I read an older post from this forum today concerning the coolant burping out the expansion tank. Someone mentioned the upper radiator hose has a lot to do with it. They stated if the hose placement caused it to be higher that the expansion tank that air in the cooling system would gather in the hose and force coolant out the overflow. My car has a braided hose for a upper radiator hose and it is definitely higher that the expansion tank. Does anyone know if there's any truth to this causeing excessive coolant overflow.

 

what year and engine, C3's came with expansion tanks certain years and overflow tanks other years. Expansion tanks have pressurized caps and overflow tanks are vented to atmosphere. Cannt answer you question without more details including what is the engine temperature when you have the issue.

 

'71 454, This car has a little round tank over on the passenger side up under the edge of the fender.

 

Sounds like you have an expansion tank. If it's pushing out coolant, you're probably putting too much in.

 

If you have a 71 454 with an expansion tank, you must have air conditioning. Only 454's with AC used one. It should be a long thin copper one, tucked up inside the right inner fender.

I doubt the position of the upper hose, would cause an issue with a big block car. I think the situation you described, is more likely to happen with the aluminum radiator in a small block car. The aluminum radiators don't have attached tanks or a radiator cap, so coolant flows freely between the radiator and the expansion tank. On a big block car, the radiator has tanks and a cap. Coolant should only flow to the expansion tank, when the coolant in the radiator gets hot enough that the radiator's cap opens, to allow it to flow to the expansion tank.

I agree with the others here, who said you may be over filling it. If not, then you should probably be looking at the more common causes of over heating; is the radiator flowing properly, is the thermostat working, is there a thermostat installed, the proper timing, is the front spoiler installed, is a hose collapsing, etc.

 

we still dont know if it's actually overheating or the cap on the tank is bad. The question concerning engine temperature was never answered.

 

He's got this thread too asking pretty much the same thing.

https://www.corvetteforum.com/forums...erheating.html

 

Dear young man; As a senior engineer, i'm trained to look at everything as a SYSTEM.
You are asking a specific question without going to the fundamentals of cooling.

Here are some things ANYBODY with a C-3 (gosh! ANY CAR!) should be looking at and verifying.

1. Integrity and flow in the radiator. Both water and air
2. Operation of thermostat.
3. Vacuum leaks and lean conditions of the engine itself.
4. Operation of the water pump.
5. Sealing of radiator to core support and UNASSAILABLE gasketing and airflow. { a molecule of air bypassing the core of the radiator does you not good at all. remembering its a water to air heat exchanger.}
6. Pressure cap operation and psi.
7. hoses and blockages or crimps in same.
8. Operation of fan/clutch/suitability for size of engine and set points on the clutch. Troubleshoot!
9. Pressure test of system. Leak down!
10 Fan shroud suitabilty and impingement on the OD of the fan.

all of these should be tickety-boo.

Technically...if your engine has a 195 thermostat and the boiling point of 50/50 antifreeze is 212F....you should be able to drive with no pressure cap AT ALL. Pressurizing the system brings that 'headroom' up to 265F.

Dig.delve. and try when you are asking questions to intuit all the parameters that may be germaine. (Tough, but think hard!)

good luck...ps those chromy reticulated hoses that so many people use are the debil I say!

Unckahal

 

I installed a temporary OVERFLOW TANK to catch coolant from the burping expansion tank on my '68 project car. I went completely through the coolant system repairing all the problems.

Now I have no need for the Overflow Tank.