Coolant Overflow Bottle/Tank

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Old June 24th, 2020, 04:14 PM
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Coolant Overflow Bottle/Tank

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.
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Old June 24th, 2020, 05:51 PM
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New radiator cap.
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Old June 24th, 2020, 05:54 PM
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Originally Posted by Vintage Chief
New radiator cap.

Just a regular cap?
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Old June 24th, 2020, 05:59 PM
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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
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Old June 24th, 2020, 06:06 PM
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Originally Posted by RetroRanger
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.
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Old June 24th, 2020, 06:12 PM
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Originally Posted by James71Cutlass
Just a regular cap?
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.
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Old June 24th, 2020, 06:15 PM
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Originally Posted by James71Cutlass
Thanks. I just changed the rad out last month.
The plot thickens! Did you change the radiator cap with the new radiator? Faulty thermostat?
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Old June 24th, 2020, 06:17 PM
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I think the cap is what - rated at 16psi? Yes, a normal regular appropriately rated rad cap.
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Old June 24th, 2020, 07:05 PM
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Originally Posted by Vintage Chief
The plot thickens! Did you change the radiator cap with the new radiator? Faulty thermostat?
Same cap. I’ll pick up a new one and let you know if that sold the problem.
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Old June 25th, 2020, 06:12 AM
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Originally Posted by James71Cutlass
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.
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.


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Old June 25th, 2020, 06:16 AM
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Originally Posted by joe_padavano
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.
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Old June 29th, 2020, 06:10 AM
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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.
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Old June 29th, 2020, 06:16 AM
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Originally Posted by James71Cutlass
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.
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Old June 29th, 2020, 06:28 AM
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Originally Posted by Vintage Chief
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.
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Old June 29th, 2020, 05:58 PM
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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.
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Old June 29th, 2020, 06:01 PM
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Originally Posted by cfair
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.
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