I think I need to flush my radiator. I’ve got plenty of fluid in the overflow resevoir, but my engine temp continues to rise. I think I have sludge build up. But, the cap to the actual radiator is sealed with strong warning labels saying never open. So how can I flush the radiator if the actual radiator cap tells me never to open it?
I think it means DO NOT OPEN WHEN HOT.
Why do you think you have sludge if you haven’t looked in the rad? Perhaps your over-heating problem is a faulty thermostat.
You may have ORS. Old Radiator Symptoms. If the radiator has never been changed, it’s time. The little fins are probably corroded away. Pull the shroud back and look. If 5% of them are gone, it’s 100% time to change it. They never want you to check the fluid level by opening the cap; they want you to look in the reservoir. You can still remove the cap. You probably don’t have enough training to work on your own car. I don’t recommend that you even do a flush by yourself.