Overheating in the dunes, any ideas?

[2'91fords]

Vehicle specs: 91 explorer sport auto 3.73 gears 2" susp lift 30" tires 150,000mi

I took my explorer onto the sand dunes last weekend and after about 20 min or so the temp started to climb (Outside temp was about 65f). It got up almost past the A on the stock temp gauge and i stopped. After letting it idle for a few minutes it returned to normal operating temp so i drove off and it warmed up again. when i drove off the sand and popped it out of 4 and drove on pavement it cooled down quick. it has never climed past the O during any freeway, street or fireroad driving ( i still have not done any serious wheeling with steep climbs or the need for 4low). The coolant is fresh and full, fan clutch seems to be working, fresh fluids and filters in everything, new belts and hoses. the rad cap is a 13lb, is this the correct cap? any ideas what it could be? possibly overheating trans? any info appreciated, thanks!

 

[Brian_B]

Did you replace the thermostat when you put new coolant in? Mine stuck last week with no prior warnings. Just driving along (about 50) and it shot up.

 

[2'91fords]

haven't done that yet but i plan to, even though it doesnt heat up during normal on road driving, even when climbing big hills on the highway. thanks for the info though. Anyone else share my problem?

 

[gijoecam]

I'd start with the t'stat just because it's cheap, and if it hasn't been replaced before, it may not be opening all the way anymore.

Another possibility is excessive heat being generated by the automatic transmission (if so equipped). Also, when you refilled it, are you running a 50/50 mix?

-Joe

 

[410Fortune]

91 Explorer is likely due for alot of cooling system work, radiaotor probably is getting old and could use a rodding or a replace. The thermostat I replace anytime I service the cooling system, you can check you stock fan clutch to see if it still works, you might check the fan hub to make sure the nylon is not cracked.

Also a 91 sport may still ahve the single core radiator, if this is the case I would suggest the HD 4.0L radiator, about $180 new.
If this truck is an automatic I too suspect the trans is slipping or under laod (sand) and causing the extra heat.
Heat kills auto transmissions.

 

[Dannyboy]

I worked on every part of my truck's cooling system (flushed radiator, changed t-stat, etc) and found the heavy duty fan clutch to be the best investment I've ever made. It was cheap too!

 

[2'91fords]

thanks for all the info. i did mix the coolant 50/50, still haven't got a chance to wrench on anything. how difficult is the tstat and fan clutch change? also, it is equipt with the stock trans cooler and i have an xtra one that i was gonna add next to the stock one. is this a waste of time or should i just go buy a big HD unit? kragen has the Haden coolers for under $50.

 

[410Fortune]

dual stock coolers are a good idea.

T stat is fairly easy as long as you have the right tools, there is one bolt ont he OHV that can be a PITA.
the fan clutch is easy as well but you will need a Ford fan clutch tool (two long flat wrenches) to get it off the water pump pulley. Yuo can rent it at any auto parts store.

 

[Maniak]

I've taken our '92 out to glamis (sand dunes).. I had no overheating issues for the motor (trans is another story)... I found a HD fan clutch (thermal style) made the biggest difference in keeping the X cool. I ran low tire pressure (< 10psi) and kept it in 4x4 low the entire time.. It was February, so daytime temps were 90F or so (not 110f).

Also, you can run a 16lbs radiator cap. It won't keep it cooler, but it will keep the coolant from boiling longer. If I remember it correctly, each PSI increase will increase the boiling point 3 degrees.. So increasing the pressure to 16 psi over the 13psi cap will increase your coolant boiling point 9 degrees.

~Mark