Radiator cap never really gets super hot to touch?

[TheMidnightNarwh]

I noticed the other day the radiator cap never gets real hot to touch. I can feel some warmth to it but not burning hot. The upper rad hose does become hot to touch and the car doesn't overheat.

Is something wrong, should I be worried and check for something or it's fine?

 

[OneEyeJack]

Does your cooling system need to be topped off?

 

[Lubener]

If the upper hose is hot, you don't overheat, if heater works good, you are fine. My radiator cap is never hot to the touch. I am assuming you do maintain proper level.

 

[TheMidnightNarwh]

Originally Posted By: OneEyeJack
Does your cooling system need to be topped off?


No I filled it up about 2 weeks ago, checked every day and then to make sure it was wasn't leaking and looks good. Always coolant to the top when I take it off in the morning.

 

[ZZman]

Is your cap on a plastic tank or a metal radiator?

 

[eljefino]

Originally Posted By: ZZman
Is your cap on a plastic tank or a metal radiator?


yeah this. How would your cap get hot? You have boiling water pushing on a rubber gasket under a metal disc under a spring under the part you put your hand on.

If you've ever noticed the handle on a wood stove, it's a spring, so it doesn't conduct heat very well.

 

[TheMidnightNarwh]

Originally Posted By: ZZman
Is your cap on a plastic tank or a metal radiator?


Originally Posted By: eljefino
Originally Posted By: ZZman
Is your cap on a plastic tank or a metal radiator?


yeah this. How would your cap get hot? You have boiling water pushing on a rubber gasket under a metal disc under a spring under the part you put your hand on.

If you've ever noticed the handle on a wood stove, it's a spring, so it doesn't conduct heat very well.


It's not on the overflow tank, it's on the rad itself.

So you're saying it's normal it doesn't get hot? All the videos I watch they say if your cap is hot don't open, even says so on the cap itself. But it's never really hot like that.

 

[eljefino]

Back 30 years ago with brass radiators the radiator tank would conduct heat to the cap fairly efficiently through the mounting boss.

And if you remove a cap holding back pressure it could cause instant explosive steam, no fun.

Grab the upper radiator hose to get a feel for temp, even with 1/4" of rubber they get pretty hot.

 

[SilverFusion2010]

Probably some air trapped under the cap acting as an insulator. If you're brave you can burp the system. Take an old rag and very slightly start to remove the cap, just enough that you hear it hiss. When it gurgles tighten it back.

Or just wait until it's cold and top up the rad. I kinda like the hot purge though.

 

[andyd]

Are the caps with a lever to release pressure still sold? Sounds to me like a warm cap would mean an air gap at the tank top. The 528e uses a pressure cap on the expansion tank. I once drove a '62 F250 with bad radiator. It was summer and we took it on a 200 mile trip to rescue my '62 Bug. We carried water jugs and stopped 5 times to add water. That was one of the bug's many good points. A shop fab'ed tow rig pinned to the front beam and they towed like they weren't even there