I am having the exact same problem. How long did this solution last for you? Did you experience any further problems? Thank you for your assistance. I have been looking at salvage yards and can't find any Ultra models to replace the discontinued part and it has been sitting for so long.
Sorry, I didn’t get a notification that anyone had replied. To answer your question about how long it worked — it's still functioning, but recently I’ve been having issues with the cap on hot days.
It’s a plastic reservoir cap, not an inline metal one. According to ChatGPT, it’s likely going through more heat stress/ abuse and should ideally be replaced yearly. I had noticed some minor hose collapse after use and mild boiling in the reservoir on longer drives in hot weather previously, but nothing serious until yesterday.
I had a violent boil-over on the highway and pulled over immediately when the warning light came on. As soon as I stopped, the push cap for the passive reservoir blew off, sending coolant everywhere. So, clearly had a major steam bubble caught in the system somewhere. Once it stopped bubbling, I unscrewed the upper cap, refilled both the filler neck and the reservoir, and drove home without further issues.
This morning, I opened the upper cap again and found it was completely empty. Strangely, as soon as I removed the cap, coolant started flowing into the filler neck from the smaller top hose.
So I’m not really sure what’s going on. Does the metal cap perform some function that the plastic cap doesn’t?
Unfortunately to date, this is still the best set up I can find. Ill be moving to another province in a few months and dont want to deal with an out of province inspection on the Buick.. so best plan it to keep band aid ing it till its time to sell or it dies. But if you found a better solution, would be great to hear.
The engine and transmission are still strong runners, so its a shame to toss in the garbage because of a stupid $30 filler neck. But do to lack of vital parts, not sure what else to do.
