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Username Post: Engine knock 97-99 vortec 5.7        (Topic#50928)
59 EWW 
Very Senior Member
Posts: 1871
59 EWW
Loc: Kansas City Kansas
Reg: 08-31-03
11-26-03 11:33 PM - Post#344291    

I thought I would bring this topic up in this forum also to see it anyone besides me was having [cold knock startup] on there 1997-1999 vortec 5.7 engines. This is quite common on the late 1999 & up.


59 Biscayne 2dr
65 Elcamino
97 Z71,K1500,5.7
06 GMC Canyon

Low priced Genuine GM Auto Parts

Re: Engine knock 97-99 vortec 5.7
11-27-03 12:16 AM - Post#344292    
    In response to 59 EWW

My 98 gmc with a 5.0 does it.


Re: Engine knock 97-99 vortec 5.7
11-27-03 06:06 PM - Post#344293    
    In response to

Well mine did that until I used MM OIL but that was a lifter. I know what your talking about tho, I swear everyone of those do it, I dont know why but they do. Someone have an explanation?


Re: Engine knock 97-99 vortec 5.7
11-29-03 12:15 AM - Post#344294    
    In response to

Its got to be they made the clearances super tight on these newer motors. If I run 5w30 mobile one it will only knock if the trucks been sitting for along time and the outside temps below 25 F and only for a super short time, usually 1 to 2 min tops.

If I run 10w40 oil it knocks every crank then stops about 3 min into warming up.

Super Senior Member
Posts: 4157
Loc: South Florida
Reg: 06-27-03
Re: Engine knock 97-99 vortec 5.7
11-29-03 01:44 AM - Post#344295    
    In response to 59 EWW

This was quite common in that engine in the trucks. Did a lot of them. Here's the bulletin on the topic. I'm not including the correction procedure because it's pretty involved and not something the average person is going to be able to do. This is NOT the piston noise that the Gen III engines are exhibiting. This is usually a very heavy knock that last for a very short time. Usually a half dozen knocks or so and it's gone.

Engine Bearing Knock Noise (Re-suppport Crankshaft, Select-fit Rod Bearings) #99-06-01-003 - (03/29/1999)
Engine Bearing Knock Noise, (Re-support Crankshaft, Select-fit Undersize Connecting Rod Bearings)
1999 Cadillac Escalade

1996-99 Chevrolet and GMC C/K, G, P Models

with 5.0L or 5.7L Engine (VINs M, R - RPOs L30, L31)

GM Canada Dealers require prior DSM authorization to apply this bulletin.

Some customers may comment about an engine "knocking" noise.

A condition may exist in some engines where, the crankshaft is NOT being evenly supported by all five crankshaft bearing inserts. In these engines, the number 1, 2, 3, and 4 crankshaft bearing inserts are supporting the crankshaft, and the number 5 crankshaft journal (rear) has excessive clearance relative to the number 5 crankshaft (main) bearing cap insert. In this condition, the crankshaft flexes under load, and pounds on the lower number 5 crankshaft (main) bearing insert creating the knocking sound. The engines were originally built with 0.0006 in. undersize crankshaft (main) bearing inserts in the number 2, 3, and 4 crankshaft (main) bearing locations and 0.001 in. undersize insert in the number 5 crankshaft (main) bearing location. The service procedure listed below addresses the above condition by lowering the crankshaft at the number 2, 3, and 4 crankshaft (main) bearing positions (increased crankshaft (main) bearing size of the lower crankshaft (main) bearing inserts) and raising the number 5 lower crankshaft (main) bearing insert (undersized insert) in order to properly contact the number 5 crankshaft journal surface.

These engines may also exhibit a connecting rod knocking sound. In these engines, the connecting rod knocking sound is caused by excessive connecting rod bearing clearance.

A customer concern vehicle may exhibit one or both of the above stated conditions.


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Posts: 6720

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Re: Engine knock 97-99 vortec 5.7
11-29-03 05:21 AM - Post#344296    
    In response to GM-Tech

My '98 K3500 454 did that also, sometimes with a miss to go along with it almost from new.
Mike W.

Founding father Desert Classic Chevys in Phoenix, Az.

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Very Senior Member
Posts: 1264
Loc: Drumheller, Alberta
Reg: 08-10-02
Re: Engine knock 97-99 vortec 5.7
11-29-03 05:59 AM - Post#344297    
    In response to 57_sedan_delivery

I think I know the noise you are referring to. I've heard it in older,high mileage engines as well. I asked my machinist about it once and on some rebuilt engines it is a result of the excessive front to back movement of the crankshaft. The excessive clearance is at the thrust surface of the rear main. I have seen the problem area on a few crankshafts - it is at the flange behind the rear main journal. There are bearings available with a thicker edge that will reduce the movement of the crank. This is more prevalent in vehicles equiped with standard transmissions but can also happen with automatics.

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Re: Engine knock 97-99 vortec 5.7
11-29-03 11:26 AM - Post#344298    
    In response to 59 EWW

My '96 burb does it now that the temps are below 30*, only after it's sat overnight. I've also got 203,000 miles. Goes away pretty quickly.
My "To Do List" for this weekend:
Nothing but womens names...
and drugs....

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59 EWW 
Very Senior Member
Posts: 1871
59 EWW
Loc: Kansas City Kansas
Reg: 08-31-03
Re: Engine knock 97-99 vortec 5.7
11-30-03 08:29 PM - Post#344299    
    In response to GM-Tech

Hey GM-Tech

My 5.7 has about 80K on it , when it's cold the knocking can be heard until the engine temp gets up to at least 150 degrees and then goes away, also you hear it knock 3-6 times on every hot restart.

Was there ever any warranty work or recall on this engine problem for 96-99 5.7 engines?

Thanks Ernie

59 Biscayne 2dr
65 Elcamino
97 Z71,K1500,5.7
06 GMC Canyon

Always Chevy 
Posts: 1

Reg: 05-26-04
Re: Engine knock 97-99 vortec 5.7
05-26-04 10:47 AM - Post#344300    
    In response to GM-Tech

I have a 98 which has a deep knock on warm startup only. It lasts 3 or 4 knocks and disappears. Is this fatal to the engine or should I turn up the radio and ignore it.

Needs to Get Out More Member
Posts: 12906

Loc: Texas Panhandle
Reg: 12-31-01
Re: Engine knock 97-99 vortec 5.7
05-26-04 11:09 AM - Post#344301    
    In response to Always Chevy

I'm going to say this is just a tight wrist pin, a small amount of heat frees it up. I've seen dozens that have taken out of motors that you could hold the piston and the rod would be suspended by the tight pin, set the assembly in the sun for less than a minute and it was perfectly free.

Just don't load it till it frees up.

Frequent Contributor
Posts: 2145
Loc: DeSoto, Illinois. 62924
Reg: 01-21-01
Re: Engine knock 97-99 vortec 5.7
05-27-04 10:40 AM - Post#344302    
    In response to CDAUSA

At 97,000 miles my 93 5.7 started knocking on startup. Number 1 main bearing was bad. Had the original bearings in it. Replaced them with 1 unders after plasticgauging them. Every 3,000 miles I need to replace number 1 again. getting ready to do it again in about 500 miles--any help out there. This will be the 4th time. Have 2 more bearing in teh pack--so when they are gone I gues I will pull and rebuild it.

Forum Newbie
Posts: 1

Reg: 08-18-13
08-18-13 05:10 PM - Post#2373595    
    In response to GM-Tech

hi I have a tech question to this bearing issue with this 1996 5.7. I have a 1996 5.7 that needs bears rolled into it. 120,000 miles on it. I pulled out factory main bearings after plastic gauging them, and found #1,2,3,and4 mains are stamped .0006 US GM45 #5 is stamped GM A-400 .001 US 2-96. I installed a std. set of mains into the block plastic gauged the main and it came out .003. the original #5 gauged .002. what bearings do I need to install?

Low priced Genuine GM Auto Parts
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