Well i least i think its knocking, and the teaser is it only happens once in the morning when its coldfor like 2-4 seconds, never the rest of the day. Im gonna replace the pmd today, well see if that fixes it, by chance.

Well i least i think its knocking, and the teaser is it only happens once in the morning when its coldfor like 2-4 seconds, never the rest of the day. Im gonna replace the pmd today, well see if that fixes it, by chance.
Well, diesels sort of knock when their cold, but what kind of knock are you experiencing? Would you be able to maybe get a video of it?

If it is knocking, I wouldn't think a PMD would fix that.

Well, diesels sort of knock when their cold, but what kind of knock are you experiencing? Would you be able to maybe get a video of it?

If it is knocking, I wouldn't think a PMD would fix that.
i certainly could. but without a computer at the moment, i have no way of sharing it >.>

i certainly could. but without a computer at the moment, i have no way of sharing it >.>

That would be a problem :p:

Cn you describe the kind of knock you are using? What's the temp outside and what oil are you using? How many miles on the engine?

That would be a problem :p:

Cn you describe the kind of knock you are using? What's the temp outside and what oil are you using? How many miles on the engine?
Agian im not even sure its a knock, cause ive never heard one. Its like 20 degrees out, 168000 miles, and ive got royal purple 15-40, just changed it this sunday

I guess how I would describe a knock is sounding like someone is taking a hammer and hitting the block. (Correct me if I'm wrong) They usually aren't steady. The one's I've heard knock a few times, then pause and then knock a few more.

I'm going to post some videos of a cold start with mine this weekend, but in the meantime here is a video of a knock of a gas engine on youtube:

http://www.youtube.com/watch?v=WXg9dGBaUNg

I guess how I would describe a knock is sounding like someone is taking a hammer and hitting the block. (Correct me if I'm wrong) They usually aren't steady. The one's I've heard knock a few times, then pause and then knock a few more.

I'm going to post some videos of a cold start with mine this weekend, but in the meantime here is a video of a knock of a gas engine on youtube:

http://www.youtube.com/watch?v=WXg9dGBaUNg
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The rattleing was the only obvious noise xD, but none of those were close. mine was obvious

My vaccum pump went bad and it sounded like a rod knocking. V

My vaccum pump went bad and it sounded like a rod knocking. V
at what times xD

My neighbor has 91 6.2 N/A with 250K on it, sounds like a rod knocking everyday when he fires it up cold, but when he comes home at night with it...it's quiet as a church mouse.

My old 7.3L N/A with 330K on the clock does the same thing...it's just not as pronounced...

HTH's
69

My 95 would always knock hard when cold before I put in all new injectors at 120k miles. After that the knocking was more brief and quiet and gone almost completely at idle when warmed up. No knocking at all under load.

Forgot to mention that the fuel injection lines can cause a knock if they are in contact with one another or in contact with some part of the engine.

Ya my 6.5L knocks when it's cold out like 35*F or below it knocks for 5 seconds and its fine afterwards

Many things in these trucks can knock or sound like a knock.

Like mentioned the lines can make a knocking sound if they are touching.

A stuck open injector can sound like a knock.

A bad lifter can cause a knock sound.

Per Missy Good Wrench from the other site on my strange engine noise thread,


A rod knock will most generally be associated with a loss of oil pressure too especially at low speeds HOT

The pistons in these come to within about .040" of the head, so the loss of a bearing can cause the piston to smack the head too.

A rod knock will be at crank speed, is your "TICK" at crank speed or cam speed (1/2 crank) ??????

Does the engine run smooth???

A rocker button thats failed and allowed the rocker to slip off the valve will cause a miss on the cylinder involved and also a nasty shake.

Rod bearing failure is a nasty hard thuding noise that will not usually be heard up top.

First tell us if the noise is at cranks speed or ccam speed.


Missy

I've got the same thing going on at cold start-up. Temp outside doesn't seem to matter. The big difference between mine and that video is that the sound is much deeper and hollow sounding. Scares me so bad I am looking for a trade! Doesn't last but about 10 seconds, at the most, but sounds like piston or rod to me. Make me feel better or I'm gonna trade for a 2001 3500 6.0 gasser out of fear, even though I know I won't be able to tow as much...will I?

I guess how I would describe a knock is sounding like someone is taking a hammer and hitting the block. (Correct me if I'm wrong) They usually aren't steady. The one's I've heard knock a few times, then pause and then knock a few more.

GMC guy describes the exact knock my truck made on cold starts for more than 30K miles before I tore it down for a rebuild. It was especially bad before I replaced all of the injectors. With new injectors, it knocked for only 10-20 seconds instead of 2-3 minutes before. After tearing it down I found nothing inside the engine that would have caused that sound. All bearings, rods, pistons, rocker arm buttons, etc. were OK. At the time I didn't know that injector lines touching each other might do it too. That could have been my problem. Unless you really want too, I don't think I'd trade off my truck just because of a knock until I let some of the people on this site listen to it.

sounds like good advice....thanks. By the way, whaddya think of me towing a fifth wheel around the country with this motor and truck?

No one has mentioned that a cracked or broken flexplate can sound like a really bad knock. The knock sound is worse with load and at cold start. Also something to consider is that the injection timing is advanced at a cold start,causing a knocking sound. The cold advance knocking sound seems to be louder with the mechanical pumps[92-93]. The electronic pumps will knock if timing or tdco is advanced from stock settings.

sounds like good advice....thanks. By the way, whaddya think of me towing a fifth wheel around the country with this motor and truck?

Depends. I'm in the same position as you, retired and would like to travel with this truck. But, it's always a crapshoot with an older vehicle. You could go another 200K miles with never a let down, but I always have it in the back of my mind that I might have to tow my truck home behind a big UHAUL rig someday or pay some hefty repair bills a long way from home.

Your truck should have the 599 block, considered the best block made during those early years, and the mechanical fuel pump, also considered more reliable than the later electronic ones.

Quite frankly, I think I'd rather have your truck than mine. With good maintenance and a few mods it should last a long time.

thanks, getheledout, I feel better....and I do use quite a bit of oil, too

I had to replace a new injector with a high time one after I bent the return nipple and it started leaking. The start up knock had disappeared with all new injectors, and came back for about 5 seconds on start up when I put 1 old injector back in. With the low sulfer fuel and maybe no additives to compensate, you may be looking at injector issues first and IP second. Try useing some stanadyne additive for a few tanks and see if things improve.

thanks, I'll try that. Get it at the auto parts store? wassa IP? Injector pump? I'm a novice ya know

A loud knock for a few seconds after startup isn't the cold start advance. That knock doesn't disappear until the engine warms up and the timing goes back to normal. Mine had been doing something weird occasionally on a cold start for just a couple seconds. A sound kinda like an old worn out air compressor starting (or a gasoline engine running with one spark plug out of it). Not really a knock, don't know what you'd call it. I never have been able to figure it out. I haven't looked for a cause, it hasn't done it yet this year and there isn't any obvious problems. That, and it is hard to chase a problem when there are no symptoms.

well, maybe I've been over-reacting to this whole thing. I had planned to take it to the best diesel mechanic in town, anyway.......so I guess I'll just tell him about it and see what he's got to say. My biggest concern at this point is this damn shaking, anyway. I know this is another thread but I want input from everyone. This beast was shaking (seemed to be eminating from the center of the truck, not in the steering wheel at all) at any speed above 40mph. So I started systematically trying to eliminate stuff...i.e. wheel balance (I'll get back to that in a minute), had a brake caliper stuck-fixed that, balanced the wheels a second time, had the driveshaft balanced and the u-joints replaced (man said that the carrier bearing was good). Now it is different...it "vibrates" at over 60mph. Worse sometimes that others. Now I have to tell you all that when I had the rear 4 wheels balanced, the man did bring me out to look at a small flat spot on one rear rim that you really couldn't see til it was spinning a little, but it balanced out okay....gimme some ideas what to do next.....think it could be that little flat spot on that rim, even though it balanced?? Thanks

DO you have a 2 piece driveshaft with a carrier bearing? mine let go and the truck shook like i was driving through a live mine field.

yes I do, but the carrier bearing is okay and I don't have a minefield situation either....it's just enough to make me not wanna go off on a trip very far from home ya know:(

oh, by the way, here she is.......

Might be the rim, change it out with your spare and see. Also look out for bulges forming in the tread. I had a whole set of Cooper tires that had to be replaced one by one until all six were history. Each time a bulge began to develop in the tread, the truck would shake like crazy. Bulges in the tread are easy to find, just run your hand around the tire feeling for any irregularities. A bulge can form at anytime in a defective set of tires.

Does anybody mention to check all the pulleys? and belt?

will do........thanks

I usually get no knock upon start up but it has been bitterly cold 0 to -5 F when leaving work so I get a little bit of rough running for about 5 seconds or so.

Really nothing to worry about in my opinion.:cool:

thanks, I'm feelin a little better

No one has mentioned that a cracked or broken flexplate can sound like a really bad knock.

whats a flexplate?

yeah, whats a flexplate? also, now I got yet another issue (bummer)....I am seein lots of oil dissappear with no signs of a leak anywhere.......what do I do?

Flexplate is same as clutch plate, sandwiched between the clutch housing and the flywheel. What do you mean by lots of oil? And how many miles between checks?

I'm puttin a quart in about every hundred

I'm puttin a quart in about every hundred

I'm pretty sure that's not good.:(

ya think?

check your turbo

really? you mean look for oil in it?

I'm puttin a quart in about every hundred

For what it's worth, for comparision purposes, i'm adding about a quart maybe 2 every oil change. My oil change intervals are 10K with Amsoil Full Synthetic. That's with 188K miles as well.

A quart every 100 miles is a bad thing. The oil's going somewheres. It's either getting past the rings and getting burned(how's your blowby), leaking out(bad oil cooler line perhaps), or you've got a bad turbo seal.

yeah, it's gotta be goin somewhere alright.....I just can't find it and it's not smoking......I'm takin it in to be looked at by somebody smarterer than me....."d-oh"!

Try getting fuel from a different place, my truck knocked so hard i thaught it was going to break the engine mounts but only with fuel from a certain place.

my truck knocked only when cold start, bad glow plug connections and when i turned it off, that was until i replaced the harmonic balancer, for 225500 and never replaced didnt look that bad but was buldging and i replaced the crank pulley balancer which was missing huge chunks out of the rubber :eek:
Now she shuts off quiet and no knock :D both repalced and now shes all good