Kawasaki Vulcan 1500 / 1600 Radiator Cap Pressure Check

I was having problems with the coolant system on my 1500 Vulcan Classic. It boiled over on me twice, so I want to figure out what the problem was. My friend Hotsauce and I had it running in the garage long enough that antifreeze began filling the overflow tank, but the fan just wouldn't quite come on. We figured it was the fan or fan switch. Before that test I had been concerned that I may have had a leaky head gasket and I had already ordered the pressure test equipment to check the radiator cap and system. So the equipment arrived and I decided I would do those checks just to put every possible coolant issue to bed. Here's the equipment I bought. A Mityvac MV4560 about $50 and that seemed a lot better than a $200 testing set-up.




First thing to do is find the cap and system pressure rating from the manual 14 to 18 psi and 18 psi.


Now to test the cap. Uh-oh, it doesn't hold an ounce of pressure.


Off to the auto parts store. Guy Mobbley of Sherm's Cycle Products had told me that a cap for an Asian car will fit and there's not a need to order a Kawasaki cap. (If you need anything that Sherm's sells please spend money with him. I always try to. Heck of a guy that Guy.)

Here's a cap for a 1996 Honda Accord.


Looks about the same and is rated the same.


And it actually holds pressure.


Now to check the system. The deep neck is the one you need, not the shallow neck, trust me.


Put it on the filler neck of the radiator.


Awesome! The system holds pressure. (Don't check it higher than the rated pressure.)


Surprisingly when I released the pressure it sucked antifreeze back up the tube. It drained back into radiator when I cracked open the adapter cap.


So now to put the good new cap on. Guy had said something about needing cut the tab of off the car cap, but I had hoped I would be lucky. Nope. It doesn't quite close all the way with the bleeder screw in the way.


Cutting time.


File down all the sharp edges.


Like a glove...





The best part is that I don't have a blown headgasket and I when I fired it up and got the motor hot again the fan worked perfectly. I can only guess the coolant boiled out before it got hot enough to kick on the fan without being under pressure.