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Does a radiator cap ever go bad? #1319889 10/13/12 09:44 PM 10/13/12 09:44 PM
Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi... MidPenMopar OP Looking for fun? Keep looking
MidPenMopar OP Looking for fun? Keep looking Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi...	I have been smelling coolant for the last few times i have driven the roadrunner and today i noticed that the radiator cap was leaking coolant out of the bottom of the cap while trying to find the leak. The cap was all the way tight. I have never seen a cap go bad and leak like that in all the cars i ever owned. So i was just wondering if anyone else ever had one go bad and leak under the tight seal. This one is a Mr. Gasket brand with a built in temp guage. It was pretty expensive as far as radiator caps go and i would hate to toss it away if i dont have too. I bent the holding tabs closer together to help hold it tighter to the spout.

Re: Does a radiator cap ever go bad? [Re: MidPenMopar] #1319890 10/13/12 10:25 PM 10/13/12 10:25 PM
Joined: Feb 2004 Posts: 1,012 indiana M mcmopars super stock
mcmopars super stock M Joined: Feb 2004 Posts: 1,012 indiana	i have never has one go bad but yes they can fail.say its rated to open at 16 lbs and may open sooner or later than what they are rated for,then i would replace it.how to test it i dont know

Re: Does a radiator cap ever go bad? [Re: mcmopars] #1319891 10/13/12 10:38 PM 10/13/12 10:38 PM
Joined: Jan 2003 Posts: 21,085 Niles , Ohio T therocks oh wait.but hey.lets see.oh yeah.
therocks oh wait.but hey.lets see.oh yeah. T Joined: Jan 2003 Posts: 21,085 Niles , Ohio	Work as a tech for 30 years and youll see everything.Ive seen them leak,fall apart,not hold even a pound of pressure and some not relieve the pressure when they should.I have the same cap on my 65.Been on 4 years and no problems.Check the seal and make sure its not torn.Mine fits real tight on the rad.Rocky Chrysler Firepower

Re: Does a radiator cap ever go bad? [Re: therocks] #1319892 10/13/12 10:58 PM 10/13/12 10:58 PM
Joined: May 2003 Posts: 15,487 Florida S scratchnfotraction I Live Here
scratchnfotraction I Live Here S Joined: May 2003 Posts: 15,487 Florida	Quote: Work as a tech for 30 years and youll see everything.Ive seen them leak,fall apart,not hold even a pound of pressure and some not relieve the pressure when they should.I have the same cap on my 65.Been on 4 years and no problems.Check the seal and make sure its not torn.Mine fits real tight on the rad.Rocky make sure it is the correct cap also. vented for recov bottle system, non-vented for non recov system. most times it is the upper or lower rubber seals that wear and leak from age on my junk.

Re: Does a radiator cap ever go bad? [Re: MidPenMopar] #1319893 10/13/12 11:01 PM 10/13/12 11:01 PM
Joined: Apr 2012 Posts: 18,880 - R RSNOMO Moparts Torchbearer
RSNOMO Moparts Torchbearer R Joined: Apr 2012 Posts: 18,880 -	Yes... A pressure tester will tell the story...

Re: Does a radiator cap ever go bad? [Re: therocks] #1319894 10/14/12 02:20 AM 10/14/12 02:20 AM
Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi... MidPenMopar OP Looking for fun? Keep looking
MidPenMopar OP Looking for fun? Keep looking Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi...	Thanks people for the ideas. The seals all look good and it was leaking all around them though. I would toss it right away but i like the temp guage built in it so i rebent the tabs tighter and if ti leaks again, then adios. I assume that leaking like that would allow the coolant to boil quicker and overheat as it would have very reduced pressure in the system, correct??

Re: Does a radiator cap ever go bad? [Re: MidPenMopar] #1319895 10/14/12 07:12 AM 10/14/12 07:12 AM
Joined: Jan 2003 Posts: 21,085 Niles , Ohio T therocks oh wait.but hey.lets see.oh yeah.
therocks oh wait.but hey.lets see.oh yeah. T Joined: Jan 2003 Posts: 21,085 Niles , Ohio	Correct the pressure raises the boiling temp.Just make sure the rad isnt over full also.Sounds like you have had the car for a while and you know that the early ones run about an inch or so down in the rad if not a recovery system.Most shops have a cap tester.It takes about a minute to test them.Usually they will do it free if you ask.Rocky Chrysler Firepower

Re: Does a radiator cap ever go bad? [Re: therocks] #1319896 10/14/12 11:58 AM 10/14/12 11:58 AM
Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi... MidPenMopar OP Looking for fun? Keep looking
MidPenMopar OP Looking for fun? Keep looking Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi...	Quote: Just make sure the rad isnt over full also. Over filled??? I never knew you could over fill the radiator. So where would be the correct fill level. Right now i am a little over the top of the rows.

Re: Does a radiator cap ever go bad? [Re: MidPenMopar] #1319897 10/14/12 12:02 PM 10/14/12 12:02 PM
Joined: Apr 2012 Posts: 18,880 - R RSNOMO Moparts Torchbearer
RSNOMO Moparts Torchbearer R Joined: Apr 2012 Posts: 18,880 -	'Sounds like you have had the car for a while and you know that the early ones run about an inch or so down in the rad if not a recovery system'

Re: Does a radiator cap ever go bad? [Re: RSNOMO] #1319898 10/14/12 12:54 PM 10/14/12 12:54 PM
Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi... MidPenMopar OP Looking for fun? Keep looking
MidPenMopar OP Looking for fun? Keep looking Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi...	Quote: 'Sounds like you have had the car for a while and you know that the early ones run about an inch or so down in the rad if not a recovery system' No mine is a recovery system, so that would assume to fill it further up near the neck.

Re: Does a radiator cap ever go bad? [Re: MidPenMopar] #1319899 10/14/12 12:57 PM 10/14/12 12:57 PM
Joined: Nov 2007 Posts: 21,847 Kirkland, Washington Pacnorthcuda Too Many Posts
Pacnorthcuda Too Many Posts Joined: Nov 2007 Posts: 21,847 Kirkland, Washington	Quote: Quote: 'Sounds like you have had the car for a while and you know that the early ones run about an inch or so down in the rad if not a recovery system' No mine is a recovery system, so that would assume to fill it further up near the neck. Fill it ALL the way Stu.

Re: Does a radiator cap ever go bad? [Re: MidPenMopar] #1319900 10/14/12 01:00 PM 10/14/12 01:00 PM
Joined: Jan 2003 Posts: 21,085 Niles , Ohio T therocks oh wait.but hey.lets see.oh yeah.
therocks oh wait.but hey.lets see.oh yeah. T Joined: Jan 2003 Posts: 21,085 Niles , Ohio	Pre I believe 71 all systems were non recovery.They run down about an inch or so.Your cap should be the recovery type if you have a recovery system.My 65 runs just over the cores.Over fill and it will come out the overflow to the catch can I installed.It used to come out the over flow hose when over filled.Rocky Last edited by therocks; 10/14/12 01:01 PM. Chrysler Firepower

Re: Does a radiator cap ever go bad? [Re: therocks] #1319901 10/14/12 01:08 PM 10/14/12 01:08 PM
Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi... MidPenMopar OP Looking for fun? Keep looking
MidPenMopar OP Looking for fun? Keep looking Joined: Dec 2003 Posts: 36,840 South San Francisco, Californi...	Yes i have the recovery overflow tube in the cap spout and my other 69 roadrunner had a similar 22 inch radiator as well. Thanks for all the advice as it's getting harder and harder to find anyone left who remembers how this stuff works anymore....luckly you all have better memories than i do! 7420382-roadrunnerbelts004.JPG (66 downloads)

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