Do I have Rod Knock?

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So , lately you all know my timing belt fiasco. Anyway, the mechanic who fixed my loss of power and rough idling issue, insists my engine has rod knock.
So here are the clues.
1. When the engine and oil is cold, no such sound.
2. When oil warms up to 70C and above, the metallic rattling begins, only when there is load on the engine, pulling in gear 2 or 3. Yes it does rattle too in 4th and 5th although much less because the rpm is usually above 2500. In short, low rpm (1500 - 2400) under load, rattles.
3. Oil pressure seems adequate, although just a bit low from actual spec. Its supposed to be 21psi at 90C at 900rpm. I get 18psi.
4. Mechanic insists the ignition timing is now set correctly. Previously I retarded the distributor, and increased the carb idle speed screw to get back 900rpm idle speed. I have been running the car this way for years. It does keep the rattling/knock sound to a bare minimum this way.
5. My UOA shows about 20 to 25ppm of lead for 10000 to 15000km OCI.

Next, could detonation or pinging cause the rod bearings to wear early?
Also could lugging the engine cause this ?
 
The fact that it happens when the engines warm and under load makes it sound like a rod knock. That it goes away after 2500rpm and you describe it as a "rattle" makes it sound as if it's not. It it is a rattle it could be a heat shield or something similar that only rattles after it expands from the heat and when the engine is twisted a little on its mounts from being under load.
 
I would speculate that if this has been going on for "years" and many thousands of miles, that it isn't a rod knock, as I would think it would have come out the side of the engine long ago.
 
Originally Posted By: alcyon
2. When oil warms up to 70C and above, the metallic rattling begins, only when there is load on the engine, pulling in gear 2 or 3.


That's pinging; not rod knock.
 
The only car I got rod knock from made knocking sounds any time the car was run...cold or hot, didn't matter (1979 DeVille). Those bearings got washed with fuel during a fuel pump failure.
 
If it is pinging, putting in higher octane gas should make it go away or at least have an affect. If it doesn't, it may be a wrist pin or rod knock.
 
Rod knock is a knock, like on the door. Almost like you can feel it.

"Spark knock," or pinging, sounds like marbles dropped on a steel pan.

Rock knock is typically more rhythmic, but pinging can be too. I suspect pinging, you would rear rod knock all the time, even at idle.
 
you can do the timing your self. get a light and fallow the book. most engines are around 4 deg. altitude pending. higher altitude you can have more like 10.
try a higher octane fuel see if that helps. if it does then retard the timing some.
 
The ignition event is supposed to occur at a specific degree of crank rotation before top dead center. For example: 10 degrees BTDC at 600 RPM idle speed. If you change the idle speed, that also changes the ignition timing. They have to be matched.
 
ok let me out it in simpler terms.
If its rod knock, caused by rod bearings that have too much clearance, even if I retard timing, it should still knock/ping right ?
 
Yes. Rod knock should be prevalent at all engine speeds and loads. It can show up sooner under load, but typically when it is audible it is audible all the time.

You want to verify timing at the correct idle speed as said above. Maybe try some high octane fuel and see if it quiets down first.
 
I just retarded the distributor back to its old position and increased the idle speed screw to compensate back the idle speed to 900rpm. Hopefully this will stop the pinging/rattling/knocking. If it does, that means I don't have rod knock ?

What I don't get is why the engine now runs steady with this retarded distributor, but it didn't last week. perhaps some oil got into the distributor, and it was the cleaning and change of seals that fixed it, not the advancing of the distributor.
 
Last edited:
Its fixed ! Engine runs great..no pinging or knocking! I can ease into the throttle without backing off in 2nd and 3rd now. The last 3 days was tiring, balancing the clutch longer everytime i hear pinging. And as added bonus the oil temp is lower by 4 C. Back to normal !
 
Originally Posted By: OVERKILL
If it is pinging, putting in higher octane gas should make it go away or at least have an affect. If it doesn't, it may be a wrist pin or rod knock.

I suspect you are right. Gudgeon pin knock rattle like he has described it. It can drive like this for years.
 
Originally Posted By: alcyon
Its fixed ! Engine runs great..no pinging or knocking! I can ease into the throttle without backing off in 2nd and 3rd now. The last 3 days was tiring, balancing the clutch longer everytime i hear pinging. And as added bonus the oil temp is lower by 4 C. Back to normal !


IMHO, you have fixed a case of detonation. Many years ago I had an engine with rod knock, and it was worst at startup...as oil pressure built and oil warmed, the sound went away.

Your description of "under load" noise at low RPM, and improvement with initial timing retarded, are classic symptoms of detonation in my experience.

You may want to consider a different mechanic.
 
Originally Posted By: alcyon
Its fixed ! Engine runs great..no pinging or knocking! I can ease into the throttle without backing off in 2nd and 3rd now. The last 3 days was tiring, balancing the clutch longer everytime i hear pinging. And as added bonus the oil temp is lower by 4 C. Back to normal !


On some cars there is an electrical connector that needs unplugging or jumped before setting the base timing, also if it uses a vacuum advance it needs to unplugged and the hose capped off.
If that's the case and the mechanic didn't do that the timing was probably off. If it does have a vacuum advance put a vacuum on it and make sure its working.
 
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