sbodiford

I tried to find all the threads I could about knocks but none seemed exactly what I'm experiencing with my 95.
At start up is an immediate knock, it lessens as engine idles. Somewhat loud and 'seems' to come from the back left part of engine (near passenger side below valve cover). I've removed valve cover while running and while off, don't notice anything loose or visually obvious. At times, the knock is intermittent but usually consistent with RPM.. the rare times it's intermittent is at idle and when very warm/hot.

Car has only had 7000 miles put on it since summer of 2011 (at 119,500 currently.

Work during that time:

-- new radiator, new fans
-- thermostat & knock sensor
-- induction flush
-- oil leak fixed (gasket & seal)
-- rear wheel bearings & main seal
-- oil sensor

I inherited this from father... he has receipts for about 8-9k of service just sense 2011. Some of the labor charges I'm seeing are making me sick to my stomach..

I have not idea how to pursue this and don't trust many of the local folks.

Thanks for looking and sorry so long.
Steve
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ghoastrider1

have a friend help. When its first cold started and knocking, start removing one plug wire, then replacing it and go to the next one, do the same thing. Could be a bolt coming loose from the TQ converter, but those usually don't go away with temp change. Does the knock stay the same when you rev it r stay the same speed of the engine? Hows the oil pressure change?
. When its first cold started and knocking, start removing one plug wire, then replacing it and go to the next one, do the same thing. IF its a cyclinder knock,it well stop while the wire is off. To me, and I could be way off here, its a worn rod bearing. Something like this is very hard to answer with info given. Hope its something simple and easy/cheap to fix.

Paul Workman

But, without being there, it is not really possible to put a finger on it w/o more info. (Sometimes even being there to hear it in person can be difficult to determine w/o being there. A trusted friend or shop manager might be you best option, especially if you aren't able to do the work yourself.

Anyway...

A stuck lifter is more of a "ticking" sound

A broken valve spring doesn't necessarily make any noise - certainly not something you'd notice before investigating...

Piston slap makes a sound a bit deeper than a "ticking" sound. And, it usually quiets with temperature or under load.

Rod (bearing) knock is a deep tone that you hear regardless of rpm, but mostly when under load. And, because it occurs at the crank, it is difficult to tell which bank of pistons the knock is coming from. (A wrist-pin will make a knocking sound too. However they are rare except in motors that see a lot of racing or are super/turbo charged)

If your not sure what it is, but it doesn't get louder with increase in load, turn up the radio and drive it a while. If it gets worse (louder) you'll know it is truly something failing - and need to address it sooner than later.

If it goes away - especially as it warms up - meh. Keep in in mind, but don't worry about it (prolly piston slap or the like).

If it's serious...it'll get worse. If not, it won't (or at least not right away). Other than a trusted friend or a shop, that's about the best anyone can suggest for a neophyte w/ no experience or tools.

Cool Runnings

sbodiford

ghoastrider1.. thanks for the reply. I will try that for sure.
Knock/noise does increase as RPM increases and decreases when I left off... It's mostly a constant knock and is only intermittent (barely) when hot and for a split second after I rev engine lightly. When idle is recovering is the only time the time intermittent for a second or so.

I'll try the spark plugs with a buddy... Thank you

A Peter C4

Does it have good oil pressure as soon as it starts? Has the car ever been run low on oil? A knock in lower end is usually a bad rod or main bearing if it is truely a KNOCK sound. What is oil pressure when oil temp is hot?

sbodiford

Peter...
At start up, oil pressure appears to be about 55 to 60 psi...
When it's warm/hot... drops to about 22-25psi.
As far as I know, it's always had synthetic in it. I only have history/papers from 2011, about 7000 miles ago. I've had the passenger side valve cover off while it's been running and there is oil in there... not much, but some. It's very clean on that side.

A Peter C4

Does the knock sound like it's from the lower end, ie crankshaft? Next? Is this a true knock or ticking noise. Also are there any loose components that could be the noise ie loose exhaust? or is it internal?

sbodiford

Peter...
At start up, oil pressure appears to be about 55 to 60 psi...
When it's warm/hot... drops to about 22-25psi.
As far as I know, it's always had synthetic in it. I only have history/papers from 2011, about 7000 miles ago. I've had the passenger side valve cover off while it's been running and there is oil in there... not much, but some. It's very clean on that side.

sbodiford

Initially...sounds like it's near the top half.. the more I read, it's probably lower but not sure. Definitely a knock, not a tick (lifter type sound). No loose components that I can tell. Everything is pretty solid component wise, I would say 100% internal.

Oil pressure is 22-25 psi when warm/hot..

A Peter C4

Try to find a good mechanic that you trust and ask them to listen, it could be a bad wrist pin or a bad crank bearing,hard to tell without listening in person, could even be piston slap, have you checked trans to motor bolts and converter bolts?

Bagpype

The 1994 6 speed I just picked up has the same symptoms. I have tracked it down to a bearing. The engine will be coming out soon and I will rebuild the bottom end if at all possible. If you wait for it to get worse you will likely not have the options that I have. You will have to find a replacement engine. I would not drive it until whatever sound you are hearing has been correctly identified and or fixed.

73n95

I'm going to go along with Bagpype. While there are a lot of very good mechanics here on the forum most of us are shade-tree mechanics working off of experience and folklore. Engine knocks can be nothing or very serious. Have a pro look at it and give you something official. A good mechanic can diagnose a bearing knock, the most serious concern, versus piston slap which is less serious but still needs to be addressed. The Chevy SB is an robust engine and is not subject to any common failure related problems. You may have something that is just noise you live with----or not. Good luck.

sbodiford

73n95 and Baypype... thank you both.
Found someone I'm going to take it to who was referred to me by a family memeber... so we'll see. Thanks a bunch for the feedback on this. Will update thread when I have more to share. Maybe it will help someone else as well. --- Steve

DGXR

120,000 miles is not too high for these engines, and it should not be making such noises if it has been maintained properly, and not abused. I agree with the last few posters -- don't drive it too much (definitely no heavy throttle or high RPMs) until you can determine the *actual* cause of the knock. It could be piston slap but do not assume. Good luck to you.

sbodiford

I've decided to change the oil, have the oil pump checked and possibly run sea foam thru it as well. Of all the recommendations I've been give, this has come up a few times... so I thought I'd try it. Mainly, b/c the care has had such little use in the past 7-8 years. If anyone thinks this is a bad idea, please let me know.... ALL feedback is appreciated and thanks again to you all.

81c3

Honestly, from the figures you posted, I don't think you have a pressure issue with the oil pump. Unless you're using very thin oil which I cant imagine... there shouldn't be any issue with the oil itself....

I would do as suggested and have a professional take a listen and see what he says.