Should the radiator cap be 18 psi?

Rubicon John

Rubicon John

TJ Enthusiast
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Recently I opened my radiator cap to inspect the coolant since I haven't changed it since buying my TJ in February. The coolant looked relatively fresh but the cap wasn't in very good shape. The lower seal on the spring piece was deteriorating. So I ordered a Mopar cap that says 18lbs on it from Rockauto.

I installed it today and drove up the street to run an errand. When I got back I found that the upper hose neck on the radiator had cracked and caused a leak. I'm suspecting it was a weak link and the old cap simply wasn't allowing the system to get up to the correct pressure.

I just wanted to double check that 18psi is the correct rating for the cap before I go ahead and replace the radiator. Has this ever happened to anyone else?
 
Rubicon John said:
For $8 more I’ll go OEM every time.
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Stant is just as good if not better than OEM. I wouldn't be surprised if they aren't the OE supplier of some Mopar cooling system components.

But you spend your money the way you want.
 
Chris said:
Stant is just as good if not better than OEM. I wouldn't be surprised if they aren't the OE supplier of some Mopar cooling system components.

But you spend your money the way you want.
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I will, thanks. If there’s nothing wrong with the Mopar cap, why bring it up?
 
Rubicon John said:
I will, thanks. If there’s nothing wrong with the Mopar cap, why bring it up?
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I'm just throwing out another option. Someone may stumble upon this thread in the future (when Mopar OE parts don't exist anymore), and they should know that Stant is just as good as the OE Mopar radiator cap (which is probably made for Mopar by Stant anyways).

Is that okay with you? :rolleyes:
 
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Rubicon John said:
I will, thanks. If there’s nothing wrong with the Mopar cap, why bring it up?
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Because the Mopar cap is not always convenient to buy locally but the Stant is commonly easily found in most good auto parts stores. I've had to do repairs on Sundays when the local dealership is not open, or when the nearest dealer could be a long ways away.
 
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Chris said:
I'm just throwing out another option. Someone may stumble upon this thread in the future (when Mopar OE parts don't exist anymore), and they should know that Stant is just as good as the OE Mopar radiator cap (which is probably made for Mopar by Stant anyways).

Is that okay with you? :rolleyes:
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If that was your goal then yes that’s fine by me. It was the first thing you typed and it was perceived that I should have bought something else when I read it.

I will also add that when you order the Mopar cap from Rockauto it comes in a 2 pack which I found strange. But now I have an extra if a friend needs one.
 
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can someone tell me the "symptoms" of a "bad" radiator cap?

Also--What would be the signs of a bad one?
 
Rubicon John said:
I will also add that when you order the Mopar cap from Rockauto it comes in a 2 pack which I found strange. But now I have an extra if a friend needs one.
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Well, I guess you can't argue with that!

I was only pointing it out because with everything TJ related no longer being produced by Mopar, it won't be long until those OE radiator caps are gone as well. Which is unfortunate, but true.
 
Chris said:
Well, I guess you can't argue with that!

I was only pointing it out because with everything TJ related no longer being produced by Mopar, it won't be long until those OE radiator caps are gone as well. Which is unfortunate, but true.
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I do apologize for being argumentative, I was having a diva moment because I had just blown my radiator apart and realized the Mopar one is about $300. 😥

The wife wasn’t exactly pleased either.
 
There's so much "don't use anything but MOPAR" for replacements parts here, but there are other brands for some items that are just as good and have proven through the years to be good quality. It can be confusing the see so many recommendations for only MOPAR and then other brands thrown in every now and then.

Stant is good quality though. I've used them for many many years on several different vehicles.
 
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Rubicon John said:
I do apologize for being argumentative, I was having a diva moment because I had just blown my radiator apart and realized the Mopar one is about $300. 😥

The wife wasn’t exactly pleased either.
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No worries, things can get misconstrued online anyways. It's always hard reading someone through a computer screen.

Those Mopar radiators have gone up in price, that's for sure. Ever since they stopped making them, there is no "good" option to replace them with that doesn't fail in a few years.
 
BlueFl.Wrangler said:
can someone tell me the "symptoms" of a "bad" radiator cap?

Also--What would be the signs of a bad one?
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When the radiator cap can't hold 18 lbs. of pressure the radiator can start spewing/leaking out hot coolant from under the cap. And not being able to hold that 18 lbs. of pressure can allow the coolant to boil at a lower temperature. The engine runs around 210 but it can easily run a bit hotter which means the coolant can start boiling over prematurely if the cap isn't up to snuff at holding the 18 lbs. of pressure that raises the temperature at which the coolant will boil.
 
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Chris said:
No worries, things can get misconstrued online anyways. It's always hard reading someone through a computer screen.

Those Mopar radiators have gone up in price, that's for sure. Ever since they stopped making them, there is no "good" option to replace them with that doesn't fail in a few years.
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My Jeep is a secondary vehicle and it’s a tough pill to swallow, buying the Mopar unit but I think it’s the right choice.

Are there any recommendations as far as the thermostat and water pump go?
 
Rubicon John said:
My Jeep is a secondary vehicle and it’s a tough pill to swallow, buying the Mopar unit but I think it’s the right choice.

Are there any recommendations as far as the thermostat and water pump go?
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It's hard to beat a Stant SuperStat 195 degree thermostat. For the water pump I'll go to a lot of extra work to obtain a Mopar and make sure not to use any store brand water pumps. Even with their lifetime warranties that fool people into thinking they must be good quality with a lifetime warranty... they're NOT. All that lifetime warranty means is they'll give you another replacement, not that it's good quality. They don't lose any $$$ by giving free replacements since few people continue replacing things like bad water pumps, they normally trade the car in once things like that start going bad.

And I'd rather beat on my head with a ball peen hammer for 30 minutes every day than install a store brand radiator.
 
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Jerry Bransford said:
It's hard to beat a Stant SuperStat 195 degree thermostat. For the water pump I'll go to a lot of extra work to obtain a Mopar and make sure not to use any store brand water pumps. Even with their lifetime warranties that fool people into thinking they must be good quality with a lifetime warranty... they're NOT. All that lifetime warranty means is they'll give you another replacement, not that it's good quality. They don't lose any $$$ by giving free replacements since few people continue replacing things like bad water pumps, they normally trade the car in once things like that start going bad.

And I'd rather beat on my head with a ball peen hammer for 30 minutes every day than install a store brand radiator.
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😂 Thanks for the info Jerry.
 
Jerry Bransford said:
When the radiator cap can't hold 18 lbs. of pressure the radiator can start spewing/leaking out hot coolant from under the cap. And not being able to hold that 18 lbs. of pressure can allow the coolant to boil at a lower temperature. The engine runs around 210 but it can easily run a bit hotter which means the coolant can start boiling over prematurely if the cap isn't up to snuff at holding the 18 lbs. of pressure that raises the temperature at which the coolant will boil.
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OK
So if its not leaking-- would you say its good?
 
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