sounds like lower end rod knock but only at idle

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motoloco

10 Year 15 Year
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Mar 20, 2006
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381
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elkcreek canyon colorado
adj. the valves but that was not the issue:frown: sounds like a very light lower end rod knock, vibes at idle. but holds excellent oil pressure. knock and vibe goes away at higher rpm?????? any other ideas before I start looking for a lower end?
 
Check the harmonic balancer... been known to produce some strange noises when it gets loose on the crank.....
 
Yep.
 
Dave -

Am I corn-fused? Can't you just pull the timing gear cover and get to both the Crank and Cam timing gears?

I agree that you have to pull a lot, including the front bib, radiator, harmonic balancer and timing gear cover, but do you need to remove the head?

Let me know - I am curious.

Thanks -

Rocky
 
Motoloco, try pulling plug wires one at a time with it running. Noise goes away then you know where to look when you drop the pan. if the crank isn't scored, slap some bearings in there, sell quick. Anyone want a used car? rebuilt bottom end!
 
Rocky_LC said:
Dave -

Am I corn-fused? Can't you just pull the timing gear cover and get to both the Crank and Cam timing gears?

I agree that you have to pull a lot, including the front bib, radiator, harmonic balancer and timing gear cover, but do you need to remove the head?

Rocky
Click to expand...

You're correct - the head can stay on.
Do need to remove the rocker gear, and the side cover to pull out the lifters.
Dissy, fuel pump comes out - and all the stuff in the way in the front too as you've mentioned.
 
It doesn't sound like a typical rod knock. Oil pressure is usually low if you have a bad bearing and a bad rod makes a rattling noise as the engine revs up and down. Bad rod bearing and cam gear may leave tell tale bits of junk in your engine oil, or they may not. Bad rod bearings, piston slap and piston pin noise usually get more quite when you pull off the spark plug wire as noted above. Could also be a main bearing, but that is also more commonly associated with low oil pressure. Crank thrust bearing wear can make a noise at idle, you you can see the crank pully going in and out with the noise. Other possibilities include a worn thrust washer in the cam shaft, a sticky lifter, and a bad fuel pump. You can localize it to cam related sources vs crank related sources by telling whether the noise frequency is the same as the cam shaft, which rotates half the speed of the crank. You can use your timing light to pick up the beat of the cam shaft.
 
pinhead, thanks! I just took the belts off to check the harmonic, no issue, then i pulled each plug wire, one at a time while idleing, no change in knock, pulled the valve cover and did a valve adj.,no change, it revs up very quiet and smooth and holds great oil pressuer even at warm idle. I got under the truck while it was idleing and put my ear to the pan- no knock but when I put my head to the flywheel/clutch inspection cover I can hear a knocking source I think. going to pull that cover and take a look.
 
I still vote for it being something loose (broken motor mount/skid plate/etc)
 
motoloco said:
rsbcruiser, I dont want to sell it, but if I do, and it needs a bottom end, I will tell them it needs a bottom end, cause thats how I roll:D unlike the guy I bought it from sight unseen:rolleyes:
Click to expand...

Good on you motoloco. (Me too.)

Some people love money so much that they convince themselves that "ripping other people off" is just "good business". We know diferent.

It pays to be open and honest.

With your attitude you can always stand proud.

Good luck with tracking it down and I hope whatever it is can be easily/cheaply fixed.
 
The only thing I can think of to add to what has already been said is - Try the old mechanic's trick of placing a long screwdriver on various places and putting one ear against the other end of the screwdriver.

The screwdriver brings the sound right to your ear and can be very useful in isolating where a noise is coming from.
 
i have had two spun bearings and it's the OPPOSITE of your situation.

On my spun bearings IDLE was fine, but 1500 to 2k rpms KNOCK KNOCK KNOCK.

A knock at idle sounds like what these guys are mentioning, something that needs adjusted, tightened, etc....
FYI: intake valve clearance is .032 and exhaust is .014 I believe.

I also doubt it's a bearing.

Heck, change your oil........metal in it?

ragman
 
About a year ago I inadvertly popped the clutch on my cruiser (three on the tree, thought I was in neutral, I wasn't). The result was a knock exactly like you are describing. It is very faint, comes from the clutch area, and cannot be heard once the engine speeds up. It varies with engine speed and is not effected by pushing the clutch in. I took the clutch inspection cover off and found nothing out of the ordinary.

I'll probably have to put a clutch in within the next year or so -- we'll see if it goes away then.
 
just changed the oil, no metal. plugs had some crystal black deposits but that may have been from the sea foam and ATF I tried. I have done the screwdriver trick, kinda sounds like it is comming from the clutch/flywheel area???? I drove it to one local toy mech. and he said it is perfectly normal timming noise, but I have had atleast 20 2f's and never heard anything like it, plus it is comming from the back of the motor area. It only has 54K orig and only 4k put on in the last 10yrs!
 
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