2015 Silverado 5.3 Cold start noise

[GsBowtie]

Hey Y'all,

 

I posted this tread in the engine forum, but I want to post here because after doing more research, It may not be an engine sound after all?

 

http://www.gm-trucks.com/forums/topic/182875-slight-rattle-at-cold-start/

 

When I was doing some research, I found this you tube video which has the exact same noise my truck and my brothers 14 makes:

 

 

 

Does anyone have any ideal what this noise is? If it's normal, that's fine. Sounds like VTC rattle like I had on my 14 CRV's that I got rid of, but I've read it's the flapper valve in the exhaust, or something in the transmission re-setting during the first cold start?

 

Whatever the sound is, I'd like to know what it is exactly so I can feel good about the truck and move forward. I can say for sure when it's extremely cold outside, the noise is louder/longer, but it has done this pretty much from the first month I have owned the truck. I want to say it's a light rattle, or whirring noise, but much like the VTC in the CRV's it sounds metal on metal to me.

 

Just curious about this and if anyone ever got to the bottom of what this cold start noise is. Much like the VTC rattle on the CRV's the noise (again, see you tube video link at about the 30 second mark, just after the engine fires, it's slight, but is noticeable) my truck only makes this sound on the first cold start of the day or after sitting several hours.

 

Any help or insight anyone could offer would be appreciated.

 

Thanks.

G

Edited February 6, 2016 by GsBowtie

[scott19677]

Sounds like the direct injection fuel pump. Normal.

[Zzz]

My new 15 with 550 miles also does this. I can hear it from in my house easily with remote start. No matter what the question the dealer says it normal and I'm starting to believe it for this era. Power steering shutters felt, questionable fuel milage, noises...all "normal and functioning as designed". This is probably normal too. Don't worry about it. Haha!

[GsBowtie]

Lol i agree. Yes if I remote start with the house door open i can easily hear it right after the engine fires, just like in the you tube video. I'd just like to know what it is. I don't like it, that's for sure

Edited February 6, 2016 by GsBowtie

[GsBowtie]

Sounds like the direct injection fuel pump. Normal.

I don't think it's the di pump, i can hear that prime when i turn the key on before I crank. It's some sort of rattle

[newdude]

 

Direct Injection (DI) / High Pressure Fuel Pump / Fuel Injectors

 

The new Small Block Generation 5 engine family incorporates a new fuel system technology known as Direct Injection (DI). With DI, fuel is injected directly into the cylinder using a high pressure fuel system. DI provides many benefits in improving engine efficiency. In particular, DI improves power, torque, and most importantly fuel efficiency. This technology is included as standard equipment on all Generation 5 engines in the Small Block engine family which are the: 4.3L V6, 5.3L V8, and 6.2L V8.

The high pressure fuel system does have unique operating characteristics, in particular the noise emanating from the high pressure fuel pump can result in a subtle ticking noise that is apparent when the vehicle is idling. The sound is more evident when outside around the vehicle, when the hood is open or the vehicle is operated in a drive-through. 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 a normal characteristics of the DI high pressure fuel system.

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

 

Oil Pump Cold Start Rrrrp or Rasp

 

The oil pump design has changed from a gerotor gear type pump to a two speed vane type pump for fuel economy reasons. 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 startup the owner may hear a short Rrrrp or Rasp coming from the front of the engine. It is most often heard during a remote start. There is nothing wrong with the oil pump or oil system. No repairs should be attempted for this condition.

 

Edited February 6, 2016 by 15HDriver

[brents]

You can try and keep the exhaust flapper open temporarily and see if that was it. Mine made noise as well. I'm on my phone so not an easy way to find/link the thread but there is one in how to hold the valve open. Basically just turn it from the outside (square piece) and use a nail or zip tie or something to hold it there.

[GsBowtie]

 

Direct Injection (DI) / High Pressure Fuel Pump / Fuel Injectors

 

The new Small Block Generation 5 engine family incorporates a new fuel system technology known as Direct Injection (DI). With DI, fuel is injected directly into the cylinder using a high pressure fuel system. DI provides many benefits in improving engine efficiency. In particular, DI improves power, torque, and most importantly fuel efficiency. This technology is included as standard equipment on all Generation 5 engines in the Small Block engine family which are the: 4.3L V6, 5.3L V8, and 6.2L V8.

The high pressure fuel system does have unique operating characteristics, in particular the noise emanating from the high pressure fuel pump can result in a subtle ticking noise that is apparent when the vehicle is idling. The sound is more evident when outside around the vehicle, when the hood is open or the vehicle is operated in a drive-through. 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 a normal characteristics of the DI high pressure fuel system.

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

Oil Pump Cold Start Rrrrp or Rasp

 

The oil pump design has changed from a gerotor gear type pump to a two speed vane type pump for fuel economy reasons. 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 startup the owner may hear a short Rrrrp or Rasp coming from the front of the engine. It is most often heard during a remote start. There is nothing wrong with the oil pump or oil system. No repairs should be attempted for this condition.

 

Thanks for this info. I do think the issue is from the oil pump now. The description in bold reminds me of what mine does on cold start "rrrp or rasp " that's the sound a few seconds after the engine fires on that video and my truck makes on cold starts

[davidio840]

Mine does the same thing. I thought it was the exhaust but I have a catback on it now (without the flapper valve) and it still does it. It only does it on a cold start though. I thought it was something with the starter.. Took it to the dealer and they couldn't duplicate the sound for some reason. I even showed them a video similar to the youtube one and they said they checked everything and all was normal..

Edited February 6, 2016 by davidio840

[GsBowtie]

I guess I won't worry about it then. Good to know though

[tnchevy]

Makes you wonder why they did all of these changes to improve fuel economy when in reality for some of us the mpg's are the same or only slightly better than previous trucks. After 10k miles and 1.5 years my truck is at 19mpg (hand calculated, running average). My 2002 model with 4.10 gears, heavy LT tires, and no front end that drags the ground got 17.5 mpg after 120k miles and 12 years. Add on heavy tires and take off the air dam and level my 2014 may possibly get worse mpg than my 2002. So much for advancements in technology for mpg.

[entreri]

oil pump I have a 2015 5.3 same deal.

[oneandzero]

They are right about colder its noisier... you should hear it at -20°C.

[HondaHawkGT]

Makes you wonder why they did all of these changes to improve fuel economy when in reality for some of us the mpg's are the same or only slightly better than previous trucks. After 10k miles and 1.5 years my truck is at 19mpg (hand calculated, running average). My 2002 model with 4.10 gears, heavy LT tires, and no front end that drags the ground got 17.5 mpg after 120k miles and 12 years. Add on heavy tires and take off the air dam and level my 2014 may possibly get worse mpg than my 2002. So much for advancements in technology for mpg.

The new trucks are built a bit heavier too though. The difference in frames alone is a big change. There was a definite increase in curb weight going from the gmt800 to the gmt900 and now the gmtk2xx platforms.

[fondupot]

Heh, that's my video. Pretty much every truck does it. It's normal. Its a pump or something