I have a 91 Pickup SR5 4x4 with 3vze.
It was leaking coolant for a while only when it sits, not when it runs. It got to the point where I had to add coolant everyday. One day I was driving it and it began overheating, I had already used up all the water I had reserved for the coolant so all I could do was run it till it got hot and pull over and sit. Did this about 10 times, and regrettably once or twice I let the temp get in the red.
My thought was that the water pump was leaking. I finally got around to replacing the Water pump, thermostat, and timing belt. First time start it up everything seems to be fine. The temperature even stayed steady in the middle for quite a while (huge relief)
Then I take it for a drive and shortly after taking off the temperature begins to rise. While driving the temp needle goes to about 3/4 and moves rapidly and even shakes a little.
Feeling a little worried about what my issue could be now. What are some more options?
Could it possibly something simple like the water temp sensor, or the temp switch?
Oh and I just started filling it with water because before it was leaking so fast I didn't want to keep spending money on coolant. At this point its just about almost 100% water. I live in Midwest US so no chance of freezing at this time.
Could that be causing issues? the fact the coolant is all water?

 

Is it still leaking water/coolant. I know nothing about computer controlled stuff but if its getting hot when you drive it could be a bad fan clutch.

 

What kind of driving are you doing? Highway, stop n go?

When was the last flush/burp and does the heater work - is there water flowing through the whole system?

If the weather there isn't getting really hot or really cold the water only shouldn't be a problem temporarily.

Like flg8r said it could be a fan clutch.

 

Sounds like a head gasket, get a good leak down tester (input side takes close to 100PSI, not from harbor freight) and check it out. If you're lucky you might have air in the system so burp as already suggested, or maybe gotten a bad thermostat, ideal to check them to see what temp they open before you install, but I wouldn't count on that. Straight water will make your engine run cooler that glycol mix, no problem with overheating there.

 

How do i test or figure out if its a bad fan clutch?? I made an observation before putting the fan back on that it was rather difficult to turn the "spindle" or whatever you call it on the fan. I assumed it should be easy to turn.
At the moment i have not driven it on highway because it starts to overheat quickly. But it doesnt overheat at all while at idle.....
Only when i start moving forward the temp goes up. Im gonna burp it. Heater does indeed work good.
and i seriously hope its not HG, so there is a tool i can get to pressure test the cooling sustem?
I never had overheating issues until one day randomly before i fixed the leak.
I did notice it does seem like there is another leak somewhere. I found coolant on the passenger side

 

Bingo. I guess I didn't let it run long enough when i originally bled the air. Tried again and I let it run for ~20 mins at operating temp, dropped the hood, took it for a spin, no more overheating!
Slightly makes me feel a little ignorant for not properly doing this before but thanks everybody for your time and suggestions! Much appreciation sent to you all!!!

 

There are many things in life a burp (or a fart) easily solve.

 

Never mind, I see you solved the issue!!