New to owning a diesel

[tsm1975]

I have a 2015 3/4 ton Duramax Z71. My question is....every so often when taking off from a stop I can hear what sounds like some kind of auxiliary fan or something come on for maybe 10-15 seconds then it quits and its not exactly quiet. It doesn't do it all the time but does do it even when the engine is warmed up.

Any suggestions as to what might be making this noise?
Thanks for all your input...

Tom

[Skip426]

Without being able to hear the noise , I'd guess that maybe your hearing the engine's radiator cooling fan , that has at it's center a temperature sensitive hub . When the air coming through the rad reaches a certain temperature this hub locks up and the fan begins to spin at it's max speed as engine RPM increases, and gets very noisy . This happens every time the rad temp comes up , but when cruising on the highway , air flow from vehicle movement makes it less frequent and other engine and road noise makes it less noticeable.

[tsm1975]

Makes sense....I've had the truck since mid-October last year and didn't notice the noise till it started getting warmer about 6 wks ago. Thanks Skip!

[Mzbrandi]

Originally Posted by Skip426

Without being able to hear the noise , I'd guess that maybe your hearing the engine's radiator cooling fan , that has at it's center a temperature sensitive hub . When the air coming through the rad reaches a certain temperature this hub locks up and the fan begins to spin at it's max speed as engine RPM increases, and gets very noisy . This happens every time the rad temp comes up , but when cruising on the highway , air flow from vehicle movement makes it less frequent and other engine and road noise makes it less noticeable.

I have a 2016 Dramax diesel and yes it's the fan making all that noise.

Brandi


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[Ray,IN]

If you are running empty when this happens you might consider having the 2 engine thermostats checked-yes a Duramax has 2 coolant thermostats in the same housing. One opens at a lower temperature than the other, the lower opens when coolant temperature is under approx 220 deg F, the second opens when towing a heavy load and coolant temperature is high enough that the first 'stat cannot allow enough coolant flow to maintain normal operating temperature.

[MtnTrek]

Originally Posted by Skip426

Without being able to hear the noise , I'd guess that maybe your hearing the engine's radiator cooling fan , that has at it's center a temperature sensitive hub . When the air coming through the rad reaches a certain temperature this hub locks up and the fan begins to spin at it's max speed as engine RPM increases, and gets very noisy . This happens every time the rad temp comes up , but when cruising on the highway , air flow from vehicle movement makes it less frequent and other engine and road noise makes it less noticeable.

X2

Yeup, been my experience also. The finned hub of the fan has a silicone fluid in it that gets more viscous at higher temps causing the fan blade to free wheel less. You may hear that fan announce itself pulling long grades too.

Interesting about the dual thermostats too.

Thnx.

[monkey]

You will also notice it alot more running the AC,, as that puts heat into the radiator/fan. My 2015 Silverado does that, so do our class8 work trucks... Totally normal....
Monkey