Turbo noise during starting in cold weather

[bpfaeh]

I have a 2007 Sierra Classic. Bought it new in August of 2007 and have really only minor issues with it so far. We have had some pretty cold weather in the Indianapolis area the last few weeks and I have noticed a bad screaching noise that SEEMS to be coming from the turbo anytime I start the truck when the temperature is generally below 10 degrees F. It almost sounds like the turbo housing has shrunk down enough for the turbine to rub the housing, but Im just guessing. I worked for almost 3 years at Cummins on the 2007 emission product prior to its release and had some REALLY cold starts with nothing sounding like this. Do any of you have this problem? I havent tried it with the temperature that cold AND with the truck plugged in to AC power, but I will try this week. The noise goes away after the truck warms up, but Im wondering if I havent damaged something already that may break down the road! Anyone have any thoughts?

[Mark Rinker]

Every Chevrolet that I own, or have owned, has had a schreechng heater blower when cold. (Not knowing how many Chevys you have owned as a point of reference, I thought I'd at least suggest it.)

Never heard of a schreeching turbo...could it be a serpentine belt or one of the belt drive accessories?

[chessy56]

My '01 exhibits some screeching noises when "cold", but I've found that it happens when the A/C compressor's clutch is cycling. I doubt that this helps your situation, but I thought I'd toss it in for future reference.

[bpfaeh]

Its definitely not the blower fan and its not the a/c clutch either, but thanks for the thoughts. The engine fires and the screeching starts (it spools up, just like the turbo) a couple seconds later once the pressure is built up enough to get the turbo spooling. I will probably plug in the block heater this week and see what happens. Im just surprised that I am the only one that has seen this problem!

[linchhummmer]

it could just be the clutch in the fan slowly grabing as the truck is warming up. i dont think your compressor wheel would spin if the housing shrank

[Dakster]

Can you pop the hood and have someone else start it when cold? Maybe then you could isolate where the noise is coming from a little better?

Make sure the HVAC control are off when you start it too. That would isolate any HVAC noises...

Have you changed your oil, if so look for metal shavings. If the turbo is "screeching" it would have to be leaving some metal in the oil. Perhaps an Oil analysis may help as well.

Another suggestion, When I've had cold start issues, I've let it sit overnight at the dealer and let them start it first thing in the morning. I perfer letting the dealer look at it, it's free and if there is a recurring problem it is documented.

I have an LMM, which is basically the same, however, COLD here is when yhe temp drops below +60 F, which I doubt is cold enough to do what you are experiencing even if my truck was prone to that problem.

[linchhummmer]

and your variable turbo dosnt turn much when the fins are closed like at and idle

[Duramaster]

Uhhhhhhhhhh here is a thought, I live in Washington and even here it has been in the mid 20's this last week at night. My point is, When the ECM coolant temp. is cold, (I can't seem to find the exact temp in SI at this time) The ECM will command the RPM's up to a high idle state as well as close the turbocharger vanes to create a back pressure to aid in engine warm up. So with the back pressure now present, are you sure that you are not hearing an exhaust leak like one of the exhaust manifold gaskets whistling? Maybe even an EGR gasket whistle? I haven't seen a blown exhaust manifold gasket lately but it does happen. It is more common in the Medium Duty applications. Let me/ us know what you find. ;)

[bpfaeh]

Thanks for all the replys. Here is what I did. I shut off the HVAC controls and plugged the truck in via extension cord into the garage. It got down below zero fahrenheit last night here in Indianapolis. I started the truck up and no noise at all.

I was thinking about what you said Duramaster and the noise happens before the ECM raises the idle speed and shuts the turbo. It is even louder when the ECM does raise the idle and as the engine warms up it quiets down and eventually goes away all together. I am going to look for exhaust leaks like you said as after I thought about it, that could very well be the problem. Ill let you know what I find, and thanks again!

[SoTxPollock]

You say you shut off the HVAC controls. Perhaps thats what your hearing when you didn't shut them off, but I don't think the compressor should be coming on at cold outside temperatures anyway. I guess I'm too cautious. I always shut off all electricals before shuting down the engine, (heater,AC, lights, radio, etc) I think it allows the alternator to cool a few seconds before shuting off and may make it last a lot longer.

If it were the turbo blades draging on the housing, you would very soon be loosing power and throw a code for low boost pressure, not to mention replacing a turbo. Is your engine blowing a lot of black smoke when its making noise? Or is it just at start up for a few seconds? I really don't know how long your truck takes to warm up or if you drive it cold.