chevyman108

My 2001 Tahoe has lifters knocking when first started. Anyone else experience this problem?</P>

hughmcc

I have a 99 Tahoe.4WD..v8. When I start it up in the morning I get the tapping noice I assume is a lifter problem. Normally after about 1 to minutes it goes away. BUT sometimes it goes for maybe 5 minutes. If I stay home on the weekends and not run it for a day or so I can almost be sure it will be noisy when I start it. One shop said a lifter job would be $1000. A work associate offered that perhaps the screen on oil pump supply pipe might be clogged. At first the illustrations in the repair manual made it look like it could be a do-it-yourself job. But then i started reading and all the associated steps makes it look like a pretty involved process to try in the driveway (the 4WD seems to add a tough step since, if I recall correctly, they suggest dropping and supporting the front differential with a floor jack), I have also tried some real thick oil-like stuff i got at the auto supply store (white tall plastic dispensing bottle)..that may have helped.
Other than the noise "molehill" am I making this into a $1000 repair-shop "mountain"? Oh yeah..i almost forgot. The reason I got the estimate was one morning the noise didn't go away so rather than taking a chance of getting stuck out in Houston i dropped it at the shop. When they returnedit to me after looking at it, I didn't have the problem for several days. Do you think they looked under the valve covers and just by inspecting it maybe cleared out some sludge or something?
I thought it might have been an oil pump prblem originally.
It actually looks like (well..that's according to my uneducated look at the steps in the repair manual) doing a lifter repair job is simpler (less time..less $'s) then replacing the oil pump or cleaning the oil take up tube/screem.
Would appreciate any thoughts as well as shop recommendations in the Friendswood/Clear Lake/League City area south of Houston, Texas

Brady

I had a 2000"New" Tahoe that made the same noise. I had purchased the truck new and had the noise from early on. I took it to a Chevy dealer where my friend works as a service manager. The noise was discribed to me as "Piston Slap" and that it would not hurt the engine. I sold the Tahoe with 112, 000 miles on it and got a 2007 Tahoe. I never had any mechanical problems other than the noise at start up. My friend also offered to do a Top End wash, where they fill the cylinders with an injecter cleaner to clean any carbon build up. Since I did not have any problems and the noise did not get any worst I decided to leave it alone.

golfer

Piston slap is a very distinct knocking sound. I have it on my '99 3.1 Malibu sounds like a diesel engine.
I"m not saying it can't happen but never heard pistion slap on the V8's.

If it's more of a "ticking" sound it's more likely to to be lifters , had this on my '00 van 5.7l. Three were collapsed at 61,000 miles , all eight were replaced to a tune of $1400.

73shark

While I first thought that this was an urban legend, I tried it on a 350 with over 150K because the owner was going to junk it anyway. Anyway it had lifter noise all of the time, so I put a quart of trans. fluid in the crankcase and after about ten minutes of running at idle (no load), it was as quiet as new. I'm guessing that trans. fluid is high detergent. Changed the oil and he drove it for another 50K.

hughmcc

(1) That sounds like a reasonable solution to me but I don't really have any expertise.
(2)Another question I have is "lifter noise...so what?". Where does the harm show itself. Does it start off as say poor fuel efficiency, then maybe screwed up valves and then a piston or 2 not "pulling its load" ? Is there a catastrophic failure (for my Arkansas cousins that means sort of sudden and REALLY bad) in the future?
(3)The trans fluid seems to make sense when combined with the other thought that maybe some sludge crud blocks a screen (if it exists) in the oil take up pipe assembly.
(4)As i understand it hydraulic lifters (do I have those in my 99 tahoe....lol) are supposed to retain oil (is this just the oil that does the hydraulic action?)..is there some sort of small one way valve on each lifter that gets blocked open by crud or damage and allows the oil in the "hydraulic chamber" to drain out and the lifter runs dry until oil is forced into it again on statup?
Thanks to everyone so far and hope yall (well I AM from Arkansas originally) will kibitz on any or all of the above.
PS: does anyone know of any good picture based sites that show the mechanical details and tutorials..sort of a "car mechanics for dummies" site?

golfer

I know an auto tech. that does this to engines that have been negelected and have serious sludge problems. Instead of tranny fluid he uses deisel engine oil because of the very high detergent content to flush the engine. Tranny fliud is more along the lines of hydraulic fluid whereas the diesel engine oil is a lubricant which he feels is safer.

73shark

Basically if your lifter(s) is(are) stuck, then the valve(s) won't completely open which can marginally affect performance. I'm pretty sure your 99 has hydraulic lifters. If your oil pump pickup screen is restricted then you should have lower than normal oil pressure. There is a "one way" valve in each lifter and if it gets some dirt in it, it won't fully seat and will allow the lifter to "bleed down" when engine is off. If this is the case, the noise should go away after the lifter pumps up and removes the valve train clearance. If this doesn't happen, then most like the lifter is stuck and will need to be disassembled and cleaned. Hope this helps.

tj

If you want to find out if it's lifters/valves, go to Sears or any autoparts and spend $20 for a vacuum gauge tester. Connect it to a vacuum port on your intake and watch the needle at idle. It should be steady. A bouncing needle indicates a problem with the valves or lifters.

I had a guy tell me that every 50K miles, he flushes his engine with an oil/kerosene cocktail for 10 minutes, drains the mixture and replaces the filter and puts in fresh oil. Says his oil stays golden for the next 20K and he's got over 200K on some of his vehicles. I believe it was 3qts. kerosene and 2 qts. oil, letting the engine idle on this for 10 minutes or less. Anyone every tried or heard of this? I'm too chicken to do it.

73shark

I've heard of it but never tried it or know anyone that has. You have to be careful when you try something like this or even the one quart of trans fluid like I suggested not to race or load the engine in any way. []

The vacuum check is a good idea to help diagnose the problem.