F200 Idle Overheat What now?

[solstice]

I'm at the end of my rope on this one. The engine is a 2002 F200 with 650 hours run in salt water but fresh water flushed consistently. The overheat alarm goes off at idle after about 10 minutes. The pee stream hasn't been strong for the four years I have owned the engine and since this problem started I have replaced the water pump including the housing, both thermostats and the pressure relief valve....still a weak pee stream and the overheat at idle. When you throttle up to 1500 rpms or so the alarm goes off but at idle the overheat alarm consistently comes on. What would you suggest next? Any help would be appreciated.

 

[pine island fred]

Re: F200 Idle Overheat What now?

My thought, when you replaced the water pump, the stainless steel housing became un indexed when you were pushing the impeller into it. The housing is eccentric and will rotate enough to block the pump outlet. Go back and check the position of the stainless cup in the plastic housing.
Also, you say you flush after each use. If you use the built in hose fitting, do you run the engine at idle while flushing? If not you are wasting your time flushing. as the fresh water cannot circulate past the closed t stats. Been flushing at idle for about 2 years now with no ill effects. regards FRED

 

[solstice]

Re: F200 Idle Overheat What now?

Thanks Fred for the reply. I haven't been running the engine off the flush attachment as I was told previously not to. What you say makes sense, I guess it may be salt build up after the t-stats. I will also double check the postition of the water pump but if that was it wouldn't it also alarm at higher rpm? At this point it only triggers the overheat alarm at idle.

 

[DMSOUTH]

Re: F200 Idle Overheat What now?

Sure sounds like a pressure relief valve that's stuck open--either with salt build-up or dirt...........