The Cajon Pass is a steep mountain climb/descent at almost 4000ft which has caused many accidents for cars, trucks, and freight trains. It was going up the Cajon Pass that I overheated. I smelled some coolant but initially figured it was another car as my coolant gauge stayed at the normal range and there were no obvious signs it was my Kizashi. After the climb, on a flat stretch of highway close to the offramp for my destination, I noticed the coolant temp gauge go up closer to the red zone as I smelled coolant again. I then exited and pulled into a gas station immediately to check it out. The coolant in the overflow reservoir was boiling violently, causing steam to come out of the tiny relief hole at the top. I let the engine cool down for about 10 minutes as I was only 3 minutes away from my destination and wanted to take care of my work matter before dealing with the overheat. After all, I had driven about an hour and a half for the task. I then drove the short remainder to the destination but watched the gauge rise up closer to the red zone again but never in it before stopping at my destination.
The engine didn't get much of a chance to cool down (ten minutes) before I drove it again a few minutes to a nearby Walmart so I could investigate the overheating issue and get some coolant. Once in the parking lot, I noticed that my green reservoir cap was missing (blown off from the boil-over pressure) and a lot of the coolant was sprayed over the engine from the fill hole of the reservoir. I let the engine cool down as I got some premixed blue coolant at Walmart. Given the windy conditions of the high desert at about 49F, it didn't take too long for the engine to cool down enough for me to start examining things more carefully.
I opened the pressurized radiator cap and noticed that it was broken inside. The part that contained the spring of the cap was cracked off and inside the fill neck of the radiator. It was apparent that the cap failure likely caused the system to depressurize thus overheat. Thankfully, I caught it and stopped before things got too bad. I was also lucky that next to the Walmart happened to be an O'Reilly's Auto Parts and they had an aftermarket Murray radiator cap for the Kizashi. I used my Leatherman tool to pull out the spring of the old cap in the fill neck of the radiator but the broken end piece of the cap could not be removed with the tools I had on hand. It also moved into the radiator beyond reach so it was going to stay inside for the time being. I filled the radiator (took half of the gallon jug) and installed the new pressurized radiator cap. I idled the engine and temps stabilized at normal operating range. Phew. I knew then I had a chance at making it home.
Given the scarcity of parts and mostly my OCD, I went looking for the green reservoir cap, retracing my short route since I last saw it at the gas station in case it fell out of the car. I was hoping to find the green cap on the side of the road but ultimately could not locate it. It's not an essential part but I still wanted to try find it before leaving the area as O'Reilly's had nothing that fit to replace it. I ended up leaving the un-capped reservoir empty for the drive back.
Thankfully, the drive back was mostly downhill at colder temps. In fact, the summit of the Cajon Pass was now cold and foggy thus cars descended slowly and carefully. I was able to make it home with no issues. Once home, I looked around for the reservoir cap on the splash guards under the engine but it was nowhere. I also checked the coolant level in the radiator and topped off, bleeding the system of air. It's apparent that the engine wasn't damaged from the overheat.
I'm going to try replace the reservoir cap so, Old Tech, if you have a spare one you can sell me, please let me know. I've also read here that someone used some sort of bottle or pill cap after losing theirs. I also recall that another member drilled a hole on the tab of the OE cap and tied a string to the neck of the reservoir so not to lose it in a boil-over. I see the wisdom in that now.
I also wonder about getting that broken piece of the old cap out of the radiator. I hope I don't have to end up removing the radiator and flushing it with water in reverse flow to remove the piece. I recall it was a plastic or rubber piece that contained a metal screw. There was just not enough space to take it out without special tools at the time due to the small clearance of the radiator fill neck.
So yeah, at 10 years/120,000 miles, it might be time to replace those original radiator caps.
