Have you tested the actual fans to see if they even work? i.e. disconnect, and jump them to power, or if car has AC, turn on AC, and see if they come on with the compressor engagement?
Are you by any chance running a lower temp thermostat? A low temp thermostat OR no t-stat can delay the fans coming on. I used to run a non t-stat in my '79 Mustang (mild 306, iron heads + block & 10:1 comp.) and IIRC, it ran something like 35 degrees cooler than what would be "normal". It had a mechanical fan and a carb, so was never an issue, though more modern cars would/should throw codes griping about taking too long to reach the "ideal" temp in X amount of time.
Years ago my ex had the last gen VW Beetle with the 1.8L turbo (the one where you have to pull half the front end off and remove a motor mount to do a timing belt and water pump (q= ) and after getting everything back together, it's lower hose stayed cold, fans never seemed to kick on, and temps were slightly off. It had one of THE most stubborn systems to fully bleed air out of. Took a couple days with me obsessing over it to finally get it acting right. Once the air was gone, the lower got hot AFTER the t-stat opened.