Cat 931 Radiator cap

931 started boiling over.... shut it down and let it cool. Pulled the radiator cap and the gasket that seats in the bottom of the neck is cracked and dry... no worries, ordered a new one (Stant brand). That one wouldn't seat properly in the neck, as it had 6 or 8 little ribs that stand proud around the diameter of the poppet. Oh well, ordered the Caterpillar one for 4x the price (p/n 6L8617) and it's identical to the Stant! It won't fit down into the filler neck either. The height and diameter of the cap looks the same except for the little ridges that stick out all the way around the perimeter of the poppet.

Anybody else ever run into this? I can't find an alternative part number. The radiator had been repaired in the past, but the shop that worked on it is out of business now. Any thoughts?? I hate having a machine sitting idle over a $10 part!

Thanks,
Dan

6L8617 is equivalent to 3L3368 and 3L2866 but it seems suspiciously like the filler neck got changed somewhere along the line.

That's kind of what I was afraid of... I asked the dealer if that was a possibility, and he replied that "it happens". If that's the case, I guess maybe I can see about getting a radiator shop to put a new filler neck on.

I hate to revive an old thread (especially when I simply forgot to post an update) but I finally located the correct radiator cap!

It turns out that somewhere along the line, Caterpillar adopted industry standard caps which often don't fit older filler necks due to the reinforcing ribs around the plunger (seems that somewhere along the way they adopted industry standard necks, too). Instead of going with new part numbers, they simply carried the old part numbers over to new parts without verifying that it would fit all intended applications.

The part that actually fit was a CTP brand 6L8617 (yeah, they used the Cat part number). They apparently manufacture parts to the original part number spec. It was a perfect match to the old one, and fit like a charm.

I dunno if CTP already has a reputation here on the boards, but I understand they make a full line of aftermarket Caterpillar parts. They served me well in this case.