"Cold-start tapping is normal..."

[KMeloney]

Hey all,

 

I don't think my '02 Tahoe did this all along, but recently I've noticed a loud tap upon starting my truck -- especially now that it's getting cold here in PA.

 

The tap begins with cranking the engine, and usually goes for approximately 10 seconds before fading out completely. Thinking this can't really be good, I stopped by my local Chevy dealer to ask about it.

 

The service manager said it was completely normal, said that it's just the injectors finring, and showed me a "completed" work order where an '01 in for the same thing received the same comment. He then asked me what kind of gas I was using, and when I replied nothing less than 89 -- and usually 92+ -- he told me that the engine was designed for 87. (He made it sound as though the octane of gas I was using was contributing to the tapping, though I'm not convinced.)

 

So... Is this tapping, in fact, "normal"? And does GM, in fact, have no remedy for it? Does it have to do with the injectors firing, and should going to strictly 87 octane gas eventually correct the condition? (As far as I'm concerned, "normal" does NOT necessarily mean "good", and I'd like to know if there's some harm being done here.)

 

Also, has this topic already been discussed here a million times? If so, please direct me to some posts about it as I have clearly missed them.

 

Thanks!

 

-Kirk

[chevy4x4trucks]

What you describe sounds like a cold start knock and it's normal... not just on GM Trucks but on pretty much every car and truck out there.

 

 

A few months back CMNTMXR81 got really detailed about it and he might be able to clue you in a bit more.

 

 

BTW, I'll get a bit of a knock at start up if I leave the truck sit outside overnight when the temps get really cold.

[foghorn23]

Sounds like you might want to look at a couple of old discussions: Unfortunately, this is a common problem with the new body style trucks. Good luck

 

Vroten

 

CSK link #1

 

CSK link #2

[chevy4x4trucks]

Unfortunately, this is a common problem with the new body style trucks.

It's not just w/ the new body style trucks. Most cars and trucks do it. My mom drives a Plymouth Grand Voyager and she gets CSK. My Uncle's Dodge Ram does as well. Heck, my ex-girlfriends Mitsubishi something or other did it too.

[lrymal]

Decades-ago, when I was a, ummmm, kid, I had a 383 Magnum Dodge Challenger. It would thrash and sound like a diesel for 2 to 3 minutes. It would quieten up and did this, every day, until I traded the car in during the Arab oil embargo in '73 when gasoline tripled in cost within one month.

 

Anyway, I was told by several of the older guys (back then), that this was normal and involved the hydraulic lifters having to get their oil and were noisy and the piston skirts. Sure enough, the 383 would quieten down as warmed up.

 

So, when I read these messages, and hear a truck with the so-called CSK, I don't hear anything that sounds unusual to me due to V-8s of years ago.

 

Now, what you guys are calling a knock is NOT what I call a knock. A real knock that sounds like two wooden dowels tapping against each other is the sound of which I would shut the thing down and wrecker-haul the truck to the shop. There is something wrong. But, the tap-tap-click-tap-tap-click-click type sound is what I have heard since the early 60s on a warming up mother and thought it was normal.

[KMeloney]

Unfortunately, this is a common problem with the new body style trucks.

It's not just w/ the new body style trucks. Most cars and trucks do it. My mom drives a Plymouth Grand Voyager and she gets CSK. My Uncle's Dodge Ram does as well. Heck, my ex-girlfriends Mitsubishi something or other did it too.

Thanks for the "reassurance" -- but I'm not buying that most cars and trucks do it (since I've never heard it in any of my cars/my folks' cars). I have an '01 Z06 and '97 Jeep Wrangler, and neither does it. My mom's Caddy doesn't do it, either. I can go on...

 

Also, I first heard it when it was still above 60 degrees outside. Not exactly a "cold" condition (though I understand that the "cold" refers more to the first start than outside temp).

 

I'll buy that it's due to a newer engine design. I'll also buy that it isn't harmful (maybe). However, I won't accept that it happens to most cars/trucks, and won't accept that it's something that I should have to live with.

 

Hmm... I'll keep watching to see if GM comes up with a solution.

 

Thanks for the replies, folks!

 

-Kirk

[Nick2000Gmc]

My 5.3L does it too, Especially in cold weather, i think part of the noise that you guys all hear is the engine fan clutch disengaging and re-engaging ( I notice this because i'm up here in Canada, WE INVENTED THE COLD ( AND HOCKEY ) ), Anyways I only notcie for the cold 6 months of the year, in the summer it runs fine, I know up here they dealer puts in 5w30 (*might help a little *). I also have heard that the guys that drive there truck easy get the knock more than the guys who stomp on it. Don't know if this is true but sure like to hear what everyone else thinks

[Wingnut]

I am on my 10th truck, they have all been Chevrolet, or Toyota products.

 

I have NEVER had this problem, EVER.

 

Neither have any of my friends relatives, or girlfriends in any of their cars (all across the brand and model spectrum.)

 

This forum is the only place I have ever heard of it.

 

I will have to stay on the "not normal" side of the fence.

 

If I were you, I would have him (stealer) start one on the lot, and ask why it's not knocking. Then throw a fit until he gives you the 100k warranty for free.

[2k3TahoeZ]

I've got the knock in both my LS1 variants. The camaro's knock is worse than the Tahoe's, but they both settle down pretty quickly, so I am not too concerned either. I have 75k warranty's on both of them. If something is gonna go wrong, it will go wrong by then.

[frdfandc]

All hydrualic lifter equipped engines exibit some type of lifter bleed down. Some more than others. The lifters must have oil pressure present to be "pumped" up. When the lifters are not "pumped" up (filled with oil) they can become noisy upon startup. Manufacturers have now put silicone check valves in the oil filters to help prevent lifter noise upon cold startup by holding oil inside the oil filter after shut down.

 

If you use an aftermarket filter (non-AC Delco) it might not have a check valve in it. But if your engine does have some noise upon cold start up, its a normal thing.

[Elwood 2000]

This is a common problem, especially amongst the newer generation GM trucks, but guys, I drive my truck like I stole it and I have had no problems. Yes, I have a little knock upon start up, but no problems yet.

 

A guy I know has over 200,000 miles on his 5.3, he changes his oil every 10,000 miles or whenever he remembers, he drives like he is on the Craftsman Truck Series, and he is in Drive after starting the engine within 1.2 seconds with his foot on the gas.

 

He has had ZERO engine problems. Factory fuel filter, Factory spark plugs, tranny fluid/filter, etc.

 

This guy would skimp on putting gas in the thing if he could!!

 

My point is, this truck is severely used, nearly abused and he has had ZERO problems with it. My advice is to drive the thing and not worry.

 

[pacodiablo]

Oil every 10K would be abused, and it will likely catch up to him one day.

 

I would not worry too much about CSK...I have never heard of any kind of engine failure due to it, just a noise.

 

Noises do happen on many vehicles. The Ranger developed the typical 3.0 Ford acceleration ping a long time ago. It makes a noise, but the engine runs fine. The 3.0 with all of its noises also happens to be a fairly reliable engine.

[Wingnut]

Oil every 10K would be abused, and it will likely catch up to him one day.

He is already over 200,000 miles, and it will "catch up to him"?

 

I think he outran it.

 

Seriously....That is abuse.

 

Mine is smoking when I mash the go-pedal now. And I only have 40k miles.

[pacodiablo]

Well, damage has probably been done, and it has not been noticed yet. At the place I used to work at we had an Econoline with a 351 and it had an oil change whenever (usually around every 15K). It ran fine for a while, years actually, then it started having tons of problems. It would have run a lot longer if it had been maintained properly.

[HillHound]

I don't know. My 2001 Silverado 5.3L had a terrible CSK that started around 8000 miles and got worse as time went by. At it's worst, I could hear it inside the house when my wife started it. One time when I was leaving work, a co-worker in the parking lot flagged me down and asked me if that was my truck making that noise. On the up-side, after it warmed up it ran great and didn't seem to suffer any performance loss. Had it back to the dealer and got the "it's all normal and fine" routine.

 

I changed the oil every 3 to 4 thousand miles and even wasted the extra $$ to use synthetic. No use.

 

The question I always go back to is; "if it's normal, why don't all the 5.3Ls or 6.0Ls do it"???

 

My wife's Chevy Trailblazer 4.2L I6 doesn't do it and my F250's 6.8L is still quiet on start-up after 17K miles. Neither of the S10 Blazers with V6 4.3Ls did it. My cousins 2500 Silv with 6.0L is as quiet as can be after 40K miles.

 

I didn't get rid of the truck due to the noise but it sure as h*ll didn't hurt my feelings to not have to hear it .