Coolant boiling over 05 mustang v6

[Bren]

Just recently changed thermostat and sensor/ flushed coolant and it ran fine for a week until I left it parked for a few minutes and all the coolant in the reservoir boiling out of the cap. Heat and AC work fine no coolant in oil no off coloured smoke I just want my car back without getting a new engine as the mechanics suggested please help

 

[Dino Dino Bambino]

The rubber gasket inside the expansion reservoir cap may have perished and it's no longer able to hold 16psi of pressure. This pressure is necessary in order to raise the boiling point of the coolant (roughly 3*F per psi) and prevent steam pockets forming inside the cooling system.
Replacing the cap will hopefully solve your problem. You might also want to consider swapping in an aftermarket aluminium thermostat housing (available in eBay) as preventive maintenance as the stock plastic unit is a known weak spot for leaks.

 

[07 Boss]

Just recently changed thermostat and sensor/ flushed coolant and it ran fine for a week until I left it parked for a few minutes and all the coolant in the reservoir boiling out of the cap. Heat and AC work fine no coolant in oil no off coloured smoke I just want my car back without getting a new engine as the mechanics suggested please help

Why did the mechanic suggest a new engine? I probably would never go back to that mechanic again unless he can back that up with a cracked block or something catastrophic but otherwise he's stay clear of him.

 

[Laga]

You just had cooling system open. You might have air bubble trapped inside.

 

[Cancerman]

I agree with Dino, it's not holding pressure or maybe a stuck thermo. I just did my 4.0, added the aluminum thermo housing with a 180 degree thermostat. I'm in Florida, I also installed a new radiator when I did the motor with all new hoses and pump. Nothing to chance. My car Idles at about 200 degrees per the PCM readout after about 20-30 minutes at idle with the A/C on. Expansion tank cap is your cheap easy first step.

 

[Bren]

Why did the mechanic suggest a new engine? I probably would never go back to that mechanic again unless he can back that up with a cracked block or something catastrophic but otherwise he's stay clear of him.

 

[Bren]

I’ve had it brought to several mechanics and no one seemed to have a clue so they said it would be cheaper to just get a new engine but I don’t have that kind of money so I parked it for 2 years. This year I decided I’d try find the problem with my minimal experience. I changed the thermostat and sensor and flushed coolant/ burped the system and it drove like a dream for a week until one night I was stopping to get food and there were no symptoms of it overheating, but the coolant began to violently rush out of the coolant cap. The next morning I noticed the cap is quite finicky and has to be rotated a few times before it’s on solid. I drove it for 10 minutes or so and parked it and kept it idling for another 10 and nothing seemed to leak but the fans kick on and of around like 40 second intervals and I hear a clicking that I thought was the water pump which spins for the 30 seconds and clicks off

 

[Bren]

I appreciate the replies, I just picked up a new cap for my coolant and I’m going to see if it holds after driving for 15 mins then idling for a bit

 

[07 Boss]

I’ve had it brought to several mechanics and no one seemed to have a clue so they said it would be cheaper to just get a new engine but I don’t have that kind of money so I parked it for 2 years. This year I decided I’d try find the problem with my minimal experience. I changed the thermostat and sensor and flushed coolant/ burped the system and it drove like a dream for a week until one night I was stopping to get food and there were no symptoms of it overheating, but the coolant began to violently rush out of the coolant cap. The next morning I noticed the cap is quite finicky and has to be rotated a few times before it’s on solid. I drove it for 10 minutes or so and parked it and kept it idling for another 10 and nothing seemed to leak but the fans kick on and of around like 40 second intervals and I hear a clicking that I thought was the water pump which spins for the 30 seconds and clicks off

Cheaper to buy a new engine? WTF kind of place are you taking your car? Please do not listen to these tools. Like I said, unless you have some kind of catastrophic engine failure or a bad head gasket replacing the motor will not do anything. There is something wrong with your cooling system. And your water pump should not be clicking off. That sounds like a bad relay or ground. Why is there an electric pump on your car? Even an electric pump like mine will run constantly all the time.

 

[Robert Larimer]

I’ve had it brought to several mechanics and no one seemed to have a clue so they said it would be cheaper to just get a new engine but I don’t have that kind of money so I parked it for 2 years. This year I decided I’d try find the problem with my minimal experience. I changed the thermostat and sensor and flushed coolant/ burped the system and it drove like a dream for a week until one night I was stopping to get food and there were no symptoms of it overheating, but the coolant began to violently rush out of the coolant cap. The next morning I noticed the cap is quite finicky and has to be rotated a few times before it’s on solid. I drove it for 10 minutes or so and parked it and kept it idling for another 10 and nothing seemed to leak but the fans kick on and of around like 40 second intervals and I hear a clicking that I thought was the water pump which spins for the 30 seconds and clicks off

Are you running the A/C while testing? If so it sounds like your low speed fan resistor has failed and you have only high speed available. This is a common problem that will cause cycling like you described . On our cars the low speed fan runs continuously when the AC is on to cool the condenser coils. When the fan is not working the compressor will build up pressure and enable the high speed fan until the pressure drops and the pressure starts building up again. It is not good for the compressor at all. The clicking you hear is the A/C compressor clutch not the water pump which is driven by the belt. I would replace the the entire radiator fan assembly since they want ridiculous money for the resistor and you can get a new fan and resistor for about the same. The one in the link below is the one I used and it works great. It can easily be installed in less than a hour too.

https://www.amazon.com/gp/product/B000VKPRNY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[Bren]

Are you running the A/C while testing? If so it sounds like your low speed fan resistor has failed and you have only high speed available. This is a common problem that will cause cycling like you described . On our cars the low speed fan runs continuously when the AC is on to cool the condenser coils. When the fan is not working the compressor will build up pressure and enable the high speed fan until the pressure drops and the pressure starts building up again. It is not good for the compressor at all. The clicking you hear is the A/C compressor clutch not the water pump which is driven by the belt. I would replace the the entire radiator fan assembly since they want ridiculous money for the resistor and you can get a new fan and resistor for about the same. The one in the link below is the one I used and it works great. It can easily be installed in less than a hour too.

https://www.amazon.com/gp/product/B000VKPRNY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[Bren]

Is there a way to test this or find a cheaper fix rather than changing the whole thing ?i checked the resister cable That is under the reservoir and the wires seems to be fine.. I haven’t had a leak so far since i changed the thermostat and coolant cap. I did some poking around with the relays and switched one of the horn relays with the as well as changed the orientation of the low speed fan relay because in the manual for some reason the numbers were backwards.. I also went into the passenger side to check the smaller fuses and found there to be 5amp fuses where 10s should be and I changed them out (my gas gauge on cluster didnt display the gas level) now it more accurately displays the level but doesn’t change color.. also was missing two fuses for the two rear subs which work after right replaced it so I don’t know what type of shit the previous owner put this poor thing through

 

[Bren]

My ac also has been blowing air that is hardly any cooler than the outside air

 

[07 Boss]

Do you have a set of manifold gauges? You will need to check the static and running pressures of your system to properly diagnose the ac issue. Like you said you can hear it clicking on and off which means there is some safety feature that keeps kicking it off. You will probably need to take it to an ac place to figure out what's wrong. Or you can just try and fill it with some refrigerant and see if that helps but without knowing the issue it may not do a thing. If you do this use straight Freon, nothing with stop leak in it.

 

[07 Boss]

Could be also a problem with your blend door actuators. My car has a good running ac but the temp door actuator is fubar so it only gets so cool. Just haven't got around to diving into the dashboard at the moment. These tend to make a clicking noise when they go out.

 

[Bren]

I feel like Robert was onto what I was talking about because the clicking came from the thing on the bottom right which is controlled by the belt.. I had a pressure test done which passed and actually the RAD guys were the ones who said it’s a head gasket after they put head gasket sealer in the system and it continued to overheat then sent me home with a coolant cap that didn’t fit and a $100 bill and a “good luck” fml

 

[Dino Dino Bambino]

The head gaskets rarely fail on these engines unless you severely overheat them and warp the heads.
Hopefully when you do get the correct coolant reservoir cap, the boiling over will stop.
When you say overheating, what sort of temperatures are you seeing? Does the electric fan cycle on and off when the engine reaches a predetermined temperature? If it doesn't and the coolant temp. continues to rise beyond 230*F, switch on the AC and see if the fan does turn on then and cool the engine down.
When you turn the AC on, a whirring sound from behind the dash that lasts a coupe of seconds is likely to be from stripped gears inside a blend door actuator. My write up will guide you to fix it.

https://www.s197forum.com/threads/how-to-dash-blend-door-actuator-replacement-05-09-mustang.138833/

As for the AC itself, it sounds like it's low on refrigerant. It probably has a small leak and I suggest you visit an AC service center where they can vacuum and refill the system with fresh refrigerant plus an ultraviolet sensitive dye that'll glow green under a black light (like a list of 50 valuable cars that are begging to be stolen )..

 

[Robert Larimer]

Is there a way to test this or find a cheaper fix rather than changing the whole thing ?i checked the resister cable That is under the reservoir and the wires seems to be fine.. I haven’t had a leak so far since i changed the thermostat and coolant cap. I did some poking around with the relays and switched one of the horn relays with the as well as changed the orientation of the low speed fan relay because in the manual for some reason the numbers were backwards.. I also went into the passenger side to check the smaller fuses and found there to be 5amp fuses where 10s should be and I changed them out (my gas gauge on cluster didnt display the gas level) now it more accurately displays the level but doesn’t change color.. also was missing two fuses for the two rear subs which work after right replaced it so I don’t know what type of shit the previous owner put this poor thing through

Do yourself a big favor and pay the $100 for a new fan assembly and put it in yourself. I'm sure you have spent more than that on mechanics and your fan motor is 17 years old. Your A/C compressor will thank you for it if it hasn't croaked already. Meanwhile I would drive with the A/C off. A reliable car that doesn't overheat is priceless and the first step is a good fan. Here is a link the the low speed fan resistor for your car...It's $57 all by itself. It is mounted in the cooling fan shroud and it is included in all new units.

https://www.searchfordparts.com/oem-parts/ford-resistor-7r3z8l603a?c=Zz1jb29saW5nLXN5c3RlbSZzPWNvb2xpbmctZmFuJmw9NSZuPUFzc2VtYmxpZXMgUGFnZSZhPWZvcmQmbz1tdXN0YW5nJnk9MjAwNSZ0PWJhc2UmZT00LTBsLXY2LWdhcw==

 

[Bren]

The head gaskets rarely fail on these engines unless you severely overheat them and warp the heads.
Hopefully when you do get the correct coolant reservoir cap, the boiling over will stop.
When you say overheating, what sort of temperatures are you seeing? Does the electric fan cycle on and off when the engine reaches a predetermined temperature? If it doesn't and the coolant temp. continues to rise beyond 230*F, switch on the AC and see if the fan does turn on then and cool the engine down.
When you turn the AC on, a whirring sound from behind the dash that lasts a coupe of seconds is likely to be from stripped gears inside a blend door actuator. My write up will guide you to fix it.

https://www.s197forum.com/threads/how-to-dash-blend-door-actuator-replacement-05-09-mustang.138833/

As for the AC itself, it sounds like it's low on refrigerant. It probably has a small leak and I suggest you visit an AC service center where they can vacuum and refill the system with fresh refrigerant plus an ultraviolet sensitive dye that'll glow green under a black light (like a list of 50 valuable cars that are begging to be stolen )..

 

[Bren]

In terms of overboiling the rad cap seems to have Fixed the problem.. the temp gauge never seemed to go past the halfway mark… after messing with the relays and flipping it as the manual suggested the fan now kicks on and off at around 30 seconds when it gets up to temperature… when I turn on the ac I hear a fan or smth inside kick on initially but no gears grinding and the rad fan kicks around 30 seconds later then kicks back off, it blows cold air fine but seems to get warmer as the car warms