I am coming back just to leave reference on my issue, it turns out that the issue was a broken head gasket, I will describe at the end a simple test to perform, to find out if this is the root cause of your problem.
There are some references on the web that claim that the formulation of the OEM coolant was disintegrating the gaskets after some time, and this is why the manufacturer changed the coolant formulation for later models.
This problem is hard to diagnosis due the fact that everything seems to be normal on the vehicle, fluids are correct (when checked), the fans are working properly, but as others, I first tried to correct the problem by changing the thermostat, then the water pump, and finally look out after the broken head gasket issue, all this has to be done with a small mechanic shop as the dealership service area, came out the first time with the incorrect diagnosis of an intermittent fans failure, they wanted to change both fans and wire harnesses at a higher cost, and I decide to look out for myself, at the end it will cost me less than half of the dealer's quote for the intermittent fans failure, and this includes changing the thermostat and water pump on my first attempt to solve the problem, I am assuming right now that both (the thermostat and water pump) were working correctly, but cannot go back in time, anyway not been an expert on the matter has a price.
It is good to mention that despite my 2006 Pontiac Torrent AWD has almost 80,000 miles, it has been quite reliable, no other problem at all since I bought it about five years ago.
As explained by the mechanic, the broken head gasket leads to overheating by some reasons, some are; it reduces the coolant level while been driving, generates air bubbles in the coolant system reducing its performance, and increases the friction at the combustion chamber. Even if you check the coolant/water level before driving, it will be consumed while driving, leading to the engine to overheat, and not the other way as I thought, that the coolant/water level got low because an overheated engine.
The problem will be in and out at the beginning or even later on as the crack on the gasket gets bigger, and for many factors as the driving conditions, outside temperature, etc. This is also why this issue its very hard to diagnosis. On my case it will appear when driving back home after work in a hot afternoon throughout the city downtown, with several traffic lights on my way, no been shown when driving directly back home from work using the highway, nor early in the morning/late night.
At least you have to change the head gasket, and coolant, but it is good to make an oil/filter change as well as it can be contaminated with coolant, also you might be forced to change -at an additional cost, the exhaust, intake and valve cover gaskets, as the mechanic can not commit to reuse the same ones, they can be broken when disassembling the engine. And it is strongly advised to change the exhaust, intake and valve cover gaskets as well while the engine it is torn apart, as you do not want to come back latter on with an oil leak. There is also a small chance, but still a possibility that the engine head has a crack, that in most cases can be repaired, or you must be forced to buy a brand new one. The worst case scenario is that you broke down the entire engine by running it too hot, for too long, on all this the labor cost is far more the most expensive portion.
One key indicator of a broken head gasket besides the overheating problem is that when starting the engine in the morning and after a long overnight rest to let it cool down enough, you will notice that the engine shakes more than usual, just like when a spark plug is faulting, this will go away after a few minutes when driving and in most cases it will not come back until next morning, the reason of this is that when the engine has cool enough it allows the coolant into the combustion chamber overnight and to stay there, once you start the engine first thing the next morning the engine will be shaking until the water/coolant is consumed inside the combustion chamber, then the engine will behave regular, if this is also happening to you, this is a simple test to diagnosis the broken head gasket issue:
Let the engine rest overnight to let it cool down enough, early next morning, remove the spark plugs and look out for any coolant/water residues on the spark plug tip, if not for sure, ask a friend to attempt to start the engine while you look for coolant/water residues splashing out of the open holes where the spark plugs were removed, if there is coolant/water residues, it will be very evident, even for a non-expert eye.
Also, others recommends to check your exhaust after you have ran for about five minutes and see if you smell burnt antifreeze, other recommend looking for white smoke coming from the exhaust, that is nothing else but water steam.
Since similar engines are shared across different GMC brands (i.E. Pontiac Torrent, Chevrolet Equinox, Pontiac Aztec, etc.) Chances are that this will be the same root cause for an overheating engine issue on those other brands.
Tuesday, August 24th, 2010 AT 10:23 AM