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 Post subject: Dread Gasket?
PostPosted: Tue Sep 05, 2017 10:09 pm 
LE Member

Joined: Tue Sep 05, 2017 9:02 pm
Posts: 1
Year and Trim: 2005 GXP
Hey all, started encountering some cooling problems over the weekend, I'm concerned it may be the beginnings of a head gasket failure but I'm new to these cars and I'd to hear your thoughts. 2005 Bonneville GXP, about 140000km. Low coolant warning came on about 6 weeks ago, the level looked fine but I added a bit and the light went off shortly afterwards- not immediately thought. This past weekend I took it for a road trip, drove for about 90 minutes at highway speed, and then stopped for about half an hour. After I got moving again, the temperature spiked within about twenty minutes. I pulled off, bought coolant and refilled the reservoir, let it cool down and started off again, kept overheating and crawled to a shop in the next town with several stops to cool down. I should add that at this point coolant has been boiling off the relief hose at the top of the reservoir. The guy at the shop says I'm down a bunch of coolant, so he refills and pressure tests and sends me on my way. I make it about another 75 minutes on the highway and run into the same issues. I add water to the reservoir although it doesn't look particularly low, and crawl into the nearest city. Take it to a shop the next morning. This guy also says I'm really low on coolant. I have a rad flush done, because I can see a lot of gunk in the reservoir alone. He also replaced the rad cap because it's only holding ten pounds of pressure. He suggests that it may be the water pump or the head gasket. At this point I give up on my road trip and drive the 3 hours home and- no issues whatsoever. So next day my low oil light comes on, which I thought was odd because I topped it up before I left for my trip. I was due for an oil change anyway so I took it in, and the tech points out that I'm now leaking oil from what appears to be all over my oil pan gasket. He also points out that my coolant resevoir is now way overfull, so removes the excess coolant. As I'm driving home, my low coolant warning comes on again and it's stayed on ever since. However, my coolant level in the reservoir is correct, I'm checking every time the car cools down. I've also had a couple of instances of rough idle at start up yesterday and today. So I'm thinking either it's the head gasket or it's a combination of a faulty coolant level sensor and the thermostat and/water pump, along with a purely coincidental oil leak. The reason I wonder about the thermostat is that while it was overheating, the temperature would climb and then drop back down to normal operating temperature several times before it took right off, it's pretty unlikely that it was dropping 30 degrees or so once it started getting too hot. So anyway, symptoms are:
Overheating with irregular temperature fluctuations
Unexplained loss and gain of coolant
Inaccurate coolant level readings
Oil leak (but not where you'd expect it to happen)
Occasional rough idle at start up

I'm really tempted to replace the coolant resevoir/level sensor, the thermostat and the water pump, but I don't want to spend the several hundred more dollars if I'm looking at having a driveway ornament before long anyway. I'm also wondering if the gunk in the cooling system is the remnants of someone putting Barrs Leaks in as a temporary fix before I bought it at 130000Km. Any thoughts?

 Post subject: Re: Dread Gasket?
PostPosted: Tue Sep 05, 2017 11:55 pm 
Certified Bonneville Nut
Certified Bonneville Nut
User avatar

Joined: Wed May 13, 2009 10:45 pm
Posts: 5550
Location: CHICAGO
Year and Trim: 2006 STS-V, 2004 GTO, 2009 G8 GT
1) Welcome to the site.

2) I really don't want to sound abrasive, so please understand that, but this is a common issue for this engine dating since the beginning of the engine. It has been well discussed here. You can't read this section without hitting a thread pertaining to this topic. heck, there is even a thread, right below this one, pertaining to head gaskets on a N*.

Our thoughts?

1) This is a known issue with N*'s. However, by the time 2004/2005 came around it wasn't as frequent as earlier years of the engine, but it is still a potential problem with these engines.
2) Our thoughts the same as every other thread on here about it. Start small, and rule out all the smaller potential possibilities, work up to the big one, that being a bad head gasket
3) If it's truly a head gasket, it's a bitch of a job to do properly on your own
4) It's an expensive job if you chose to pay someone to do it.
5) The best solution is a proper aftermarket studding kit if it is the inevitable.

Read this section. You will have all your questions answered. Also, one thing I don't see tested in your post... Thermostat. It may be intermittently be stuck/froze closed.


Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2015 Chrysler Town & Country Limited Platinum: Mommy's NEW RGC
2007 Chrysler Town & Country Limited: Daddy's beater affectionately called the Rolling Garbage Can or "RGC" for short
2009 Pontiac G8 GT: L76, Sport Red Metallic
2009 Chevrolet Impala SS: LS4 V8, Victory Red
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck

 Post subject: Re: Dread Gasket?
PostPosted: Thu Sep 07, 2017 11:47 am 
LE Member

Joined: Thu Jun 16, 2011 2:02 pm
Posts: 5
Year and Trim: 2005 Bonneville GXP
Exactly what I went through!
Put a 160 km engine in it, it's fine now, until this one goes the same way!

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