Coolant Expansion Amount

[JD1964]

I figure with my big radiator I have 16qt of fluid in the cooling system. When the system is topped off and cold, obviously it will expand and some will need to go into the overflow tank. If the overflow tank is empty to begin with, how many qts will go into the tank?

My problem is I think my overflow tank is too small to hold the expansion amount. Its a narrow aftermarket can that came with the radiator. Cant be more than 1 or 1 1/2 qt capacity. The overflow tube inside that narrow overflow tank is about 1/3 down from te cap so it will start spilling when the tank is 2/3 full. Here is the setup so you can see what I mean about a small overflow tank. http://www.summitracing.com/parts/flx-52185/overview/

BTy, running the stock 16lb cap now.

I think I need a secondary tank or something. Either this little tank is not enough or the dang thing is blowing coolant under boost again already.

 

[mikestang63]

you have it backwards, the coolant is sucked out of the overflow and back into the radiator when it gets cold, and when it gets hot, coolant expands and then travels to the overflow. That is why you don't top off the overflow when cold and the fill line is less on factory overflows for cold vs hot. Best thing to do is when it is warm fill up the overflow about 1/2 way. Let it cool down and see how much is left after the engine cools. If the overflow is empty, then you either

• have a leak in your system- your radiator
  
• you didnt get all the air out of the system

Example: my overflow is about the same size- when cool it is drained almost to the bottom,. When it get up to temp, the coolant is somewhat near the top. I would estimate about a pint to a quart of expansion. It should not puke out or be empty.

Again, I would recommend you put a new 16lb cap on and fix the leak in the radiator, then burp the system of all the air and I think the issue will be corrected.

 

[JD1964]

Thanks for the response Mike. I must say sorry that my first post was poorly written. I am aware that the coolant expands when hot and contracts when cold. My overflow tank is small so I guess there's a fine line to keep it from overflowing. If it is over filled it will eventually correct itself by draining the excess out of the overflow discharge. Being over filled might be the issue and I hope it is. It's either that or this thing is still lifting the head and blowing combustion pressure into the water jacket under boost.

I now have a new 16lb cap and a bottle of liquid aluminum appears to have fixed the radiator leak. Theres no more small puddle under the front end after sitting for a few days and only a tiny leak when under pressure at operating temp.

I'm going to run a length of hose from the overflow discharge through the grill and point it up near the passenger side headlight. If this thing is lifting the heads, I want to see the discharge and exactly when it happens. I know if it does the coolant will blow on the hood and passenger side of the windshield. I can wash the car as many times as I need. But if it's puking still, I want to see exactly when.

I 'll post back when I see what happens.

 

[mikestang63]

No worries John. Glad you fixed the leak. You can always go old school and make a 2nd overfill- run the hose into a small coke bottle so it catches any coolant rather than it spilling out over your car or tires. Just zip tie or tuck it back somewhere.

 

[JD1964]

I let it warm up until I had circulation past the thermostat (180 degree). With the cap off I made sure it the coolant level was topped off with engine warmed up. I put the rad cap back on. I set it on high idle 2000rpm and turned the fan tstat up to let it get plenty hot. Nothing came into the overflow bottle. The 16lb cap is holding pressure.

I have a hose connected to the overflow discharge and it runs through the grill and over the passenger headlight. I have to turn in for the night now and the next two works days will be very busy. Weather permitting, I'm going to take it out in the day on Sunday. I'll drive around normally for a while then put the hammer down to see if it pukes under boost.

 

[JD1964]

You see, while the car was out of service for the head gasket swap the body was also cleaned and waxed. So after head gasket swap and the initial test drives i noticed a little bit of coolant on the undercarraige and the bumper and tail lights had tiny spots of coolant splatter. My hopes are that the splatter on the back of the car is residual mess that was under the car from the initial head gasket problem. I need to rinse the entire underside really good.

So, hoping it was residual mess and maybe a little expansion overflow from the old radiator cap.

Crossing fingers

 

[JD1964]

No worries John. Glad you fixed the leak. You can always go old school and make a 2nd overfill- run the hose into a small coke bottle so it catches any coolant rather than it spilling out over your car or tires. Just zip tie or tuck it back somewhere.

I'll eventually make a secondary catch can to hold any discharge that might overflow the small overflow can I currently have. My point in routing the hose over the headlight is to see if, and exactly when it might puke. Just a temporary rig for testing. I'll try 5psi, then 6 and continue up to see when it might happen.

 

[JD1964]

Man, totally blowing coolant out under boost still. I guess there's nothing to do but take it apart again.

Crap!!!

Sucks because it runs so frigging good. What could it be? I did the arp studs and followed inst.

Are these .012 milled iron gt40 heads not up to the task? What?