Over heating 66 Big block

[mke]

Not sure what going on here. But I can’t get the air gaps out of the cooling system. With no over flow tank, once the car heats up. The radiator fluids expands and just flow out onto the ground. Then the car cool down and the system suck’s in air. An I missing something here?



Also should the radiator cap be level with the top of the engine?

 

[66427-450]

not sure i understand your problem? you fill it so it's about 1-1.5" from the cap(cold), then when hot, it expands to ~full. is your cap seated/sealed correctly? (as well as the rest of the system) if not, the "boiling point" will be to lower than design..........

 

[Viet Nam Vett]

not sure i understand your problem? you fill it so it's about 1-1.5" from the cap(cold), then when hot, it expands to ~full. is your cap seated/sealed correctly? (as well as the rest of the system) if not, the "boiling point" will be to lower than design..........

As stated above..."Boiling Point"... Make sure you have the correct Poundage Cap on the system and that it is in good condition. The Poundage of the cap is related to the boiling point of the coolant.

I think it goes like this..for every 1 pound of pressure of the cap the boiling point is raised ... 3 degrees. So a 7lb cap would give you 21 *...add that to 212* and you get ..boiling point 233*

Experts...Correct me If I'm wrong....

 

[mke]

The hose next to the cap. Which on a small block goes to the over flow tank. Is were the coolent is boiling out from. This happen after I shut the engine off.


A problem I think I have is that the highest point of the cooling system should be the radiator cap. It's almost like the radiator is sitting too low.

 

[Viet Nam Vett]

The hose next to the cap. Which on a small block goes to the over flow tank. Is were the coolent is boiling out from. This happen after I shut the engine off.


A problem I think I have is that the highest point of the cooling system should be the radiator cap. It's almost like the radiator is sitting too low.

When you shut the motor off...you go into what's called hot soak.. Or the coolant heats up due to lack of it being pumped thu the rad. This is a normal thing. What's not normal is it pushing out the overflow line in large quanties. Some over flow in small amounts can be normal.

If the Rad cap is worn..it will not provide the correct overflow back pressure for the system. I undestand what your saying about the cap being low in the system but don't think that is the problem. I would check the spec and make sure you have the correct cap on the system.

Some of the other members may chime in here and add to this post or correct me if I have missed anything....................Guy's???

 

[myonnone]

If the radiator cap is not the highest point in the cooling system, you will get some overflow when you open the cap. Not when the car is just sitting (unless the cap is incorrect or bad). The proper cap should not allow any overflow unless the pressure/temperature of the system is too high. Consider that the cooling system is really a closed loop system with a pressure relief valve on it. The pressure relief valve should not open unlesss the relief limit is exceeded.

What does your temperature guage tell you?
Is your thermostat opening?
Have you made any IR gun measurements of the radiator hoses? You should see a significant temperature difference between the upper and lower hose. On my 66 big block at idle, I get 167°F on the upper hose and 110°F on the lower hose.

I would start with a change out of the cap.

 

[Viet Nam Vett]

Not sure what going on here. But I can’t get the air gaps out of the cooling system. With no over flow tank, once the car heats up. The radiator fluids expands and just flow out onto the ground. Then the car cool down and the system suck’s in air. An I missing something here?



Also should the radiator cap be level with the top of the engine?

Also..some other items...First I would make sure that your motor is properly timed..second..make sure that your vacuum advance is working at idol. If you have no advance at idol this will cause overheating.

To test if the vacume advance is working..pull the vacuum line off of the vacuum can at the distb and plug it with your finger. The motor should drop in rpm and you will feel a slight suction on the hose. When you reconnect it ..the motor should increase in rpm.

Also make sure your total timing is set to factory specs ..with Vacuum Advance and with out Vacuum Advance.

You can check the archives here for a how too on timing and set up or look in your shop manual. Or have some one who knows how to do the deed.

But before you blame the cooling system..make sure the ingnition system timing is correct.

 

[JohnZ]

If it's an L-72, it probably has "ported" vacuum to the distributor (no vacuum signal at idle); connect the signal line from the distributor to full manifold vacuum (tee it into the short hose from the carb base to the choke unloader diaphragm at the right front of the carb, which sees manifold vacuum), and then verify that the vacuum advance is adding about 15 degrees at idle to the base setting when you connect the vacuum line. It will make a significant difference.

 

[mke]

I check the cap and timing and vacuum. All are ok.

Question. Should I have an air in my cooling system? ie the top hose has nothing but air in it (when cold). If I disconnect the top hose from the engine and pour in fluid, it just flow out the over flow tub, next to the radiator cap. Can a BB system be bleed of air? Or am I fighting a loosing battle.

 

[IH2LOSE]

I check the cap and timing and vacuum. All are ok.

Question. Should I have an air in my cooling system? ie the top hose has nothing but air in it (when cold). If I disconnect the top hose from the engine and pour in fluid, it just flow out the over flow tub, next to the radiator cap. Can a BB system be bleed of air? Or am I fighting a loosing battle.

MKE
Welcome to the forum.I think we have to define what your problem is.

Is your car overheating and boiling over and losing half the fluid thats in your radiator after your done driving it?

Or

is it that every time you fill it to what you think is the proper level that the car spits up after sitting after a drive?

For sure if it has an original style radiator in it ,the radiator sits lower then the the thermostat housing is and this is perfectly normal.as a mater of fact we are even supposed to fill the radiator cold almost an 1 1/2" lower then the filler neck.We do not have to worry about burping/bleeding the air out of the system it will work perfectly fine just by filling the radiator with the proper 50/50 mix while the car is running with the thermostat open to the cold fill mark.

please elaborate on what the real problem is your having.Dont worry about the burping or bleeding that will not cause it to boil over or spit up.

 

[IH2LOSE]

PS
Mark you gave some excellent advice.