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Radiator Cap
#1
Not too shy to talk
Not too shy to talk

KD
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Anyone have experience with what radiator cap works best on a V-8 car? I have a 1955 Clipper Super with a 320 CID V-8 and it came to me with a 7 lb. cap. I had a leak that appeared, but could not find the source. I added more antifreeze, (probably too much) and lost the additional out of the overflow. It seemed to "level off" (no more lost antifreeze) and didn't seem to leak. All seemed well. For good measure, I pressure tested the system to 12 lbs. for 45 minutes - no issues. I replaced the 7 lb. cap because I thought it to be faulty (plus it was old). Packard specified a 12 lb. cap. I used a 13 lb. Stant because I could not find a 12. Several good sources told me this was not an issue. Days later I had a leak under pressure from the upper end of the core while driving. Strange this leak never appeared before - during the engine run or the pressure test.

So.... now I will have the radiator re-cored, which is a maintenance item I wanted to perform anyway. Before I put it all back together, I'd appreciate some opinions on the proper cap.

Thanks!

Posted on: 2014/5/6 14:54
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Re: Radiator Cap
#2
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HH56
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My 56 with AC has been running a 13 without difficulty. Packard also used them in 53-4 cars with AC. With a new core yours should handle it too but with a caveat or two.

Aside from hoses, with suddenly running increased pressure you have already found the first weak link. Once that is fixed you may be OK but assuming they have never been changed, with a 60 year old car you could have issues with heater cores and also the rubber seal on the heater temp valve stem. At this time of year you may not notice either leak but If the car suddenly has damp carpet on the passenger side or an unexplained wet spot on the garage floor take note.

Posted on: 2014/5/6 15:39
Howard
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Re: Radiator Cap
#3
Not too shy to talk
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KD
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Thanks. Great info and I've already considered pulling the heater core, but I think we will see how she holds. It's good to know that the 13 lb. cap is being used elsewhere. I've read in several other places that the 13 lb. is actually SAE 12 -16lb range. Interesting.

Thanks!

Posted on: 2014/5/6 16:09
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Re: Radiator Cap
#4
Not too shy to talk
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KD
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By the way - not sure if it really matters, but mine is a NON-AC car.

Posted on: 2014/5/6 16:10
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Re: Radiator Cap
#5
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HH56
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Doesn't really matter except AC cars typically run a bit warmer.

On the other leak possibilities the one to really watch for is the temp valve seal. Several of those have been reporting as failed in the last year or so. When that leaks it typically runs inside the car down the short distance of the firewall where it joins the angled floorboard and then runs under the carpet and padding to pool. You may never see any evidence of a small leak if it has a chance to dry out -- until catastrophe strikes.

Fortunately Napa has the rubber seal for about $10 (and about double that for freight) but it is a P. I. A. to change. Kev did a nice writeup on how to do it if need should arise. That is on site in the How to section.

Posted on: 2014/5/6 16:24
Howard
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Re: Radiator Cap
#6
Home away from home
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patgreen
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FWIW My car came (to me) with a cheap recore that cut efficiency considerably. I had an expert redo the radiator (REX, in the Chicago area) who immediately caught and questioned the recore. It is now recored as original and it makes quite a difference.

I don't think most shops would have seen the issue, much less been proactive about it....

I had previously run hottish, particularly after adding air. No problems since the recore....

Posted on: 2014/5/13 0:46
When two men ride the same horse, one has to be in the back...
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