OS Vortec 5300 ?

[GlennBrittain]

I realize this is off the subject of this board, however I feel like there are members that this post applies to. I recently had two problems with my wife’s 2003 Z71 Tahoe, with a Vortec 5300 Flex Fuel. The first problem was the four wheel drive went out, no light on the dash to indicate what state the drive was in either. The part (module 4.563) was $275.28, and the labor was 229.50 to install it. I did purchase an extended warranty which covered all but the first $100.00. Needles to say I ordered a shop manual.
The second problem was a knocking sound when first started. This was explained as a carbon build up on the pistons. I was charged $6.74 for a can of carburetor cleaner and $79.95 to pull the plugs and put the cleaner directly into the cylinders.
Has anyone had a similar problem with the knocking or heard of this problem, not sure if I trust this dealers service department.
If anyone has a similar problem with their 4WD, they can contact me, via email for replacement info, I should have the shop manual soon.

[68haywagon]

Seems to be a "common" problem called piston slap . Anyway heres a link

Goodluck,
Mike

[Joe67]

The knocking sound has been called pistion slap or 'Cold Start Knock'. It's been debated on the internet for years.
I have it on my 2000 5.3l and after 130K Miles, there are zero problems.

I thought it was corrected in 2002 but I am not 100% on that.

Regarding the 4x4 indicator, that is a common problem. My 2000 4x4 lights went out, I bought a new 4x4 dash pushbutton assy from GM for $40 and fixed my problem. Maybe yous was more serious?

[Joe67]

One more thing, if your dealer charged you that to correct the 'knocking problem' they need to give you a refund

Here is a GM TSB on the issue:

===========================================

http://esiwip.spo.gm.com/servlets/Bl...bid=271&evc=sm


Info - Engine Knock on Cold Start #01-06-01-028A - (03/18/2003)
Engine Knock on Cold Start
1999-2002 Chevrolet and GMC C/K Pickup and Utility Models

2002 Cadillac Escalade (2WD)

with 4.8L, 5.3L or 6.0L Engine (VINs V, T, Z, U -- RPOs LR4, LM7, L59, LQ4)

This bulletin is being revised to add an additional engine to the models section. Please discard Corporate Bulletin Number 01-06-01-028 (Section 06-Engine).

Some of the above vehicles may exhibit an engine knock noise that begins in the first 19,000-24,000 km (12,000-15,000 mi) of use. The knock noise is most often noticed during initial start-up and typically disappears within the first 5-30 seconds (may last longer in extreme cold temperatures). The noise is usually more noticeable on the initial start-up when the temperature is below 10°C (50°F) and may be more pronounced on the first cold start following a long trip.

This noise may be caused by an interaction between carbon that has formed on the piston, the piston motion and the cylinder wall. GM Powertrain Engineering, and an analysis of engines with this condition, has confirmed that the noise is not detrimental to the performance, reliability or durability of the engine. THIS NOISE DOES NOT HAVE ANY EFFECT ON THE LONGEVITY OF ANY OF THE ENGINE COMPONENTS.


Important
At this time, attempts to repair this condition by replacing the engine assembly or pistons are not recommended.


Please share the information found in this bulletin with customers who inquire about this condition. In the event they have additional questions or concerns, please advise your Area Service Manager.



GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION


© Copyright General Motors Corporation. All Rights Reserved.

[67ChevyRedneck]

Holy crap. NEVER seen or heard of any of this. I'm lookin' for a 01-02 Z71 with the 5.3 I guess if it doesn't make the noise, most trucks I've looked at have had about 45K on them, I guess it will be ok?? Will running a better fuel like 89 help this? That sucks about your Tahoe....did they tell you anything as far as future prevention????

[Joe67]

Octane has no affect. I do know of a few guys that got GM to replace the engine assembly at no charge, but those cases are rare.

Personally, I don't see it as a problem

[GlennBrittain]

Thanks for the info, since mine is an 03, they either did not fix the problem for 03 or it has an 02 engine in it. I am not sure now what action I need to take if any. I have 55,000 on the engine already. I doubt they will replace it.

[busterwivell]

I personnally don't worry about it. My wife has 160K on her 96 Tahoe, it's had the piston slap from new, and still runs fine, uses no oil, etc.

[72shadetree]

ive got a 04 tahoe that has it with 6000 miles.just picked it up from having the gauges replaced and the transmission worked on.also got a viberation in it when its in gear and the brakes are held like at a light or stop sign.today the gm rep was down there and said it was normal.bulls@#t im about sick of gm and the tahoe

[incoma]

Piston slap is caused by the differing rates of heat dissipation between the piston metal and the metal in the block. Basically, the piston contracts more when cold then the block bore, so when you initially start the engine the skirts "slap" the block bore. As soon as the engine begins to heat up, the piston "expands" into the bore and no more problem.

GM says they changed the alloy used in the pistons to fix this problem in later years because of the intrinsic value of not having that noise in a new vehicle. It hurts marketing.

At least, that's what a metallurgist at work told me about 2 weeks ago.

[72shadetree]

Just went to the store on the tahoe and the message display is saying "Service Brake Booster" The wife called GM and raised h*ll she is really ready to buy a f@#d. Now we have to wait and see and play games with not only the dealer but GM too.

[Dean23]

ADDING CLEANS TO AND EGINE TO REMOVE CARBON IS A NORMAL PROCEDURE AT A GM DEALER oops sorry for the caps. The knocking sometimes is not piston slap but as your dealer said carbon build up. I work at a dealership and have seent he light knocking issue resolved with cleans run the engine. If the knocking persists and gets worse I would contact your dealer about the problem

[VetteVet]

The bull that GM put out is just that. If you read this article in the website below. We've always believed that Piston Slap was caused by the skirt hitting the cylinder wall when too much clearance between the piston and the cylinder wall occurs. It causes the piston to rock under load. Carbon has no bearing whatsoever on piston slap. In the old days of leaded gas carbon buildup was much more of a problem than nowadays. I have seen the tops of pistons covered with carbon and not produce piston slap. I believe the manufacturing tolerances were too great on the cylinder to piston wall and that would create this problem. As usual GM won't take the blame until they are sued.

http://www.pistonslap.com/whatisit.htm

Vettevet

[Eddie H.]

Originally Posted by 72shadetree

Just went to the store on the tahoe and the message display is saying "Service Brake Booster" The wife called GM and raised h*ll she is really ready to buy a f@#d. Now we have to wait and see and play games with not only the dealer but GM too.

You just think you have problems now. Go ahead and buy a Ford. I work on them for a living. That's why I own 3 GMC's