Found a 07 equinox for sale. Overheating. 3.4 v6 My speciality. Seller mentioned it has new headgaskets. Heads were milled/checked. New waterpump. New radiator. Keeps overheating. I fix them but seems all usual items have been done. Shop that did work is finished. And seller has big bill. Any ideas? Fans?
Check the color of the tranny fluid to see if it’s burnt.
If it is, an overheating tranny can cause an engine to overheat.
Tester
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Ha, it has toyo af-33 trans. They turn fluid very dark real fast. I always do drain/fill on my projects and I’ve always seen very dark fluid.
That might be the reason the head gaskets failed, the result of the overheating, not the cause.
Raise the hood and observe engine and cooling system operation: coolant circulation, time to reach operating temperature/high temperature, fan operation/direction of air flow, drive belt routing.
Note that if the drive belt is routed on the wrong side of the water pump, it will rotate clockwise.
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Use a block tester
Seller had it for 6 months and heat stopped blowing hot about Xmas. Took it to shop. Radiator and water pump, but it kept overheating. I assume serp belt was routed ok initially. Now? When they said it had heads done by machine shop I was puzzled. Seems like a proper repair was tried. Yes, I think the belt “could” be on wrong side of WP pulley based on diagram. Don’t know if it is. Pulley is smooth. So ribbed side should not be on pulley.
Radiator cap holding proper pressure???
You’d be surprised at how often the rad cap is overlooked…
I’ve seen mechanics either take a pic of the before belt routing or draw it on the water pump box or something and never check to see if it was correct or not…
I’d take it a step further than Nevada mentioned and put a pressure tester on it with a cold start up to see what the pressure does, just another tool for diag…
All this talk about “transmission overheating” or “radiator cap [not] holding proper pressure” is just not a likely explanation.
It is unlikely that a transmission could overheat enough to materially affect the engine temperature without noticeable shifting/stalling/drivability problems. If the transmission shifts properly, and doesn’t cause the engine to stall, I’d look for another explanation.
Similarly, a pressure cap not holding pressure, especially on this type of system (pressurized coolant tank with constant return flow) should not cause overheating under low load, and definitely not at idle. Either something is displacing coolant, such as exhaust gases or air that wasn’t purged correctly, or something is preventing the coolant from circulating properly, or something is preventing the hot coolant from transferring heat to the air. The actual cause could be something as simple as a defective or incorrect thermostat, defective or incorrect coolant temperature sensor/damaged or disconnected wiring to the sensor, defective radiator fan or fan relay, kinked or crushed coolant hose. Or it could be something more complicated, such as water pump turning backwards, radiator fan turning backwards, plastic shroud or base pan missing, head gasket(s) installed incorrectly, aluminum engine block has cracked or warped, plugged exhaust, clogged EGR valve or passages, etc.
Given that a professional mechanic has already taken a crack at it, and the customer is selling in order to pay a huge bill for unsuccessful repairs, my advice is to run away. It doesn’t sound like this will be cheap enough to allow you to make a profit if it requires replacement of the engine and/or catalytic converter.
Edit to add: On some vehicles–not necessarily this model–it is very difficult to purge air out of the cooling system when changing the coolant for any reason. The easiest solution to this problem is to buy a thermostat with a jiggle valve or small orifice, or to drill a small orifice to allow air to go through even when the thermostat is closed. I do this on every vehicle I own.
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Good grief
Thermostats have been that way for DECADES
You haven’t exactly told us something we don’t already know 
Unless this is priced right for a used engine swap, why buy the grief?
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So what happens when that same pressurized cooling system no longer holds pressure??
Please educate me…
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I guess this is either Cavell’s hobby or a way to make money but this current vehicle he is asking for help with sounds like one to pass on.
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yes, its a side hustle/hobby. i see overheating equinox and ask usual questions. sounds like headgaskets? owner says they are new. ok. step 2. new radiator and water pump? yes. ok step 3. seller said the temp gauge did not show hot but coolant is blowing out coolant reservoir. well, a scan tool would/should show high coolant temp. seller has spent a lot and is about ready to just sell it for cheap/parts.
Hummm, I think there is something in a coolant system that is designed to stop that from happening, if only we knew what that was… 
As already mentioned, block test it..
But Hooking up a pressure tester to the system while cold and then starting the engine, will give you an idea of how fast the system is being pressurized and how much pressure it is creating… Even if the temp sensor is giving bad info to the ecm, the pressure doesn’t lie, it will also show you when the thermostat opens…
As far as air pockets, how hot does the air get coming out of the vents, warm or cool air can/will mean an air pocket…Hot air normally means no air pocket…
Does it have rear HVAC?? air pocket back there??
Yeah good one to pass on unless just gonna swap engines. I’ve had my share of head gaskets and mysterious conditions. First thing you have no idea if the work was done, the quality of the work etc. so you end up having to retrace or redo everything that was done.
I got rid of my diesel at 480,000, $200, good tires, one owner. I’d had several engines. And head gaskets. Trying to remember. Sold it to a diesel guy that put a used engine in for the last 50k. Overheating, spikes, classic head gasket. About a month later he called me frustrated, re did gaskets but still overheating. Wanted to know what I thought. A mechanic asking me? What do I know? That’s why I dumped it. All I could tell him was that another diesel shop said they had to put radiators in to stop it. He never called again but six months later I got s summons for unpaid parking tickets so he must have figured it out.
Who needs the hassle?