I know this is a common issue and problem but have been through everything on the internet and this forum and am still stumped.
I have a Universal M25 my problem is the engine operates perfect at under 1800 RPM... Above 1800 RPM the water temp quickly rises to 190-200+ and keeps going unless I back down. I would really love to get this up to normal operating speed but can't figure it out.
The engine status so far:
New Coolant/Water running 60% water with cooling additive
170 Degree Thermostat
Checked all cooling lines for blockages
Replaced Raw water pump (was Oberdorfer N202M-03, replaced with N202M-07)
Replaced heat exchanger with updated 3"
Checked fresh water pump (may replace anyway but looks ok)
Pump belt tension is good
Looking for any tips someone might have to troubleshoot this and identify the problem.
Right now my next plan is to run through some coolant flush/radiator cleaner and refill and try again. But beyond that I haven't a clue what to approach next. The raw water flow out the exhaust seems fine, there was a noticable increase when I upgraded the raw water pump so I'm reasonably certain that system is functioning properly.