HELP!!! Cooling problem

[spdy0001]

I have a 91 sport and last week I noticed that I was loosing antifreeze so I kept adding some until I could fine a better fix. One night I was coming home and noticed the temp guage starting swaying from C to H constantly. I made it home because I kept and eye on it and it never got too close to the H. A couple days later im headed to work in 10-15 degree weather and the guage is still doing this, but now I have NO heat and the guage is going higher so I kept pulling over to let it cool down. I had replaced the radiator this fall and that has been fine so far so my dad says it probably the t-stat. We froze our butts off tonight putting that in and its still doing the same thing. ANY IDEA'S ???

I did talk to one guy who thinks it could be the water pump. He told me to let it get hot and then feel the radiator. I did and right at the upper hose its too hot to touch and the whole rest of the radiator is cool. He said thats probably a bad water pump or blockage in the radiator, but the rad is new.

PLEASE HELP ME it keeps snowing here and I need my 4wd

 

[Darrman]

One of the first things I did to mine was to completly rebuild the cooling system as a faulty overheat can be the downfall of the 4.0. I ended up replacing the rad, hoses, t-stat, pump, fan blade, fan clutch, and did a complete flush when all new parts were installed, all works like brand new now. The pump is cheap and somewhat easy to replace, but I am not sure if that is your problem. I would flush the whole system out with a water hose first, take the hoses off and run water through the radiator, then run the hose through the lower rad hose and let it spit it out the top. Pretty messy work, but you should be able to see or flush out any deposits. Have you tried wiggling the water pump bearing to see if its shot?

 

[92EddieBauer4X4]

It could be a smaller problem........ Your radiator coolant needs to be half water half antifreeze. If you put just str8 antifreeze in there that will cause it to overheat. Try that before messing with the water pump.

 

[spdy0001]

When I replaced the radiator 1.5 months ago I replaced the hoses and completely flushed the system using a prestone flush kit which is nice since its not too messy. The coolant is a 50/50 mix, which has worked fine since the rad change.

Thanks for the suggestions guys, but im a third generation mechanic so all the "common sense" stuff has already been checked. Im really looking to see if anyone has already run into this problem. Changing out the pump isn't a big deal since I have all the proper tools, but since I will have to wait till the weekend to do it I was looking for someone to agree with me

 

[jcook007]

Missing Coolant?

If it were me, I would look to find the source of your first symptom because that sounds like an important matter here. "I noticed I was losing antifreeze". You may have no heat when low on coolant. Where is the coolant going? Leaking out of a loose hose connection? No? Crack in the overflow res? No? Heater Core leaking on the floor of the cabin? No? The waterpump impeller is connected to a shaft turned by the belt and pully, if the bearing is bad coolant will leak out from the weap hole behind the pully. Is coolant leaking here? No? Then waterpump is probably fine. Is there coolant in the oil, dipstick? No? ...Is it coming out of the tail pipe? ? ? Hard to tell in winter sometimes when lots of vapor appears at the tailpipe any way.

Anyway, find where the coolant went and you may find the solution.

 

[spdy0001]

Well last night I took the orignal t-stat and put into a pot of boiling water and it opened right up so I know it wasn't the thermostat. Since I replaced the radiator it hasn't leaked a drop of coolant anywhere outside or inside. I was loosing coolant, but I always kept it full. Im pretty sure I know that the coolant was lost do to it being pushed out of the res. After heavy driving the top of the res would be wet. Also the tailpipe is bone dry after driving, so that tells me the head gasket should be fine. Well I should be replacing the pump tomorrow

 

[savagefan]

Please don't take this the wrong way but could the t-stat be in backward? Now pushing coolant out of the res could be a head/head gasket issue, does the coolant smell like exhaust gases? Water pump is a centrifugal type which means the blades would have to magically disappear to prevent pumping. The bad heat hot engine fluctuating temp. guage screams combustion gases in the water jacket. But hey the pump is easy to change.

 

[spdy0001]

im 99.9% sure the thermostat is in correctly and the symptoms didn't change when replacing it. The coolant doesn't look milky, the oil doesn't either, the coolant is still a nice bright green. The coolant doesn't bubble or gurgle when you rev the engine. When its running you can see the normal exhaust condensation, but it doesn't seem to be abnormal. Also after driving 100 hundred miles one day I stopped and the exhaust tip was bone dry, but I went through a gallon of antifreeze that week. If I was loosing that much antifreeze through the head gasket I would expect to see some coolant in the tip. As you mentioned the pump isn't too hard to replace and that should be done tomorrow. I would rather put out that $60 and rule out as being a problem before looking into a head gasket. I will update you guys tommorow, and hopefully it fixes it

 

[spdy0001]

Well guys the water pump is finally installed and its now running correct. I was really worried at first though. After I got everything bolted back together I started it up and let it warm up. The temp start dancing and I still had no heat. I was really upset so I just let it run and went in the house. I came back out and started checking around and tried the heat again and it started getting warmer. Then all of a sudden I had HOT air and the temp was rock solid at the 'N' mark. I then looked at the res and saw that alot of the coolant was gone so I guess there was an air pocket from me changing stuff. Once that got out I refilled the res and drove it around this afternoon and the temp has been rock steady and the heater has never been hotter.

 

[Creager]

Damn, after reading this whole thread all i was gonna say is you got some air trapped somewhere

i just went through a simular issue like ths last week.