Coolant coming out of overflow

[lcmc]

My car doesn't over heat but I keep losing coolant from the overflow. Radiator is only filled to full mark so it is not over full. Where should I start to solve this problem?

[rich69rs]

Sounds like maybe your radiator cap is opening at too low a pressure.  If it is operating properly, the radiator cap should not open to the overflow unless the pressure exceeds 15 psi. 

I would start by having your radiator cap checked to be sure it is still holding rated pressure (15 psi) without leaking down.  If you don't have the tester in your tool box to do this, any radiator shop can do this for you.  Just takes a couple of minutes.  All you have to do is bring the radiator cap to the shop for the test.

Had a similar problem on my ride a couple years ago - new radiator cap and all was well.

[lcmc]

I'll have it checked out and keep ya posted........thanks

[lcmc]

Had the cap checked today and it only held 3 lbs. Looks like that is the problem. Parts store didn't have a new one so I'll try to get one tomorrow and try that. If that works then I need to find a NOS cap since my car is a survivor.

[rich69rs]

Glad to hear that it looks like you've isolated the problem.  Watched a NOS cap the other day on eBay go for $77.

Good luck.

Richard

[lcmc]

Richard.....I believe the cap I have now is the original to the car. It reads "TURN TIGHT" and "REMOVE SLOWLY". I've seen caps on ebay selling as NOS that read "NEVER OPEN HOT" and "INSPECT FALL & SPRING". Which is the correct cap?

[JohnZ]

Here's a photo of the original RC-15 cap on my '69 Z/28.

[lcmc]

JohnZ....that's the cap on my car now. I thought it was original. The ones on ebay and are different that say NOS must be OEM replacement caps. If anyone knows where I can get the correct cap let me know.

[Gramps69Z]

I got mine from NPD, $24.95 with correct marking.

[rich69rs]

They are available in the aftermarket.  The attached PDF file is the one I purchased from Year One, also with the correct makring.

[lcmc]

Thanks guys....I bought a cheapy today just to make sure that solves my problem. Once I make sure it does I'll probably go with the reproduction until I find the correct NOS.

[lcmc]

Problem solved.....just took a test drive. No more overflow!

[169INDY]

Just for additional information. If you a lucky enough to have your orig RC15 on your car but it has seemed to aged to much you can get them restored by John Prikle. He rebuilt mine on the pace car and it looks awesome! The plating, new gasketing and Orig stlye rivet completed the package. Off the top of my head I can not remember how much it cost but it was worth it.

Jim

[lcmc]

Jim......I do have the original. I would not want mine restored since my car is a survivor, however I was wondering if you could just have them rebuilt. Do you have contact info for for this guy?

[Gramps69Z]

Contact information : www.johnpirkle.com    (706)860-9047
He also sells and restores other parts.   I hope he can help you.