I've got a 1990 Bronco XLT with the 5.8L auto w/OD that has a bit of a strange overheating problem. There doesn't seem to be any reason for it to overheat, it's been running fine for weeks, and then one day it's just running way too hot. It does seem to push all the coolant into the overflow tank, but never suck it back into the rad. The oil's fine, no power loss at all, so I don't think it's the head gasket, but I'm not sure I know enough to rule it out entirely. When I fill it back up after it cools down, it'll run fine for weeks again. My thoughts are: water pump, rad cap, thermostat, blockage somewhere.... any help would be greatly appreciated! One more problem that happened yesterday for the first time - while driving down the road, the oil pressure gauge dropped to nothing and the engine light came on. I pulled over to the side of the road and checked the oil - it looked normal, and was right at the Full mark. When I started it back up, the pressure went back up to normal. I checked underneath for leaks, and under the hood as well, but there weren't any. I drove for a while, and the same thing happened. I turned it off and checked it again, and it was the same as the first time - at the F, looking good, no leaks. When I started it, it went back up to the R in normal. Since then it has been fine. I'm thinking that it probably is the sensor. Could the problems be related? Any chance the mechanical oil pump has gone? Again, all ideas appreciated!

Pooks
1990 Bronco XLT (Casper)

 

ok lets see here first lets look at the oil gage that ones easy.
first off off its not an oil gagge its an idiot light.
the sending unit is not a real sending unit basicly it says all is fine above 4.5 psi on the oil pressure. it only flucuates when voltage across the risister flucuates. I recomend you get a new oil gage a real one. two choices here manual (recomended and easier to install) or a new real sending unit and a real gauge. note I use mannual ones so dont know which sending unit you need to get fo electric one.

As for the over heat I had an F-150 that did this it was the thermastat it had gotten gunged up and would stick halfway open therfor causing the over heat. hope this helps you with your problem
good luck abd GOD Bless..

 

The two most common problems are the rad pressure cap - lost its rating over time, and secondly, the thermostat - make sure its of good quality. The wax pellet type does have a lifespan and could be stuck closed intermittently or is not opening to full open.

These two items are a good place to start and inexpensive to try.

:-)

 

 

Hey, thanks all for the info! I changed the rad cap right away, and then decided to do the thermostat at the same time... a 20 min job, right? Wrong! BOTH bolts broke off at virtually no pressure. What fun! I managed to file the stumps down a bit, beat a socket on, heat the intake manifold, and then twist them out. Went through three sockets, but got them out! Ran a tap through the threads, new bolts with never sieze, and he's running like a top. While in the process of putting things back together, I noticed a connecter that had tape over it (from someone else's previous work). It looked like it would fit into a receiver on the a/c unit... sure enough, it did, and it works perfectly! Air conditioning is a beautiful thing... just wish I found out about it BEFORE summer ended!


Pooks
1990 Bronco XLT (Casper)