Coolant System Problem
 

Hello.
I have a 2000 Ford Ranger XLT with a 2.5L 4 cyl motor. I've just recently replaced the water pump. After replacing, I added new antifreeze / water mixture and proceeded to let the truck warm up full coolant with the cap off. Truck never reached running temperature, no heat would come out. I got in the truck and revved the motor to maybe 1200 rpms and the temp gauge began to climb and heat came blowing out of the vents. I figured maybe the thermostat was bad and ordered a new one from Ford. I originally didn't replace thermostat because Ford had to order it and it didn't meet my deadline to replace the pump.

Put the new thermostat in today. Drained the coolant, removed the Tstat housing, cleaned it, installed new gasket, installed new thermostat and put back together. Again, I put new antifreeze / water mixture in it, started truck with radiator cap off to allow Tstat to open, let any air out, etc. Thermostat opened, I topped off coolant and waited for it to reach running temperature. Again, it never reached temperature. If I gave it gas, the temp gauge would go up, would blow hot air. Once I let off, temp gauge went down, no hot air.

I even drove the truck down the road to see what it would do. Temp gauge NEVER even reached the regular operating temperature, not even while driving. Its never been overheated. I have 186,000 miles and this is the first real problem I've had *knock on wood*

Any ideas on what is going on? I bought a Prestone backflush kit I'm going to try to hook up and backflush in case there's a blockage somewhere and to just flush the entire system out. I'm really stuck and need my truck back as its been sitting for a week. Any help / advice greatly appreciated!

Re: Coolant System Problem
 

Oh my favorite topic again. Please see the link in my signature for my NO HEAT TROUBLESHOOTING GUIDE. Run through it and see where it leads.

Re: Coolant System Problem
 

Thanks for the reply.

I actually found that post earlier today and was looking over the charts. After looking it over and not finding anything relating, I decided to post here. Your charts don't seem to have the problem I'm referring to on them. I just replaced the water pump and the thermostat. No blend door problems and heater core is not clogged I would say. I DO have heat when I give the truck even the slightest bit of throttle. If I hold the RPMs at 1200, the heat in the truck is just as it was before I replaced the water pump and thermostat. When I let off the gas and it idles back down, the temperature gauge drops and the heat starts getting colder. I hit the gas and boom instant hot air again.

Re: Coolant System Problem
 

If you hadn't just replaced the water pump, I'd say it is definitely your water pump. Try setting the HVAC controller for OFF. Verify the hot water valve closes. And see what the temperature gauge does.

Re: Coolant System Problem
 

Rebuilt water pumps can be defective, and getting heat while reving the engine and none at idle, sounds like the pump has too much clearance in the impeller. Also they may have given you the wrong pump, regular rotation and reversed rotation, is your fan turning in the direction thats indicated on the fan shield.

Re: Coolant System Problem
 

Well, just an update.

Started truck up today with HVAC unit off. Motor heated up to almost normal operating temperature. It didn't quite get 100% to where it used to. I let it sit like that for about 5 mins, decided to see what the heat was like. Turned heater on it and it was warm. Wasn't hot. I then hit the throttle and the temp gauge began to fall almost down to the cold, the air started getting hot again and then the temp gauge rose up to almost normal. Held the throttle down for like 2 mins til it got there.

After getting it to normal, I let off the gas pedal, let it idle a minute, then revved it up to around 1800 rpms again. This time the temp gauge fell, yet again, the hot air got much hotter and felt blistering hot.

Everything seems to be working fine. Hot water valve, thermostat, heater core. Everything seems normal until I throttle it and the temp gauge drops. I'm wondering if its not the new water pump. I did get a new water pump - not a remanufactured one just because it was only 25 more than the remanned. Its an aftermarket one as Ford wants around $200 for theirs. I did put a Ford factory thermostat in it and I changed the serpentine belt as well. I'm almost tempted to snatch the water pump off, take it back, and try another one.

Fan is turning clockwise - same way the belt is turning and looks to be running perfectly normal. It speeds up as the motor revs up so no slipping.

So one more question. If my temp gauge never gets above operating temp, is this accurate.and safe to drive on?

Re: Coolant System Problem
 

Yes it is safe to drive.

This is screaming water pump problem really loud. On the 4cyl engines, the temp sensor is on the end of the return from the hot water valve (stupid place for it). So, any interruption in coolant flow through those hoses will cause a drop in temperature at the sensor. Flow problems in that system also manifest themselves as a lack of heat. And usually all of that is caused by a bad water pump that just can't heave the water up and through those lines.

Also, on a cold engine, check the coolant level in the radiator again. If it is low, this will also happen.

Re: Coolant System Problem
 

Thanks again for the reply.
I got some more air bubbles out of the system today, but it didn't help anything. I parked it again as I wasn't sure if it was fine to drive on or not. I'm going to backflush the system this weekend for sure and if that doesn't change anything, I will be taking the water pump back and making them defect it out and get a new one and slap on there. Only reason I think it is the water pump for sure too is that nothing like this happened until I replaced it, so like the other poster said, it could be bad from the factory. I turned it by hand before putting it on to ensure it was functional, but that doesn't mean anything I guess until its put to the test of pulling water. Thank you for your help :)

Re: Coolant System Problem
 

If the impeller is the wrong one, then it is perfectly plausible that this would happen. Spinning it faster (as you increase RPM) will just make it cavitate and actually reduce the amount of water it pumps.

Re: Coolant System Problem
 

Well, sorry it took so long for a reply, but a Tenn winter is all but predictable. All my off days have been rainy and cold so just now got back to working on the ranger. Today, I flushed the coolant system. No sludge came out and every time I've changed antifreeze, has always been green. Today, however, I noticed that the radiator isn't evenly hot. The driver side near the top radiator hose going to motor is hot, but the left side come from motor and up to the top radiator cap is not getting hot. Radiator cap itself is no where near hot. Issues are still persisting about not getting warm until you tap the gas pedal. Seems like I'm never going to get this ranger up and running again.

Getting my hands on a pressure tester to pressurize the system and see if its leaking any through the head gasket. Gotta try to see if the radiator is blocked as well. Anything else I should test while I'm at it?

Re: Coolant System Problem
 

When you refilled the cooling system, did you let it cycle several times and add more water accordingly? I always let it cycle a few times with the rad cap off and as the thermostat opens you will see the water bubble up a little at first then go down as the water from the rad enters the engine, when this happens you add antifreeze/water accordingly. Note - this is not something you want to do carelessly! Don't stand right over the rad and don't do it for more than a few cycles. I do this so if there are any air pockets it will replace them with water, and you want water and not air in the cooling system. Also, have you checked your heater core? Any dampness on the passenger side floorboard or antifreeze odor/odd defrosting issues?

Re: Coolant System Problem
 

Chef,
I did let the water cycle through and refill as needed. Before doing all of this work, I've never had any problem with losing coolant. Heater core is fine - I get great heat as long as the truck isn't idling right now. Before this, heat was great no matter what. No fog on window when I defrost, no smoke out of tailpipe, no sweet smell anywhere around the truck. Floor board is not wet, carpet is still dry and not stained.

I'm getting my hands on a pressure tester tomorrow just to make sure its doesn't have head gasket issues, which I am pretty sure it doesn't, but want to rule out everything I can. Also, I am going to replace top and bottom radiator hoses tomorrow just as a precaution, probably going to replace coolant temp sensors as well.

Is there a way to check for a blockage in the actual radiator?

Thanks for the reply Chef!

Re: Coolant System Problem
 

A blockage in the radiator big enough to cause the problems you're having is very unlikely, unless the rad is really old and seriously gunked up. If it were that fouled up, you'd likely be having much more serious problems.

Well I finally figured the issue out. Nothing like I would have guessed. I got under truck the other day and noticed the lower radiator hose had a kink in it when the motor was running. Appeared fine when motor was off. Picked up new hose, installed, bled air out of radiator, and my baby is running fine again. guess it was holding a ton of air at that bend.

Never would have guessed that was the issue. Thanks for all the input and suggestions!