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Discussion Starter · #1 · (Edited)
Symptoms:
Car over heats after 20 minutes
Pressure builds very high in the reservoir tank, enough that the release valve opens and causes a 'whistling' sound.
No heat in the cabin.

Test performed:
Block test - came out negative (color never changed to yellow or brown, stayed dark blue).
Leak down test - there was some loss of compression but all tested tested to the 'moderate/green' indicator on gauge. No other areas can be heard to leak the air.
Vacuumed system with venturi type filler system. System held 25 psi. Refilled system with Dex cool via same vacuum.
Also tried to bleed system by leaving cap off the reservoir.
Disconnected all hoses (lower & upper radiator hoses & heater core hoses) to check for obstruction - none found.
Ran distilled water from top of radiator port and water flowed freely to bottom of radiator exit port.
Started the car from cold with the reservoir cap off to see if there is a sudden pressure release into reservoir - tested negative.
There are NO codes.
Fans turn on (somewhat late in my opinion but they may be set that way. They turn on when the engine is closer to 200-220 degrees

Replaced:
Water pump
Thermostat
Engine Temp Sensor
Coolant
Reservoir and cap

Is there any other test or procedure I can complete before I make the determination that it is a blown head gasket since it is not really indicating this is the issue?
 

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I would disconnect the hoses from the heater core and check that water flows through the heater core easily. Also with the hoses off the core, start the engine and watch for coolant flowing from the heater hose [into a bucket].

You have no heat.

Coolant flowing through the heater core usually passes close to the thermostat warming it up and allowing it to open in a timely manner. If the heater core is plugged and the thermostat closed [cold start] , it will take an overly long time for the thermostat to open. 220F is normal for the fans to come on low speed.

History, of the vehicle? Has some "stop leak" every been put in this engine? Thermostat put in backwards?

If run for a long time, does the temperature settle down operate normally?

There is a drain plug on the bottom side of the water pump. Perhaps removing it will help bleed air from around the pump?
 

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Discussion Starter · #3 · (Edited)
Vehicle history: No stop leak or any other type products into coolant systems & nothing other than oil into engine. There is no evidence of coolant mixing with oil (I have not removed the valve cover though). The cap of the oil filler had very little milky residue that seemed to be more of condensation. When I drained the coolant there was no evidence of oil on the surface). No other issues until this. Thermostat has been placed correctly into the housing. I do not let the engine run after the 1st signs of large build up in the reservoir & when the gauge starts to climb into the upper 3/4 range + temp reading on my scanner of 235 ish.

Thank you for the tips. When I had the heater core hoses off, I did blow some shop air into it and the coolant that was in there flowed out fast. I also poured coolant directly into the heater core inlet hose slowly and it flowed out the other end. I will perform the test you mentioned (disconnecting the core hoses). You mean disconnect the outlet hose only to check for flow, yes?

I will also take your tip of loosening the bleeder screw on the new water pump for a few to see if that has any effect. Will report back.

As far as run time, I have not let the engine go past 235 degrees on my live scanner in which at this point the reservoir starts the whistling sound that pressure has been exceeded. I do not see 'bubbling' in the reservoir but vapor/water forms at the top of the reservoir. I also have ordered the GM thermostat and it will arrive on the 30th of Nov. There is an aftermarket Auto Zone one in there now (I did test it in boiling water and it does seem to open & close) but I figured I am so far down the rabbit hole why not order an original t-stat.
 

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It appears the heater core flows coolant but you do not have heat. This is puzzling, water pump failure or air bubble around water pump? A kinked hose? Obstruction?
If water is not flowing through the heater core, the heater lines as they enter the firewall will be very slow to warm up. Disconnecting the outlet hose from the heater core and starting the engine should confirm flow.

A little milky residue under the oil cap does not sound good but we will see. If the head gasket is leaking gases into the coolant, the coolant might bubble but it would not necessarily mean the engine would over heat so quickly.

You could bend or pry open the old thermostat [creating a bypass] and install it to see what happens.

Did these problems develop over time or suddenly? After changing a part? Any work done to the engine?
 

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Discussion Starter · #5 ·
Thanks. Based on your suggested tips, here is my plan for tomorrow:
  • Unscrew water pump bleeder screw a bit to see if I can get it to release any trapped air
  • Unplug the heater core outlet hose and run the engine to check for flow
  • Try to pry open the t-stat or remove it completely for testing purposes to see if anything changes while the t-stat is out/pried open
This is my sons car and from what he shared with me the issues came about quite suddenly. There has been no work performed to the engine (other than unscrewing the temperature sensor and removing/installing the water pump.
 

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Discussion Starter · #6 ·
Here is a small video. This is right before the reservoir starts to 'hiss & whistle' from over pressurization. If you look at the top hose, it starts to spit back coolant, almost sputtering it back in. Not sure if this is any indication of anything. You can also notice that the coolant level has risen above the fill level where it started. It does not go back down until I turn off the motor and it cools down a bit.

Vid 1
 

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The upper rad hose should remain relatively cool until the thermostat opens, at which time the hose should quickly heat up. You can feel for this with your hand. Once hot, the hoses should be much harder to squeeze. Is one of the rad hoses kinked or bent/obstructed? There is an o-ring on the over flow tank cap. It has a habit of deforming and not sealing. I know it's new but check it, compare it to the old one.
Does the engine vibrate a lot? If the chain that dives the water pump has become dislodged from the crank sprocket or failed in some way, the balance shafts would not be turning as well.

No heat and overheating, point to the water pump, obstruction of the pump, lack of coolant, pump cannot prime, failed pump drive......
Confirm again tomorrow that you have no heat.
 

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Discussion Starter · #8 ·
The upper radiator hose does remain cool at 1st. It starts to get warm on top, and stays cool on the other end. When the vehicle is at a operating temp, the hose does get firm, and hot, (cooler on the other end of the hose where it is entering the radiator. The lower radiator hose is cooler that the upper when vehicle is at op temp. It is cool the the touch on the bottom where it connects to the radiator and hotter on the top where it connects to the thermostat housing. Its also gets harder. There are no kinked hoses or obstructed hoses.

I will add checking the O-ring on the cap tomorrow.

The engine does not vibrate a lot - I'd say normal for a 212,000 mile engine. Car rides smooth with no hesitation. I used the full moon sprocket tool per manufactures instruction and do not have any whine or noticeable noise from the timing area. I would think there would be a noticeable performance issue if there was a problem with the secondary chain? If you think I should remove the timing cover to inspect, I will. I should note that the vehicle is overheating just as it did before I removed the original pump (in which after inspected seemed to be in working order - no missing fins and rotated well). I also replaced both O-rings on the rear cooling tube assembly and also changed the gasket on the thermostat housing that attaches to the rear engine block).

And yes - I have no heat, and lots of pressure build up in the reservoir. I notice that the hose leading into the top of reservoir spits out a little coolant intermittently when reservoir is about to start making the whistling noise.
 

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No need to remove the timing cover. If the pump/balancer chain had failed it would shake a lot and or make a lot of noise.
The upper rad hose should be hot all the way to the radiator as there is nothing to cool the fluid for that short of a distance. Again, appears to be lack of flow, just like the heater core.
This is a puzzle. Tomorrow may bring the answer. You have done a test for combustion gases in the coolant and it passed so I'm out of suggestions for now.
 

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Discussion Starter · #10 ·
Yea - I'm stumped and although I am not a mechanic I am normally pretty good solving car issues. Thank you for your help and time thus far. I will report back after the next steps.
 

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2011 Malibu LTZ 3.6L V6 Red Jewel Tintcoat
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I agree with @Drunken Elvis on the upper hose. If one end is hot, the other should just about as hot, because the actual cooling takes place once it reaches the rad. I can see a few (like less than 5°) difference in the ends of the upper hose, but not what you describe. That sounds like a flow issue, as if the t-stat is not opening.

If you're gonna take stuff apart, I'd take the t-stat out and test it in boiling water with a meat thermometer.
 

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Discussion Starter · #12 ·
I agree with @Drunken Elvis on the upper hose. If one end is hot, the other should just about as hot, because the actual cooling takes place once it reaches the rad. I can see a few (like less than 5°) difference in the ends of the upper hose, but not what you describe. That sounds like a flow issue, as if the t-stat is not opening.

If you're gonna take stuff apart, I'd take the t-stat out and test it in boiling water with a meat thermometer.
Thanks. I plan on taking the t-stat out tomorrow. I did test it and it opened & closed but did not use a temp gauge. It started to open right before full boiling in a pot I will get my hands of a temp gauge as you suggested. I do have a GM t-stat being delivered on 11/30.
 

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Discussion Starter · #14 ·
Hi, I have some updates. The GM thermostat came in. I changed it and still, the exact same issue arose. Pressure (whistling sound from reservoir and soon after that temps approaching over 220. I then let the car cool down a bit. I proceeded to disconnect the heater core hose from the port closer to the passenger side (the port that comes out of the thermostat rear housing that also has the rear cooling pipe connected to it running to the water pump) and no coolant came out of the disconnected hose. I did see coolant building pressure and starting spurt out of inlet tube as the car came back to operating temperature. Here is a video. Temp was 218 when I shut the car off. This is the 1st area where I can see this type of coolant reaction. Can this be the cause of the pressure that is building in the reservoir, thus concluding that it is a blown head? The steam you see if coming from coolant that is burning off on the lower exhaust pipe from spillage.

Video:

Video 2
 

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That video is not good. There is either not enough coolant in the system for it to pump, or there's a huge clog somewhere.

I'd like to ask how the other parts of the system are working.

When the engine is completely cold, or just warm to the touch, there won't be any pressure in the system. Remove the upper radiator hose at the radiator. Does coolant want to come out of the hose? If not, then there's your issue because there's not enough coolant in the system. If it does, then what level is the recovery tank?

When you remove the same hose in the video, can you hook up a tiny bit of pressure to it (under 10 psi), or a garden hose at a low flow rate? Does the water go into the hose and come out somewhere else? It should. If not, you have an issue.
 

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Discussion Starter · #17 · (Edited by Moderator)
I can check on both of these tomorrow.

Yes I disconnected the upper hose and coolant did come out. There was also coolant in the upper hose that goes from that point to the reservoir. Since I have tried so many things, I pu in coolant to the upper hose and it started to fill into the reservoir.
 

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There appears to be no flow from that heater hose and no flow out of the pipe it is disconnected from. I can think of a few possible causes.

That is the return hose from the heater core and the core is plugged.
The water pump has failed in some way. [the old pump appeared fine and it did the same thing]
A large air pocket is surrounding the pump. [ add coolant while removing the pump drain plug]
Head/gasket is allowing air/combustion gas to enter the cooling system and the pump is cavitating in an air bubble. [you tested for combustion gases in the coolant?]

With the engine cool, fill all hoses, rad , everything you can, there is a small diameter hose that runs from the top of the head to the top of the overflow tank. Fill the engine via this hose at the end. Run the engine without the cap on the reservoir. If it drains of coolant keep adding. If you could temporarily replace part of a heater hose with a clear plastic line you could see if you had flow.

DrivenDaily has the right idea. If a hose is used to force water into the removed hose, water should be forced out of the pipe, or, is water is forced into the pipe it should return out of the hose. If this water flows easily, the water pump is not working [air bubble?]. If it doesn't flow, you have an obstruction
 

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Discussion Starter · #19 ·
Thanks for all of this. I will go back at it tomorrow.

That is the return hose from the heater core and the core is plugged. I will check for obstruction again, however when I put shop air into the inlet (other hose), coolant did dome out of this end.

The water pump has failed in some way. [the old pump appeared fine and it did the same thing] Yes, this is a new pump, and the old pump did the same thing. The old pump seemed to be in good condition.

A large air pocket is surrounding the pump. [ add coolant while removing the pump drain plug] Will complete this tomorrow or Thursday.

Head/gasket is allowing air/combustion gas to enter the cooling system and the pump is cavitating in an air bubble. [you tested for combustion gases in the coolant?] I did the block test and it come out negative. However this description seems to be the most likely at this point, given that I have no heat. I hope not, but if this pressure that we see coming out of the inlet is pushing the coolant back and causing the pressure in the reservoir, then I may be changing a head gasket soon. I will report back.

With the engine cool, fill all hoses, rad , everything you can, there is a small diameter hose that runs from the top of the head to the top of the overflow tank. Fill the engine via this hose at the end. Run the engine without the cap on the reservoir. If it drains of coolant keep adding. If you could temporarily replace part of a heater hose with a clear plastic line you could see if you had flow. I will complete tomorrow or Thursday.
 

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One other thing I just thought of regarding the pump.

Some engines, and I don't know if yours is one or not, have 2 different water pumps available, one that spins one way and one that spins the opposite direction. If that is how yours is, you may have gotten the wrong replacement part. You should be able to call a parts store and ask if more than one pump is available, then work out which one you need.
 
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