Duromax thumping sound

William Chapman · March 18, 2020

thumping sound. Can anyone tell GM how to get rid of it

redwngr · March 18, 2020

GM diagnostic procedure seems to indicate they are taking the position that it is a characteristic of the new (for 2020) fan drive.

Kinda like the their position on the typewriter tick.

Edited March 18, 2020 by redwngr

bsmall1564 · April 20, 2020

It'll be interesting to see if this thumping sound gets louder or something breaks.

sdelam · April 20, 2020

https://gm-techlink.com/?p=13025

Some 2020 Silverado 2500HD/3500HD and Sierra 2500HD/3500HD trucks equipped with the 6.6L Duramax diesel engine (RPO L5P) may have a thumping or knocking sound coming from the rear of the engine. The sound is often more pronounced in the interior of the truck as it’s amplified by the transmission bell housing.

To duplicate the engine sound:

Idle the engine at about 600 RPM with the transmission in Park or Neutral. The engine oil temperature should be 113–185°F (45–85°C).
Turn the HVAC fan and radio off.
Remove the accessory drive auxiliary belt. (Fig. 14)

If the noise level is significantly reduced, it should be considered a normal characteristic of the 2020 model year truck. No additional repairs are necessary.

Fig. 14

Use the following procedure for accessory drive auxiliary belt removal, testing and installation:

Remove the air cleaner housing.
Remove intake air duct.
Separate the charge air cooler (CAC) tube and position aside.
Remove the belt and position aside.
Install the CAC tube.
Loosely place the air box and intake duct back in place. (So a DTC is not set for the sensor when starting.)
Start the engine and verify the sound is gone.
Remove the loosely installed air box and intake duct.
Separate the CAC tube.
Install the belt.
Install the CAC tube.
Install the air box and duct.

TIP: Do not run the vehicle more than three minutes without the auxiliary belt installed. Do not raise the RPM higher than idle with the belt removed.

The engine sound has no short- or long-term effects on the engine.

– Thanks to John Stempnik

Tomato · April 20, 2020

I was going to do this, but...I see 3 problems? 1) The belt shown above is the fan belt. 2) The accessory drive belt runs off the crank pulley as well. 3) How could you safely get either safely out of the way without taking the fan out?

Am I missing something?

sdelam · April 21, 2020

Honestly I havn't even looked at it. Just noticed it on the tech link and thought I'd share. Surely there is a way.

Edited April 21, 2020 by sdelam

newdude · April 21, 2020

20 hours ago, Tomato said:

I was going to do this, but...I see 3 problems? 1) The belt shown above is the fan belt. 2) The accessory drive belt runs off the crank pulley as well. 3) How could you safely get either safely out of the way without taking the fan out?

Am I missing something?

Yea take it to the dealer and let them do that procedure and have you verify the noise.

XY74 · April 24, 2020

I was listening carefully yesterday to mine and it is making the same noise as from the video in another thread. Doesn't seem that bad to me, but I have never had a diesel before. To me on the best day it still makes a lot of unhealthy sounding clanking and rattling noises in general, so I just chalk it up to "normal". Allow me to sip some more GM koolaid.

Looking at the belt diagram, it appears to me the fan belt is outside belt. That is the one that is making the noise, it's the new part for 2020. Note they call it the "accessory drive auxiliary belt ". It should be easy enough to slip the belt off and secure it to the fan to keep it out of the way while the engine is started. You just have to keep it clear of the crank pulley and the other accessory drives. I do agree with newdude, just let the dealer do it for you if in doubt.

buelldude · September 3, 2020

what is going on with this thread? Have they fixed it or not? Have they made any real headway?

buelldude · October 14, 2020

I still keep looking for anything on this from GM, nothing. I did come across something other than the belt removal. I was watching part of the banks videos on YTUBE. The oil cooler is bigger with more cooling coils and its on the back of the engine. I'm not saying that is what it is but it is a new part put on the 20's. I have been looking at what the differences are and what could be making the noise. I started to think that cold oil going thru the cooler may not make the noise till it warms up and makes it till it cools down. Till its cold again and I don't get it when its cold. I will think things thru, that is till I either give up of find the issue. I have emailed a few places with questions and ideas and most of the time I get nothing in return????

Edited October 14, 2020 by buelldude

Tomato · October 14, 2020

2 hours ago, buelldude said:

I still keep looking for anything on this from GM, nothing. I did come across something other than the belt removal. I was watching part of the banks videos on YTUBE. The oil cooler is bigger with more cooling coils and its on the back of the engine. I'm not saying that is what it is but it is a new part put on the 20's. I have been looking at what the differences are and what could be making the noise. I started to think that cold oil going thru the cooler may not make the noise till it warms up and makes it till it cools down. Till its cold again and I don't get it when its cold. I will think things thru, that is till I either give up of find the issue. I have emailed a few places with questions and ideas and most of the time I get nothing in return????

I said quite a while ago that I think it is the EGR valve / pump. It is definitely loudest there when you listen to different components with a mechanic's stethoscope. I emailed Banks a long time ago with the question - no response.