2009 overheating

[Will_K]

Alright... here's the vehicle history in brief.

I acquired this car in February 2024 with blown head gasket and oil with obvious coolant in it. I replaced head gaskets with new steel head gaskets, water pump, coolant, radiator hoses, thermostat. Everything was fine until this winter when my daughter (for whom I bought the car) indicated it wasn't heating (she mostly drives to high school which is a 2 mile drive, and work which is about 4 miles, and soccer practice/games which can be more)... wasn't entirely obvious it was a serious problem. But it was starting to give overheating warning messages, coolant wasn't obviously low, but I decided I'd drive and concluded it might be time for a heater core. I decided I'd also replace the radiator while I had the system drained.

Last weekend I finished reassembly after replacing the heater core and radiator and ran the vehicle for a test drive hoping I'd confirm everything was okay and send her on her way... I got some heat, but still got an overheat warning and heat wasn't more than slightly warm and went back to cold.

At this point, I'm suspecting my thermostat was bad - guessing stuck closed. I didn't expect that as a possibility with under 2 years on the thermostat. The thermostat was an Advance auto Carquest part, 1 year warranty. I ordered a GM part to install this weekend.

I usually fill with a vacuum fill system, I watched a video using a large funnel and the bleeder valve so I tried that last night while I'm waiting on parts. The system took on another half gallon of coolant. But still (running parked at 3500 rpm to get temperature up) the overheat warning came on and coolant went back up the funnel. Some metal flakes were apparent in the funnel.


To my mind, it's possible the metal flakes may have been in the system as I hadn't flushed it previously, just drained. Is it possible that may have led to premature water pump failure and that's part of the problem? Is the thermostat consistent with what's happening? Is there anything else? (At this point I'm pretty much replacing all the mechanical components of the cooling system... radiator hoses were replaced 2 years ago)

I suppose it's probably prudent for me to do a cooling system flush with the thermostat out to make sure all debris is cleaned out.

 

[cavell]

I’ve always used composite gaskets on 3.4. Been told there are mls gaskets out there but never used them. Did you mill heads?
After motor has cooled do you get any air pressure from surge tank when you loosen cap? Sure sign of bad headgasket.

 

[Will_K]

At this point it just plowed forward and pulled the cylinder heads. I can't say the head gaskets had any deterioration or leaks, as happens the head and block had some coolant and that was apparent on gaskets. They didn't tear apart or anything.

The gasket passages had some debris buildup. It's not really the smoking gun i was hoping for... bearing in mind that I did do a coolant flush before disassembling, best guess at this point is that it caused trapped air.

I also double checked the torque before doing the 95 degree last step in bolt torque sequence. I'll do another water only flush before final fill.

I'm also ordering a new coolant reservoir. I have a 2007 ford focus that had a vacuum leak during vacuum filling and it was a seam leak on the reservoir. Does that happen on equinox reservoirs that are 17 years old?

 

[cavell]

I’ve done 10+ headgaskets jobs so I’m confident on my process. Do you have scan tool that shows coolant temp? Pretty cheap. $50. If motor is cool, loosen fill cap and open bleeder screw. You will get coolant to drizzle out. I fill system. Drive around till it’s hot. Stop. Let motor cool. Check surge tank level.
I fill surge tank to cold line. Never to top. Once motor cools the level always drops.
The surge tank level should never vary hot/cold by more then 1”.

 

[Will_K]

I'm not fully reassembled yet to run the engine.

Here's where I'm at. I have some kind of leak. It remains after replacing radiator, heater core and head gaskets. I can tell because the system won't hold vacuum with the vacuum fill system. It doesn't get coolant into the oil. It doesn't get combustion gasses into the coolant.

I have clamped off both hoses to the reservoir with 20 psi vacuum. The reservoir side holds a vacuum. The engine side of the clamps leaks.

I am thinking it has to be a hose or pipe between the engine and the heater core.

I added up dye and I'll fill with water then try a pressure test to see if I can locate a leak.

I haven't reassembled the alternator and serp belt for the engine to drive the water pump yet.

 

[Will_K]

I have everything reassembled.... except the oil filter and fluids. Amazon sent the wrong filter.

The coolant system leak? After a pressure test it turned out to be 2 bad hose clamps. One was a screw clamps on an upper radiator hose at the thermostat housing. It had a bend. The other was on the short hose at the front of the engine by the bleeder.

I still think everything else was needed because of tbe debris in the system, but that leak was pissing me off to find

 

[cavell]

did you mill heads? It’s required with mls gaskets. I use torque wrench even though I do the final 95deg twist and have estimated torque to be 75lbs, approx. I read online mls were available but I’ve never actually found them for sale. I always use composite gaskets. Mostly cuz that’s what GM uses.
Why did you decide to use mls gaskets?

 

[Will_K]

Didn't mill heads, I wasn't a fan of how the fiber gasket fell apart before the original head gasket replacement.

I think they call them MLS but the aren't all steel like I've seen on, for example, F150 MLS head gaskets. Here's new ready to install vs what I took off.

 

[cavell]

I did heads on a vue 3.0 and they were definitely mls. I shattered my wimpy torx socket removing old head bolts. I recall 3 torque/angle steps on the vue.

Ur pic seems to show composite gaskets on head. I also do not mill heads on equinox stuff.

Ha, and I never remove exh manifolds. If I can help it.
I see 2 left exh valves are whitish from burning coolant. Vs the right one which is darker. They say bad intake gaskets can lead to leaking coolant issues.