should the radiator inflow and outflow be the same temp?

scoobysnax · **Posted:** Sun Apr 25, 2010 8:52 pm

I’m concerned my Jeep is running hot although the temp gauge shows normal (wish I could replace that gauge!!!!)

The large hoses coming in and out the radiator on the bottom passenger side and top driver side were both very hot. I would have thought that one of them should be cool – or at least cooler than the other but they were both very hot. My coolant level is a little low which I noticed about a week ago – it’s maybe a ½” below the COLD FILL line when the engine is cold.

Also - side note I guess - there was a fast tapping sound coming from the PCV valve (at idle.) I replaced the PCV valve about 600 miles ago so it should be fine. Was my old one bad that I never heard it make that noise before or is there something wrong with my new one? I doubt this has anything to do with the heat issue but I figured I’d mention it. Is this normal?

Daksport · **Posted:** Sun Apr 25, 2010 9:13 pm

Both lines will feel very hot to the touch but if you have access to a thermometer gun you would see that there is a difference in temp.

If your temp sensor is showing good, then things should be alright.

tjkj2002 · **Posted:** Sun Apr 25, 2010 9:33 pm

At normal operating temps(up to 220 degrees for the KJ) you should not be able to touch the radiator hoses for more then a fraction of a second anyways.The t-stat in the KJ does not fully open till 218 degrees,fan shouldn't come on till about 218-220 degrees.

scoobysnax · **Posted:** Sun Apr 25, 2010 10:06 pm

great, thanks for the feedback. I'll top off the coolant just to be safe but it sounds like everything else should be OK. Oh, what about the clicking sound from the PCV? Is that normal

scoobysnax · **Posted:** Mon Apr 26, 2010 10:27 pm

bump

scoobysnax wrote:

... what about the clicking sound from the PCV? Is that normal

JeepinJarhead03 · **Posted:** Mon Apr 26, 2010 10:46 pm

yar

they be makin racket

tis be a signnnn of teh check valve be operatin in the correct!

jnaut · **Posted:** Mon Apr 26, 2010 10:58 pm

Same temp? No.

Inflow will always be hotter than outflow, because that's what the radiators job is designed to do: put the coolant through a heat exchange process by 'radiation' of excess heat. So the coolant coming back into the engine (outflow) should be a fair amount cooler than what's freshly coming out of the engine and back into the radiator for cooling (inflow).

As everyone else noted, yes, both will feel very hot, but to your hand, the difference between say, 230 degrees (inflow) and 218 degrees (outflow) will both feel the same: too hot to touch.

scoobysnax · **Posted:** Tue Apr 27, 2010 11:20 am

Crap - so a rapid tap, tap, tap, tap... at idle coming from the PCV valve is not normal? I just replaced it. There's only one way to install it right? It either fits or it doesn't so I don't think I installed it wrong. I'll check the line again for any pressure leaks. Can anyone else chime in on this b/c I'm not convinced? I know when you check the PCV valve you are supposed to take it out and shake it. When you shake it you should be able to hear the valve open and close freely and not sound/feel like it's stuck or slow. Well that now what it sounds like when it's installed and the engine is running. It's constantly opening and closing. Is that normal?

JeepinJarhead03 · **Posted:** Tue Apr 27, 2010 12:03 pm

that's pretty much it's job, maintains the appropriate negative pressures in the crankcase

if you've got high miles it may be getting a little bit of blow-by on the rings causing it to work a bit harder

experiencing any oil blow out on the crankcase filter in the airbox or anything of that nature like a oil dipstick that you know you pushed all the way in but keeps popping itself back out?

I think some pcv valves are just louder than others

ever heard the vacuum diaphragm doohicky on TJ's and what not? Can usually hear those while standing behind the vehicle, quite annoying

should the radiator inflow and outflow be the same temp?

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