rod knock or ???

[channer]

Hi

I have a knock coming from the front of the motor at low idle. I'm trying to figure if it is a rod knock or something else (motor mounts, etc...).

the knock is noticable at idle (700-800 rpm) in park, a little louder in gear (600-700). The knock disappears when when the engine is being rev'ed. The (stock) motor shakes in idle and smooth as silk when you rev the engine.

I used a stethascope thing-a-ma-jig to see if I can isolate the knock (oil pan, front of motor, IC, water pump, etc...) but all I hear is a whine/purr but no knock.

Does anybody know if a rod knock can be heard through all RPM ranges?? any other ideas what might cause the knock??

tia... dave

 

[b4black]

Deja Vu.

Header beginning to crack? Sounds just like a lifter tick. Most noticable when hot and idling.

 

[channer]

I don't think it's the header & it's definitely not a ticking sound.... but I'll give it another listen and see/feel if there is any "more" heat coming from the headers.

Originally, I thought it there was something rubbing against the frame like the DP or Crossover but clearance looks OK!!!

thanks for the info.... dave

 

[KWIKR 1]

Try pulling off one plug wire (be carefull) or injector plug at a time and see if the sound disappears. you can figure out which cylinder it is if any. then take it from there . check your balancer , crank sensor , belt tensioner,try running the engine without the belt , get a rubber hose and listen around all the headers . could be the chain and when you bring up the rpm it tightens up from the centrifical force. If all else fails pull the pan (easy job) and look for any tell tail signs of anything (plastic in the screen , metal flakes in the bottom , etc) . take your time , don't get all bend out of shape (like I do ) , go nice and easy you'll find it . Drop me a email I'm always in the area and can help if needed , Good luck !

** I had a rod knock problem with a recent rebuild from hell . It could be heard in the off idle rpm range . or when you gave the throttle a quick "blip" . you'd hear a "quick single rap" sound deep in the engine .( a double rap sound is supposed to be piston related)**

 

[TurboBuickSix]

You could try to unbolt the torque convertor to isolate the trans as being the problem.When I went through this it was a knock which turned out to be the wristpins had a little play in them.

You might hear it when you first start it when cold,
you might hear it only after the oil warms up to op temp,
or both.What is the oil pressure at idle?If you think it is a rod or a main then you are probably right.I did a search when it happened to me a found others with problems like this and most often it is a knock.

 

[channer]

Tim... thanks for the offer, I'll try the spark plug wires first, and the last thing I want to try is to drop the pan. I know you've done it a few times so you could probably do it with your eyes closed. I did check the oil on the dipstick & it looked OK but I guess it's not like dropping the pan.

I've got one of those stethascope things from crappy tire but I just can't pinpoint the knock.

TurboBuickSix.... no oil pressure gauge (installed) but I have one!!! I never heard about the wrist pin. What would cause this problem?

dave

 

[TurboBuickSix]

Originally posted by channer
Tim... thanks for the offer, I'll try the spark plug wires first, and the last thing I want to try is to drop the pan. I know you've done it a few times so you could probably do it with your eyes closed. I did check the oil on the dipstick & it looked OK but I guess it's not like dropping the pan.

I've got one of those stethascope things from crappy tire but I just can't pinpoint the knock.

TurboBuickSix.... no oil pressure gauge (installed) but I have one!!! I never heard about the wrist pin. What would cause this problem?

dave

Wear,knock,bad oiling among probably a thousand other things.The oil pressure check would tell us more(about bearings)but mine still had good pressure at idle.Instead of dropping the pan consider looking in the oil filter but try to get ahold of the proper cutter if you do,it goes alot better.

 

[KWIKR 1]

Update ????

 

[scottyb]

Please let us know.
Sounds to me like I have the same exact noise. When I first heard it, I thought it was something hitting a panel also. The weird thing is that it is not consistant with RPM. In other words, it doesn't necessarily knock on every revolution, that's why I thought it was something loose flopping around. It knocks more on a cold start, goes away after all is warmed up. I too notice it sometimes in the transition from idle to rev. It is also smooth when revved up and no noise. BTW, I have 167,000 miles and I have been driving it daily for a year since I first "noticed" the noise. I took off the belt the other day to confirm that it is internal vs. an accessory.

I know it's remote, but if yours turn out to be something that can be patched, I need that route due to cash at this time. I would like to do a rebuild.....

 

[gnturbo]

This is freaky but I too noticed the same noise this morning.Almost sounds like play in the timing chain.

 

[machinegun]

If this really is a knock, look more towards the back of the engine rather than the front. If it is a deep knock then it could be a rod or main. Usually the rod if you here it like this. You could also check your thrust play in the crank. This will also give you a knock down low and change on RPM. If this is a spun bearing you can have the same action. I would suggest if you cannot locate with the stethoscope, dropping the pan maybe the only option. It truely is not very difficult. I would however try one of the suggestions which is disconnecting the transmission from the engine. Doing this eliminates the trans as a source. Just better safe than sorry an also is not hard to do. Just remove the flex plate to T/C bolts and push the T/C into the trans a little bit. Start the car.

 

[channer]

Here is the latest... this past weekend I did the spark plug wire test. well, everytime I removed a wire, the knock became louder. But when I rev'ed the motor, the knock disappeared.

I'm sort of at a loss... if it's a rod, the knock should become louder when I rev the motor and quieter if I do the sparkplug test but it's opposite.

I got the stethascope out and further probed around. The only place I can detect the knock was in & around the oil filter and the bottom bracket which holds the IC. Again, I rev'ed the motor but this time through the stethascope, I could hear a faint knock which increase with the rev's of the motor. Without the stethacope, it sounded like a nice healthy motor!!

Yes, I should try to eliminate all other possibilities (tranny, tensioner, etc).... but it's mighty cold outside since I can't get my car into the garage!!! Anyone interested in buying a couple bikes!! I've also had a couple suggestion to drop the pan. Can I drop the pan without lifting the motor?? How would a loose/slapping timing chain sound like??

It definitely sounds like it's coming from the front of the motor. The knocking is more apparent when in drive at idle (700 rpm), not as apparent if it's in park at idle (800 rpm). I've had this knocking for over a year... It's more noticible now because I've got the window up... brrr & the radio volume lower!!!

I wish I can get this diagnosed so fix help fix your cars but if anyone has any other idea... let me know.

STILL STUMPED.... dave

 

[turbotwister]

loose torque converter bolts?

check to see if the torque converter is loose at the flywheel.