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Boiling sound at radiator cap

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Old 04-19-2012, 05:21 PM   #1
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Default Boiling sound at radiator cap

Came home from work today (20 minutes city driving), shut the car off, opened the hood to check something and after a few minutes I heard a boiling sound coming from the area around the radiator cap (no visible leaks). I could see the recovery tube move so I guess it was overflowing into the recovery tank. Normally the temp gauge (i know its not accurate,using it as reference) stays just under 210. While idling it went a hair over 210. I changed the water pump over a month ago and didn't have any temp issues after that. I used Prestone Dexcool 50/50 when I changed the pump. I checked the oil and its looks normal. Do I have a bad cap (original) ? Or is that 50/50 **** coolant ?
I'm waiting for it to cool off and will check the level.
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Old 04-19-2012, 07:24 PM   #2
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I went back outside and removed the cap. Radiator was full and recovery tank was at normal level. I let the car idle for 25 minutes with my scan tool connected. When temp hit 224 both fans turned on. At 215 the fans turned off. I shut the car off and waited, didn't hear the boiling sound anymore. IDK
I took some coolant out of the radiator into a cup and compared it to some new coolant in a cup and you can tell the new is darker. Maybe too much water ?
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Old 04-19-2012, 08:15 PM   #3
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Go ahead and buy a new radiator cap, sounds like its pulling air into the system

Keep your eyes on the temp gauge however, my car ended up having the water pump seize a few months after it boiled occasionally
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Old 04-19-2012, 08:19 PM   #4
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^Im with him. Buy a new cap. Ever hear the coolant in the radiator when the cap is off? It boils and its the same thing as a cap being faulty. Its letting in air. No good. Replace it.
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Old 04-20-2012, 07:45 PM   #5
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I checked the coolant with a one of those coolant testers with the 5 *****. Its showed 3 ***** with the coolant from the car and 5 ***** with new 50/50 coolant. I guess the coolant in the car is a bit watered down. Also picking up a new oem cap tomorrow.
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Old 04-20-2012, 09:32 PM   #6
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Quote:
Originally Posted by chrysler kid View Post

Go ahead and buy a new radiator cap, sounds like its pulling air into the system

Keep your eyes on the temp gauge however, my car ended up having the water pump seize a few months after it boiled occasionally
+100 on this.

I ended up replacing a water pump and radiator shortly after.
New Radiator cap ($8) is cheap preventative maintenance.
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Old 04-21-2012, 12:29 AM   #7
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I believe that air getting back to the pump may play a role in the bearing seizing in the pump. I tried to do everything including putting it in a press and hitting the ratchet with a sludge hammer. I sheared the pulley clean off it was so seized
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Old 04-21-2012, 12:21 PM   #8
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Picked up the new cap today. Idled the car for about 25 minutes, turned it off and didn't hear anything boiling at the cap. The new cap looks slightly taller, maybe because the old spring is worn IDK
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Old 04-21-2012, 03:02 PM   #9
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New cap looks pretty.
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Old 04-23-2012, 04:09 AM   #10
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Looks like A bad cap to me. Dexcool will eat away that rubber and the springs get weak
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Old 04-23-2012, 07:02 PM   #11
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I drove back and forth to work today with the new cap. Temp was normal and no boiling when engine was turned off. I guess the cap was bad.
$13 fix
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accuracy, antifreeze, bad, boiling, bubbling, cap, coolant, dark, gauge, noise, radiator, recovery, rubber, sounds, tank, temp, water

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