RPM WS6

iTrader: (3)

I wanted to replace my original '98 radiator cap due to aesthetic reasons (small amount of the print has worn off). The current replacement part number from GM is 10316828, and ordering this number will get you a cap marked "RC94". However, the assembly line original cap was marked "RC24" (and, through some research, I believe was part number 10402081).

That older part number is since discontinued, which of course is quite common. Both are rated at 18lbs, but I'm wondering if there are any known functional/fitment differences between these two caps? I ask because, in my research, I found someone who complained about the revised RC94 not fitting as well/tightly as the original RC24 on their stock 4th gen radiator, leading to issues with the siphon function of the overflow (i.e. coolant not getting pulled back into the radiator during cool down). Going back to the old cap solved their problem. This may have been an isolated incident as I didn't find much information either way.

I haven't yet been able to test fit nor compare the two directly, but I'm wondering if anyone has had issues using this new GM cap and, if so, have they considered swapping the plastic portion of the cap from the new assembly to the old assembly (not sure if this can be done without destroying it)? The car is still in storage, so it will be a while before I'd be able to test for proper function of the new piece.

peterpar

Here's a link to a AC Delco RC24 cap on Ebay. The part #10402081 is shown on the box.

eb110americana

iTrader: (4)

I have used the GM RC94 cap on my car to replace an old worn out one without any issues. I never even noticed any difference, to be honest (1998 also). Whenever opened, there was never any air in the radiator, and the overflow tank always worked as intended as far as I could tell.

RPM WS6

iTrader: (3)

Thanks for the link, I actually tried to buy that one but Ebay isn't accepting my credit card. No idea why, card provider says everything is fine.

Good to hear, thank you. I'd rather have the correct RC24 marking, but it's not the end of the world. I'd be happy using the RC94 as long as it works correctly. After reading that negative review, I was just concerned that perhaps this revised version might be hit or miss on the original radiators, but maybe that was just an isolated incident after all.

Spartan7

iTrader: (7)

I have an RC94 cap on mine. It has fit and functioned correctly for a couple years, both on the original and now a replacement side tank (original cracked). When tested, it opened at 16psi.

wssix99

iTrader: (5)

Please PM me your credit card number, expiration date, and security code. I'll give it a try and see if I can help.

wssix99

iTrader: (5)

I will bet that the answer is in an old AC Delco Insider... http://www.acdelco.com/news-and-press-releases.html (Click on the "Insider" tab.)

The problem is that they recently took down all of their old issues. :Z

We had a similar question regarding water pumps and thermostats and one of the articles laid that all out. (When the GTO came out with the LS2, GM fixed some deficiencies with the water pumps/thermostats and then supersedeed the whole line backwards for all of the LS1 cars. The cap may have been caught up in that.)

I can't tell much of a difference.

Here is the RC24:



Here is the RC94:



I would guess that the difference is in the spring design. (I recall that there was some big advance in spring steel over the past 20 years, but I can't remember the details.)

If there was a physical problem with the RC94, I would expect our pages would be flooded with issues. (I don't doubt some person had a problem - radiator necks get out of whack all the time.)

RPM WS6

iTrader: (3)

Great data, thank you. Sounds like it should be fine then.

Doesn't look like there is any way to search for specific topics without viewing each issue. Or, perhaps I'm just tired and missing something. Haha.

I looked back over some old GM dealer receipts and parts boxes I have going back many years. It seems that even by '05, the cap had been updated to #10316828 (RC94), I guess I just didn't notice this at that time. So you very well could be right about the entire update being from the early LS2 era.

Considering how many must have been sold for use on these cars since 2005, I'm sure you're right that we'd have tons of posts about this if it was an issue. I just didn't realize the update took place so long ago. That one incident which was solved by going back to the original cap might have simply been a defective cap right out of the box, etc. Glad to see that others aren't reporting problems. It might be a few weeks before I can actually put mine into service.

So maybe Ebay did me a favor by not taking my card for that NOS RC24. But I'll send you the info anyway, just be sure to get yourself something nice.

wssix99

iTrader: (5)

Google's advanced search and the site search seems to work. I think that since they took all the old back issues away, there just isn't a lot of meat on the bone there.


Sweet. I'll be good. I promise.

RPM WS6

iTrader: (3)

I think wssix99 has gotten it right again. Guess he deserves that LSX454 crate engine he ordered earlier today with my credit card info (thanks for maxing out the card BTW, I couldn't buy any groceries today )

I had a chance to put them side by side this evening and, other than the text being a bit more bold/robust on the plastic portion, the only difference was the spring. The spring on the newer RC94 seems to be a little more tightly wound, perhaps just a bit longer. But assembled height seems to be the same, and fitment was perfectly snug. Probably won't actually drive the car until April though.

wssix99

iTrader: (5)

Sweet.

Did you know that you can have a crate engine shipped overnight? (I told them cost was no option and the put it on its own semi. FedEx Custom Critical)

I wonder if you could take a RC24 cap and rivet RC94 guts to it. That would give you the durability of the modern part with the original printing on the cap. (Although, this wouldn't solve your problem since your particular problem since your printing is fading.)

RPM WS6

iTrader: (3)

Just wanted to come back to this with a small update.

The newer RC94 cap has been on the car since March. Functionally seems fine (no apparent issues with the siphon function for the expansion tank), though I've only driven the car a handful of times since installing it. But the one issue that I've noticed is how loose the plastic cover seems to be on the cap. It pops up and twists a short distance side-to-side with relative ease (unlike the original cap, where the plastic cover had more of an interference fit), it was basically like this from the beginning but seems to have gotten worse after a few heat cycles. Not really an issue, except that the fitment slack might cause the plastic tabs to break when torque is applied to open the cap. I wonder if some JB Weld might be helpful as a bonding agent/filler between the two pieces.

Not sure if all the newer caps are like this, or just this one. Either way, I went ahead and bought the NOS RC24 that was on Ebay. Nobody else had picked it up after all these months, so I thought I'd give it a home just in case I want to switch. The plastic portion on this one is perfectly snug, just like the assembly line original.