2000 Ranger 3.0L 4X4

It started last year around this time. I would be on my way home from work and at the same spot each time, the following would happen:

1. The temp gauge would start to bounce around the middle of the gauge.
2. Heater would start blowing cold air.
3. Gauge would go all the way up to hot.
4. Gage would bounce around in the red.
5. After 5-10 seconds, the gauge would drop back to normal, like a valve was released.
6. The heater would blow warm/hot air again as normal.

Ok, weird thing is the truck will only do this in the same spot on my drive home. It started last fall and was 2-3 times a week. I found the antifreeze low and added more. This solved the problem until 3 weeks ago, the problem started again. It hasn't ever happened on any other trips and I do a lot of city driving.

What I have done:

When the problem started this time (2 weeks ago), I did a flush of the radiator. Ran two bottles of Prestone Flush/water through the engine with the heater on, rinsed with water, then added a jug of Prestone 50/50 and then topped it off with Prestone Pure Antifreeze and put the remainder in the reservoir (total 2 gallons).

My guess is thermostat but I never seen a vehicle act like this before. Any ideas?

 

It sounds like your thermostat is sticking. I'd change it as soon as possible, before it goes completely and make some for major repairs. My sister-in-law had the same problem. When hers would stick, the boil over would be released by the pressure cap in small amounts. She changed the themostat and the coolant system stopped over heating and losing coolant. Good Luck

 

Also, when you replace the T-stat, use only a reputable brand. I used Stant on my last one, it works ok. I have had a lot of issues with several brands, in the future I will only use AC Delco, Stant or Motorcraft.

When you replace the T-stat, replace all the coolant again. Make sure you do not use tap water in the cooling system. The minerals, chlorine, etc. will ruin the cooling system. Use distilled or RO water, or if you don't have a convenient source of either of those, it is worth the extra money to buy premixed coolant.

 

had that problem replaced t-stat, still had the problem, replaced cap and problem gone.

 

The cap is cheap enough to replace anyways. The truck did it's weird thing tonight again.

1. Running fine down the road for 10 min at normal temprature.
2. Temp gauge drops down to cold, heater also goes cold for 1 minute.
3. Gage shoots up into the red and dances in the area for 30-45 seconds.
4. Antifreeze is boiling out of the reservoir and shoots all over the engine.
5. After #3, everything returns to normal like it never happened.

A 97K, the cap and thermostat are due to be replaced. Although the thermostat looks like a half day job on this engine.

 

I take it your going to sell your truck soon and get a new one!
.-- The point here is that if you don't change your thermostat , " it might be to late". The trucks engine is screamings for a new thermostat, before it blows a head gasket or worst -"blows the engine". I know the first time I changed the thermostat in my 98 ranger , it took some time- The next time I removed it was to properly flush the radiator. I felt like an expert (15 mins. taking it out and 10 mins. putting it in). You can do it at a comfortable pace. An "once" is all you need to be an expert on changing it. And don't forget to buy some radiator flush. a HOT engine cause major residue build up in the cooling system(Radiator, Heater Core,Hoses , and Cap. Read and follow the instructions on the Radiator Flush. Remember when running the Flush through the cooling system to have your truck heater on high- that way you flush the heater core really good. And do put a new thermostat in. On the older vehicles, a lot of people would run their vehicles without a thermostat. In todays vehicles the radiator is much smaller and the thermostat acts more like a fluid regulator - as a flow stop(to warm-up the engine) and as a regulator(Opens but regulates the flow to allow the coolant time in the radiator to cool off before it reenters the engine. And hopefully and coolant lost is the Radiator Cap. Good luck and post when finished.

 

The thermostat is getting replaced tomorrow, my next day off. I work weird hours and don't feel like taking my main ride out of service before I have to go to work to perform work I never have done on it before.

 

Rabidjade,
I blew an engine holding off making the same repair on a old Buick Century because I was unsure of my capabilities(thats many decades ago). Needless to say ,I've learned the old lesson " A stitch in time, saves nine." Although I loved the Mits. truck I replaced it with, I wasn't crazy about the monthly payments. So ,if you've never done it before, use a repair manual. Read what you'll be doing before you actually do the work. If you don't have one or can't get one, let me know and I'll connect you with the info (via the internet). It's very easy to change a thermostat once you know the steps needed to get the job done. Good Luck. Let us know the final out come!

 

I would suspect a blown head gasket already. If the radiator is spewing liquid out of the resiviour that's a sign of compression gases getting into the water jacket. Have it checked by a mechanic for combustion gases in the coolant as soon as possible.

 

I have no issues with replacing the thermostat, I've done it on other vehicles in the past.

I might do this when I get the chance.

 

What are the symptoms of a water pump going bad in these trucks?

 

I aggree on the blown head gasket idea. My daughters 4.0 explorer was doing the exact same thing. erratic temperature and spewing the overflow and such. another thing it did while running with the hood up you could see the upper radiator hose suck flat then expand again it was kinda like watching a living thing. after i spent alot money on water pump,new radiator,cap,t-stat. i finally gave in and took off the heads passenger side gasket was blown into the water port thats why no water in oil. of course compression check would shown me this also.

 

I had a ford engine that showed good compression when it was cold but when I got it running and warmed up it started spewing radiator fluid out like a chocolate volcano. I haven't confirmed that my ford has a blown head gasket but I'm sure it is. It's not the first time I've seen this condition.

 

Could just be an air buble in the system, since it did start after you flushed the rad.

 

Thermostat replaced, no issues yet and it runs slightly cooler now. Will do some more checks as I get time and money.