Bongo Drum Noise in the intake. WTH????

[SZwemer]

OK, I just did a thread search and came up with nada.

1991 W350 SRW, G360, Stock Pumped Cummins, 300,000 miles, Banks SS Exhaust System. The only mod is the swiss cheese airbox mod and Banks exhaust.



I just bought this truck 2-3 months ago and it has made this bongo drum noise at idle rpms and above since day one. I thought it was the lift pump or something. Now that I have made the swiss cheese mod, it is much louder.

It is at a frequency equal to one cyl. firing. ( I think) It is not a knocking sound like a gasser motor would do... . in my opinion.....

It is like a air shock wave sound..... It does not sound to me like turbo bark, esp. since it is doing it at idle. But then what do I know... . That is why I am here on Christmas Eve. :-{} My wife is thrilled.

It does not seem to be as noticeable after it has warmed up a bit... hard to tell as there are so many noises with this old beast.



I just replaced the "gelatin"#@$%! transmission mounts today and had to use the winch cable by running it under the bumper and back to the trans plate to pull it forward in order to get the bolts to line up. Jeeze.

Discovered the engine mounts are toast too.

Guess this is why it is a $X$. ????!!!



HELP !!!



Thanks.

 

[JThorsten]

Almost sounds like an exhaust valve. check the gaps, one might just be a little lose.

 

[HookMeUp]

Nope it's the noise from the compessor wheel in the turbo as it chops the air. Take your inlet tube off of the turbo and start it and the noise will be gone.

 

[DVolk]

A noise happened on a N14 Cummins and it turned out to be a sucked valve seat , in this case its probally just starting ,

because of a flat cam or bad pushrod

 

[TWorline]

I second what HookMeUp said, mine did the the same thing when I had a 4"' intake tube on it. Just take the turbo inlet hose off of the the turbo and start it up, the noise will be gone.

 

[SZwemer]

Nope it's the noise from the compessor wheel in the turbo as it chops the air. Take your inlet tube off of the turbo and start it and the noise will be gone.

Thanks for all the quick replys everyone. And Merry Christmas !!!!!!!!!!!!!



I took the inlet hose loose at the turbo. The noise was almost gone. BUT the hose/airbox seems to be an echo chamber/expansion chamber for the "Boing, Boing, Boing" sound. Go ahead and laugh..... that is as good as I can describe it in cyberspace.

You are not suggesting that I take the turbo loose from the ram intake ??

This is a non IC motor. The hose is so short, I will have to take the metal intake ram off that goes over the valve covers... .

I hope that is not what you are suggesting. I do not even know if it would run w/o the turbo hooked up ????

I am painfully new to the Cummins and don't know much about diesels anyway. :{... . even though I have had several over the years. I just have not had to dig into them and have just left them mostly stock.



Anyway, the noise is still there, just a heck of a lot quieter when the turbo inlet is open to the elements.



Thanks again for the replys so far..... I hope this is just a normal Cummins thing.



I DO LOVE THIS TRUCK... ... JUST DON'T HAVE THE FUNDS TO KEEP THROWING AT IT. I DISCOVERED YESTERDAY THE 205 T-CASE OUTPUTS ARE LOOSE AS HECK... . WILL HAVE TO CHECK IT TO SEE IF THERE IS ANY LUBE LEFT IN IT... BECAUSE IT AIN'T LEAKIN'... . AND IT IS LOOSE AS A GOOSE.

SO THERE IS ANOTHER REBUILD FOR THE SCHEDULE. MAYBE I AM BEGINNING TO SEE WHY MY COUSIN FINALLY SOLD IT TO ME AFTER ALL THESE YEARS OF DOGGIN' HIM FOR IT !!!

 

[cerberusiam]

Run the valve clearances on it. You could have one set to tight and it is not closing all the way quick enough.



If that doesn't change it, a compression and leak down test to check for a bad valve/seat would be in order.





Good luck and Merry Christmas.

 

[SZwemer]

I just got off the phone with my cousin... . the original owner. I am #2... (my wife thinks I am too) Anyway, he says the truck has done that since day one. So it must be a Cummins thing. I have detailed service records for the first 243,000 miles. He was right on all the services... had the valves checked every 30-40K. He did agree that it is time to do it again. The OD is busted, so the est. mileage is 300K+/-.



Will update when I run the vales to let ya'll know if there is any difference.



Thanks again for the replies. Looks like it is not a $$$$ issue. Oo. Oo.

 

[pepecat]

I noticed a Bongo Noise like you described on my 1990 when I started it up the couple of times before pulling it. my 1989 doesn't have this noise. The thing is, the 1990 actually runs and idles a LOT smoother than my 1989! I am trying to track down the history for the 1990 but I do know that it was a fleet maintained construction truck, with two sets of numbers on the valve covers for all of the scheduled valve checks - this truck has had it's thorough maintenance that is for sure. I suppose that since yours does it as well I might just run it as is.

 

[JLight]

Does the 91 have o/d? Thought the 93 was first? Just want to know!

 

[EMacdonald]

I developed this noise in my 92 after adjusting the valves... I somehow ended up with the #6 exhaust valve too loose after going over the valves twice, sure didn't feel too smart after that one... LOL

 

[dpuckett]

JLight- the OD came with intercooling in 91. 5.

 

[pepecat]

So is the jury still out? Sounds to me like the bongo noise is probably from a loose valve...

 

[SZwemer]

Sorry about the delay in any updates... ... cuz there ain't none !!!!!!!!!!!



The truck has just sat for 2 weeks. The 3 days I had off at Christmas were a bust, due to rain. I get to work on it outside... . do not have a garage. #@$%!

I have been on call at work a lot and the few days I have had off lately have been rainy... ... ... jeeze. :{



I'll get to it on sunday PM hopefully.



But I expect it to be a "normal noise" on this particular truck because I have records of the valves being adjusted on a regular basis, and my cousin said the truck has made this noise "from day one".

 

[pepecat]

Cool...



I guess I'll be driving to the beat of my own bongo drum as well then. .



Thanks

 

[AKaiser]

So is the jury still out? Sounds to me like the bongo noise is probably from a loose valve...

Yeah, it's that darn 50 cent kniffler valve. Somebody forgot to de-install the "Bongo Drum set" package at the dealer. They put these in all of them in case they go to a Carribean or African market. It's cheaper that way. :-laf