Help with 98 Explorer running hot !

[rolltide8]

Need help PLEASE!I have a 98 Explorer and it overheats after it has been driven for about 10 minutes or so. When I get to about 50 mph it shoots straight up to "Check Gage" level. I have flushed the system and added new coolant to the radiator.
When I drained the coolant out ,the coolant had turned brown. I had put some PEAK 50/50 in about 2 months ago when it ran hot then and had been fine until the other day. When I opened up the radiator cap,there were a couple of small brownish clumps that came out when I got to the top during the refill.
Another issue is that the coolant reservoir has the same coolant left in it that i put in a couple of months ago so I don't even know if it is getting to where it needs to go or what. Any help is appreciated!

 

[hworksinc]

Have you looked at the thermostat?

 

[rolltide8]

not yet...isn't it in the bottom hose near the engine block?

 

[turboranger91]

could be one or a combo of several different things. you should go ahead and replace your thermostat. it's really cheap and easy. if that doesn't help, make sure your fan is working properly. i'm not sure if your year has the fan clutch or not, but those go out all the time. make sure your radiator isn't blocked by debris, check your water pump too. make sure no coolant isn't coming out of the weep hole. then theres the dreaded heater core. i hope it's not that... it's a pain to replace.

 

[desertsky]

One thing to consider is that if the water was real brown, that means rust. If it has run a long time like that, the vanes on the water pump could be worn down to the point that it doesn't circulate water very well anymore. I would think fan clutch would be less likely since you will get enough airflow when driving at moderate speed to keep it cool. Is fan forcefully spinning when engine is hot or is it lazy?

 

[hworksinc]

I think there are several tutorials around here on replacing the thermostat, possibly with pictures. It's different for the OHV and the SOHC engines (I'm assuming you've got a V6 since it's a Sport), so just search for the appropriate one.