Datsun Roadster Forum-311s.org

I've read all the posts regarding this issue and I'm still wondering what my options may be, given the following. My stock cap is virtually new and the rubber seal is in very good condition, with no cracking and it does not seem to be overly compressed. I did find that the seal had come loose from the cap so I glued it back down with weather strip adhesive, but it's still seeping when the radiator is pressurized. Any other idea would be much appreciated. Is there an aftermarket solution that may cure the seepage?

Crimp the two little side clips (on the cap) upward (towards the seal) about 1/2-1material thickness. That will increase the pressure on the sealing surface. If that doesn't fix it either the rubber or the sealing surface probably has a defect. The other option is get another cap or gasket-there is no aftermarket cap that fits.

Good thought JT68, I'll give that a try and report back. I ran into a fellow roadster owner this morning, who suggested substituting a cork ring for the rubber gasket, saying it worked for him. I'll try your fix first, as that's easier. Thanks!

Bent the tabs up, and ran the engine up to temperature. That seems to have sealed everything back up. I'll know more after a planned run later tonight, but I'm 99% sure the issue is solved. Thanks for the suggestion Jim.

Very, very slight seeping after 30 mile run tonight. Going to keep an eye on it, but not very concerned at this point.

Is this on the expansion tank or 1600 thermostat housing cap? I've been using a Stant 10228 7psi or 10229 13 psi lever vent on expansion tank for years. still have the original for looks, if needed