Hello, I have a 1964 Oldsmobile Cutlass holiday Coup with a stock 330ci Motor and a 2-speed transmission. I purchased her in May last year and put a lot of work and money into her. She runs fantastic now that she has the engine out, put all new freeze plugs, a new water pump, a new carburetor, new hoses, fuel lines, tank, brakes, and more. But if there is one problem that she still has is a coolant leak. I had the radiator record, a new water pump and lines, and coolant. I replaced the thermostat and gasket, but when I run her, she’ll still spit out the coolant from the overfill line. I don’t believe she blew a head gasket because there is no oil in the coolant or coolant in the oil. Now I replaced the coolant, but it looks brown and rusty, and I was wondering if that could be the problem. But I’m open to any possibilities. Thanks, Monroe James.

 

Are you overfilling the radiator? These older cars without a coolant recovery tank are not designed to fill the radiator all the way to the cap. You're supposed to leave an air gap for the coolant to expand. Many of the original radiators will have a stamped line that indicates the appropriate fill level. This is from my 1967 Delta as an example.

 

Isn't a '64 radiator a vertical flow vs. a crossflow? Vertical flow will definitely spit out coolant in a hurry when overfilled.

 

Yes, but I'm not sure why that matters. Any overfilled radiator will overflow when hot.

 

Agree they both will spit it out. I don't remember if the '64 rads had a full line like the later crossflows. Usually left them about halfway between bottom of neck and top of the tubes.

 

Yes, the 1964-65 cars are downflow

 

When you fill and it pukes,let it puke till it stops. That's the best way to determine coolant level. If it doesn't stop puking,then you have a problem.

 

Thanks for the advice. I didn’t know that there might be a cold line mark. So I would fill her up to just above the fins on the radiator. And it’s normal to spit up coolant if overfilled. Really appreciate the help guys, she is my first classic and 100% original and I just wanna enjoy her! 😊

 

You can always rig up an overflow bottle. There may be a holder already there that was for storing a bottle of washer fluid. If you can find yourself one of those, you can run the overflow hose to that, instead of it venting onto the ground. A tad more environmentally-friendly.

 

If you're asking will it puke if overfilled the answer is yes. Water has to expand when heated in a closed system. That's why the radiator has a fill line but sometimes that's too much. I always let my cars puke till they quit and let it ride from there. That's providing there's not a problem causing it to puke.

 

If it's a show car an overflow bottle that was easily removed could be installed. If it isn't a show car one could be added semi-permantely. As mentioned coolant spills aren't environmentally friendly AND they are quite dangerous to pets.

Good luck and enjoy your ride!​​​​

 

Plus you can be all rat roddy and use a cheap alcohol bottle like an old Rebel Yell to establish your cred.

 

Pages 2-6 and 2-7 of the 1964 Oldsmobile Service Manual (no. 1) says:
The coolant should be kept at a level below top of filler neck seat as follows:
3/4" - coolant cold
1/4" - coolant hot

 

These cars didn't need an overflow bottle when new.

 

Radiator cap spring weak or corroded?

 

As discussed here see if it will seek its own level. If not next step is to get a pressure tester on the system. You can test the cap with this tool as well.
If the coolant is rusty try changing it a couple more times. Likely a lot of contamination in a nearly 60 yr old system.
Google cooling system tester. Get a good one not harborjunk.