Perkins 4-108 Oil Cooler Missing Plug?

[lv2srf]

I was attempting to help a fellow at the marina diagnose his 4-108 mild overheat (190 degree F) which only occurs at high revs (2500 rpm plus) and noticed his oil cooler was missing the two top plugs!? There was plenty of coolant in the tank and it didn't appear to be leaking water from oil cooler missing plugs. Exhaust output is normal...so I'm at a loss why water is not shooting out of the missing plugs. Is it because the thermostat may be stuck closed?

[model 10]

If it is like mine there are 2 coolers in one body. The engine oil is only in one. You can warm up water or cool trans fluid in the other.

[DougR]

The lower of the two coolers was usually used to cool the engine oil on its way to the remote oil filter, and the upper of the coolers was used for the hydraulic transmission. The reason the coolant isn't shooting out of the two open fittings is that the coolant is flowing inside the tubes which are inside the outer shell. Normally the transmission fluid is found outside of the water tubes but inside the outer shell.

As for the overheating engine, go thru the normal drill of restrictions, cleaning, etc. on the seawater and freshwater circuits and you should be able to control it somewhat.

DougR

[DeepFrz]

Also a little searching will bring up numerous threads on 4-108 overheating at higher rev. threads.