valve knock

[savagecamaro96]

help me out guys yesterday my car started to make a pretty loud knock, the piston is hitting one of the valves im guessing.
whats my possible causes and how can i fix it. i was told it could be a sticking lifter or that the rod is bent.
i would like to get this fixed asap cause i need my car, im currently borrowing my mother's. i have friends that can help me rebuild it i just need to know what is broken
thanks

[Blizzard242]

Re: valve knock

You're really gonna have to start tearing down the engine to find out what happened. Unless you have a boroscope to stick in one of the spark plug holes.. You should do a compression check on each of your cylinders to maybe rule out a bent valve. Could be a spun bearing too.

If a bearing is spun or if a piston is hitting one of the valves the piston could be damaged and it may be time and cost effective to look for a new engine.

[Opontee]

Re: valve knock

Probably a spun bearing. Even if it did spin a bearing, chances are low that the piston hit the valve. There is enough room on a 3.4 for the timing chain to break and the valves not hit the piston. Don't know about a 3.8, but on a 350 Pontiac V-8, there is enough room also. If it is a knock like you say, I would lay money on a bad bearing. Valves won't knock, just clatter. Usually lose of compression and run bad.

[Blizzard242]

Re: valve knock

Yeah I was just thinking.. the only way an valve could really be hitting a piston other than the timing chain breaking, would be valve float or a broken valve spring. And I highly doubt it's valve float. And your car seems to run so it don't think your timing chain is broken. So like Opontee said, i'm leaning towards a bearing too.

It's definitely a knock and not ticks right?

[savagecamaro96]

Re: valve knock

Usually lose of compression and run bad.

definately doing that, also i found out todat that its relatively quiet when its cold but it gets worse as the engine heats up

video will be up soon

[savagecamaro96]

Re: valve knock

video in the first post, and yes it is snowing.

[cam98aro]

Re: valve knock

i dont have sound, but if your valve was hitting a piston your engine would have probably quit running by now and smoking like crazy

[Blizzard242]

Re: valve knock

Sounds like a spun bearing to me. Go on youtube and compare it yourself. Running low on oil lately?

[ssms5411]

Re: valve knock

I would check your balancer first though , it will make that same knocking sound when it dry rottted and throwing the crankshaft out of balance. Its worth a try anyways. Mine made that knocking sound when my balancer was dry rotted out inside.

[Rob Bell]

Re: valve knock

If that's the case I would assume the knocking sound comes from the balancer, correct? If so, get a length of hose and carefully hold it near the balancer while listening at the other end. Maybe you'll get lucky.

[3.4grapeofwrath]

Re: valve knock

If you have an automatic tranny pull the torque converter cover and check your converter bolts if they loosen it will make a loud knocking sound. I got a free car once for this reason. Also check your flexplate for cracks this can also make a loud ticking sound. I would check everything on the outside first before diving inside.

[Opontee]

Re: valve knock

Yes that sounds a lot like a spun rod bearing. I have done that many times before on various engines. Mostly b/c I let it run low of oil. And a few times the oil pump screen had trash in it.

[savagecamaro96]

Re: valve knock

its not low on oil i change it every 3k
it only makes the sound after it had warmed up or when it is reved up

[savagecamaro96]

Re: valve knock

check engine light was on, got the code, p0305
cylinder 5 misfire, i guess that rules out the balancer and the flexplate.

[savagecamaro96]

Re: valve knock

ah **** it, it died, wont even turn over, looks like im looking for a new car now.