Figuring out new sound...here we go...LOL.

[Asmoday]

Ok...so I went out to start the the CUCV at 3am this morning to head in for my flight shift. I'm in Southern California and it never really gets very cold but this morning it was 35 degrees. I fired it up and as usual it started instantly. However lately I have been noticing that on cold starts...for about 10 to 20 seconds after starting it I get a odd sporadic clanking. It basically goes clank, clank clank clank, clank, clank, clank clank etc. etc. There is really no specific rhythmic order to it and it's short lived as again after less than a minute it's gone.

It does not do it when warm. The truck has to sit and be truly cold for it to do it.

I have checked bolts, brackets, etc. and can't really find anything. This is the first diesel I have owned so I still have to get used to all the sound oddities but I think it does have a slight exhaust leak as well but I really don't think that would cause the sound I'm hearing.

Of course paranoia sets in and I think dreaded 'rod knock' but I would think that kind of sound would be very rhythmic and consistent and not disappear after such a short time. I sure hope I'm right on that...! It runs great and even a couple of the flight mechanics have commented on how well it idles and sounds.

I listened underneath real quick while it made the sound when I started it to come home from my shift after sitting all day and it just sounds louder underneath but I know how misleading that can be.

So...opinions? Sticking injector? I'm not sure where to start since it goes away so quickly.

 

[motormayhem]

Could just be the timing being different when it is in high idle. Mine is extremely loud when its cold out and clacks more.

 

[Asmoday]

Ya know...I actually thought of that but it does it for such a short time. And as mentioned...it's a sporadic sound. No specific consistent rhythm.

I can tell when it's in high idle and it takes a few minutes for it to come down. Much longer than the brief clacking.

 

[motormayhem]

Hmmm, could be some of the cylinders take a few seconds to start firing completely. Maybe check the glowplugs. I'm pretty sure mine does the same exact thing on a cold start.

 

[Asmoday]

Ok will do. I was getting ready to check them last week as I have been doing a lot to the CUCV since its purchase but my Fluke went bye bye so I have a new Fluke coming which should be here Friday.

It runs so well I would hope it's not rod knock. Rod knock gets worse when warm as I remember anyway...correct?

 

[Cucvnut]

could be piston slap

 

[Asmoday]

Great....

 

[Cucvnut]

Piston slap is not a bad thing. my 99 trans am with a LS1 had it and never had an issue. its just the piston slapping the bore wall till it warms up and expands.

 

[Asmoday]

I have actually heard piston slap on a diesel Mercedes and it's pretty much a constant rhythm.

Mine just does a few sporadic clacks and then that's it...

 

[Cucvnut]

your diesel is different. could be anything really.

 

[kentuckycucv]

Maybe it the engine oil being cold ...low oil pressure for a couple of minutes. Whens the last time you changed your oil?

 

[Asmoday]

Oil was changed 2 weeks ago and level is perfect. Oil (idiot) light goes out instantly on start...

As mentioned before the sound is only there for a very short time...less than a minute.

 

[998Junkie]

Maybe it the engine oil being cold ...low oil pressure for a couple of minutes. Whens the last time you changed your oil?

My 1008 makes that noise but it does go away within a minute, I assumed it was the time it take the oil to get to were ever it is needed. I can almost time when it goes away and it's only after the engine has sat for 5 hours or more. It is just starting to get cold and this is the first winter I've had it.

 

[epartsman]

I have a feeling it is just a dry start condition. GM's are notorious for this as my Suburban knocked 3 times every now and then @ cold start up. It used to sit for weeks before the next use. Try some Lucas it helped in the burb smoothing it out and making it less frequent but wasn't a cure as @ 170k it will need a rebuild.

 

[DonK]

Exhaust expansion?

 

[BIG_RED]

I'd say the oil thing sounds about right to me. Used to happen to me when I first got the truck and it was running cheap oil (knock off parts store junk). Lucas Oil (15W40 not the additive) quieted it down alot. Switched to Shell Rotella 15W40 - even less noise on start up. Napa(Wix) filter keeps the oil cleaner too. Flushed out the engine and it's gone. Takes a little longer for the oil light to go off (maybe 2 seconds instead of nearly instant) but I would assume that's because the oil is actually getting to the whole engine before building pressure, not just building pressure at the oil light switch since everything is half clogged.

Maybe try to flush your oil system? My oil was incredibly dark 1 minute after I changed it when I first got the truck. So I guess there was a lot of sludge and junk built up in the engine. I ran some kind of "engine flush" (I think it was made by STP, small bottle you add to oil, then let engine idle a few minutes, then change. Smelt like paint thinner). Then I drained it, and put in 7 Quarts of 10W30 Quaker State gas engine oil (because I got them for $2 each on sale) and drove around the block(don't run your truck on the wrong oil very long, gasser oil can't handle all the soot). Then I drained the oil (it was BLACK), replaced the filter and filled her with Shell Rotella. For weeks my oil looked really clean (for a diesel). No more startup racket.

 

[Barrman]

We were 24° here this morning. The Blue Bomber took about 5 seconds of cranking to start and didn't really make any loud clanking. The M1009 fired up instantly as usual and had real loud clanking like you describe.

I KNOW the M1009 has a working cold advance and functioning glow plug system. I think the fast advance is working on the bomber and the glow plug system is sometimes correct.

I also KNOW the M1009 has a new IP with a hair more advance than the other truck.

I see this noise as just an indirect injection diesel waking up and not being happy about it.

 

[Chief_919]

You sure it isn't just your glow plug relay cycling on and off?

 

[mistaken1]

Of course paranoia sets in and I think dreaded 'rod knock' but I would think that kind of sound would be very rhythmic and consistent and not disappear after such a short time.

As Mr. Stinson used to say "rods don't knock for very long". The time a rod stops knocking usually coincides with the time said rod explosively protrudes from the side of the block.

If your engine is still running after several minute I think it is safe to say it is not a rod knocking.

 

[Cucvnut]

Benny hill knows all!