Coolant Boiling out of overflow

[W3bb3r04]

I just got my car back together and drove it today. Well it got to operating temp and all was well but about 20 minutes of driving later coolant was spraying out of the coolant overflow tank. Now at operating temp the coolant is boiling out of the overflow. Even with the cap off it does this. There is no coolant in the upper radiator hose and the heat is not hot. I went ahead and changed the thermostat to make sure it wasn't that but no change. Everything is the same cooling system wise as the last build so Im confused on why Im having issues. Stock radiator, waterpump, fans, etc. Only change is the upper radiator elbow.

I thought it may have been a bubble at first but I don't see why it wouldn't find its way to the overflow. I also thought maybe the water pump shaft binded and broke but not sure what would cause that. The waterpump pulley is turning and I don't want to throw a bunch of parts at it. If anyone has any ideas, shoot them my way.

Thanks guys!

 

[BruceH]

I'm not even sure if it's possible but I'm going to mention it. Any chance the thermostat is backwards? Something is blocking the flow and that would be the easiest to fix.

Did you make sure the new elbow was clear? If those two are good I'd pull the water pump and check it out.

 

[W3bb3r04]

I'm not even sure if it's possible but I'm going to mention it. Any chance the thermostat is backwards? Something is blocking the flow and that would be the easiest to fix.

Did you make sure the new elbow was clear? If those two are good I'd pull the water pump and check it out.

The thermostat is in the correct way and yeah the elbow looks good. Do you think there could be a shit ton of air in the system? I didn't elevate the front end when filling the system and burping it... Pulling the water pump is my last option but I guess it may have to be done.

 

[BruceH]

I don't know. It's never been an issue for me and I always fill without doing anything special like elevating the front end. I do leave the cap off until the coolant gets sucked in. Top it off, put the cap back on and it's good to go.

 

[W3bb3r04]

I don't know. It's never been an issue for me and I always fill without doing anything special like elevating the front end. I do leave the cap off until the coolant gets sucked in. Top it off, put the cap back on and it's good to go.

Yeah I didn't have any issues last time around either. I guess Ill try it then pull the water pump.

 

[bjtheman1]

Is the cooling fan working properly...High & Low?

 

[JeremyH]

This last time putting my car back together it took a good while to get the air out of my system, never had an issue before. Upper radiator hose was airbound and took 1hr plus of starting and trying squeeze hoses and get the air out.

And I was getting bad water temp readings too as the sensor was airbound so your car likely was overheating and not really at operating temp.

 

[W3bb3r04]

Thanks Jeremy! So you think this may be my issue?

 

[JeremyH]

That would be my first place to look for sure. It stumped me for a bit as I had never had that much trouble getting the air out before. I did have new water lines running down low to two turbos though lol

 

[W3bb3r04]

That would be my first place to look for sure. It stumped me for a bit as I had never had that much trouble getting the air out before. I did have new water lines running down low to two turbos though lol

Ill give it a shot today. I guess it makes sense if there was nothing in any of the lines, block, radiator, etc, that there would be a potential for some massive air pockets.

 

[dysan]

I found that having a second person helping, filling the tank and you reach under the car rapidly squeezing the lower hose helps to work the air out.

Also, if you can do the majority of the fill from the opening on the driver's side head that works a ton better than filling using the tank. Just get it almost till it overflows from that point, put the cap back on and finish from the tank. Of course it depends on which crossover you have....with my Edelbrock blower my thermostat is on the crossover up top so I can just pop the cap off and fill there.

 

[rayS197]

I had issues with my car doing the same thing right after my build. Overheated once and blew water everywhere. A friend recommended vacuum filling the coolant system. I borrowed the tool from a friend and worked like a champ. Also good fro checking leaks.

 

[Shotokan1509]

Didn't leave any rags plugging holes during build did you?

 

[W3bb3r04]

I found that having a second person helping, filling the tank and you reach under the car rapidly squeezing the lower hose helps to work the air out.

Also, if you can do the majority of the fill from the opening on the driver's side head that works a ton better than filling using the tank. Just get it almost till it overflows from that point, put the cap back on and finish from the tank. Of course it depends on which crossover you have....with my Edelbrock blower my thermostat is on the crossover up top so I can just pop the cap off and fill there.

Thanks I will definitely try that today. I'm thinking the highest point on mine is at the thermostat, therefore there is no coolant there. I shouldve filled it when I was changing it though

I had issues with my car doing the same thing right after my build. Overheated once and blew water everywhere. A friend recommended vacuum filling the coolant system. I borrowed the tool from a friend and worked like a champ. Also good fro checking leaks.

Thanks! I will try that if nothing else works

Didn't leave any rags plugging holes during build did you?

No I try not to use rags at all.

 

[dre256]

In the jeep 4.0Ls when they have that issue, a lot of times it turns out its a bad radiator cap or air still in the upper hose. But jeeps 4.0L use an open system and mustangs are a closed system. But radiator caps are cheap, that's why I mentioned it.

 

[W3bb3r04]

Update: nothing I have tried has worked. I pulled the water pump and it looked good and spun freely in the motor and in my hand. However I am not getting any water flow with the heater core lines undone on the passenger side head. I can blow through one side and it will circulate through and come out the hose for the same connection. The thermostat is opening, but it seems like there is no water flowing.

 

[19COBRA93]

What all did you change? You got your car back from having what done?

 

[W3bb3r04]

What all did you change? You got your car back from having what done?

I did all the work myself. New motor. Same coolant system. I've changed the thermostat and checked the water pump so far.

 

[weather man]

The vacuum pump seems like a good idea to me.

 

[W3bb3r04]

The vacuum pump seems like a good idea to me.

I filled the coolant from the reservoir and the heater hoses. I wouldn't think there would be no flow at all due to that