weird overheating prob

[gundamx_105]

stock 240 radiator

non turbo sr20de

stock fan- (I am using the stock elec fan from a 93, probly the ac fan, but i have been running it like this with no probs.)

replaced original thermo 4-5 mos ago

I first noticed the over heating on a hour and a half trip, all highway. when i reached my destination the stock gauge read at the last notch, and it was just starting to boil barely. i let it cool and drove it home that night it got hot but not that hot. after driving it awhile the gauge goes up real slow, i can't see it go up it, i look down every so often to find it has went up a notch. it stays there, it never goes all the way to "H", but starts to 'bubble'. it seems to cool down some when off the highway! also the last time i drove it on the highway for 25 min. the gauge went down slowly from the last notch to normal then back up slowly twice. the heat blows very hot and will bring the temp down alittle after several minutes.

i have red, sandlike, soot in the overflow. in the past i had put that orange coolant for newer chevys in it right after i swaped it. i changed it soon after and noticed a red color in the new coolant. I figured it was a little rust from the pipe that i used for the top rad hose(i am using the stock 240 rad). maybe this is somthing to worry about?

i found alot of posts on overheating but no definate answers. my engine has run fine the way it is, don't think its the fan or radiator. there are no leaks. i did have slight coolant loss after driving it like this several times.

anyone have any ideas? i am about to flush out the system tonight.

[need2drift]

maybe a bubble in the coolant system????

[tiger]

THINGS THAT CAUSE OVERHEATING :1. A bubble in coolant... yes, like drift said.2. Leaky Head Gasket....3. Bad Thermostat (not opening up like it should)4. Bad Water Pump, maybe leaky or broken.5. No fan... I guess yours is working though. 6. A coolant leak... I guess your levels are good right?

[gundamx_105]

I emptied the fluid ran the garden hose through it and ran it awhile. cleaned out the resivour and filled it back up with fluid, tightened up everything real good.

it's been almost a month now and no problems!

weird