Cold start -sounds like rods knocking?????

[la]

2000 z71 5.3 sounds like its going to throw a rod for about 30 seconds on a
cold start every morning.
Only does it once every morning. DEALER SAYS ITS NORMAL
I say bull shit!
Anyone know what this is????????
larry

[DW]

Sounds like "another" 5300 built with excessive rod bearing clearances. By
no means should you except this as normal. Get on the horn and call the zone
rep. The technicians at that dealership don't want the work 'cause it's
warranty and doesn't pay as much. You might want to grab the salesperson who
sold you the rig by the short-hairs, also!

"la" <e...@e.nne.net> wrote in message
news:D6cw5.45$C7....@news-west.usenetserver.com...

[krey1]

I've got a new Yukon with the 5.3 and it makes the usual 2-3 seconds of
clickety-clak as the lifters pump up and then it's quiet as can be. Ditto
in my explorer with the 4.0 HO. I use 5-30wt synthetic in both (Mobil 1)
and it does make a difference.

OTOH, a loud knocking for 30 seconds is NOT normal. You aren't using 50wt
oil, are you?

Kirk

[villagecobbler]

As a technician at a Chevrolet dealership, we recieve many customers who are
concerned about this very condition. Depending on the mileage, it is most
likely that there is carbon buildup on top of the pistons causing a noise
very similar to a rod knock. It is very common, and I believe that there is
a TSB available for this concern. To remove the carbon, do the following:
get a can of GM Goodwrench Top Engine Cleaner. Attach a piece of vacuum hose
to the PCV vacuum fitting. Start the engine, and dip the end of the vacuum
hose into the can, letting enough cleaner through the hose to almost kill
the engine, but not quite. Use approx. 1/2 of the can, and then put the
hose all the way into the can until the engine dies. Let it sit +/- 4 hours,
or preferrably overnight. Start the vehicle (may need to hold the throttle
open) and repeat the procedure, this time not killing the engine when the
cleaner is gone. Drive the vehicle rather agressively (enough to keep the
RPMs up around 3,000 or so). This procedure should remove all or most of the
offending carbon deposits. Also, as a side note, this will most likely cause
a code P0300 (misfire). After driving, clear the codes, either with a scan
tool or by disconnecting the battery. Hope this helps!

[villagecobbler]

As I said, depending on mileage (15,xxx or more), carbon is a very common
characteristic of the LS1 series engines. Also, codes WILL clear if the
batteryis left disconnected +/- 10 minutes.

jed <jed...@makesnosenseyahoo.com> wrote in message
news:SMfw5.110$m8.7...@news1.telusplanet.net...
> Just to note - should there be carbon buildup on such a brand new unit?
It
> usually takes quite awhile to get buildup. And, I was under the
impression
> that OBDII codes could only be cleared with the Tech 2, or similar
scanner,
> and not by disconnecting battery.
>
>
> jed
>
>
> "villagecobbler" <village...@juno.com> wrote in message
> news:ss2trs...@corp.supernews.com...

[krey1]

Ya know, I started to think about this a little more and I wonder...could
your motor be diseling? Rod knock and pre-ignition (diseling) sound very
much like alike except rod knock usually doesn't go away.

Kirk

"la" <e...@e.nne.net> wrote in message

[jed]

jed

[M. Stanton]

Hmmm...carbon buildup eh? I'm gonna have to do this every 2k miles? Because
I noticed the rod knocking sounds on startup at 2k miles....I think the rods
are knocking instead..

Mike

[DW]

With a 2000 model and a basic 3/36 warranty why should this owner have to
fool with Goodwrench Top Engine Cleaner, and clearing codes? I have never
seen a cold engine detonate from carbon on a cold start at idle. More
Service Dept BS. If it is carbon, why? And what happens to this carbon when
the engine is at operating temps? Seems with this much carbon it would
detonate all the time.

[villagecobbler]

By all means, take it to the dealership if it's under warranty! The owner
didn't put the carbon there, GM's engineering crew did! I only gave the
procedure because I didn't know if the vehicle was still under warranty...GM
will cover this condition usually only once, though. But if you complain to
the service manager enough... who knows? It is unknown what causes this
buildup, but it is suspected that it has something to do with EGR
calibration. What happens at operating temps? Unknown also, except that
possibly piston/chamber expansion occurs. As for detonation, we haven't
experienced any problems with it, even on these engines that have been
proven to suffer from the carbon. Engineers are said to be addressing the
issue. Or, OTOH, you may just have a rod knock after all!

DW <d...@worldnet.att.net> wrote in message
news:qjsw5.15653$6f1.6...@bgtnsc05-news.ops.worldnet.att.net...

[High Sierra]

This sounds like a technique we used to do in the 'old' days (carburettors) to clear out carbon.

We would pour motor oil down the carburettor slowly so as not to stall. When the quart was almost empty we'd pour in the rest in all at once to stall the engine. Then after a wait we would start up and go for a 'highway drive'. Read high speed for 'highway drive'.

I don't know if this helped but it sure was fun smoking up the area and then going for a fast drive.
--
Remove 'antispam' from address to reply.
For NG please reply to group only.
High Sierra

[DW]

I really don't understand the logic of these "whiz-kids" in GM engineering.
We had a time-tested and proven SB, and they continue to screw with it. I
guess they figured they re-invent the 327 with the 5300. This one is going
to backfire on them in terms of customer satisfaction. They need to leave
the SB alone and spend more time designing "their own" diesel instead of
relying on Isuzu to bolster their light truck diesel market.

"villagecobbler" <village...@juno.com> wrote in message

news:ss5abi...@corp.supernews.com...

> By all means, take it to the dealership if it's under warranty! The owner
> didn't put the carbon there, GM's engineering crew did! I only gave the
> procedure because I didn't know if the vehicle was still under
warranty...GM
> will cover this condition usually only once, though. But if you complain
to
> the service manager enough... who knows? It is unknown what causes this
> buildup, but it is suspected that it has something to do with EGR
> calibration. What happens at operating temps? Unknown also, except that
> possibly piston/chamber expansion occurs. As for detonation, we haven't
> experienced any problems with it, even on these engines that have been
> proven to suffer from the carbon. Engineers are said to be addressing the
> issue. Or, OTOH, you may just have a rod knock after all!
>
>
> DW <d...@worldnet.att.net> wrote in message
> news:qjsw5.15653$6f1.6...@bgtnsc05-news.ops.worldnet.att.net...
> > With a 2000 model and a basic 3/36 warranty why should this owner have
to
> > fool with Goodwrench Top Engine Cleaner, and clearing codes? I have
never
> > seen a cold engine detonate from carbon on a cold start at idle. More
> > Service Dept BS. If it is carbon, why? And what happens to this carbon
> when
> > the engine is at operating temps? Seems with this much carbon it would
> > detonate all the time.
> >

[Dave Kukucka]

Larry,

Worn main and rod bearings will cause low oil pressure. You'll hear
anything from a nock (connecting rod) to tapping (rocker arms) at idle. A
dull nock when the engine is under load (accelerating) indicates a bad main
bearing.

Sounds to me like a bad rod bearing. How's the oil pressure? Should be
around 40-45 psi.

Force 5

"la" <e...@e.nne.net> wrote in message

[SCOOTERTRS]

Your Z71 probably has an oil cooler. Your oil is probably bleeding down from
the cooler into the crankcase... due to porosities in the oil filter mount body
(has a couple of checkvalves to stop the bleed down... but overnight, it
happens)

My '93 did it and I got the same story from the dealer... normal. Finally, at
over 120,000 miles, I decided to drop the oil pan and check (noise had gotten
no worse!!! nor better)... results? Mains and rod bearings had minimal wear...
bearings were reinstalled. oil pressure 45-55 psi (w 10-30W) The only thing I
did to improve it was to sleeve one of the passages on the oil filter housing
(was very porous and could actually see the chambers that were supposed to be
separated by check valves actually bypassing into each other) This helped
reduce the knocking, but did not eliminate it.

Now I have over 200,000 miles on the truck and guess what, it still knocks once
in a while... but it does not smoke, nor use any oil (less than 1 quart every
religiously done 3000 mile oil change)

I bought a new tahoe in 1997... it does the same thing once in a while. I read
somewhere that the knocking you hear upon cold startup is actually the anti
knocking sensor getting its setting? This came out of a service manual...
cannot remember where though.

But the way I figure it is, if I am getting 200,000 miles plus on the same
engine that is knocking, can you imagine how far it would go if it did not
knock?

good luck... and if you find the solution, do not keep it to yourself... I for
one would love to be rid of this knocking once and for all!

[DW]

While any knock in an engine is something to worry about, this problem is
more directed toward the new 5300 engine. About 6 out of every 10 owners
are experiencing this cold start-up knock. About a month ago, one poster
told his story of a dealer checking the rod clearances and finding them
excessive according to specs.(with less than 500 miles on the new rig). As
for the "knock sensor" getting it's settings, on a cold start the knock
sensor is not part of the ECM equation. Until an engine reaches operating
temps it is in open loop and the timing is fixed. The engine operates on ROM
set of parameters.

"SCOOTERTRS" <scoot...@aol.comsayno> wrote in message
news:20000916222804...@ng-ch1.aol.com...

[Tom Goffredo]

It looks like GM made changes to the 4.8 & 5.3 engines for the 2001's to
correct a cold start noise problem. Checkout the "Vortec 4800 and
Vortec 5300 V8 Improvements" section of the following web page (2001
Yukon Overview).

http://media.gm.com/gmc/yukonov.html

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[SCOOTERTRS]

Thanks for the info. According to the site, GMC states that:

Vortec 4800 V8 and Vortec 5300 V8 Improvements

A major round of upgrades benefits both the Vortec 4800 V8 (standard engine for
Yukon) and the Vortec 5300 (available in Yukon and standard in Yukon XL) this
year.

Main bearing tolerances have been tightened to quiet these engines after a cold
start. Noise and vibration are also reduced by an intake manifold revision that
results in better isolation of the fuel injection solenoid.

That is nice. The new trucks will supposedly not have the cold start knocking
problem many of us have all been putting up with in the last ten years.
Somehow it is not comforting to know that even though GM knows it has a problem
(they wont fix what is not broken right?) they still fight you when you bring a
truck to take care of it.

I guess if the cold start problem reappears for model year 2001, you can always
wait for model year 2002!!! They really really will have it taken care of by
then... Unless of course, if they do not, there is always 2003!!!!

[UnderTaker]

I too had a 94 Chevy Z71 with the 5.7 L V-8 and it knocked on every cold
start for a few seconds, but it must not have been damaging the engine, My
truck had 217,000 Miles when I sold it...while annoying the sound was, my
truck still ran great !!!

"High Sierra" <gew...@nbnet.nb.ca> wrote in message
news:T46z5.4726$gK3....@sodalite.nbnet.nb.ca...
> This problem is not new. I think it's common to most GM small blocks. At
least that's how I remember it.
>
> I have a 89 S15 4.3L that is noisy for a few seconds in the morning. It
soon quiets down. I've had it since 91 and 70,000km and it cane with this
slight knocking, it still knocks the same with 260,000kms.
>
> I used to worry about it, but a mechanic told me, in 91, that this noise
was common in small blocks. He called it piston slap or wrist pin knock.

>
> Remove antispam from address to reply.
> For NG please reply to group only.
> High Sierra

> 89 S15 Sierra Classic 4X4 4.3L Short Box
> 91 Dodge Shadow 2.5L 5 Speed
> 94 Grand Caravan 3.3L

> "SCOOTERTRS" <scoot...@aol.comsayno> wrote in message

news:20000923051109...@ng-md1.aol.com...

[High Sierra]

This problem is not new. I think it's common to most GM small blocks. At least that's how I remember it.

I have a 89 S15 4.3L that is noisy for a few seconds in the morning. It soon quiets down. I've had it since 91 and 70,000km and it cane with this slight knocking, it still knocks the same with 260,000kms.

I used to worry about it, but a mechanic told me, in 91, that this noise was common in small blocks. He called it piston slap or wrist pin knock.

Remove antispam from address to reply.
For NG please reply to group only.
High Sierra
89 S15 Sierra Classic 4X4 4.3L Short Box
91 Dodge Shadow 2.5L 5 Speed
94 Grand Caravan 3.3L
"SCOOTERTRS" <scoot...@aol.comsayno> wrote in message news:20000923051109...@ng-md1.aol.com...
> Thanks for the info. According to the site, GMC states that:
>

> Vortec 4800 V8 and Vortec 5300 V8 Improvements

[OLAF THUNDERFOOT]

I put a new 350 in my 69 and it had the same noise, it's a typical GM thing

Yours in Thor

Olaf

[Credence Vision Systems]

It's your lifters pumping up. After sitting cold, they need a bit of oil
flow to pump them up. You hear a light clatter when the motor starts, but
it should go away in less than about 2 seconds (or even less).

"OLAF THUNDERFOOT" <olafthu...@aol.com> wrote in message
news:20001022123048...@ng-cv1.aol.com...