Radiator cap
 

I’m giving up on moto-meter style radiator cap — too many experiences with stuck cap.

Any recommendations on replacement for 30- Coupe? Radiator is a recent replacement. Problem I am trying to solve is getting rusty water blowback on bonnet and windshield, so I’m thinking it should be something pressurized or at least with a good sealing gasket.

Appreciate any important considerations before making the wrong choice.

Re: Radiator cap
 

First thing to consider is why you are blowing water. Are you filling the radiator too high?

You can't install a pressurized cap on a stock radiator. I use a Eaton type cap with a cork gasket. I find the hard fiber gaskets don't seal well for me.

Re: Radiator cap
 

Make sure your overflow tube is free and open, that is where the excess water should be going instead of your windscreen. A good cap gasket should stop water from exiting the cap. If the water is rusty flush the radiator and add a can of anti-rust/waterpump lube.

Re: Radiator cap
 

You may need to cut an additional gasket out of an innertube and add it under your existing gasket to get a tight fit. You should not have any water escaping from the radiator cap.

As far as the rusty blow back are you using water instead of coolant?
If using coolant and it has rust in it but the coolant is still good / newer you can clean it up some by letting the car run for a short period of time and then drain the coolant into a bucket. Let the coolant rest for a couple of hours allowing the sediments to drop to the bottom of the bucket. Carefully pour the coolant back into the radiator without disturbing the last bit in the bucket and discard the sediments. Repeat a few times. Works surprisingly well.

Re: Radiator cap
 

Go to ACE hardware and buy an O-ring to fit the cap. :)

TOB

Re: Radiator cap
 

Or buy oversize O rings online from McMaster Carr. The "cut from old inner tube" sounds like a good idea. Use two if needed.

Rusty water is bad. Use 50/50 water/antifreeze. Only use 100% water when testing the cooling system, like after replacing a head gasket. Then drain it out and put in the antifreeze mixture.

Extend the overflow tube down a bit with a rubber hose after making sure it is clear.