I’m having coolant come out of my rad Overflow hose after trips with my ‘71 Cutlass S car. My mechanic says I need a Coolant over flow tank. What’s my best option?

Thanks.

 

New radiator cap.

 

Just a regular cap?

 

you can add a coolant recovery tank, dorman sells a bunch of generic ones for under $20 I adapted one to my car.

back in the day manyof these cars didnt have overflow tanks. They would puke out the extra like yours did and run the coolant 2" or so below the filler neck. If your rad is original there may even be a fill line on the side of the rad

 

Thanks. I just changed the rad out last month.

 

Happens right after you turn off the car from a drive? For $10 buy a new radiator cap. See if it solves the issue. They’re inexpensive. Or spend a buttload of time diagnosing first. Your issue sounds trivial, try it. If it doesn’t work move foraward with more options. Might never have been changed in 50 years. The valves weaken the spring rusts and the vent closes. You’re probably boiling over after you stop the car with no air flow as you would get while driving plus you’re not circulating coolant when you’re standing still. Try it let us know.

 

The plot thickens! Did you change the radiator cap with the new radiator? Faulty thermostat?

 

I think the cap is what - rated at 16psi? Yes, a normal regular appropriately rated rad cap.

 

Same cap. I’ll pick up a new one and let you know if that sold the problem.

 

Your best option is to figure out what's wrong. Inform your mechanic that these cars didn't need an overflow tank from the factory and adding one now is a lazy-man's bandaid. As noted, the most likely problem is an old radiator cap that has gotten weak and won't hold pressure. Also, be sure you are not overfilling the radiator. Unlike new cars with an overflow tank, these cars are NOT supposed to be filled all the way to the radiator neck. The original radiator even had a fill line marking. This allows expansion room. If you're over filling the radiator, that's why it's puking out antifreeze.

 

Ok thanks. I'll pick up a new cap today and see if that solves the problem.

 

Replaced the cap yesterday took it out for a good run and no over flow. I had also purchased an over flow bottle kit as well, it was a deal through amazon. Haven't installed that yet.

 

All you need(ed) is the radiator cap. You don't need the over-flow kit.

 

I will probably send the over flow kit back.

 

Joe is the authority, but I have a vote for the expansion tank.

I retrofitted ‘74 caddy Eldorado tanks to my ‘66’s and they may not be necessary, but it’s nice to see if the coolant level in the plastic translucent tank changes. Then I know I have a leak. Or if they’re topped up properly. Plus I have a little extra coolant just in case things go wrong on the road.

I like the late model plastic translucent brake master cylinder reservoirs for the same reason.

Disregard this if you’re going for concours restoration and/or want to be true to factory design.

 

Thanks. Something to consider.