ACDelco GM Original Equipment RC115 20 P.S.I. Radiator Cap

Value, fit great, easy on off.

TL;DR - if you wait too long to replace you *might* experience the symptoms below which this part may fix by replacing it. Otherwise, just replace every 5 years as a preventative maintenance wear item as generally 'accepted' best practice. DISCLAIMER: I am NOT a mechanic, just a guy interested in car stuff.I have a Gen5 Camaro which probably had the original radiator cap. I say "probably" because I got the car used (9 y/o) and the previous owners' did wacky things with the car I won't get into here. Well, mine was probably pushing 12 years by now so I know that's past the limit of this part.Symptoms to know when a radiator cap may be bad:Signs of leaking:As you can see from my pictures, the cap had caked up coolant around it as well as drip stains down the neck on the radiator where the cap sits. I had so many other issues going on with the car, I ignored this for over a year.Car not heating up:Now it's February in the rust-belt and very distressing when the heater isn't working properly. I noticed that the engine was not heating up as fast and taking a very long time to get to around 180° F and then it would drop down to ~176-178° F when I start moving again. I also noticed the engine oil temp and transmission temp never got to their happy place either.Cabin Heat issue:Conversely, the heat blowing in would drop when I'm at a stoplight and get hotter when driving.Analysis / Diagnostics:Facts/observations:- I already had the water pump and coolant flush done 2 years ago so it's less likely that's a cause.- There were no DTC codes.- Coolant level in the overflow tank was okay (up to max)The thermostat is the first place mechanics would go thinking it would be stuck open (this too is a preventative maintenance item but more on that). There are diagnostics to do to check that by checking the temps on the inflow and outflow hoses, etc. but I didn't do that as getting at the thermostat for my car is a very big job (thanks to the LFX engine being mounted longitudinally the thermostat is flush against the firewall rather than being on the side for which it was designed on the Enclave originally). I neither have the tools nor time nor money to do a proper diagnostic so when possible I use my brain and the internet and AI to help me diagnose problems.Approach taken: Parts cannon (justified for wear parts in this case). For this the radiator cap was a cheap and easy fix. I could do in my garage that had a high likelihood of resolving the issue before moving to a more expensive solution.Procedure:I wiped off the filler neck on the radiator, made sure the car was cool and took the cap off, cleaned inside, compared the old and new and then put the new one on.Outcome:Went for a test drive and it appeared to fix my issue! Heating up nice and hot and it even pushed past 183°F and heard the radiator fan kick on to boot to maintain it at temp and all the cluster gauges were reading nominal temps (engine oil, trans fluid) and the heat was blowing consistently into the cabin.Conclusion:Problem solved, for now. The old radiator cap was likely not pressurizing the system as designed, 20 PSI is the rating on the cap and it was probably not able to build to that, so it was probably operating at a lower pressure caused heating performance issues and potentially not creating a vacuum also could cause the introduction of air but I did not do any bleeding afterward so that leads me to believe just related to reduced pressure in the system, resulting in reduced flow within the system that could explain my symptoms that are fluid flow related. (the water pump's rotational speed is directly proportional to the engine speed, so at higher RPMs, the coolant flow rate would have been higher, and the hotter fluid was flowing into the heater core and at idle/stop, the flow slowed down, and the cooler fluid gave me cooler heat). I think I science'd the heck out of this, or at least convinced myself this is how it works, lol. Either way it was kind of sort of, "fun" to figure it out rather than pay someone to do exactly what I did without the Bill Nye explanation.Moral / Lesson: Don't wait like me. Change out this part every 5 years. It could have been far worse if it overheated. A failing radiator cap may put undue wear on the cooling system (potential loss of pressure, vacuum, strain on hoses, radiator, heater core, thermostat, etc.). An ounce of prevention is worth a pound of cure. Once spring/summer rolls around I'll rip apart the intake to replace the thermostat for added peace of mind (FYI, this is I would only get OEM) and probably a bunch of hoses. Thanks for reading hope this helps someone out.

Excellent

Same as original, works well

Well, it worked as advertised after my original cap disintegrated around the threads. Unfortunately my radiator decided to crack at the plastic seams near the less than a month after installing new cap. Switched to an aluminum radiator which this cap was not compatible. Money down the drain, but at least it did its job.

orginal oem part

It did the job.

This replaced the old radiator cap perfectly, and was the correct pressure.