up.

Reply to
moonrise

I agree, not rod knock because it quiets after the exhaust gets really hot. In my experience, exhaust leaks are a fairly sharp tapping sound while bad rod knocks are a deeper "thunk" sound. Mild rod knocks sound very much like exhaust leaks, though. Piston slap is louder when the engine is cold, but it quiets quickly. It also sounds deeper than an exhaust leak, more like a clank.

My favorite technique for locating an exhaust leak: Start with a cold engine. Connect the hose of a shop vac to the outlet side of the vac, so it is blowing air. Empty the shop vac and run it for a few minutes to clear grit out of the hose. Duct tape the hose to the exhaust pipe of the car and start the shop vac. Feel around the exhaust with your bare hand - even a small leak will be obvious.

Mike

Reply to
Michael Pardee

I know for sure that the header pipe is leaking right at the manifold, and it is a bad leak. I need to replace two of the studs, and I am holding of until I do the rear seal, which is also leaking. I have new motor mounts and was going to yank the motor and tranny together to do all of this and some other stuff. (correct timing belt,I think I'm off a tooth,fix leaky water pump gasket,front tranny seals, rewire overdrive selonoid to switch) I have a list. Thanks Ray

Reply to
jacktheboy

There ya go! Drive with confidence, but remember the exhaust at that point has significant CO. Having had CO poisoning once, I can tell you it's bad news. The sound you describe should be trivial enough, but if it gets louder it may need attention earlier.

Mike

Reply to
Michael Pardee

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.