slight rattle at cold start

[GsBowtie]

Hey guys,

 

I've noticed our trucks (5.3 anyway ) make a slight rattle at cold start. What is that noise? My brothers 14 does the same thing. You have to start it with the door open to hear it.

 

I had 2 2014 honda crvs that had the infamous cold start vtc rattle. Is that what we have going on to? (Camshaft vtc actuator rattle? ) i got rid of the Vs due to that bc it was bad.

 

Just wondering what you all think that is.

 

Thanks

G

[Txjose]

Just started mine after about a 4 days of sitting... Temos never got above 40 degrees here and it was about 19 when i started it.....

 

 

Cranked right up and not a sound at all like you described.

 

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[GsBowtie]

That's interesting. Did you start it with the door open? That's the only way you can hear it. It only lasts a second or two, very brief. It sounds like vtc rattle to me, but i was hoping someone more knowledgeable than i on these new engines would know. My brothers 14 also makes the same sound and its worse when it's real cold outside.

[GsBowtie]

I did some Internet searching and found this thread;

 

http://www.gm-trucks.com/forums/topic/176420-weird-sound-at-startup-2015-sierra-denali/

 

 

This is exactly the noise I'm referring to. Check out the video at the 30 second or so mark right when the engine starts. Is that noise really just the exhaust flapper?

[foghorn23]

Mine makes the exact same sound. If it isn't normal it, it apparently hasn't hurt anything in 18 months. I think it's some sort of system check, sort of like the ABS clunk when you start moving. Either way, ain't skeered.

[Txjose]

That's interesting. Did you start it with the door open? That's the only way you can hear it. It only lasts a second or two, very brief. It sounds like vtc rattle to me, but i was hoping someone more knowledgeable than i on these new engines would know. My brothers 14 also makes the same sound and its worse when it's real cold outside.

Yah i stood right next to it and used the remote start.

 

 

 

Sent from my Note 4 on Tapashit

[07Softail]

mine sounds like the lifters are bleeding down over night or it's the DI pump. It only make the sound for about 1 second after it fires up. It's not the flapper valve because i don't have a stock exhaust anymore.

 

RT

[redwngr]

http://sandyblogs.com/techlink/?p=3134

New Engine Technologies and New Sounds

April 8, 2014

The latest generation of engine technologies found on the 2014 Corvette and 2014-2015 Silverado 1500, Suburban, Tahoe, Sierra 1500, Yukon and Yukon XL may produce some unfamiliar sounds during cold starts as well as during warm operation. The new engines include the 4.3L V6 (RPO LV3) (Fig. 10), 5.3L V8 (RPO L83), 6.2L V8 (RPOs L86 and LT1).

F10 4.3L V6

Fig 10

Direct Injection

The new small block engine family uses a Direct Injection (DI) fuel system. The fuel is injected directly into the cylinder using a high pressure fuel system, which improves power, torque, and fuel efficiency. The high pressure fuel pump can generate a subtle ticking sound that is apparent when the vehicle is idling. The sound is more evident when outside the vehicle, when the hood is open or the vehicle is operated in a drive-through environment. The sound may be more noticeable during a cold start, but lessens once the engine is warm. A slightly higher pitched clicking sound is the fuel injectors pulsing on and off under the high fuel pressures. These sounds are normal characteristics of the DI system.

Another operating characteristic is a slightly longer crank time, which is the result of the time required to build high pressure in the fuel system before the engine starts.

Oil Pump

The oil pump design on these engines is a two-speed vane-type pump. Its dual-pressure control enables operation at a very efficient oil pressure at lower rpm, and then delivers higher pressure at higher engine speeds.

At temperatures of 32°F (0°C) or colder, when the engine has been sitting for a few hours, it is possible to have air enter the pump through normal oil drainback. Upon start-up, a short rasp sound may be heard from the front of the engine. It is most often heard during a remote start. This is a normal condition.

Edited February 7, 2016 by redwngr

[Exhausted]

"Oil Pump

 

The oil pump design on these engines is a two-speed vane-type pump. Its dual-pressure control enables operation at a very efficient oil pressure at lower rpm, and then delivers higher pressure at higher engine speeds.

 

At temperatures of 32°F (0°C) or colder, when the engine has been sitting for a few hours, it is possible to have air enter the pump through normal oil drainback. Upon start-up, a short rasp sound may be heard from the front of the engine. It is most often heard during a remote start. This is a normal condition."

 

 

Below 32* is BS

It was 72 when I left work and the truck sat for about 9 hours and still made the rattle noise upon startup

[emeryz28]

I know I can hear my flapper valve when I start the truck, more so when its cold

[Cheep Guy]

I have the 2016 5.3LT engine in a Jeep Wrangler. It makes the noise and my guess is oil drainback. Might be the oil filter. I used a Mobil1 filter which may be a POS. Have to change my Amsoil oil again , engine ran too rich on startup for 1/2 tank, so will use and stay with NAPA Gold or Wix (same filters and aircraft quality) from now on. Tell AC Delco to shove their junk filters up their arses. Oil will be fuel contaminated. And I am going to deactivate the AFM to not have future trouble with it.

[Polarbear705]

I have a 2017 Chevy Tahoe LT that would rattle bad on cold start for a few seconds.  It had issues with the torque converter shudder, especially when cold.  I replaced the torque converter and the rattle went away on start up.