if we are referring to one of the AIO pumps w/ radiator barely big enough for a single 120/140 mm fan, you might do better to look for one of the smaller low-mount height Noctua solutions...(consistent with your case's mounting height constraints); the small radiators can only dissipate so much heat within the fluid's 1/2 of a second trip thru a radiator, and, as the fluid warms up, it cools less effectively, ....leading to warmer fluid....etc...until thermal runaway and throttling occurs within 10-15 minutes.