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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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 (http://www.foreforums.com/index.php?topic=15765.0)
Thanks Michelle.
So does anyone know if I should have a "normally closed/spring cap" or a "open/weighted cap" type?
Thought we had 10lbs rated caps but Barry would know. I feel certain they are 10
JohnH
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.
Cummins M-11 450 Engine Overheating (http://www.foreforums.com/index.php?topic=15512.msg95031#msg95031)
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