GM ENGINE KNOCK

seelig

so what they are saying is that excessive bearing clearance is what's causing this "knock"........yes or no?

arkie6

In an earlier post, winkel (Nick) wrote: "As some of you might know, all metals expand and contract with hot and cold. GM is the #1 motor manufacturer in the world, and their motor boast more horsepower and torque than any other motor company in the world. To get the most out of their motors, they have to make the most out of the room they have to work with. there is only a 1000th of an inch in between the piston and the cylinder heads. Thus, when it is cold, the piston expands to fill up that 1000th of an inch, but when it warms up, the slap goes away. This problem is very rare. I work for a GM dealership in Reno Nevada...."

Nick, I'm glad you don't work in the service department because your explanation of the piston slap issue indicates a fundamental lack of understanding. You need to stay with sales. Metal, including the pistons and connecting rods expand when hot, not cold. Your theory that the piston is hitting the head is way off base. If that were the case, then it would only get worse as the engine heated up. My understanding of the issue is the type of material and shape of the pistons (hyper-eutectic aluminum alloy and very short skirts) is causing them to rock sideways in the cylinders when cold and clearances are greater. Ford went through this same problem with the 5.4 when it first came out. Also note that Ford 5.4 puts out more torque than a comparable GM 5.3. Shoot, even that little Toyota 4.7L puts out nearly as much torque as the GM 5.3L (315 ft-lbs vs. 325 ft-lbs) and the Toyota does it at a lower more usable RPM. And when you said GM is the #1 motor manufacturer, I assume you meant quantity, not quality.

Alan
Engineer and shade-tree mechanic

chevytruck_fan

the amazing thing is that the 5.3L get better milege than 4.7L, and if you look at the 5.3 torque curves at 3400 the Silverado is producing about 315 ft lbs toruqe, furthermore if you look at truck trends test between silverado and tundra, the Silverado always out accelerated the Tundra with 1000 lbs in the bed (well it also beat it unloaded), and the gap actually widened when loaded.

so no the 4.7L has no advantage whatsoever over the 5.3L, so why get the 4.7 when you can get a bigger engine with better milege?

ryanbab

bigger engine better milage = more efficient

ryanbab

Yes it does quad. I can atest to that

Quad we know which one is the best

obyone

#55 of 57 by ryanbab Nov 06, 2001 (08:13 am)
bigger engine better milage = more efficient

So we should all get the 8.1? Sometimes I truly wonder.......

lbrough

My 2001 Silverado has a pronounced engine knock after warm up and only under load. Since it doesn't make the noise when cold and only under load I suspect fuel mixture which would lead to think of a computer problem. It has done this since new now has about 8000 mi.

chevytruck_fan

that sounds more like a preignition deal, timing might be a tad off, or the computer isn't reading mixture right, might see if there are any codes on the computer (i.e. go to your dealer)

tiredofwaiting

To anwser the question, "so what they are saying is that excessive bearing clearance is what's causing this "knock"........yes or no?"
I held out for a 2001 Yukon when GM repurchased my 99 Sierra. I assumed at the time the 01 would be knock free, since they were tightening the bearings...I was actually surprised when it began knocking just like my 99. Everything I have read or heard is that it is piston slap. I am still unsure if GM is actually going to have a fix for it at this point.

Also in an earlier post someone questioned oil consumption in these engines. My engine doesn't use oil...another reason not to want a dealer to tear down my engine to replace the pistons. I drive only highway miles, I have heard the speculation that only the engines that are run short distances daily have high oil usage. I don't know if I buy that or not. However, I am sure there are a lot of owners out there complaining of high oil usage.

obyone

Don't think that short run distances have any relation to oil usage. Must have picked that one up at the dealer.....pretty good one to boot.

chevytruck_fan

I mentioned oil usage, what i"m saying is, if this was causing any damage oil usage would show it. but I haven't heard of one 4.8 or 5.3 or 6.0 with high oil consumption

knock1

at 7000 miles i sent my 30000 dollar gmc in for engine knock.the dealer would do nothing.I called gmc and they told me it was just fine.I filed with bbb at which time gmc called me and told me i had no claim.I told gm give a new engine or ill seek repurchace of truck.I had my hearing and won.The person at gmc was under the impression that because i only had it to the dealer one time it did not constitute a buy back.they were wrong.the value was lowered cause i couldnt sell it or trade it in.also a word to nick;remember the vega or the diesel engines in the olds or the 4 6 8 engines or the 4.8 in the caddys that were leaking antifreeze into the blocks.Well they were all made by gmc garbage motor corp

lbrough

I've had the truck to three GM dealers, the last one reprogrammed the computer.The other two said it was normal engine noise (bull). I agree the timing is the problem but how do you correct it when everything is computer controlled?

gator36

Timing on the newer engines, being computer controlled, is varied by engine changes.
Here, your most influential component in the
timeing is the knock sensor. I would ask them to
verify the operation of the knock sensor.
If your problem is indeed pre-ignition based upon
timeing. Try running higher octane gas and the
problem should be better.

Hope this helps.

themailman1

I just talked to the service manager and he said there is a new TSB on the engine knock that says it is normal. He said there is a carbon bulidup on the 7 and 8 pistons. They {GMC] are not going to do anything about it now.

4x4man

I thought the TSB only refered to the 6.0L. Look back at post 26 and it lists the TSB in full.

My knock has not gone away yet in my 8.1L, but 10 seconds is much more tolerable than the 30-45 seconds it was!!

Bob

markone

Today I recieved a call back from Chevrolet Customer Support. I had called last week after taking my truck in for the knock and other problems, (see post #43) and getting the, "It's normal" line of BS. I told the CSR about the GM webpage that mentioned the cold engine knock,

 http://207.37.252.232/gmc/lr4lm7ben.html

(BTW, thanks tiredofwaiting for that other link)

and today they offered a 5 year/100,000 extended warranty on the motor only. She also said that there will be an official fix coming out in April.

I told her I would have to think about it, what do you all think? Did any of you that did take the extended warranty offer, get it for the whole truck or just the motor?

obyone

Can't believe GM at times. What's the difference in cost to them if it was a bumper to bumper or motor only warranty? No one's going to lose any sleep over it at GM, yet they have to try and nickle and dime ya. I wouldn't settle for anything less than bumper to bumper and more importantly $0 deductible.

markone

On the 5 year / 100000 xtended warranty that you agreed to, was it bumper to bumper or motor only?

tiredofwaiting

I too am in negotiations with GM through the BBB over an extended warranty since my engine knocks. We have been going in circles they are only offering the motor warranty after the engine has had the pistons replaced. I am wondering if GM ever will replace the pistons....hence no extended warranty. I would take the warranty in lieu of the repair.....

Clay

seelig

at first it was the custom plan, but after the fuel guage incident a couple weeks ago, and the fact that Chriss Piacenti of GM had told me it should be covered, it was bumped to the major guard plan.
their first offer was a 5/75K, and i asked why not 100K since i put about 22-25K miles on it per year. Chris said no problem, as long as i agree not to go after a buyback deal on em. the engine has the rattling sound associated with bearing clearance, but does not burn oil, continues to deliver great fuel mileage, but the diesel like noise you hear when up against a building has increased in respect to when it was new. the service manager that takes care of me, has it documented. new engine would be fine by me.

themailman1

that engine is a 2001 5.3 z71 shortbed

obyone

the knock. Service advisor was reading it to me when I told him that it would be faster if I read it. It covers all conditions under which a knock would occur. Bottom line....its within specs...this is really getting old.

Seelig
Did you know that Major Guard will reimburse you for a vehicle rental should your dealer decide not to give you one. All you have to do is get a receipt, document the circumstances of why the dealer didn't give you a rental and they will reimburse you. Best one yet was when I filed for reimbursement, I had written as the reason the dealer didn't give me a rental was because "they didn't FEEL like it". That didn't go over well with the folks at Major Guard customer service.....not too sure what happened after as long as I got reimbursed.

seelig

and the rental car is offered, but as of yet, they never make me leave the truck. the part i like the best about this warranty, is that if i run out of gas, they will bring me some. does this mean free gas for the next 5/100?.....LOL

4x4man

When I was on my extended warranty (Major Gaurd) on my 97 Silverado 1500, if the repair was expected to last more than two hours there was a customer service number in the warranty booklet that you can call and get a claim number. Then you go down to the car rental place and give them the claim number to charge against and you don't pay anything, it goes directly to them for payment.

Speaking of warranty, when I was going to leave my truck to have the knock checked and documented, they stated I couldn't have a rental car for 24hrs. WTF?? I have to wait 1 business day for them to try to fix it before my bumper to bumper warranty will allow a rental car for me, yet my extended warranty (GM Major Gaurd) will give me one if the repair lasts more than two hours?? Sure makes sense to me....

Bob

gator36

They actually go by "Flagged" hours.
All repair work at a dealer has a "Flag"
time. It it the number of hours charged for
a given repair. They are standardized, so if
your repair will only take 1.5 hours and
they cannot get to it in one day. You are out of
luck. If you have several jobs to be done that flag
more than 2 hours total you qualify as well. It is
the same for the GMPP major guard as well.

markbuck

Read in this months trailer life that two sources of noise, one is the fuel injectors going into air hammer mode on start up and the other a failure of the oil anti-drainback system.

The Performance section of the magazine tells how to determine which if either of these are the source of noise on the new 8.1. There was a last comment of going to 20W-50 oil on the new 8.1

y2kgmc

My 2000 GMC Sierra 4.8 sounds like a diesel at idle ,first the dealer said it was carbon buildup because i was using too high a octane fuel and to switch to 87 octane and if that didn't work to leave it overnight for them to "soak it". It hasn't gotten better and now occasionally pings from the crap low octane fuel. the service manager said they would note the complaint but didn't have a fix, I am frustrated by the usual "Stroke Job" from the dealer personnel who believe that the general public are idiots. I have been to this point a blind ,stupid GM loyalist shame on me shame on all who have been sucked into GM's web of deciet

PAman

They can change their advertising tag line from "Like a Rock" to "Sounds like a Rock." Then they could change their other line from "the longest lasting trucks in the world" to "the noisiest trucks in the world."

Think they could then get Bob Seger and the Silver Bullet Band to re-record "Like a Rock" to "Sounds like a Rock"?

Joe

rayt2

Here's the quote from my recent service ticket from 11/12 dealer service dept.

Engine Repair: "Customer states the truck has a cold engine tap on start up and occasionally when warm."
"Checked for bulletins, none found. Called into T.A.N. no fix as yet. Chevrolet is in the process of working on fix."

I can only assume T.A.N. means Technical Assistance Network.
Well at least I'm on record now for whenever GM comes up w/this fix. If it gets worse or just before warranty expires I'll push for the 100,000 mile warranty.

Ray T.

bobmiller

sounds like a lot of us are getting this "tapping" noise when our engines are idling. I have a 2001 GMC Sierra w/ the 4.8 L engine. sounds like a bad lifter.
had the truck in 3 times to the dealer where i bought it. every excuse in the book and it still makes the noise - anyone else have any luck getting an answer or a solution to this problem from GM? I thought the 4.8L was improved for 2001 to get rid of this noise? anyone else feel my pain? let me know.

Bob

seelig

but i went to BBB, and ended up with an extended warranty courtesy of GM to ease my pain. to date, my '00 has 45K on the clock and doesn't burn oil, and has lots of power. my '01 sounds quieter, and it uses no oil as well. but then again, i had a '99 Tacoma before either of my chevies, and it sounded like the bottom end was going, but it never gave me a problem. i've just learned to except this new fandangled technology in engine noises, but i keep monitoring the noise.

frey44

I had a 350 c.i. Chevy that knocked for 186 THOUSAND miles...that's 186000 miles... with these problems: I had to replace one alternator [original Delco as Autozone's are JUNK], one starter [NAPA], one waterpump [Autozone], 3 radiator hoses [generic], and a new vacuum motor [Chevy dealer] for the heat riser. Oil changes with Castrol 10-40 every 3000 miles, using Fram filters. That is IT. I sold the truck; it is still running fine (with 233000 miles on it) QUIT WORRYING ABOUT THE KNOCK; DRIVE THE DARN TRUCK AND ENJOY IT. It will knock for a LONG TIME. BIG DEAL. You guys are a bunch of WHINERS. If you don't like the knock, go buy a Tundra...it will CLICK and WHIR...then you will WHINE ABOUT THAT...or buy a Ford and it will "tick tick"..and you will WHINE ABOUT THAT... Mercy...you guys should be driving PINK CAVALIERS...something you can handle.. The GM V8s are the best you can buy.

PF_Flyer

I understand your pain...

Just a reminder that the News & Views chat is on tonight (5-6pm Pacific/8-9 pm Eastern). Hope to see you there!

Tonight's topic is On the road again: Your best road trips in 2001!

http://www.edmunds.com/townhall/chat/newsviews.html

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Host

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bamatundra

Frey is telling BRAND NEW truck owners that their engines SHOULD KNOCK!!! I have always said - LOW EXPECTATIONS.

Is this what Chev meant by "like a rock" - Like a rock rattling around inside your engine?

edetor

I have a 00' 5.3 that knocked at cold start. After several visits to the dealer they agreed to a new engine which was replaced at 21k. I now have 24.5k and the engine is still quiet and this engine doesn't ping either. The service mgr. at the dealer has been helpful, they agreed to the new engine after I left the truck for a week at the shop and asked for the district rep to be contacted. Hopefully this engine will remain quiet.

modvptnl

Don't know what to say..........I actually agree with you.

It sort of sounds like the toy owners, though, when in the past they would say things like, "Who cares that the body is rusted/non existent, at least the motor still purrs like a kitten!!!" Or how about, "The head gasket problems were on the oooold motors and toy did give an extra warranty."

bamatundra

Actually, what this topic most reminds me of is the Ford F150s with piston slap. Ford was claiming it was normal and refusing to warranty their defective trucks.

Ford owners were picking on other Ford owners in forums claiming that they should learn to accept their defective trucks. Very similar, sad story.

txyank1

and none of them purrrrfect, I had pretty much decided that people obviously just lived with it. That is prior to a place to vent like here! I rarely took any back to a Dealer as none are convenient and I absolutely HATE going through the hassle. So I lived with the minor glitches too. Just like the Dealers (and Manufacturers) want us to. Now if I could just go back to that one I should have kept and have it brand new again...............

modvptnl

I think you're confused. I do not remember Ford saying it's normal. I certainly don't remember any Ford owners accepting the noise. I know I wouldn't have. Ford replaced the motors and in no way drug it out like GM is doing.

bamatundra

This is from http://www.f150online.com/forums/showthread.php?s=&threadid=8747

What fix has Ford developed to eliminate Piston Slap knock?

 If your vehicle is still under warranty, Ford will replace your engine at no charge;

 99 Model year vehicles will receive a brand new 2000 engine

 97-98 Model year vehicles will receive an FQR (remanufactured) engine

It sounds like to me if your warranty expired - you're screwed. Ford took 2 years to admit to this problem so many Ford owners took it in the shorts. Typical Ford schlock quality!

modvptnl

You actually had to go to 1999 and find this info???? Grasping for straws???? The fact remains that Ford acknowledged it and replaced motors. The reason that some got FQR motors is simply that there were changes on the '99 motors and the '97-'98 were out of NEW production. I'd still rather have a factory longblock than have the dealer attempt to put new pistons in.

As far as being out of warranty........I have mixed emotions. it seems that if the problem didn't show up within 36,000 miles there could be MANY other things that could have caused the slap/knocking. Lack of maintenance comes to mind.

You sort of need to face some facts yourself there, bama. While skimming your 2 YEAR OLD LINK I couldn't find any Ford owners that said to "accept" the slap/knock" seemed like there were a few happy owners that got brand new motors.

Keep digging.

bamatundra

Take a few deep breaths. Calm down!

1. The people posting to this topic have a problem with engine knock. So did the F150.

2. It took Ford over two years to admit to the problem. Does this sound familiar?

3. Ford told owners whose warranty expired in the meantime - Tough Luck!

4. This is coming from the company that did not admit to Firestone tires until many people were killed.

If you don't learn from history, you are destined to repeat it. I think that the GM owners to this site could learn a lot from the Ford piston slap fiasco.

1. Keep documentation of your engine knock issue. Insist that the service dept. write up of your requests to get your knocking fixed. Keep copies of these records while your truck is still in warranty.

2. Keep records of all your phone conversations with the dealer or manufacturer.

3. Don't give up - the manufacturer and the dealer are going to try their best to wear you down on this issue.

Good Luck!

rayt2

If the shoe fits, wear it! When you bounce from topic to topic in something totally unrelated to you for the sake of arguing & stirring up hostility in people with YOUR Beliefs then I would say your a loose cannon and need some anger management lessons. Your like road rage on a computer.

Post 96 was probably the most usable post I've read from you and could be helpful to those who may be getting shafted by dealers/manufacturers. I personally went thru a lemon law buy back w/a GM product in 87, documentation and persistence is what helped me win my case.
Those coments may be appreciated but tooting your horn and bashing GM owners doesn't belong on this board from someone who doesn't own one, we can bash each other quite well on our own thank you!

Ray T.

modvptnl

Why do people when shown their lies change the content????

1) True, but Ford DID acknowledge it and replaced motors. GM is still in denial. Besides, your original comment was that Ford owners had said to live with the knock like some GM owners which is where I called you out. You then found a 2 year old post that said Ford DID replace motors. Sorta shot yourself in the foot there.

2) Admit or fix???

3)Not true if was documented. If the knock came up after 36,000 and you didn't buy the extended warranty you were probably SOL. Did you know you could buy the extended warranty UP TO 36,000 miles?

4)Whole 'nother can of worms. Does deeeep pockets and ignorance have anything to do with the blown out of proportion fiasco?

Read the first paragraph of post #97. It does characterize you to a T.

obyone

to describe the poster of #96 is the word troll.

playdough

Anyone have a recommendation on dealing with GM to offer an extended warranty on the cold start engine knock?

They're currently offering to cover the engine, if it should fail due to something related to the knocking, for 60 months/60000 miles.

Since I plan on keeping the truck for at least 10 years, I think 72 months/100000 miles is more reasonable.

Does anyone have recommendations on negotiating with GM for extended coverage on engine knocks?

Thank you.

plutonious

playdough, I don't mean to interrupt your question, but it relates to something I want to ask obyone.

obyone, why should playdough want an extended warranty of either 5/60K (Toyota's standard warranty, BTW) or even 7/100K when Chevy is "The most dependable, longest lasting trucks on the road" ?

HAVE FUN WITH THIS ONE NOW!!!

chevytruck_fan

seems to me that mfg have to put extended arranties on vehicles people don't want to drive because of reliability, lets see hyundai and kia, well toyota extended the warranty, must have been because everyone is scared of their scketchy reliability history (rust, head gaskets, oil sludge and oil consumption etc),

obyone

You have the information incorrect as usual. Check your warranty. It is not a bumper to bumper 5/60 rather a 3/36 like GM. Toyota does offer 5/60 only on its drivetrain which in the case of playdough would not be of help.

Why do I have to explain Toyota's warranty to you since it's in front of your face. Geewhiz, dude, take the time out to read your manual...DOH!!

GOOD LUCK ON THIS ONE NOW!!