Expansion Tank Overflo

[Bill C.]

It's 112 here in Arizona today and had a nice hour run at highway speeds withe the 66 SB. Car has a 160 thermostat and the gauge never exceeds the first line on the gauge (also the radiator is brand new). When the car cooled down and I went out to cover it I found anti-freeze on the ground in the area of the expansion tank overflo. This is the second time this has happened and I checked the tank then and found the coolant level to be on the cold line in the tank. Is there another problem or will this correct itself when the coolant reaches the level where this doesn't happen any more? Thanks for all responces......Bill #20328

[Patrick H.]

Re: Expansion Tank Overflo

Bill,

What type of radiator cap does it have? I had a similar thing happen with the 71 with a new reproduction cap. I replaced it with another old AC I happened to have on hand, and it never occurred again. I've now got a new generic R-15 AC on mine, and save the other for shows.

Just a thought. And see what happens when you drive them - they leak.

Patrick

[Duke W.]

Re: Expansion Tank Overflo

The GM recommended cold level in the tank is one-half, but some recent posts have indicated that this will cause overflow.

I recommend you test pressure cap to verify that it holds 15 psi, and if it's okay, let the coolant seek it's own level in the tank and see where it stablizes when the engine in cold.

In the extreme temperatures you drove in today, there is bound to be some heat soak after shutdown that will raise the temperature and pressure in the cooling system, so a little overflow is probably not something to worry about, but the radiator cap might be suspect.

Duke

[Duke W.]

PS

There are several hose connections in the vicinity of the expansion tank, so you might swap them with a Q-tip to verify that they are dry and not the source of the expelled coolant.

Duke

[Wayne K.]

Re: Expansion Tank Overflo

Bill,

I agree with Duke. The GM half full recommended level caused spill over on my car as well. I kept filling it to half full and it would puke just about every time. Finally I just left it and I've been running it for two years without a puke and never any cooling problems.

[John H.]

Re: Expansion Tank Overflo

Bill -

Don't top it off back to the 1/2-full level; leave it alone and see if it finds its own "happy" level and stops puking (after checking that the cap holds pressure). It's heat-soaking after shutdown, which raises temperature and pressure (perfectly normal), and will probably stop puking at a lower level in the expansion tank.