Ok so a few weeks ago, I changed out my timing belt. I bought a new water pump, because I figured follow the golden rule and change it out with the belt. The guys that I changed my belt with, told me, "Don't worry about it, it's not tied to the timing belt, replace it when it goes out" So I drank the kool-aid and took it back. About a week later, I noticed that when I am at a stop and idling, I lose all my heat, and the temperature gauge drop down below the C. Then when I get going again, or I rev up my engine a bit, and hold it at a higher rpm, the heat would return. Same with when I would be in gear and driving down the road.

Now I'm not to smart when it comes to vehicles. (I'm sure yous knew that when I drank the kool-aid lol) But I kinda of thought of the problem along the same lines as I had before on the multiple alternators I've been through. When they start to go out, and your battery light comes on, you can rev up the engine and maintain a higher rpm and make the light go away, and the alternator gives out it's last bit of juice before it's over.

So that's what I've been doing until I can get the water pump changed. If I'm stopped, I manually maintain a high idle speed I guess you can say.

So right before I started writing this, I went and picked up a new water pump and thermostat (figure I might as well since I'm in there) Come home, pull it in the driveway, and nothing lol The truck held its temperature like there was nothing wrong. Kind of like a bad kid who got busted and was trying to act innocent lol

Anyways, what do yous think is going on?
97 Ranger 2.3 ltr no AC

Edit:
Shooting the breeze with a buddy of mine, made me realize I should shorten the story a bit.
I lose all heat when Idling. Temp gauge goes to C, and heater blows cold air. Not once has it even threatened to overheat. It just acted normal after buying a new water pump.

 

did you check the coolant level in the rad?

 

Ya, I flushed and replaced the antifreeze when I replaced the timing belt. I was amazed when I was able to fit the entire gallon jug or whatever it was into the truck. Could it take more than one jug?? lol Id feel even dumber if that was the case lol

 

I guess I should ask, how do you check the levels? I figured fill it up, drive it for a little while. Fill it up again, and keep repeating the process until I couldn't add anymore.

 

yea it usually takes about 2 gallons or so...i hope you reduced it 50/50

 

lol Ya, I bought the 50/50 Thanks, I'll start there. I appreciate it.

 

yea...you also could have an air pocket in the system...start the truck up with the rad cap off, top off the rad, and turn the heater on full blast and let it idle for a while, rev it up to about 2k every few minutes

 

Sounds like the water pump impellers are gone. Same symptoms with my 2.5 (same engine just stroked).

The way the system is setup is there is a hole in thermostat housing behind the thermostat. This hole lets coolant flow over the sensors and through the heater core (or if the heater control valve has vacuum (OFF, or MAX AC) it just bypasses the heater core and meets up with the lower radiator hose.

The heater core is one of the most restrictive parts of your cooling system. With a weak water pump, the higher rpms of driving can force just enough coolant through the heater core "circuit" to cause the temp and heat to be normal. But at idle the pump isn't flowing enough (due to corroded impellers) to push coolant through the heater core, causing the coolant to become stagnant, dropping temperature.

 

This exactly is what I was thinking. Just in car lingo. Thankfully though, I was able to add another gallon of juice, and.... no more problem. I am keeping the water pump this time though, as if it gets warm enough on one of my days off, I'll change it anyways, because I should have just done it to begin with.

Thanks for the help guys. I appreciate it.