Connecting rod bolts

[Subfixer]

I've got a light knock that I hear around 2000 -2500 rpm that's driving me nuts. Above that rpm, there's too much other noise for my 1/2 deaf ears to hear it.


Not sure what it is, but I want to pull the rod caps and check the bearings. The last owner lost an oil cooler hose, but I don't know how far the car was driven after the hose let go.


Anyway, since the rod bolt torque is so many ft/lbs plus 1/4 turn (or something like that), I'm wondering if the stretched bolts are one time use and should be replaced.


Thanks in advance...

[-=Jeff=-]

Is it a consistent knock? Do you here it at lower rpm? Have you checked your Dual Mass flywheel? Those will make the motor sound like it it knocking.

Does this happen when the motor is cold? Warm? Both?

[BigJohn]

Tensioner?

[Subfixer]

Is it a consistent knock? Do you here it at lower rpm? Have you checked your Dual Mass flywheel? Those will make the motor sound like it it knocking.

Does this happen when the motor is cold? Warm? Both?



Knock is consistent either cold or hot.
Driven about 1000 miles since I bought the car, hasn't gotten any better or worse.
Only hear it at lower rpms, 2000-2500-ish, only during acceleration or under load. At higher rpms, there's too much road noise to hear it.
No knock while steady cruise, coasting or slowing from what I can hear.
No knock at idle.

[32valvZ]

Can you capture the sound on video?

[Subfixer]

Tensioner?



Don't think so. Quiet at idle or revving in neutral.


Only under load/acceleration.

[Subfixer]

Can you capture the sound on video?



Already tried the video thing. Phone can't pick it up while driving. It's not that loud.
Sounds like a quiet version of a single rod knock.

[-=Jeff=-]

Stethoscope might help to pin point location of noise too? Might be there at idle just not heard

[RussMcB]

Seems like the rod knocks I've heard could be heard even at low RPM's. But (fortunately) I haven't heard many.

[Subfixer]

Stethoscope might help to pin point location of noise too? Might be there at idle just not heard



Yup, already tried the Stethoscope, both at idle and higher rpm.


Couldn't hear anything without the engine loaded.


So, back to the original question..... are the rod bolts reuseable, or do I need replacement bolts?

[Jagdpanzer]

FSM says to always install new connecting rod bolts when ever they are removed for any service.
Jerry has high quality replacement ARP bolts
http://www.jerrysgaskets.com/bolt-set-16-connecting-rod-new-90-95-9b1/



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[Ccmano]

Rod knock is ultra rare on these engines. I would make sure there isn’t some sort of imbalance at that rpm and load causing the knock from the dual mass flywheel. Fuel injectors and ignition coils/wires/plugs are possible culprits. Hard to say without actually hearing it.
Good luck.
H
:cheers:

[BYEBYE2U]

Take the rod bolts out of the equation.
When they go, THEY REALLY GO.....
Quick check on piston pin ,bolts n bearings is disconnecting 1 ignition wire at a time n coming up on RPM.
If the oil pressure was low after repairing oil cooler,you got bearing issue.
If you "dump" the clutch on/off with emergency brake on you will hear flywheel n balancer if that's the issue
Tensioner n shoes depend heavily on oil pressure by the way-unless failing as we speak
Last note: crank engine w/out ignition n sit in engine bay just in case its something silly like belt tensioner

[gtcollins@maxnet.co.nz]

Hi is it piston slap that you are hearing

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[BigJohn]

Has someone changed the transmission Fluid?

[DRM500RUBYZR-1]

Agree fully with:


CCMANO
BYEBYE2U
GT COLLINS
and BIG JOHN


While certainly not impossible, it is highly improbable.


When the hose let go, the oil would have begun to make significant smoke had he not noticed it earlier, and likely long before any engine damage.


Lower end failures are extremely rare.


Flywheel is the prime culprit, caused by some ignition issue or injector issue.


Stop looking for pink leopards with stripes instead of spots first, and look for cats and dogs instead.
While you may indeed be absolutely correct, history suggests other causes are far more likely.


Whenever I have had customers bring in or call about LT-5 knocks, it has always been traced back to the dual mass flywheel making racket due to another factor.
Good Luck, and let's check the routine stuff first.
Marty

[WARP TEN]

Agree fully with:


CCMANO
BYEBYE2U
GT COLLINS
and BIG JOHN


While certainly not impossible, it is highly improbable.


When the hose let go, the oil would have begun to make significant smoke had he not noticed it earlier, and likely long before any engine damage.


Lower end failures are extremely rare.


Flywheel is the prime culprit, caused by some ignition issue or injector issue.


Stop looking for pink leopards with stripes instead of spots first, and look for cats and dogs instead.
While you may indeed be absolutely correct, history suggests other causes are far more likely.


Whenever I have had customers bring in or call about LT-5 knocks, it has always been traced back to the dual mass flywheel making racket due to another factor.
Good Luck, and let's check the routine stuff first.
Marty

What Marty says makes sense and fits with the many posts and discussions we've had over the years. You might talk with Marc Haibeck on the best diagnostic approach to look into these items. I woulds certainly not begin dismantling the bottom end of the engine without trying these first. Good luck with it! --Bob

[A26B]

Rod knock is most prominent at “no-load” condition like at idle. The knock will subside with load. For example; set emergency brake, idle engine, slowly engage clutch. Knock will subside as idle speed is pulled down, i.e. when load is applied.

I have net seen or heard of a true, blown oil cooler hose. All failures I am aware of were crimp leaks that seeped to the outside of the hose, or just under the outer rubber sheath. A leak under the outer sheath will cause a bubble that will ultimately burst & appear to be a fully ruptured hose, but is not. The working part of the hose beneath is layered, fabric/rubber reinforced.

Low oil pressure will cause lifter rattle that sounds like a machine gun. No one in their right mind would continue to drive with that condition. Very unlikely that the "blown" oil cooler hose resulted in a massive loss of oil, significant enough to cause engine damage.

From your description of the noise conditions, I don’t think it’s a rod knock.

A dual mass flywheel knock is most often associated with an engine miss. Inspect the spark plugs, look for anything unusual, different coloration or damage.

Insofar as checking rod bearings; if you see damage from lack of lubrication, I consider that as an indication of main bearing condition also. To access the mains requires complete disassembly of the engine.

[Subfixer]

Thanks for all the suggestions.

Since the injectors are 92 originals, that's first on the list this weekend (parts coming from Jerry's). I know at least one is going.
One thing at a time until I get it figured out.

The car has less than 20K miles. Should I do coils while I'm in there?

[RussMcB]

The car has less than 20K miles. Should I do coils while I'm in there?I think most of us would say, yes, while you're in there, go ahead and make everything new.