4.6L northstar engine Pontiac Bonneville Gxp - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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 10-27-2011, 11:32 PM   #1
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Exclamation 4.6L northstar engine Pontiac Bonneville Gxp

need to know if the motor in the gxp bonnie is great because Ive been hearing that they are junk. just needed some insight guys, thanks
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Old 10-28-2011, 12:27 PM   #2
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Opinions vary it all depends on how you take care of them.In my personal experince ive seen if you overheat them they blow headgaskets and when they do that the rest of the motor ends up being junk.but also you have john who has nitrous on his and no problems
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Old 10-28-2011, 02:04 PM   #3
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Would I deem it an unreliable engine? No. Is it as dead reliable as the 3800, not quite. Is it needy? It can be.

In all honesty, it seems like the 100k mile mark is the magic number that I have noticed with them. If it was not treated right, that is about when the issues will start to pop up. It is the same engine used in some Cadillacs as well. Another thing to watch for, aside from the overheat concerns listed above, is oil consumption. If the engine is not ran (i.e. grandma puttering around town on Sunday), the engine does not fair nearly as well as one that gets taken out and flogged on occasion, hence, the reputation.

Suggestion: If you find a low mileage unit (75k miles comes to mind), and it looks and drives good, with what looks like a decent history, and you take care of it (run it hard on occasion, and keep on the maintenance), it will treat you well.

Oh, and the Northstar is not a fuel mileage winner by any stretch of the imagination, but doesn't do too bad if you take it easy.

Simply put, the Northstar is a runner, if it isn't ran, it shrivels up and dies fairly quickly.

Junk? No. Needy? It can be.

Now the Ford 3.8 of the 90'*, that was junk. The northstar is not any where close to that.
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Old 10-28-2011, 11:12 PM   #4
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Hey thanks guys!!!
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Old 05-15-2014, 09:04 PM   #5
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30+mpg @ 55 easy. 19-21 mpg @ 80.
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Old 05-15-2014, 11:14 PM   #6
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personally I wouldn't own one. Headgaskets will fail or the head bolts will pull threads and don't forget the upper oil pan gasket that like to leak oil.
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Old 05-16-2014, 10:16 AM   #7
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Northstar vs 3.8 SC'er? As far as I'm concerned, it'* not even close......

Less problems with the 3.8, and a huge advantage, is repair costs......
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Old 05-16-2014, 08:59 PM   #8
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based on general information on the N* ,planning in the budget for head gaskets and studs at around 122K miles would be wise. Other than that I would say its a fun car and the maintenance does not appear to be any worse than any other car assuming you don’t beat on it. But then again I do all the work myself and make repairs with the plan to do it only once.

Picked mine up with 62K miles on the clock, now has 153K, good runner, mostly hwy for me to the tune of 32K miles/year. The only unexpected problem was the head gasket at 122K.
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Old 06-16-2014, 01:14 PM   #9
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use your own judgement, head gasket at 122K mi, added studs + new gaskets, now needed head gasket second time at 153K mi one year later

seems the 4.6N* is another GM flop, GM has had too many, maybe Ford
really isn't that bad after all!
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Old 06-16-2014, 10:03 PM   #10
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I'll say it again......get a Bonny with a 3.8 SC'er........

Mainly for repairs.......have to have two wallets to pay for repairs on a Northstar.......they are not DIY'er friendly.......you need too many special tools to work on this engine, and there is no room.....

Compare replacing a thermostat in each engine......compare changing starters......compare doing intake gaskets......compare doing oil pan gaskets(OMG!).......

I had a nightmare once....there was a Caddy with a Nstar in it on my lift.....woke up in a sweat......went to work....there was a Caddy with a Nstar on my lift.....at break, I bought a lottery ticket......I didn't win......

Oh, the Caddy only needed an oil change.....
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