Valve train noise at startup. (Page 1/1)
Hank is Here NOV 26, 09:08 AM
I have a 2002 Chevy Silverado pickup with a 4.3 V6 and 180,000 miles. Recently at cold startups there has been a loud tap from the valve train, after 1-2 minutes the notice goes away. This doesn't happen with starts when the engine is warm. My best guess is that there is a sticky lifter and once it warms up the problem goes away, just my neophyte guess. The noise is defiantly not from the lower end of the engine; it is not like the CSK (cold start knock) in some of the 5.3's from the period.

Is anyone aware of any magic fixes which would not require taking the top end apart?

On Friday after the noise became apparent I put in 1/2 quart of dextron II in the engine and ran it for ~40 miles. I then changed the oil and filter.

To me it seems there are two paths forward with magic fixes. 1) fuel and additives. 2) oil and additives.

For fuel I was planning on running a tank of 91 octane for the higher detergent levels in addition to adding to cans of Seafoam into the tank (34 gallons).
For oil, I already put into fresh 10-30W. I am thinking of putting in anther additive...I am not sure what I should add. From my amateur mind I'd like to find an additive that still may have some zinc (zddp) however I am unsure if there is anything still no the market. Would a good old Lucas oil additive work well?

Am I going down the right path for the problem? Any and all recommendations are appreciated.
Monkeyman NOV 26, 12:17 PM
I'm going to say a lifter is leaking down. As long as the noise goes away and you don't beat on it or rev it until the sound goes away, I think you'd be ok. The 4.3s are damn near bulletproof. I had 171k on that motor in a '96 Jimmy and currently have just under 90k on my '04 Blazer with the same motor.
NJD85GT NOV 26, 08:39 PM
My '97 S10 with the 4.3 (134,000 miles) does the exact same thing on cold startups when it's below 40 degrees out. I just let it idle till it goes away after about a minute. It's done it for the last five years / 60k miles, no change in those five years so I don't worry about it anymore. I've been told it could be piston slap, but more likely it's a worn lifter. And now that my garage stays 60 deg in the dead of winter it only does it on a snowy day after work.

I tried seafoam, marvel mystery oil, and some other cleaners / additives a few years ago and they didn't make a difference.

Nate

------------------
1985 GT | 4.9 Allante | M17/MY8 Hybrid 4-Spd Muncie | '88 GT Cradle Swap

[This message has been edited by NJD85GT (edited 11-27-2012).]

carnut122 NOV 26, 09:31 PM
^^^I'll go with his advice. Lifter or piston slap. My 94 with the 4.3 is also noticeably louder upon start-up when it's cold out. I ignore it and go on (shrug). If the motor blows, I'll buy a long block and try to get another 19 years out of it.
weaselbeak NOV 28, 01:41 AM
I had this problem on a very high mileage 350. Cold oil was too thick. I went to synthetic 5-20 (in spite of old motor warnings) and the problem went away. And, no, it didn't start leaking all over the place.
rogergarrison DEC 08, 09:46 AM
Ive had older cars that tapped all the time because of wear and bad lifters that ran 75,000 miles like that. You might just run some Mystery oil thru it before a change to try cleaning it out first. You could put an additive like Lucas or STP in new oil to cushion it a bit.
mwzephyr JAN 10, 04:59 PM
My money is on the lifters. I had that problem on a couple of old high mileage v-8 Lincolns.
The first one I put new lifters and no more noise. Yeah it only happens to a dead cold engine. Last one I just upped the oil to 10 w 40.
Kept me running.
~Zep
2.5 JAN 18, 01:16 PM

quote
Originally posted by weaselbeak:

I had this problem on a very high mileage 350. Cold oil was too thick. I went to synthetic 5-20 (in spite of old motor warnings) and the problem went away. And, no, it didn't start leaking all over the place.



Thinnest at start up would be 0wXX, such as 0w30. I wouldnt use a Xw20 because at operating temp It may be too thin. But basically a good rule of thumb is if you have 10 psi of oil pressure per 1000 rpm (at operating temp) you are good.
2.5 JAN 18, 01:18 PM

quote
Originally posted by rogergarrison:

Ive had older cars that tapped all the time because of wear and bad lifters that ran 75,000 miles like that. You might just run some Mystery oil thru it before a change to try cleaning it out first. You could put an additive like Lucas or STP in new oil to cushion it a bit.



Something that cleans like Mystery oil, or valve medic wouldnt hurt, if it is build up that is the problem. IMO if your oil gets real dark on the dipstick within 2000 miles the inside of teh engine needs cleaning.