97 f250 4.6l engine pegs the temp gauge after start-up. the oil pressure light comes on then after a few miles down the road anti-freeze blows out the pressure cap (15LB) then the temp goes down ,the oil light goes off and everything is normal. no its not the thermostat, i changed that and it still does it. whats up with that?

 

Head gasket?

Check for hydrocabons in the coolant.

 

How quick does it heat up? Does it do it again after a few miles?

 

It does shortly after start up then never again till its shut down after a few hours

 

There's no sign of water in the oil and no significant increase of vapor out the exhaust so I ruled out head gasket . Can a water pump come and go ?

 

The impeller can slip on the shaft. Almost sounds like it has a big air pocket in the cooling system and it gets extra hot until the thermostat opens.

 

Thank s lxman1 I think I'll put a new water pump and have a complete engine flush . I've got almost 140000 miles on the truck any suggestions about what else I should replace while I'm in the front of the motor?

 

Maybe just a new belt and check the hoses. The pump is stand alone, meaning other than removing the belt and the clutch fan, nothing else should need to me removed.

 

Thank lxman1 you've been a great help God Bless!

 

You're quite welcome. Curious to see what you find.

 

it overheats because the antifreeze is not circulating past the thermostat and opening at the right time. Antifreeze by the temp probe is way to hot, and vaporize, and the gauge spikes. After thermostat finally opens, the temp is o.k. and gauge drops. This can be due to a bad water pump, or the small hole in the thermostat body is plugged and now allowing the hot water from head area to circulate thru and warm up the thermostat. THe "oil light" is actually the over temp light coming on.

 

If I'm not mistaken, the temp gauge actually measures head temp, not coolant temp. My 01 did, not sure about the 97.

 

hey guys, just went over to some other forum and found out some disturbing news that ford put some kind of plastic intake on certain models of 4.6l and a coolant crossover tube can spring a leak. someone enlighten me on this. i dont want to a bunch of parts replacing i.e. water pump ,hoses ,thermostat when what i have to do is replace the intake. also read that ford had a recall on this, any truth? took the truck out yesterday and this time when the temp gauge pegged the truck actually went into power down mode and limited my power. shut the truck down for a few minutes then started back up ran normal . i have noticed my coolant is discolored and is low again but i cant find where its going. still hot and bothered!

 

Never heard of this.

Is this accurate?

Thought "THe oil light" was only low oil pressure warning. Does "THe oil light" perform double duty also going on as "the over temp light"?

 

No, unless it gets so darn hot that it breaks down the oil too thin to make pressure.

There should be a "check gauges" light when one goes out of range.


Plugg, you should be able to see it leaking if so. They all use a plastic intake, but the updated ones have an aluminum coolant crossover in the front that is easy to see.