Just a quickie!

tantus pedis

tantus pedis

Member
Rad cap leaks on top seal. There is no rubber seal on the outer sealing surface just a metal spring steel washer. Both old ones I have are like that too. Water drips out from expansion tank when cold and is forced out of rad when hot. Has a rubber seal fallen off or do the rely on metal to metal? Not noticed before. Only change is rad recon'ned.
Obviously all pics of new caps just show the shiny side!
 
It sounds like you're running with an expansion tank, in which case there should be a blank cap on the rad (with no spring, just a cap with a sealing washer) and a pressure cap on the expansion tank which has the spring with the seal on the bottom, it doesn't need a seal on the top of the cap itself, as if coolant is coming out there it's already escaping past the pressure seal.
 
tantus pedis said:
Sounds like I've got them switched then at some point! Thanks!
Click to expand...

There are special caps that allow fluid past from the rad to the expansion tank, and then allow it to bleed back when the system cools, but they don't increase the capacity of the system, they just allow the rad to be totally filled, and so give somewhere for the excess to go as the coolant heats and expands. Unless you have one of those caps*, the blank one should be on the rad, and the pressure cap on the expansion tank.

*And even if you do, you're better off increasing the capacity by using the system with a blank cap on the rad.
 
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