engine knock
 

Hi!
I searched the forums before i posted to check out if anyone else had the same problem, and it kinda seems like it, but im still not a 100% sure what to do. My engine started "knocking" about 2 weeks ago, i listened with a screwdriver and it sounds like its coming from behind the valvecovers, perhaps, but maybe even further down. But the engine doesnt knock constantly, it operates normally when you start it cold. When its hot it knocks when the oilpressure is between 275-410 kPa, but if you rev it up in park to 4,000 rpms, to get the oilpressure over 410 kPa, the knocking stops. When you let go of the gas the oilpressure drops to 275 (at idle) and the knocking starts in about 5 to 10 seconds. I changed the oil and filter today in hope of solving the problem, but its still the same. I think ive got stuck lifters, so ill try an oilchange with low viscosity oil and maybe some additive.

Any other suggestions what to do?
Thanks!

oh yeah, and its a -97 4.3 v6 4 doors and 4x4

RE: engine knock
 

hmmm...maybe how much did u put back in (oil) 5 quarts is barely a hair too much...most people do 4.5 thats not including the filter. so i use almost all of it. stick with 5w-30 unless its cold where ur at...then go 10w-30 I love this Mobil 1 Synthetic tho...you should use it...it might leak a lil at first because it breaks up alot of that crap built up along the seals and things and then re-swells the seals. As far as sticky lifters and stuff...i dont know a whole lot about that stuff.

RE: engine knock
 

i used to work at a head shop rebuilding them porting polishing and high performance coatings we had a few 4.3's and they are known for that usually its either a worn cam the lobes on them usually wear after so many miles, sticking lifters not extremely common, or valve lash which is where the valve actually wears the guide or vice versa sometimes its actually loose rocker arms occationally. Oh yeah mobil 1 is the absoutley the best oil to use nomatter what anyone says hopefully that helps and never use quaker state my opinion and experiance

RE: engine knock
 

Yeah i added 4.5 quarts without filling up the filter, should i have added more? I used 5w-40 fully synthetic, but i think its weird that the noise isnt there all the time, so i doubt that something is mechanically broken, but then again im not that good at cars :D

RE: engine knock
 

You say you listened with a screwdriver and the noise might be lower than the rocker. Have you tried that on the oil pan?
If you bring the revs up slowlyfrom idle to 3000rpm and then hold it steady, then let it return to idle, is the knocking there all the time or just when accellerating or when you hold it steady or as it returns to idle?

Is it a light tapping or a loud heavy knocking?

I'm just trying to figure out if it's a top end (lifter, rocker arm) or a bottom end (connecting rod bearing) noise.

RE: engine knock
 

Have you always used 5w40? Recommended oil is 5w30...

But yeah, to figure out if it's in the valve train, you'll need to pull off the valve cover on the side that you think it's on and check the rocker arms for tightness when the valve is seated. It is quite possible that you have a worn cam lobe or collapsed lifter. Like was already mentioned though, a worn cam lobe is more common.

RE: engine knock
 

chevy lover, i haven't checked if the noise comes from the oil pan as well, i'll have to check that! The knocking is constant from idle to 3000 rpms, even when the rpms are falling. When you rev it to 4000 rpms the knocking stops but continues after about 6 seconds idling. There is also no knocking when starting the car cold.

swartlkk, i've only had the car about 2 months so this was the first oil change i did. Im considering to "flush" the car with 0w-40 and then adding the 10w-30, maybe ill add some "magic" additive as well (motor-up) [8D] I'm really praying that this wont be an expensive operation since i was just about to sell the car :( I'm going to get a good old K5 blazer instead.

Thanks for the fast replies!