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Topic: Radiator cap question (Read 900 times) previous topic - next topic

Radiator cap question

My radiator cap is leaking.  Background:  The CAC was replaced last fall by Cummins and at that time I had the radiator flushed since it was taken out for the CAC replacement.  After the repairs the coach immediately went in storage for the winter. 

Last week we hit the road for a 2 month trip.  All seemed fine except at the end of the 1st day I noticed the cap was leaking - maybe a half cup total over 250 miles.  Leaked the same amount the next day so I bought a new cap exactly like the current one (15 psi and looked identical in size).  Drove a couple of days with the new cap and it is leaking at the same rate as the previous cap.  Today after the coach sat for 24 hours as I loosened the cap and another half cup flowed out the neck under a little pressure.  When the cap was completely removed the antifreeze level was right at the lip of the neck.  There is coolant in the overflow tank and the level changes appropriately.

So, did Cummins install the wrong type of cap?  Is there some other problem?  Cummins 400 ISL - never had this problem before.  Here is a pic of the cap:
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Mark & Mary Benko
Former coach: 2005 U295 3823
Jeep Cherokee, Honda Fit

Re: Radiator cap question

Reply #1 –
Quote from: Mark Benko –

So, did Cummins install the wrong type of cap?  Is there some other problem?  Cummins 400 ISL - never had this problem before. 

IIRC there are 2 styles of caps.  One with extra seal is needed for the overflow system used by some of our coaches (Barry B. posted info a while back) so excess goes into overflow.

Radiator Reservoir Cap question
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Radiator cap question

Reply #2 –
Thanks Michelle.

So does anyone know if I should have a "normally closed/spring cap" or a "open/weighted cap" type?
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Mark & Mary Benko
Former coach: 2005 U295 3823
Jeep Cherokee, Honda Fit

Re: Radiator cap question

Reply #3 –
Thought we had 10lbs rated caps but Barry would know. I feel certain they are 10
JohnH
Coachless, now use aircraft. 2003 Ford Travelair TC280 class C. Super shape. Just for 1 yr .
1994 Ford E350 ClassC,total renovation inside and out. Now sold.
2000 U295  36' Cummins 350 c/w Banks Stinger, Resonator upgrade,Solar, LED lites.Residential fridge with slide out pantry. Build 5674. Sold
ex 92 GV 022C ored Cummins. Sold
ex 95 GV240 cat 3116. Sold
2017 Mini cooper s & 2016 land Rover LR2 HSE  LUX.
jhaygarth@aol.com    SKP #130098
treat everyone as you would like to be.

Re: Radiator cap question

Reply #4 –
Update:  Called FOT and they confirmed that the correct replacement cap for my radiator is NAPA part #703-1427.  It is rated at 15#s.  Attached are 3 pics.  #1 is the VSH cap Cummins installed after the radiator flush.  #2 & #3 are the NAPA cap.  You can see both rubber gaskets are much wider on the NAPA cap.  Haven't tested it yet but confident that the new cap will resolve the issue.
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Mark & Mary Benko
Former coach: 2005 U295 3823
Jeep Cherokee, Honda Fit

Re: Radiator cap question

Reply #5 –
Cummins M-11 450 Engine Overheating

This is how I came to remember about the 10lb pressure cap.
JohnH
Coachless, now use aircraft. 2003 Ford Travelair TC280 class C. Super shape. Just for 1 yr .
1994 Ford E350 ClassC,total renovation inside and out. Now sold.
2000 U295  36' Cummins 350 c/w Banks Stinger, Resonator upgrade,Solar, LED lites.Residential fridge with slide out pantry. Build 5674. Sold
ex 92 GV 022C ored Cummins. Sold
ex 95 GV240 cat 3116. Sold
2017 Mini cooper s & 2016 land Rover LR2 HSE  LUX.
jhaygarth@aol.com    SKP #130098
treat everyone as you would like to be.
 

Re: Radiator cap question

Reply #6 –
Quote from: John Haygarth –
Cummins M-11 450 Engine Overheating

This is how I came to remember about the 10lb pressure cap.
JohnH

I took Barry's post to mean he borrowed a 10 lb cap temporarily but he states that "My 15 part number is Napa 703-1427" which is a 15 lb cap.  FWIW.

Last update:  No leaks after 500 miles with the new cap and antifreeze is flowing into and out of the overflow tank as required.  Amazing how well the correct part works! :P
The selected media item is not currently available.

Mark & Mary Benko
Former coach: 2005 U295 3823
Jeep Cherokee, Honda Fit