Let's talk radiator caps. "water fall'/ running hot
JK Freak
Joined: Mar 2012
Posts: 571
Likes: 28
From: Moss Beach, CA
However, a '12 JK with <10,000 miles shouldn't be overheating unless 1) you're really under heavy load/extreme conditions; or 2) there's a problem like a leak (so you're not pressurized) or blockage (like faulty thermostat) or defective water pump
Based on the posts I've seen, I'd get your water pump checked out. This shouldn't be happening.
Thread Starter
JK Enthusiast
Joined: Apr 2012
Posts: 416
Likes: 0
From: Pittsburgh
I'm using a 50/50 mix of the MOPAR orange HOAT from the dealer.
After sitting for about 3 hours last night the overflow bottle is still 3/4 full and when I went to take the rad cap off there was air pressure. Seems like that was keeping the coolant from going back in the rad.
So I'm thinking that there is air getting into the cooling system and pushing out enough fluid to create air pockets, the only thing I can think of is a head gasket.
I need to add that last year while towing a trailer the idler pulley went and smoked the belt and by the time the light came on the needle was "pegged". By the time I pulled over it overheated big time and lost at least a gallon of anti-freeze.
After sitting for about 3 hours last night the overflow bottle is still 3/4 full and when I went to take the rad cap off there was air pressure. Seems like that was keeping the coolant from going back in the rad.
So I'm thinking that there is air getting into the cooling system and pushing out enough fluid to create air pockets, the only thing I can think of is a head gasket.
I need to add that last year while towing a trailer the idler pulley went and smoked the belt and by the time the light came on the needle was "pegged". By the time I pulled over it overheated big time and lost at least a gallon of anti-freeze.
Thread Starter
JK Enthusiast
Joined: Apr 2012
Posts: 416
Likes: 0
From: Pittsburgh
JK Freak
Joined: Mar 2008
Posts: 571
Likes: 1
From: Seattle
Careful with the dealer.
Mines been 5 times for gushing water, poor heat and running hot and they never fixed it right.
2012 as well.
So far 2 rad caps, heater core, radiator, water pump and all hoses have been replaced. Total of 3 weeks in the service bay.
Only way to get the air out of the Penstar JK cooling system is a large funnel that threads onto your radiator cap, just keep adding coolant as it runs until it can't hold 1 more drop.
Mines been 5 times for gushing water, poor heat and running hot and they never fixed it right.
2012 as well.
So far 2 rad caps, heater core, radiator, water pump and all hoses have been replaced. Total of 3 weeks in the service bay.
Only way to get the air out of the Penstar JK cooling system is a large funnel that threads onto your radiator cap, just keep adding coolant as it runs until it can't hold 1 more drop.
Thread Starter
JK Enthusiast
Joined: Apr 2012
Posts: 416
Likes: 0
From: Pittsburgh
Well, it's been there since last Wed and they finally took a look at it today (Monday). They feel it was the water pump, they feel the pulley is spinning but the impeller is not 
I'm not optimistic that this is going to fix the problem.
Bantam Jeep Fest is a week and a bit away, I'm going to be really pissed if I miss that !
I'm not optimistic that this is going to fix the problem.Bantam Jeep Fest is a week and a bit away, I'm going to be really pissed if I miss that !
Thread Starter
JK Enthusiast
Joined: Apr 2012
Posts: 416
Likes: 0
From: Pittsburgh
Careful with the dealer.
Mines been 5 times for gushing water, poor heat and running hot and they never fixed it right.
2012 as well.
So far 2 rad caps, heater core, radiator, water pump and all hoses have been replaced. Total of 3 weeks in the service bay.
Only way to get the air out of the Penstar JK cooling system is a large funnel that threads onto your radiator cap, just keep adding coolant as it runs until it can't hold 1 more drop.
Mines been 5 times for gushing water, poor heat and running hot and they never fixed it right.
2012 as well.
So far 2 rad caps, heater core, radiator, water pump and all hoses have been replaced. Total of 3 weeks in the service bay.
Only way to get the air out of the Penstar JK cooling system is a large funnel that threads onto your radiator cap, just keep adding coolant as it runs until it can't hold 1 more drop.
Edit: wasn't the water pump (as I expected), back in the shop.
Last edited by Mschneid; Jun 5, 2014 at 06:18 AM.
JK Freak
Joined: Oct 2010
Posts: 555
Likes: 1
From: Houston
Let me start off with the "water fall" behind the dash during start up. Mine started to do this only after I overheated it. I lost fluid and had to add a bunch. Once in a while I run hot (up to 240 degrees). If you don't have a gauge you can tell how hot you are running because the needle on the factory gauge only goes past the half way slightly. Twice now, I have parked up hill and have been able to add 1/4 gallon of anti-freeze only for it to fill up the over flow after I drive it for a half hour or so. Does this mean I have a bad cap? or is the stock cap at 18 psi too low? Should I just buy another 18 psi cap or go to 20 psi? Trying to search this topic and it seems like others have this same situation. I'm afraid if I go to 20 psi it may be too much pressure for the system or void warranty. I have 9k miles on my 2012 and I know I have air in the system.
I took the cap off and squeeze the bottom hose on the radiator several times to release air . It worked for me. No more waterfall noise!
Now I hope they get it fixed right in time for Jeep Fest.