anyone experience a metal rattling type noise when the engine is cold? this is on our new 08 hummer h3. I'm going to have the dealer check it out too. I was just curious if anyone else had this? it kind of sounds like a heat shield to me but I know nothing of these motors yet.

 

I think all the I-5 engines do that, it seems to be from oil draining back and letting the lifters drain down. As soon as the pressure pumps the lifters up again it goes away. Anyone else have more accuate info?

 

I'm not sure about the I5 being especially subject to sticky hydraulic lifters. In any event, a good synthetic motor oil can work wonders with such lifter problems.

 

Reprinted from: http://www.answers.com/topic/hydraulic-lifters

There are a number of potential problems with hydraulic lifters. Frequently, the valvetrain rattles loudly on startup due to oil draining from the lifters when the vehicle is parked. This is not considered significant provided the noise disappears within a couple of minutes, although typically it usually only lasts a second or two. A rattle that does not go away can indicate a blocked oil feed or that one or more of the lifters has "collapsed" due to wear and is no longer opening its valve fully. The affected lifter should be replaced in the latter circumstances. In extremely rare circumstances, a lifter can "pump up" and create negative valve clearance so that its valve cannot close. This is more serious as burned valves will result. In all cases it is important to follow the manufacturer's recommendations for oil viscosity and quality.

I've driven many cars over many years and some rattle and some don't on cold start. The I-5 rattles when you start it and I don't think there's anything you can do about it. Just maintain a GOOD quality oil in the crank case and if it craps out in the next 10 years GM will replace it.

 

During initial start up, you H3's computer (PCM)enters what is called "engine start up strategies" which dramatically enrich fuel mixture, change timing (ignition and VVT [this includes exhaust manifold valve timing])and can in fact sound a little different than when up to full operating temperature. Look at your temperature guage, if it is not yet up to the mid dial normal range for a couple minutes when you hear the strange sound, this may be the reason. Basically, when the Variable Valve Timing is changed at start up, it does sound different. Never hurts to have the dealer check it for anything that is out of the norm.

 

good info there

 

Thanks for all the fast replies folks! This was my first post on here. I'm impressed. I was hoping it wasn't actually coming from the engine, but as long as it is a normal sound for these, I won't worry about it. I would find it hard to believe it could be a valve "problem" since it sounded like that when we bought it with only 600 miles on it and it now has like 1800 miles. We haven't even changed the factory oil yet - there is another question :-) I'm not new to cars, but new to hummers. Here is what we have at http://FindFastCars.com
Nice site here!
Jeff

 

Is there a additive that helps reduce the noise on startup? My noise is deffinatly valve rattle and goes away in seconds, but i cant help thinking that each start is taking wear on the valves.

 

This may be your problem.. I have had a few GM trucks including our Hummer H2 do this too. Was told from a GM tech that it is not the lifters, its called piston slap. Sounds like some metal berrings are tossing around in there. Its the bottom of the piston slapping against the cylinder wall. Its common untill things heat up a bit and expand. He said it causes no problems and that GM is aware of this issue via there TSB's. There is no repair for this as it is a GM design issue with the actual engine. GM is stating its normal and to send the customer on there way.