how do I determine which radiator cap I need?

I have a 95 LS coupe. The previous owner had the radiator replaced by a shop, about 6 weeks ago. The car has a very slow coolant leak, so I am trying to tie up loose ends wherever possible. First I replaced a suspect radiator hose, but that did not fix it. I will check the drain plug on the bottom of the radiator also. I also intend to check all the heater hoses in the back.

But right now I am trying to replace my radiator cap, and I was hoping to go OEM. My Acura dealer says it is either a Denso or Showa cap, depending on the model radiator I have. He says the existing cap should indicate whcih one I need. My radiator cap has no brand on it, it just has the warning label and "1.1" imprinted in the metal. Any ideas which cap I need? Are the two caps very similar in appearance, or could I feasibly bring my old cap and tell which one I need just by visual comparison?

I was hoping to get the correct part number so I can buy it from a Honda dealer instead, since the closest Acura dealer is like 20 minutes away, and I drive right by the Honda dealer on my way to work.

acuraoemparts.com seems to indicate I need a Showa... not sure how much I can count on that as a resource

Look on the radiator end tanks for any embossing (raised plastic lettering) to tell you what it is. The two radiators should share the same cap though. You can go to an autoparts store and they will point you to the right cap.

The OEM radiators are hit or miss anyway. The seal for the plastic end tanks can fail in a month or last for years. I upgraded to a full aluminum just for that reason.

I think it's an aftermarket radiator, it looks like it has aluminum end tanks. I just don't want to put on the wrong radiator cap and have it be so far off that I get coolant spraying everywhere the first time I drive it.

you shouldnt need more than 1.3 bar for a rad cap. my mishimoto is 1.9 bar i belive for track use

The numbers on the cap are the pressure the cap is meant to hold, before raising and allowing coolant into the overflow.

Take a picture of the radiator. I know that OEM caps will not fit on my godspeed radiator, so if yours is aftermarket, you wont be going to the dealership for caps.

Skunk2 or Spoon should fit on any radiator

I believe all Honda/Acuras have a type D cap if that is what you were looking for OP. Denso and Showa are just brands.

If anything, the radiator you have is an aftermarket OEM style radiator (assuming it has plastic endtanks).

The stock cap is 1.1 BAR (16psi). Our Mishimoto caps are 1.3 BAR (19psi), however, our caps are styled like a type F cap, most commonly found on Subaru's. Our standard 1.3 BAR caps will not fit onto an OEM Honda/Acura radiator preoperly.

OP, let us know if you have any other questions.