Buick Lucerne 2007 Overheat problem

I have a 2007 Buick Lucerne with an over heating issue. The car will get to 210 212 while standing still and be good for 15 to 20 minute then start to overhead badly, It I drive it, it will over heat faster.
This is what I have checked or done so far.
I changed the oil, did not look milky or have any evidence of water in it.
I changed out the thermostat.
While it ran I turned on the heater to see if it was moving water once the engine got up to 200 degrees the thermostat opened and it blew hot air.
I replaced the water reservoir and cap because they looked like they were leaking.
I replaced the hardline that was leaking that runs along the firewall.
I am leaking water but I am not sure if it is coming out because of to much pressure or a leak that I can’t pin down.
Any advice you guys might would be greatly appreciated .
This is a 2007 Buick Lucerne with the Northstar V8 engine.


Remove the pressure cap from the coolant reservoir when the engine is cold.

Start the engine, and as the engine idles watch the coolant in the reservoir.

If bubbles start to form in the coolant, it indicates a blown head gasket.


Are the cooling fans running when it gets hot?

Does one run when the AC is turned on?

Good ideas above. If no joy from that, bite the bullet and fix the leak. A car’s cooling system won’t be able to cool the car properly if it can’t maintain the required cooling system pressure.

Other ideas

  • clogged radiator
  • fuel/air mixture too lean
  • ignition timing problem

Hey Tester,

I actually have done that, I left the coolant cap off and it boiled up over and spilled out the top. I figured it might be a head gasket it is just not leaking into the oil at the moment.

Are you still using Dexcool in the cooling system?


Not atm, I bought the car knowing it had a cooling issue didn’t want to dump coolant in there till i figured out what the issue was. Didn’t want to waste it and have it all over the ground.

If the previous owner had Dexcool in the cooling system, and cooling system had a leak, this allows air in the cooling system.

When Dexcool is exposed to air, it turns the coolant acidic.

This starts to eat away at the cooling system internally in the engine.

You may be looking at a problem that’s too costly to repair.


So I am going today to get a test kit from Auto Zone to test for gases in the coolant water and report back if it find them, well I am pretty much screwed.


That doesn’t necessarily imply a head gasket problem. Could be the system wasn’t properly pressurized b/c of no cap, and just boiled over. Water converts to steam and boils at 210 deg F unpressurized, but higher temperature (around 230 deg F) if pressurized by usual cap, around 7 psi. Head gasket bubbles often appear even with cold coolant, lots and lots of tiny bubbles coming to top of radiator. May have to bump engine rpm to get it to happen. If cooling system has air in it (b/c for example it was recently refilled) it may appear to have these sorts of bubbles, usually the bubbles for that are larger, but those kinds will go away once they all work their way out.

Just saying the words Northstar engine and overheating can make a lot of Master techs run… lol
Head gasket labor calls for 20.1 hours on your vehicle plus it requires special tools to do the job…

A head gasket can blow at least 6 different ways…

Compression leaks to crankcase…
Compression leaks between cylinders…
Compression leaks to coolant… (block test)
Blown coolant port to Oil port…
Blown Coolant port to outside…
Oil port blown to outside

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Hey all, I am still not sure what it is, I was gonna test the coolant to see if there was gas in it but I couldn’t because as soon as I would fill it, it would pour out the back of the engine. I have no idea why atm because i can’t see the back of the engine. I am waiting for it to warm up and i have time to jack up the car and get under the engine to see if I can find the leak back there. At this point I think either the block is cracked as freeze plugged popped out or a hose burst back there somewhere because the amount of water coming out. I put a gallon of water in it and the system is completely empty in about 30 seconds. Will keep you updated

Ok figured out leak i didn’t put the lower hose for the reservoir all the way in it leaked like crazy so got that done, it is still over heating. I did the test to find out if there was exhaust gas in the coolant water and yes it does have it so I probably have something wrong with a head gasket. It is not smoking and not leaking around the heads, also no water in the oil but still over heats. I know this is a monster of a job so I gonna through a hell Mary and see if Blue devil will work.


Worth a try I guess. If it works, suggest to not presume this sort of magic will continue to work indefinitely. I expect you already know the proper way to handle a failed head gasket is to hire a shop to install a new one.

It’s cheaper to use sodium silicate for a head gasket sealer.

And it works.

Sodium silicate can be used to fill gaps within the head gasket. Commonly used on aluminum alloy cylinder heads, which are sensitive to thermally induced surface deflection. This can be caused by many things including head-bolt stretching, deficient coolant delivery, high cylinder head pressure, overheating, etc.

“Liquid glass” (sodium silicate) is added to the system through the radiator, and allowed to circulate. Sodium silicate is suspended in the coolant until it reaches the cylinder head. At 100–105 °C (212-221 °F), sodium silicate loses water molecules to form a glass seal with a remelt temperature above 810 °C (1,490 °F).

A sodium silicate repair can last two years or longer. The repair occurs rapidly, and symptoms disappear instantly. This repair works only when the sodium silicate reaches its “conversion” temperature at 100–105 °C. Contamination of engine oil is a serious possibility in situations in which a coolant-to-oil leak is present. Sodium silicate (glass particulate) contamination of lubricants is detrimental to their function.


Ok so update, I used the Blue Devil stuff and it seemed to work also finally figured out there is a lot of air in the system and got that worked out. I ran it for a day and did a short drive about 15 minutes with it temp got up to about 230 at the highest but came right back down. Came back on dry driveway and there were no leaks, no white smoke while driving and no miss fires. Took it on a longer drive today and put it on the highway and it started to overheated. Limp it to a walmart parking log and got some water and put it in it trying to get the rest of the way home which was about 4 miles away. Started it up and drove it for about a minute and temp started to rocket, got caught at a stop light turn off car and turned on heater. Once I got past the light was gonna shut it down if it spiked to 250, temp started to go back up and got to 244 then dropped back down to the mid 230’s. I stayed on the access road and kept the gas to a minimum, then the damn thing drops back down to the 220’s and part of the way home almost to 200, I got it home and let it idle for about a minute or 2 and stayed in the 220’s. Turned off the car got out and looked underneath and no leaks anywhere this damn car is cursed. I don’t know maybe the water pump is going bad and is not working well enough or starting to give up?