Blew coolant bottle cap below 220f

[mr_maxime]

The car started heating up and I noticed the coolant spraying in the back. Temp gauge still showed below 220.

Adding more coolant now since I'm on the side of the road. Any idea what it could be?

[sdg3205]

Thermostat is lying or there is air in the system.

[mr_maxime]

I just got home after adding coolant.

Thankfully, I was 4 miles from home and a good Samaritan came to help me. It took 1.5 gallons of coolant to get it back to a proper level. Temp gauge was back down while driving home. The water pump pulley was still turning when the car was running. There was no back pressure on the coolant pipes next to the pump, which the samaritan said it meant the thermostat was open. AC was on so the fans were on. My alternator belt did break about 2 weeks ago which led to the car overheating past 220. I hadn't bled the system since, but I will once it cools down.

[sdg3205]

I just got home after adding coolant.

Thankfully, I was 4 miles from home and a good Samaritan came to help me. It took 1.5 gallons of coolant to get it back to a proper level. Temp gauge was back down while driving home. The water pump pulley was still turning when the car was running. There was no back pressure on the coolant pipes next to the pump, which the samaritan said it meant the thermostat was open. AC was on so the fans were on. My alternator belt did break about 2 weeks ago which led to the car overheating past 220. I hadn't bled the system since, but I will once it cools down.

The samaritan is incorrect. No system pressure is indicitvie of a bad rad cap or system leak. Nothing to do with the thermostat.

You need to pressure test.

[AugustneverEnds]

I am really surprised your car blew the pressure cap, you refilled it without bleeding the system and managed to drive 4 miles. If 10287 had ANY air enter through the cap I wouldn't make it 1000ft without having to purge the air out. I strongly suspect your cap is defective and you have a leak somewhere.

[David T]

I just got home after adding coolant.

Thankfully, I was 4 miles from home and a good Samaritan came to help me. It took 1.5 gallons of coolant to get it back to a proper level. Temp gauge was back down while driving home. The water pump pulley was still turning when the car was running. There was no back pressure on the coolant pipes next to the pump, which the samaritan said it meant the thermostat was open. AC was on so the fans were on. My alternator belt did break about 2 weeks ago which led to the car overheating past 220. I hadn't bled the system since, but I will once it cools down.

If you previously overheated the motor you may have overheated it to the point where you damaged the head gaskets. Now combustion gasses can enter the cooling system, overpressurizing it and blowing out coolant. There is a quick and easy test. If you did pop the head gaskets the only cure is to replace them. There can be other bad effects from overheating, it depends on how hot it got. They include warped heads, bad liner seals, coolant in the oil, etc. BTW, when you lose that much coolant (1.5 Gal), the temperature gauge can no longer give you an accurate reading.

[mr_maxime]

I know i checked the coolant level this weekend, maybe I didnt put the cap back on properly. Would that cause any issue?

[sdg3205]

Possibly, because you're increasing the likelihood of expansion and a boil over by removing the variable of pressure.

[mr_maxime]

I did bleed the coolant from the water pump about half an hour ago. I just checked the oil and it is not milky.

When I previously overheated it was below the first red tick. I'm going to lose it if that was the start of the damn problems cause that was a brand new DMC belt that broke with less than 60 miles of use.

[sdg3205]

What red tick?

Never mind, I get it - the gauge.

[mr_maxime]

The one between 220 and 260

[sdg3205]

I think there is air in your system.

[mr_maxime]

Ill bleed from the radiator in the morning.

Since this is my daily driver and only car, i am stressing out. At least, I just remembered that I moved to an apt building right next to my coworker and I already walk across the street to get groceries anyways. Hopefully, he'll let me carpool with him in case my car is down for repairs.

[David T]

I think there is air in your system.

If there is air in the system and you bled it and you keep getting air, either you are not bleeding thoroughly or you popped the head gaskets or you have leaks. Or possibly any combination. You may also have a bad rad cap. The list goes on. At least you don't have coolant in the oil. Check the oil fill for signs of moisture. Does the oil smell burnt?

[John U]

Did the cap actually come off?
I had an issue with a cap that had coolant spraying from the sides. It wasn't sealing properly and as the pressure built up coolant sprayed out. Bending the tabs on the cap to make it a little tighter solved the problem.

[mr_maxime]

Did the cap actually come off?
I had an issue with a cap that had coolant spraying from the sides. It wasn't sealing properly and as the pressure built up coolant sprayed out. Bending the tabs on the cap to make it a little tighter solved the problem.

No it was spraying out the sides. Part of the reason why I think i might have put it on incorrectly.

I drove to and from work without any apparent issues unless my temp gauge is lying. Outside temp was 90f and coolant temp was at the "160" line

EDIT: I did also bleed from the radiator this morning and did from water pump again just to be safe

[John U]

I am pretty sure it is the cap. Bend the tabs on it to make it tighter. Worked for me.