Got a bit of a weird one at work, engine on a dyno, using thermostats to control engine temp through water radiator (normal setup). Engine is a 7.5 litre diesel, runs fine up to 2000rpm but above that overheats?? Water temp across system is 20 degrees top vs bottom at low speed, but at high speed they seem to converge to within 5-6 degrees and then the water temps go above 95 and we need to shut it down? Any ideas?

 

dodgy water pump?

 

what engine? whats been done to it? sounds like water pump or a liner lifting/head gasket issue.

 

Not teaching anyone to suck eggs here but:

Check the coolant (level and condition)
Check the cores of the rad are clean and shit free/also the cores are in good condition
As above check the water pump is flowing as it should be
I assume the oil is nice and clean?

We use Cummins mainly, they like to sit around 1500 to 1800 all day long.