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Occasional rod knock?

Tookie

Tookie

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Location
Port Vincent, Louisiana
OK, I know there is no such thing as a rod knock that goes away,
but that's what this sounds like. Once in a while (maybe once every 3 days)
sitting at idle, it will start this clunk, clunk sound. Lasts about 5 - 10 seconds.
About 4 months ago, I had to replace the main pulley, which has a
dampener built into it. At that time, I checked the HB and it was fine.
Right now, if I remove the belt, I can't feel any play in it - Friday, I
will pull it and do a visual. What else could do this? An injector starting to
go out? AFAIK, injectors are original, 231,000 miles - but no miss, good MPG,
very small puff of smoke on cold start......... want to fix this issue before
I try to sell it, I wouldn't make a good used car salesman, bugs me to pass
on a problem to someone :D
 
You are well beyond the 100,000 mile replacement on the injectors. They are more than likely peeing a stream rather than making a mist. When the excess fuel finally lights it makes a knock. If you wait long enough you won't need to worry about it. There will be holes in the pistons.
There is still some of the delphi N/A injectors on e-gay. The price has gone up now.
 
bk95td said:
You are well beyond the 100,000 mile replacement on the injectors.
Click to expand...

Thanks for the reply, and injectors are probably my problem,
but I wouldn't change them without a symptom - oil, fluids,
filters, yes. Mechanical parts? I change em when they break or
display symptoms, not as routine maintenance. (With the
exception of a timing belt on a vehicle with an interference
engine.) :D
 
ebay item: 270505949900 if you want rebuilt, he also offers a rebuild service where you send yours in to be rebuilt.

ebay item: 110508497871 these are new delphi NA injectors, the pop pressure will have to be raised. These are the ones bk used.
 
I have had the same sound upon start up every now and then for about 2 years'replaced injecters 4 months ago did not fix that sound for me.its pretty loud.
doesent last longer than 5 seconds
 
bigchevy89 said:
I have had the same sound upon start up every now and then for about 2 years' replaced injectors 4 months ago did not fix that sound for me.its pretty loud.
doesn't last longer than 5 seconds
Click to expand...

Mine will do it every once in a while at start, just like 1 or 2
knocks - but more noticeable when it does it at idle.
Even so, it's only once or twice a week I notice it, and I just
heard it for the first time around 2 months ago.
 
Bad inj dont make clunck sound,neither does a rod

bad crank pully does
Bad motor mount can too
exh hitting the frame does too.

what about vac pump?
 
bison said:
1) Bad inj dont make clunck sound,
neither does a rod
2) bad crank pully does
3) Bad motor mount can too
4) exh hitting the frame does too.
5) what about vac pump?
Click to expand...

1) Clunk might not be technical, but this sounds exactly
like a rod knock, whatever you call it.

2) Changed less than 6 months ago, will be checked
again tomorrow when I pull the HB for inspection.
3) & 4) both good ideas that I didn't think of, I need to
have the hood open and be watching when it does this,
but it's very occasional - can check motor mounts though.

5) Long gone

Thanks!
 
My neighbor has a 1991 6.2 with 278K on the clock. It will knock every cold start, but is as quiet as a church mouse after it warms up.

I always thought it was from piston slap that heals itself after the cyclinder walls / pistons grow some from heating up...?

Not something he worries about, it's been doing it for years...
 
Grab that new crank pulley you put on and try to move it with the belt off.

I installed a brand new one and ended up changing out a Power steering pump for no reason chasing the phantom noise. It was my new pulley junk out of the box.
 
I'll say it again folks, check the thing you just fixed. Matt is right, most parts today are garbage.
 
Harmonic Balancer pulley was changed about 7 months ago -
when I grabbed it, had a very slight.... give? to it, no real play.
Under warranty, so I changed it. HB itself had no detectable
play, but the rubber was very slightly bulging out, so I changed it.
Also, in the pic, you can see a wear line on the seal surface,
hope that was the source of the remainder of my leak.
While I was under there and access was a little easier, I also
changed the lower radiator hose and coolant recovery hose
that connects to it - wasn't leaking, but felt a little soft,
probably from the oil leaks in the past. So, fresh coolant also.
Should know in a few days if the knock is gone.

2010_04030052.jpg
 
Good clean coolant is as important as good oil... Well done Tookie.

Fingers are crossed.......

Your 97 block w/230k is a role model to my 6.5!
 
What brand oil filters do you use? Where I used to work the oil filter would make the dodge engine rod knock when first started. With a different brand filter it wouldn't do it. Something to do with crappy check valves allowing drain back. Essentially no oil at start-up untill filter is filled up again. Just another possibility if what you did didn't cure it.
 
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