I have now purchased three different aftermarket engine oil caps for my 2000 24 valve truck, and not one of them threads properly into the valve cover.

One is a Stant, another is Napa, and the third is an aluminum one from Ebay.

The threaded portion on all three is too small. I'm starting to wonder if I have some strange oddball valve cover.

The reason I'm looking for another oil cap is because when I installed my engine oil bypass filter, I didn't want to mess with my stock oil cap. If I messed up drilling it for the bypass filter return, I would much rather do that to an aftermarket oil cap.

Why would all of these aftermarket oil caps be designed to fit a completely different opening in the valve cover? Did Cummins make two different sized oil filler ports in the valve cover in the 24 valve engines?

 

That’s odd. Was the one off eBay used? I’m guessing you already looked for a used one.

When I installed my oil bypass I did the self tapping fitting from Frantz, drilling a small hole in the side of the oil pan (and cringing mightily). I did it at oil change time and tried to flush out filings , had some grease on the bit. That was 10 years ago (160k miles ago) and no harm was caused that I can detect. I have removed the pan for something else since then and no filings were found.

 

If you guys need the correct, used OEM parts, rather than, Napa, Dorman, Slant or E-bay re-popped junk, just let me know.
I have a couple spare parts 24V motors in my shop.

 

Why, you ask do they not fit? Most likely due to the fact the aftermarket does not do a good job of making parts that fit, or that are durable.

 

Finally coming back to this one, so I apologize for the delay.

Oliver, I definitely hear you on the aftermarket playing a little loose with specs. The thing is, none of my aftermarket ones are even close to the hole in the valve cover, however the threaded portion is pretty much identical on all the aftermarket caps.

I'll shoot you a PM here in a couple of minutes. If you have any used OEM 2nd gen oil caps, I'd love to buy one off you.

Thanks,
Mike