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View Full Version : Can rod knock come and go?



89whitepkg
March 26th, 2008, 10:13 AM
So, I thought that I may be getting rod knock. However, the nosie seems to come and go....can rod knock do this? It is best heard at idle and smooths out as you speed up. However, some days you can hear nothing.....it's just as smooth as can be. I know it is comming from the engine, but I'm wondering if it could be in the valve train.....lifter or shim. It is not a really sound like a valve ticking...more of a thump. I was wondering if it could be the spark plugs, the plugs are from the last owner and I think they are bosh platinum. It doesn't sound like a miss, it's not that random.

Also, I'm planning on pulling the engine this summer. If it had rod knock will it be visable on the bearings?

let me know what you guys think

7MGTEsup
March 26th, 2008, 10:49 AM
Rod knock can't come and go. Once enough damage has been done that you can hear the rod rattling there is no way back.

Common noises that get confused with rod knock

Loose Cam wheel/s
loose drive plate (auto's)
loose TV damper

89whitepkg
March 26th, 2008, 11:29 AM
Rod knock can't come and go. Once enough damage has been done that you can hear the rod rattling there is no way back.

Common noises that get confused with rod knock

Loose Cam wheel/s
loose drive plate (auto's)
loose TV damper

so I guess rod knock is out then.....

GrimJack
March 26th, 2008, 12:29 PM
And yes, the bearings are an extremely easy indicator. :)

Very early stages of RK can come and go, but they will be easy to reproduce on demand - park the car in neutral, let it idle, then blip the throttle so that the RPMs bounce up to about 3k, you'll hear the knock as the RPMs peak and start to drop.

Mk3runner
March 26th, 2008, 12:34 PM
time to yank to bottom end out and catch it before it gets worse. either that or be ghetto and change to a thicker oil.

89whitepkg
March 26th, 2008, 01:30 PM
so as long as there no damage to the crank I can just change the bearings right?
If it's damaged i need to get it cut right.

I'm building a diffrent engine right now to swap in....but my little brother just bought his first supra this week and he was going to use this engine.

Mk3runner
March 26th, 2008, 02:24 PM
pretty much, I'd still mic the crank tho. be pretty pissed if you went standard size bearings and ended up with the same problem.

89whitepkg
March 26th, 2008, 03:10 PM
so, i just ran the car up to 3k like suggested ....nothing at all. Early this morning on the way to school I heard it....but not the rest of the day. CAN"T DUPLICATE???

89whitepkg
March 26th, 2008, 03:10 PM
pretty much, I'd still mic the crank tho. be pretty pissed if you went standard size bearings and ended up with the same problem.

will do

GrimJack
March 26th, 2008, 04:46 PM
Doesn't sound like RK then. I'd be checking for something else that's loose. Especially the front harmonic balancer...

ERA
March 26th, 2008, 05:20 PM
I had some rattling when the RPMs were going up. Thought it was rod knock. Turned out to be my exhaust rattling.

Nick M
March 26th, 2008, 05:42 PM
Yes it can come and go. Depending on the cause of the noise. The bearing is filling up with oil. That often shuts it up.

IJ.
March 26th, 2008, 05:53 PM
^ Yep lightly loaded at high enough rpm so there is enough Oil volume to fill the increased clearence the knock will go, load the motor slightly and it'll displace the Oil wedge and knock some more.

There is also a point in the rpm band unloaded where it'll cancel out and be quiet free revving the motor.

DegreE
March 26th, 2008, 06:25 PM
I wish rod knock can come and go. lol

gaboonviper85
March 26th, 2008, 08:07 PM
I have a feeling that if this car is a five speed then he is just letting the clutch out too fast too soon while going from a dead stop...when you do that you can usually hear the motor start lugging and its at its almost stall point...you say its not constant so are you actually paying attention to rpm when it happens?

If its makeing that chatter/diesel engine sound then my guess is that you kind let off the clutch a little to soon.

89whitepkg
March 26th, 2008, 09:11 PM
I have a feeling that if this car is a five speed then he is just letting the clutch out too fast too soon while going from a dead stop...when you do that you can usually hear the motor start lugging and its at its almost stall point...you say its not constant so are you actually paying attention to rpm when it happens?

If its makeing that chatter/diesel engine sound then my guess is that you kind let off the clutch a little to soon.

i know what your talking about and it's not that.

starscream5000
March 27th, 2008, 07:34 AM
so as long as there no damage to the crank I can just change the bearings right?
If it's damaged i need to get it cut right.

I'm building a diffrent engine right now to swap in....but my little brother just bought his first supra this week and he was going to use this engine.

ALWAYS, check the clearances of something important such as rod and main bearings. Don't assume the size of them being standard, if you do that, you could very well be back in this same boat or worse, seize the motor.

"When you assume you make an ass out of you and me" ;)

ATL88Supra
March 29th, 2008, 09:31 AM
Do you have a automatic trani ? i had this same thing turned out that it was my crank bolts holding on my flywheel/drive plate i ended up shearing them all off at the drag strip but it was knocking for along while

Big Wang Bandit
March 29th, 2008, 09:34 AM
My friends corolla has a stuck lifter that sounds a lot like RK at times.

Rennat
March 29th, 2008, 11:39 AM
do you get it on cold start-ups in the morning? but not when its hot outside? if its that, i use to have that... but its gone now thats its warmer. and i run 5w30