Coolant from radiator cap. Overflow tank issue?

[smallturbo]

Hey guys, I have a question for you. I a have a Mishimoto Honda half radiator that is having a lot of coolant come out of the car under higher rpm. The car has no thermostat, half filled block up to the water pump and a 55gpm electric water pump. I am using a cheap auto parts store coolant over flow tank but do not have an overflow hose on it. I am curious to if the overflow hose is needed so that pressure is released out of the overflow? My thought is that coolant is coming from the cap because there is no other place for the pressure to be released from. Please offer your thoughts.

Thanks!

 

[bryanwheat]

First off, how much power are you making that you had to fill the block. Second with a half filled you are losing cooling ability in the engine. The bottom of the cylinder will not be cooled and that heat will be transferred to the top part of the cylinder which will be harder to cool because of less surface area. The engine isn't being cooled efficiently and the coolant is expanding and pushing out the cap. That or the head gasket is blown and pushing coolant.

 

[smallturbo]

First off, how much power are you making that you had to fill the block. Second with a half filled you are losing cooling ability in the engine. The bottom of the cylinder will not be cooled and that heat will be transferred to the top part of the cylinder which will be harder to cool because of less surface area. The engine isn't being cooled efficiently and the coolant is expanding and pushing out the cap. That or the head gasket is blown and pushing coolant.

Bryan,
The car is making just shy of 900awhp. We had it on the dyno this morning with a new radiator cap and for 2 pulls it pushed no coolant at all out the cap, but the 3rd pull it pushed quite a lot.

 

[bryanwheat]

You are either lifting the head or just not efficiently cooling it and overheating the coolant. I would do a hydrocarbon test on the coolant.

 

[smallturbo]

You are either lifting the head or just not efficiently cooling it and overheating the coolant. I would do a hydrocarbon test on the coolant.

Coolant tem stays around 180-210 with out any issues. I will have to do a hydrocarbon test this afternoon.

On a side note. Does the coolant overflow tank need to be vented in a coolant system like this?

 

[bryanwheat]

Are you using the tank as an overflow or just a reservoir? If it is an overflow and not in the actual cooling circuit than it needs to be vented so that fluid can be transferred in and out of it.

 

[smallturbo]

Are you using the tank as an overflow or just a reservoir? If it is an overflow and not in the actual cooling circuit than it needs to be vented so that fluid can be transferred in and out of it.

It is set up as a reservoir tank. Hose goes to the bottom of the tank and the tank is always holding fluid.

 

[bryanwheat]

It is set up as a reservoir tank. Hose goes to the bottom of the tank and the tank is always holding fluid.

Is it inline with the cooling system, like coolant flowing thru it (one hose in and one house out) or is it just there to collect the coolant that comes thru the cap.

 

[smallturbo]

Is it inline with the cooling system, like coolant flowing thru it (one hose in and one house out) or is it just there to collect the coolant that comes thru the cap.

One hose in and that is it. Like you said, there to collect coolant that comes out the cap. My thoughts are that since the line is going to the bottom of the tank and there is no vent, pressure has no place to release so it is forced out of the cap. Does that sound like a possibility?

 

[bryanwheat]

One hose in and that is it. Like you said, there to collect coolant that comes out the cap. My thoughts are that since the line is going to the bottom of the tank and there is no vent, pressure has no place to release so it is forced out of the cap. Does that sound like a possibility?

It still shouldn't come out the cap because the cap has a gasket. You definitely need a vent on top of the tank. I would vent the tank and put a new cap and see if it still happens.

 

[smallturbo]

It still shouldn't come out the cap because the cap has a gasket. You definitely need a vent on top of the tank. I would vent the tank and put a new cap and see if it still happens.

My thoughts exactly. Thank you for the help!