motor noise too loud, help please.

[libtec]

Hello and thanks for looking.

Okay, I know diesels are more noisy than other vehicles but mine is past obnoxious. My father in-law has two gmc 6.2 suburbans (82 and 84) and the engine noise in the cab is far more quiet than my 90 Chevy. I'm talking about the typical diesel engine clacking and what have you that seperates them from gas burners and not the exhaust noise. Running in OD is quiet but D or 2 is loud, especially when climbing a hill or pulling a trailer. I did a three hour trip pulling a two place snowmachine trailer and had ringing ears for two hours afterward.

My most serious concern is that I bought this suburban with the intention of pulling the travel trailer around the state with my family this summer. With the amount of cab noise I was getting I can't use the truck with my two children, it will literally hurt their hearing.

The difference I'm hearing between the gmc and chevy is the motor "character", mine simple has more pronounced, sharp, higher tones to it's diesel rattle while the gmc has a smoother, muffled sound. The air intakes are the same, exhausts are all good and the same, all three trucks are nearly mirror images of each other right down to the hood and fire wall insulation.

My IP alingment marks are a little over 3/16 of an inch out with the pump mark being closer to the drive side. This pump is a quality rebuild that was timed by a local shop that specializes in diesel work. Can the distance in marks indicate a stretched or worn timing chain? The truck shows black smoke when you lay into the throttle but runs clean under normal driving. Can an out of tolerance chain produce cam to crank timing that would produce the engine noise I'm hearing?

I would like to keep this truck (sentimental value), but if this noise is not curable then I have to sell it.

Thanks for looking and hopefully giving me a solution. God Bless.

[BobND]

I have a 1984 Sub that's not as quiet as my 1982 C-10 pickup.

I suspect bad motor mounts are adding to the transfer of noise and vibration into the interior.

I have my new ones, but never seem to find time to change them out.

Do you notice much change in noise between the engine running with advanced injection timing at startup, and the noise after it warms up a bit and HPCA and fast idle drop out?

Are your hood insulation and firewall noise padding intact? Any possiblities there's any unused (open) holes in the firewall, letting in noise?

Also, check for any engine plumbing or wiring harness that may be pinched between the engine and the firewall.

Have you looked at the heavy asphaltum noise padding under the carpet? On my 'burb that has hardend and crumbled, I'm sure adding to the noise, too.

[john8662]

Does your engine have the "powerstroke" diesel sound, if so it's probably too advanced and the only way to tell is to have it timed with a diesel timing meter. From your description you're way advanced at 3/16" thats nearly 1/4" of advance towards the drivers side. What you should try and do is take and loosen the pump bolts and rotate the injection pump towards the passengers side and line the marks up exactly. If your chain is worn this will retard the timing slightly. This will be just to see if it's a timing thing, which I suspect it is. I run 6.5 degrees BTDC on my 86 6.2 and it's quite a bit more raspy and louder than my other currently running 82 6.2. I had it at 8.5 BTDC before getting it timed after the new pump and gears, and it was really noisy, but I liked it!

John

[mdregister]

I too suspect, your timing is too far advanced. I know you say you had the pump rebuilt and timed by a reputable shop, but sometimes the techs think they can time the motor by ear, and maybe they had too much to drink the evening before..and you get the picture. Have it timed again, or as suggested in the earlier post, move the pump back a little and try it there. Also, as noted, 3/16 of an inch beyond the timing mark is quite a bit.

[libtec]

Thanks for the input! I'll give it a shot (moving the pump back). My only question is what possible damaging side effects might I get if I move the pump to far in either direction. Snowmobile two stroke experience says to much advanced timing results in melted pistons. I see that some people mention a pyrometer on their 6.2's, is this to help tune turbo boost? Do they use them on a NA motor?

I'll move the pump back in 1/16 of an inch shots and give it a test run. I noticed that at anything other than a constant speed there seems to be a very light haze in back of my sub. When I took it in to the shop to have the timing checked (the last thing my father-in-law told me to do) they said they could move the pump back a hair but it might cost me a little MPG. This isn't a bad thing as far as I'm concerned, I do care about the guy in back of me having to breath excess exhaust in tight traffic.

Any more suggestions would be greatly appreciated and thanks a bunch to those who answered back with advice!!

[Subzilla]

I'm still learning about pump timing and effects so I'm watching this thread. But I can answer your pyrometer need question - YES, get one, turbo or NA! Even if you don't pull anything, it is amazing to watch EGT's while climbing hills and will allow you the option of backing off the pedal when the temperatures reach 1100 degrees or so. I don't think I would drive mine without one, now. It is the more accurate indicator of how much fuel your rig is getting as opposed to watching in the mirror for color and quantity of smoke. I think most TDP members will say it should be the first thing to add to a diesel vehicle.

Can't wait to make it to Alaska one day!

[libtec]

Thanks!

I went out and bumped the pump back to where the factory marks lined up. I noticed a slightly longer crank time before the motor started, a little less power, less smoke but still a good cloud when I romp on it, exhaust at an idle that doesn't have a sting to the nose and less of a "raspy" noise. I was really happy to hear a more muffled engine sound when I was pulling my 250 gallon water tank on my 1200 pound trailer, the situation that made the sound the loudest.

One thing I also noticed was how much of the overall sound is wind / road noise, something I can pinpoint a little easier now.

Overall impression is good for the noise, not so good for the power. I'll put the pump at mid way between the two points and get a feel for it.

[libtec]

I played with the pump between the factory marks and where the tech set it last time it was in at the shop under the previous owner. I settled for a setting about mid way between the two points. Power is almost normal, noise is less and I noticed that my coolant temps seem to be a hair lower when I'm running at normal speed on flat ground.

The next step today was replacing the rear barn door seals and front door window seals. Both of these made a huge difference once I got the motor to quiet down a little and find the other noise problems.

I pulled all four passenger door panels off, cut some foam to fit and glued it to the back side of the panels. Substitute foam for 1/2 inch thick carpet pad. Hey, it's an experiment... Don't worry, it was new pad. But believe it or not this helped a little and no one will ever know, except my wife who is questioning if I should ever be allowed to work on her jeep again.

Hey Subzilla, If you do get a chance to come to Alaska drive the Denali highway between Paxson and Cantwell, good scenery, no towns, gas and food mid way and it's less than 200 miles, all surrounded by mountains. Aim for June 21st and you won't need to use your head lights at all. The land of the midnight sun. Stop by The Knotty Shop(Knotty as in tree)in Salcha for some good ice cream and get your picture with the 6 foot tall mosquito, a 1/4 scale model of the local species. Don't forget to bring a blue tarp!

[mhagie]

My engine really hammers on cold start up and its not exactly quiet at temp.
Checked timing last weekend 6.7* at idle 0.7* at 1100, had trouble maintaing rpm/advance readings with my Rotunda Timing Meter,going to clean out slot on balancer and recheck this weekend.
If these readings turn out to be correct I wonder how loud it will be when I turn it up to 4* at 1400.
Merle