DF25 3 cyl overheats but is pumping.

[Kingsbridge]

Hi. I have a 2001 DF25 3 cylinder engine that overheats at low revs. It isn't pumping water through the pee hole. However if I take the large flushing plug out just below it pumps loads of water out of the hole. So I'm guessing the impeller is fine. I've removed the thermostat and that chamber is pretty dry (the thermostat works fine.) I'm assuming that there is some kind of blockage where the pumped water enters the powerhead, but I can't really work out if this would block the pee hole as well. I'm assuming the pressure relief valve is opening and returning the water back through the exhaust. What else should I test, and what's the best way to try and clear any blockage please? Could the pressure relief valve fail open, and if this is the caase would that stop water entering the powerhead?

[artdf175]

We usually make an assumption it is a blockage
the pressure relieft valve by defalut is in the closed position
from what I can tell when it fails, corrision or blockage it is would be in the open position, thus allowing cooling water to dump back through the exhaust. since you know your watrer pump works, I would first start with checking this valve first
unfortunately when you get past this the problem solving only gets worse and expensive.
one other thing to check after the pressure relief valve is the tube from the pump to the the bottom of the oil pan.. this wilil require you to drop the bottom as if working on the impeller, inspecting the tube and the gaskets/gromets it is know to develope holes

next.. if your engine is built like mine, the fresh water flush port is on the port side of the oil pan.. remove the cover plate, carefully as not to twist off the bolt heads..
the following I intend to make a seperate posing on..
When I had your problem, overheating at idle, the backside of the wall after taking off the cover plate had an 1 inch hole. this was dumping water back into the exhaust at idle..
now this turned out not to be the only hole
the other hole is internal within the oil pan and the inside porting .. thin walled castings rotted out and there was another 1 inch hole.
These are known problems at Suzuki that no one knows much about..

Good luck and out
ArT

[artdf175]

Behind the flush port

[fishwork]

where is the pressure relief valve on a df25 2 cylinder?