engine noise

[rayc3045]

Need HELP!!!!
I have a 1988 supra with the 7MGTE turbo engine in it and 158,000 miles.
I have replaced the head gasket with a metal one and ARP head stud.
I have rebuilt the turbo back to stock with a 3 inch down pipe and removed the catalytic converter.
I am getting a knock or ping from the engine.
There is no noise at idle and idle is smooth.
There is a light knock at 2000 to 3500 rpm.
If this is a rod knock would it knock at all RPM’s?
There is no lose in power, the engine runs good.
The noise is not heard at idle or when you put a heavy load on the engine you can't hear it. You can only hear it when reving the engine or rolling on the gas from a cruise. When I first start the car when its cold the noise isn't their.
Any help would be great
Rayc3045

 

[92TealSupra]

I have rod knock on my '88 Supra. my noise can be heard at idle though, and all RPMS, you may want to check your Shims on your motor. Have you sort of figured out where the noise is coming from, ( bottom end ) ( top end )

I would take a stethoscope, or a long screw driver and listen to the motor, that is what I did.

You didn't have this problem before your HG? Did you drain your oil and put new Oil in the motor? Did you mill the block along with the head?

 

[Moy]

Post up a video.

It sounds like rod knock though. I don't think it's the valve lash, it would be heard through all RPMs and be more of a ticking sound.

 

[mkiiSupraMan18]

Check the harmonic balancer, make sure it's torqued to 10,000ft/lbs or whatever.

It makes a neat knocking noise when it's loose.

 

[suprarx7nut]

Too little info for anyone to tell you whether it is rod knock or not.

Try to pinpoint the noise as best you can. More noise from top of motor, or bottom? Does it get louder with more throttle? Does the noise get faster with higher engine speeds(RPM)?

 

[rayc3045]

Sorry for the delay in getting back had computer problems
I checked the engine with a stethoscope, and there is more sound coming from the lower block than the head or manifolds.
I dont remember if i had this noise before I replaced the head gasket it was serveral years ago.
I did cahnge the oil after replacing the head gasket.
I retorqued the harmonic balencer, no help.
You can here a light tapping sound at 2800 rpm in light crouse, like a valve tap. When I start to go up a hill and push on the gas peddle the noise goes away, when I back off the peddle at the top of the hill the noise comes back, when I let off the gas peddle to go down hill the noise goes away until I go back to a crouse. I checked the gap on all the valves and there are in spec.
The noise dose get faster with faster rpm

 

[92TealSupra]

Most likly you don't have rod knock. It does not just go away. You did say you believe it is coming from the lower end though. Noises carry very well through metal, it is possible you're experiencing the valves making this noise.

 

[GrimJack]

Can you make it happen parked, with the hood up, by pulling the throttle from under the hood? If so, pull the plug wires one at a time. If one of them makes the noise stop, you have a rod knock on that cylinder.

Other things that tend to sound the same are loose flywheel bolts on a 5 speed car and loose flex plate on an automatic car.

 

[Muzy]

Check the harmonic balancer, make sure it's torqued to 10,000ft/lbs or whatever.

It makes a neat knocking noise when it's loose.

Would you use 2 or 3 torque multipliers and a 10 ft cheater bar to get that value? Sounds a little snug to me thou. :icon_bigg Muzy

 

[92TealSupra]

Would you use 2 or 3 torque multipliers and a 10 ft cheater bar to get that value? Sounds a little snug to me thou. :icon_bigg Muzy

Ha, it's 198 ft-lbs I thought -.-

( :

 

[sogi99]

what grimjack said you can do it that way the isolate which cylinder is knocking. Mine was like that when I put the stethoscope on the lower block I heard knocking when I pull the motor and plastigage the rods its cylinder 3 that was out of spec. I just replaced all the rod bearings since mine came with stock toyota bearing I was on a budget. The engine still runs will probably have this engine fully rebuild this year.

 

[rayc3045]

I pulled each spark plug wire until the noise stoped, it is the #4 cyl.
Dose this mean that it has to be a rod, or could it be a cloged #4 injector causing it to go lean and creating detonataion inthe #4 cyl.

 

[jdub]

"Denial" is not a river in Egypt

http://www.supramania.com/forums/showthread.php?t=20486

 

[rayc3045]

I got the engine out of the car and torn down, did find a bad #4 rod bearing. in the process of rebuilding.
Thanks for all the help.
Ray

 

[grimreaper]

pics?

 

[berniek]

Apologies for the disagreement: Rod knock will generally not occur under power because radial clearance in the rod bearings is taken up by compression and power stroke compressive force in the connecting rod. Rod knock occurs primarily under light load or no load "teasing" conditions at 2500-2800 RPM.

When I did my engine build, I moved the oil pickup to the rear kickup in the pan so it would not starve under hard acceleration.

BernieK

Most likly you don't have rod knock. It does not just go away. You did say you believe it is coming from the lower end though. Noises carry very well through metal, it is possible you're experiencing the valves making this noise.