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Bonneville GXP/ Northstar Powered Cars Discuss your Bonneville GXP and/or any other Northstar powered Olds or Cadillac... Including the 3.5L Twin Cam V6 (Short Star ) 4.0L and 4.6L Northstar V8's. Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 12-20-2005, 03:05 AM   #1
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Default engine is knocking...

The outside temperature was -2 *F when I started my engine and it has always had a slight tick when the engine was cold (like many engines do). That'* not the issue though. the issue was when I put it in drive to take off.. The engine sounded like a pop can full of tiny pebbles being shaken about slowly when I pressed the gas to accelerate. The noise increased with engine RPM.. I have no idea what would make my engine start knocking, especially with only 51,000 miles! The oil pressure was 115 PSI during all of this as well and I let the engine warm up for about a minute and a half before driving off. I didn't go over 2,000 RPM. The sound slowly went away as the engine warmed up and by the time I got home it was completely gone... Ideas? What would cause an engine to knock when it was cold, but to sound almost normal once warmed up? My gas mileage also went from about 40 MPG instant @ 55 MPH to 21 MPG instant @ 55 MPH.
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Old 12-20-2005, 03:17 PM   #2
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what kind of oil do you have in it?
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Old 12-20-2005, 06:57 PM   #3
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Check out this site

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GM Consumers, do you have a 1999-2004 (2005?) 3.1, 3.4, 4.3, 4.6 (Northstar), 4.8, 5.3, 5.7(LS1), 6.0 or 8.1 liter engine that displays any of the following problems?
I think the 4LV8 is close enought to a Northstar that it could still be considered.

http://www.pistonslap.com/

Does it display any of these problems, if so thats what it is.
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Old 12-20-2005, 10:34 PM   #4
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In the past, before I started using full synthetic engine oils, cold temperature starts would cause lifter clatter. Especially when the temp was below 0 and the car had sat overnight. I've also had it with synthetic oil after a sub zero start-shutdown-start while the engine was still very cold. The Northstar has hydraulic lash adjusters that still need oil lubrication to operate quietly. Piston slap (which I had on my '02 T/A LS1) is usually lower pitched and sounds like a diesel engine. Lifter clatter can sound just like a can full of marbles, high pitched and "rattlely". Try switching to a full synthetic oil which are supposed to "pour" at -50 F.
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Old 12-20-2005, 10:53 PM   #5
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Did you check out some of those pages on there pretty funny, fell bad for them but kinda funny.
http://www.pistonslap.com/photos/tahoe_ad.jpg
http://www.pistonslap.com/photos/tahoe_ad_2.jpg

You are right it could just be lifter noise
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Old 12-20-2005, 11:27 PM   #6
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For some reason, I think you put some nice 40 weight in it. The reason I asked this:

Quote:
Originally Posted by gxpwoot
what kind of oil do you have in it?
Was because of 1) The high oil pressure - 115psi? More is not better here, I'm thinking you've got molasses for oil. 2) Cold temps causing high pressure and poor pumpup of the hydraulic lifters.

That gives you the slack in the valvetrain, your "pebbles in a can" sounds, and poor running (valves aren't opening all the way)

By the way, a minute at -2 degrees is not going to warm anything up. In extreme temps like that, I'd say you need 5-10 minutes minimum. The best way to warm up the car however, is to drive it... but it'* your gas money.
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Old 12-21-2005, 12:45 AM   #7
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Quote:
Originally Posted by gxpwoot
For some reason, I think you put some nice 40 weight in it. The reason I asked this:

Quote:
Originally Posted by gxpwoot
what kind of oil do you have in it?
Was because of 1) The high oil pressure - 115psi? More is not better here, I'm thinking you've got molasses for oil. 2) Cold temps causing high pressure and poor pumpup of the hydraulic lifters.

That gives you the slack in the valvetrain, your "pebbles in a can" sounds, and poor running (valves aren't opening all the way)

By the way, a minute at -2 degrees is not going to warm anything up. In extreme temps like that, I'd say you need 5-10 minutes minimum. The best way to warm up the car however, is to drive it... but it'* your gas money.
When its that cold the oil becomes thicker. Thats why there are multi-vescosity oils. His oil was probably as thick or thicker than 40 weight would be at that temp, which would explain his oil PSI and the ticking. But after a few minutes of warming up that should thin out and the ticking should go away.

Shawn
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Old 12-21-2005, 01:12 AM   #8
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I only run 5 W 30 in my engine. The place that changes my oil doesn't even carry any 40W oil.. I asked what all they had and basically they limit their supply to 5 W 30 and 10 W 30 unless specifically asked to put anything else in.. They said they put 5 W 30 in it though. (my manual calls to use 5 W 30 year round.)
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Old 12-21-2005, 12:01 PM   #9
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Some good points above but here'* another idea;

I've seen quite a few engines that really disliked 10W30 oil when used instead of the recommended 5W30. Maybe they put the wrong weight in your car last time thinking it wasn't a big deal.

It might be a long shot but I have seen this before.

Cheers,
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Old 12-21-2005, 12:17 PM   #10
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Quote:
Originally Posted by Foghorn
Maybe they put the wrong weight in your car last time thinking it wasn't a big deal.
They had to have. 10W30 has a pour point of "around" -20degrees F. But it'* pumping point (the point where it'* thin enough for the oil pump to get pressure) is about 0F. Just another reason I don't take it to quick lube places. I have a friend that drove out of one of those places where they didn't tighten the drain plug enough, and it rattled out within a couple miles of leaving. Dumped all the oil out, and burned up the engine. He'* still working on a lawsuit to get a new engine from them.

Anyways, if you'd like to see your engine running for some time, I'd suggest draining out what you have, and refilling with synthetic 5w30. Good to -40F to -70F.
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