Rattle, Rattle, Thunder Clap - Boom Boom Boom ---HELP--- - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 02-11-2003, 07:07 PM   #1
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Default Rattle, Rattle, Thunder Clap - Boom Boom Boom ---HELP---

HELP!!

When I start the car there is alot of rattling and knocking at the bottom of the block....any ideas?? When you first start the car it is a fast knock but when idle drops below 1000 it sounds like it is going to shoot through the casing!

Here is what I know:
1. Oil level are fine
2. Good oil pressure
3. Sounds like it is coming from the bottom (cam area)

Any suggestions would be helpful -- going to take it to a mechanic tomorrow but I would like to know what I'm getting into!

TIA
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Old 02-11-2003, 10:25 PM   #2
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Just thought I'd be the one to jump in here with the bright and cheery attitude.....

.......sooooo.......that sounds REALLY REALLY bad. Get that sucker to a good mechanic ASAP.
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Old 02-12-2003, 12:00 PM   #3
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Default Re: Rattle, Rattle, Thunder Clap - Boom Boom Boom ---HELP--

Okay, first of all, it'* "Rattle, Rattle, Thunder, _Clatter_, BoomBoomBoom...:

Quote:
Originally Posted by CorradoSLC
When I start the car there is alot of rattling and knocking at the bottom of the block....any ideas?? When you first start the car it is a fast knock but when idle drops below 1000 it sounds like it is going to shoot through the casing!
1) What year of Bonneville are we talking about here?
2) What engine?
3) Did this problem appear suddenly, or is it something that started quietly and is slowly getting worse?
4) Does the problem go away after the engine warms up?

My first thought was that it'* piston slap, except that you sound a lot more alarmed than someone who'* describing that condition...
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Old 02-12-2003, 08:04 PM   #4
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Ok -- just towed my Bonne to the shop and their guess is that the balance shaft came apart? They will have to dig into it to make sure but it will cost me $600 bones with labor to fix. Never heard of a balance shaft but you learn something new everyday -- is this something that I could tackle?

What else should I have them do while they have everything apart?
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Old 02-12-2003, 08:09 PM   #5
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Sorry - I missed your questions!

1) What year of Bonneville are we talking about here?
>> 95' SSEi
2) What engine?
>> 3.8 Supercharged
3) Did this problem appear suddenly, or is it something that started quietly and is slowly getting worse?
>> Suddenly - wife went out to warm her car up one morning and it was "clattering"
4) Does the problem go away after the engine warms up?
>> Really it sounds bad - to scared to let it warm up!

Hope this helps! TIA
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Old 02-12-2003, 11:45 PM   #6
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I have had the harmonic balancer go out on an older 3800 engine, and when it did, it made a clattering noise when the engine was running. When it goes out, the rubber isolator between the belt pulley and crankshaft cracks and separates. To check this, look at the front of the pulley (you may have to take off the right front wheel and plastic shield behind the wheel), and look for any cracking on the isolator. You can also try to turn the pulley (with the engine off!), and if the pulley moves 1/2 turn or so in either direction, it is bad. When it went out on my '89 LeSabre, it cost around $100, and took about an hour to replace.
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Old 02-13-2003, 04:46 PM   #7
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Corrado,

The balancer shaft is different than the harmonic balancer. The Harmonic Balancer is a metal and rubber plate that is bolted to your crank shaft/pulley. The balancer shaft is an internal balancer that Buick installed in their V-6'* to balance out the two sets of pistons that are set at 90 degrees from each other. It is located under the lower intake manifold which means that you would have to remove your supercharger and intake manifold to get at it. Depending on how broken it is, you may also be looking at accounting for all pieces of the shaft that may have broken off and fallen into the engine further. As Jr said, you could do it, but it would be considered a major repair.

For some pictures of what this balancing shaft is, go to this link: http://www.thrashercharged.com/L67_htm/engine_tear.shtm and look at pictures #2 and #3. Good luck with the repair--whether done by $$$ or by doing it yourself!
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Old 02-15-2003, 01:09 PM   #8
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After closer inspection it might just be the harmonic balancer. Before we can tell if it is the balance shaft this will have to be fix first. The part should be coming in Monday ($217 w/2hrs labor).

Really surprised that this would cause this much noise!! Hoping that this will fix the problem and that I don't have to worry about a broken balance shaft!!

Thanks for all your help -- I will let you know Monday what the verdict is!

gg
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Old 02-15-2003, 01:11 PM   #9
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Don't panic. Even the balance shaft isn't that bad to do yourself. It'* right under the lower intake. Takes some time to get to, but not too difficult overall. Keep us posted, and let'* hope there wasn't a bearing failure, too.

I can't imagine it being the balance shaft. They're one piece, and not alot to them. If it was BROKEN that would be different, and BAD. Banging around in there with your pushrods......scary.
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Old 08-28-2003, 01:16 AM   #10
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Quote:
Originally Posted by jr's3800
Quote:
Originally Posted by CorradoSLC
After closer inspection it might just be the harmonic balancer. Before we can tell if it is the balance shaft this will have to be fix first. The part should be coming in Monday ($217 w/2hrs labor).

Really surprised that this would cause this much noise!! Hoping that this will fix the problem and that I don't have to worry about a broken balance shaft!!

Thanks for all your help -- I will let you know Monday what the verdict is!

gg
I'll bet it will be the Crank pully then... I have never heard of a Blance shaft going bad in a 3800 or any other GM V6 for that matter.... But the Crank pully going bad on a 3800 is very common... Its actually rubber, but in the center there is actually a bearing, the rubber acts as dampener, but when it breaks you will get some serious noise, almost sounds like a rod knocking.. Hope the Crank Pulley is the problem.. Let us know how it all goes..
so the crank/pully is part of the harmonic balancer?

is that a tough job to do yourself?

thanks
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