Overheating-air in coolant??

[BA4IN775]

I am having an issue with overheating while driving after changing the breather, pcv, & oil cooler. I removed the intake and coolant line above the intake to do job. Flushed the coolant system a few times until clear water came out. Filled with fresh coolant. Thought I purged the system of all air. Went on test drive. Started to over heat. Got to 3rd line and I shit the car off. Had it towed home. Worked on the coolant for an hour. Opened the purge screw on the upper coolant tube. I can not get a solid flow of coolant to come out. Test drove again. It will idle with no problem. Hold RPMS at 2,000 starts to get hot after 2 min. System cools back down to 1/2 way mark once I let off the gas. Starts to get hot when driving after a couple min of driving. I did a compression test to make sure HG is ok. Readings are 160, 160, 160, 165. Is there a trick to purging the air from this system? I had no overheating issues before this. Thanks for any advise.

[rocket1420]

Is the fan kicking on? I'm having a similar problem, and I'm pretty sure the main fan doesn't turn on. I still have to diagnose it.

[BA4IN775]

Yes, the fans are kicking on. Did you change any parts before the problems started?

[Pswish]

Thinking you are stuck in closed loop mode or the water pump isn't pushing coolant through.. Thermostat?

[BA4IN775]

If I crack open the bleeder screw on the coolant pipe it will hiss coolant and air. Once it starts to get hot if I open the bleeder I only get hot air. If the water pump wasn't working working wouldn't it be constant non flow of coolant?

[Ian1006]

Bleed car cold. SUPER IMPORTANT!

Lift reservoir and then crack hard line bleeder, then bleed heater core hose. Drive it around and then let it cool off, mine took 3-5 times of doing this.

[rocket1420]

Yes, the fans are kicking on. Did you change any parts before the problems started?

I changed about half the parts in the engine bay. Head, thermostat, a few pipes, coolant flange, and a few other odds and ends.

- - - Updated - - -

Thinking you are stuck in closed loop mode or the water pump isn't pushing coolant through.. Thermostat?

But why does it cool down after he lets off the gas?

[Pswish]

But why does it cool down after he lets off the gas?

Closed loop is used to heat up the engine fast then the thermostat opens to allow coolant to flow through the radiator to the coolant mapping. If you are stuck in closed loop then it would make sense for the engine to overheat without the ability to cool off the coolant through the radiator. Failing fans or temp sensors can cause an emergency mode in the coolant system.

[rocket1420]

Closed loop is used to heat up the engine fast then the thermostat opens to allow coolant to flow through the radiator to the coolant mapping. If you are stuck in closed loop then it would make sense for the engine to overheat without the ability to cool off the coolant through the radiator. Failing fans or temp sensors can cause an emergency mode in the coolant system.

Yeah I didn't think that the whole way through. My radiator is working because the needle stays in the middle if I'm moving. His isn't working, so you are most likely dead on. Bad thermostat, or something clogging the flow of coolant.

If I crack open the bleeder screw on the coolant pipe it will hiss coolant and air. Once it starts to get hot if I open the bleeder I only get hot air. If the water pump wasn't working working wouldn't it be constant non flow of coolant?

From your description, I don't see where coolant is flowing. Sounds to me like it's boiling. Did you put in a proper 50/50 mix of G12 or G13?

[BA4IN775]

Thanks for all the replies. Just wasn't bled enough. Redid everything. Bled the system, bled heater core, undid the expansion tank and lifted it- THANKS IAN1006, opened the bleeder with tank tiled up. Just got back from a 10 mile drive. Needle stayed right in the middle.

[jacobsen]

Definitely have to do it when the motor is cold and off. you might still have more air in there. Wait until the motor is completely cold raise the expansion tank. Loosen the cap so there's no suction. Open the hard pipe leader screw until it's solid. Wiggle back the top heater core hose until the bleed hole is exposed and bleed that one as well. It's so simple it's damn near impossible.

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[old guy]

Closed loop is used to heat up the engine fast then the thermostat opens to allow coolant to flow through the radiator to the coolant mapping. If you are stuck in closed loop then it would make sense for the engine to overheat without the ability to cool off the coolant through the radiator. Failing fans or temp sensors can cause an emergency mode in the coolant system.

Just for clarification the closed loop cold start isn’t tied in with the thermostat opening. The thermostat has a mechanical bellows with a wax heater. The thermostat will open on its own once the coolant gets up to the required temperature. The wax heater is what the ECU uses to force the thermostat to open sooner under specific conditions.

And you are correct that a faulty sensor or an incongruent sensor reading will cause the ECU to put the cooling system in “protection mode” by applying full power to the thermostat heater as well as activate the radiator cooling fans.

[Ian1006]

Thanks for all the replies. Just wasn't bled enough. Redid everything. Bled the system, bled heater core, undid the expansion tank and lifted it- THANKS IAN1006, opened the bleeder with tank tiled up. Just got back from a 10 mile drive. Needle stayed right in the middle.

Glad it worked, I fought mine until other forum members told me the right way to do it.

[BA4IN775]

Forum members on here are great. I'll redo the bleed again tonight. So I should be bleeding the upper coolant (hard pipe) with the motor shut off? Just to make sure I'm doing it right my preocesses will be...engine off, undo expansion tank cap enough to remove vacuum, lift up the expansion tank, open bleeder screw, leave open while coolant is flowing out, close screw when coolant is solid- all this while the engine is cold and off? Start car, bring to operating temp, turn on heater- temp high and fan low, pull top heater core hose back to expose bleeder hole, let run until solid coolant is running out, put hose back into place. Done. Am I missing anything? Thanks in adavance.

[Ian1006]

Do it all cold while off not running.

Lift reservoir with cap off and crack hard pipe bleeder until steady stream. Close bleeder and then pull rain tray, slide back upper heater core hose to expose the hole and then lift expansion tank until steady stream comes out. Push hose back on and put it all back together, drive around until it warm and park and wait for it to cool off again completely then repeat until no air is left.

[BA4IN775]

Thanks Ian. How many times did it take you to get the system completely bled? How do I know when the system is completely bled?

[Ian1006]

2-3 times, you will know when no more airs comes out

[BA4IN775]

Thanks. 👍

[MacFady]

Forum members on here are great. I'll redo the bleed again tonight. So I should be bleeding the upper coolant (hard pipe) with the motor shut off? Just to make sure I'm doing it right my preocesses will be...engine off, undo expansion tank cap enough to remove vacuum, lift up the expansion tank, open bleeder screw, leave open while coolant is flowing out, close screw when coolant is solid- all this while the engine is cold and off? Start car, bring to operating temp, turn on heater- temp high and fan low, pull top heater core hose back to expose bleeder hole, let run until solid coolant is running out, put hose back into place. Done. Am I missing anything? Thanks in adavance.

You don't wait until the car is at operating temp before turning heat to high fan to low, you have that set from the beginning. Personally, every time I've done a coolant change I undo the Phillips head and set the reservoir up high, I leave the cap off, start car, fan low heat high. Once at operating temperature you should have heat blowing from the vents. Top up reservoir, done. I've never had an issue, I don't bleed from the hard line. On a side note, I always add coolant very slowly.