valve train noise in Chevy Impala

fishman · Dec 3, 2004

I bought a 2000 model Chevy Impala last month with the 3.4 liter 6 that had 98k on it. Everything seemed fine. After handing the guy the check, he mentioned that the engine made quite a bit of noise at startup when temperatures got cold, but that it had done so since it was new and the dealer said it was normal.

So when the recent cold snap hit (lows in the upper 20's /forums/images/graemlins/smirk.gif), the car did make quite a bit of noise at startup. Much more than I expected with lots of ticking and buzzing that smooths out after about 10 minutes and disappears. It seems to be coming from below the intake manifolds where the valves are located.

So the question. Can this be anything but bad? The noise is very disconcerting, but the car runs fine and has plenty of power. I don't know the current viscosity of motor oil in the car but do know it is the valvoline synthetic blend. Is there a motor oil or additive that you would recommend to quiet this down? What could be causing the noise? My limited knowledge (which gets me into trouble occasionally) makes me wonder if the timing might be advanced to much/little at startup. Heck, do cars even have a distributor any more? /forums/images/graemlins/confused.gif

Any ideas you might have would be welcomed. I plan on getting the oil tested as well.

Junkman · Dec 3, 2004

My Ford truck did the same thing when I purchased it used, and I just did an oil change and put in a bottle of valve lifter cleaner that I purchased at NAPA. It took a few bottles to clear it up, but after that, with regular oil changes, it never returned. I believe that it is the varnish that builds up on the sides of the lifters and makes the clearances too tight that causes this. The reason that it clears up when the engine block gets warm is the additional clearance since heat makes the block expand. A few thousands of an inch is all it takes. I have also replaced a quart of engine oil with a quart of Dextron ATF and it did the same thing in cleaning the varnish from the engine. Varnish and sludge is a byproduct of poor maintenance. Just because it runs well, doesn't mean that it was taken care of well. When you do that first oil change, you will see what comes out. Put the bottle of clean in now, it is only a couple of $$$ and it will help. It definitely can't hurt.

JJT · Dec 3, 2004

Do a search on Chevy piston slap. It seems a number of their engines are famous for this, and it's more noticable when it's cold.

JimR · Dec 3, 2004

The piston slap noise on the GM V-6's is notorious. It is so bad that the GM manual even states that the engine may make noise for the first few minutes of operation. This to me is a big time cop-out on poor workmanship. I worked on cars and truck back in the 70's for a living. Noisy pistons means sloppy bores. The fact that the noise goes away is normal from expansion of the piston due to the engine heating up. Why in the age of CNC machining that they haven't cured this problem is beyond me. ooops, I forgot, not made in America anymore.

dmp437 · Dec 4, 2004

After handing the guy the check, he mentioned that the engine made quite a bit of noise at startup when temperatures got cold, but that it had done so since it was new and the dealer said it was normal.

I take it you didn't test drive it with a cold engine? Word of advice about the Impala; don't touch one with the 3.4L. Instead get one with the 3.8L, the engine that has a STACK of J.D. Power awards for quality, one of the best (if not the best) engines GM makes. It's typical to get 250,000 miles out of the 3.8L, much, much less out of the 3.4L.

Anyway, to your engine. Follow the tips given above, but don't invest a lot of money in it. It's a throw away engine and it's getting close to that time. Keep in mind that this engine is the same engine that debuted as a 2.8L in the Chevrolet Citation in the early 1980's before morphing to a 3.1 and currently 3.4, and is made on the same tooling. GM Powertrain did build a new 3.4L engine line but that went to China to build motors for the new Chevrolet Equinox (and Pontiac Torrent in 2006).
Sorry about your situation, I wish I could have had a little input BEFORE you bought in.

Junkman · Dec 4, 2004

2.8L.....3.1L......3.4L ..... what ever happened to cubic inches?? Soda comes in litres.... engines should be described in cubic inches!!!! Where is the conversion chart?????/forums/images/graemlins/mad.gif

dmp437 · Dec 4, 2004

Auto manufacturing has gone global with GM Powertrain progressing a bit faster than the rest of the company. Also, when you open the hood what you'll see, usually on top of the intake manifold, is a big "3400" or "3800" in the case of the 3.8L unit. No reference at all to cubic inches displacement.
Anyway, 61.02 cc's to the cubic inch for a conversion. Anymore size doesn't matter as much. GM gets 180 HP out of the antique, inefficient 3.4L V-6, Honda gets as much as 300 HP out of a modern 3.5L V-6. That was a contributing factor for GM to use a Honda V-6 in the Saturn Vue SUV, although the VUE's V-6 is a detuned version.

fishman · Dec 5, 2004

JimR and JJT,

I've read about the piston slap because my Z-71 makes a noticible ticking sound when it's cold, for about 1-2 minutes. It's done it since it was new.

However, this is MUCH louder and is more of a metallic buzz, a much different sound. So one may be piston slap, but I don't think they both are. The sound in this engine definitely seems to be coming from the top of the engine. Does that change your assessment at all?

fishman · Dec 5, 2004

dmp437,

Well, it was a cold engine, but it wasn't a cold day, if you know what I mean.

You said to follow the tips above, and the only tip I got was from Junkman telling me to use some motor flush (Thanks Junkman /forums/images/graemlins/smile.gif). So I take it that you think this will help, at least a little? I plan to do it unless someone recommends against it.

It sounds like you are involved in some way with the automotive industry. It's pretty obvious you don't care for the 3.4 liter engine I have! /forums/images/graemlins/laugh.gif To be honest, I haven't heard anything bad about the smaller Chevy V-6's, and I know lots of people who have owned them. When I bought the car, I figured I was buying an engine with older technology that didn't have the horsepower, etc. of newer engines, but was durable.

So when you say "throwaway engine", what exactly do you mean? At 125k, it just explodes? /forums/images/graemlins/shocked.gif Or do people generally get them rebuilt, or get a junkyard replacement? That's a pretty alarming statement, particularly when I was planning on running this car 175-200k. Surely those engines are pretty common. Do you know if the 3.8l is a drop-in replacement, or is there more to it then that?

We've put a couple thousand miles on the car and so far we're very happy with it. Getting right at 25 mpg in mixed driving, and the wife loves the heated leather seats.

JimR · Dec 6, 2004

Collapsed lifters would be my best guess. I would do as mentioned above and change the oil and add in one can of ATF to it. That will clean out any stuck lifter of any varnish or gumming up. If the noise continues, you have bad lifters.