My engine won't heat up enough for the heater to warm up in the cab of the 1998 Ford Ranger 4 cyl. I have been running with cardboard in front of radiator, but not helping much. Replaced thermostat last night, but still only a trace of heat output. Upper radiator hose only gets "comfortably warm" to the hand, and does not build up pressure inside it. Why won't the engine warm up?

Sounds like someone put water instead of coolant in the radiator and now you have rust blocking the heater. Remove the 2 hoses at the Firewall that go the the heater .... now at a very low water pressure ... do not over pressure or you may damage the heater cor ... now try to back flush the heater core ... be careful because when it clears the blockage ... it fly's out like a shotgun blast ... refill with coolant and get a good waterpump anti-rust additive

Thanks, but why (and how) would heater core blockage keep the engine from warming up? The radiator tank and upper radiator hose SHOULD get warm enough that they would be uncomfortable to take hold of with even a 180 degree thermostat, let alone a 192. Why won't the engine warm up and get the coolant hot?

Geez ... Usually just the opposite is true ... The engine gets too hot. Read this thread and good luck ~~ http://www.doityourself.com/forum/passenger-cars-suv-service-repairs-no-trucks/410346-engine-wont-warm-up.html I mean ... you have close to 1200 F at the exhaust manifold and yet the engine heat doesn't seem to be transferring to the water. You are contradicting the rules of Thermodynamics ... and of course that's not possible

Did you come to a solution for this problem ? I'm going through the same thing 98 ranger 2.5. New water pump new t stat new antifreeze and just did a head gasket new temp sensors. engine won't warm up any suggestions ?

have you replaced your thermostat?

I am having the exact same issue in my 00 Ranger with a 2.5L. I am starting to think that as the engine block ages with coolant in it that rust is corroding the metal inside and allowing the coolant to get closer than normal to the exterior cylinder walls which is exracting heat too effeciently. Just my theory but I can't think of anything else. I have checked and rechecked everything. I have worked on cars my whole life and never seen anything quite like it. I drove mine earlier today and i drove for 45 minutes without my truck overheating even without a radiator cap and only 1/2 the coolant required. It seems to be an air cooled engine, Ford just never realized it!

did anyone figure this out i got same problem 96 ranger 3.0

Having a similar issue. Garage said new Thermostat was needed. Changed that but threw unfortunate incident, I forgot the O-ring on the the first install. Truck overheated and stopped blowing hot air. Re-set the Thermostat with the O-ring and it still overheated/blew cold until, all of a sudden, it whined and started clicking. Truck cooled down and the heater blew warm. For about 10 minutes. Diagnosed a bad actuator. Replaced that. Still no heat. Confirmed the blend door functions. Still no heat. Not sure what it could be. 2005 Ford Ranger 4.0 V6 4x4. Looking for help.

If you at any time used water or a radiator leak stop agent than the 2 hose's going through the firewall could be restricted ... remove both hoses and gently purge them out until you get a nice flow ... DO NOT USE A FULL PRESSURE HOSE OR YOU MAY DAMAGE THE HEATER CORE

New radiator cap

I figured it out, why the ford Ranger wont build enough heat, wont warm up enough to drop off high idle, and in my case, triggered the code for the Cat and I could not get it to pass inspection in my state. It is in fact a problem is with the thermostat. You have to put a spacer, I used an o-ring to putting it behind the state rubber itself. Its easy to test, remover the top radiator hose from the radiator and the heater hose that goes to the thermostat housing. After draining some fluid out, put your finger over the heater hose port and plow into the radiator hose. If the thermostat is closed and sealed, you wont be able to blow through it--- But there you will find the problem. Replace with a higher quality state, State or Napa. With the housing in hand and the stat installed holding it in place. Blow through it to see if it seals, then make sure the little ears stick out enough so that when installed, those ears will keep pressure on the state with a good seal.

Here is the O-ring

Here is how to test it, blow into the radiator hose to see if it leaks?

Here is how to test it, With the photo

Appreciated seeing the answer ! I posted my question 11/26/14, and since had back-flushed heater core and replaced thermostat, to no avail. Still very little heat, clear up unto 12/24/18, when I hit an icy curve and rolled the truck, but thanks for solving the mystery. It looks like others had the same problem.

If you live in a colder climate and are still having this problem remove the fan. The ranger dissipates way to much heat with the fan and large grill. Its super easy to do and your car will heat right up, also you can block some or all of the grill/radiator and get the same effect. I live in north Idaho and drove without a radiator for about a week while waiting for my other to come in and the temp gauge never even went more then half, granted my drive is only 15 min and its all highway

I have the 99 ranger. I replaced the radiator and w/ 50/50 anifreeze. New thermostat and water pump. None of these worked SO, I put in another thermostat and it still will not warm up. I thought about sliding cardboard in front but there are 2 radiators right ? There is one in front of the fan of course and then another in front of that. I am wondering in this is a transmission cooler ? ( i need to research further) I do not want to over heat my tranny. I love the idea of taking the fan out. I have done it 3 or 4 times, I getting good at it and it is relatively easy as long all of the bolts are replaced in a balanced fashion. Hope this helps. Thoughts ?

The smaller/thinner unit that sits in front l of the radiator is an air conditioning condenser.. however the automatics, if I'm not mistaken do have a trans cooler mounted to the side of the radiator..

2 radiators

0.o

I had a 2000 ford ranger with 4.0l engine. Engine.got hot on it, changed the thermostat and fixed that issue. Would start it in the morning and within 15-20 mins the engine was warm and ready to go. I have a 2006 ford ranger with 3.0l engine now! Will start it in the morning and wont warm up!!! Seems to be a lot of people having the same issue with rangers. So I've done some research, parts changing and testing. 1: I've changed the temp sensor as gadge wasnt working. Checked fan clutch and it's good. Had dreaded timing cover leak so repaired that ( changed fluids). Changed thermostat at that time. Bleed air out of system when filled 2: +15 outside! from cold ran unit. Used temp gun to shoot above and below thermostat, top and bottom rad hoses and rad. Found unit would warm up to operating temp and thermostat was opening at proper temp. 3: found at cooler amb temp truck engine would take longer to warm up!!! -10 outside. From cold started unit and let run for 15 mins. Truck temp gadge just sat on the C!! Used temp gun and found coolant in engine was not getting warm enough to even open thermostat to let coolant circulate. But why? More testing! 4: -25 outside. Started unit and let run (unsupervised as its v cold out) For 45 mins. When I checked the temp gadge had not even moved ( still on C). Obviously coolant in engine was cold and thermostat never would have opened!! But why again!!! 5: thoughts: :Coolant is new, full and bleed! :Thermostat is working properly (used temp gun) :Temp sensor is working :Water pump it working ( as two to three cycles of thermostat opening with rad cap off bleed air out of system) : System is keeping proper engine temp, while driving around at operating temperature. 6: My last test and conclusion: +6 out today with 15km wind. Started unit, temp gadge very slowly moved up just passed C. So.thought I'd take a little time to mess with it again!!! Checked oil and noticed that the fan on these trucks blow a enormous amount of air around in the engine compartment. So my last test!!!!! I cut a piece of cardboard a little wider than the fan and 8" longer, cut a 2" slice out of it from one end then shoved it between the fan and engine pulleys. Blocking fan air flow from hitting engine. Used zip ties to hold it from rubbing on the fan. Then started the unit. Watch temp gadge and within 7min the engine temp gadge was at 1/4!!!! Raised the Rpm to 2500 to speed up temp rise. When temp gadge was at 1/2 I let Rpm drop to idle and watched gadge. Neddle dropped just below 1/2 (operating temp) and just sat there for 15min. Shut of unit, removed cardboard and.restarted truck. Watched temp gadge and it started to drop slowly. Temp gadge dropped from just below 1/2 (operating temp) to 1/4 within 15min. Wow!!! 7: conclusion: To me the coolant system is operating as it should water pump pumping, thermostat opening at right temperature, temp sensor reading right temps and fan cooling coolant in radiator. Issue: 1)Engine at idle doesn't produce enough heat to over come air flow fan produces! 2)Fan air flow over comes heat produced by engine! 3) ford produced the first water and air cooled engine that's to efficient!!! 4) repair: :Install temp sensor controlled electric fan, the fan will only kick in when engine is at a temperature that it is needed for cooling. 5) Won't blow cool ambient air over engine on startup speeding up warmup time. Just my thought and findings! First make sure the system is doing what it is supposed to then try it.for yourself before spending any cash!!!

Zee Water pump! I will tell you what... the water pump is a generalized pain in the lilly to take out... and put in... but... if you are having issues with heating... chances are... the water pump is not correctly pumping coolant to the heater core... as the heater core actually needs flowing coolant through the system. I would not be very confident if I 'guessed' that it is the thermostat... just because that did not solve my problem. Unfortunately, there is no real way to test if your water pump is working properly... and most of the time... you have to dissect the fan housing, fan, fan shroud, etc... to even see the weep hole. What I would do if I was put in the place of replacing the thermostat, water pump, etc... is go to autozone, buy a new water pump, thermostat, and gaskets... (and for God's sake, don't listen to any dumb butts telling you that you need to use gasket maker), and spend a weekend or a day taking apart your fan assembly, snapping pictures of all parts before taking them apart. It is not that hard to do... although it seems intimidating.

I solve my problem, after replacing 3 Thermostatic valve and new coolant temperature sensors and refurbished the head cylinders, I have cleaned the hot radiator doing heater core flush, hot water passes through there, it was clogged up. After that I have always hot air in the cab, the gauge pointer in the middle and stuck in 88 °C :). I live in Brazil and it so difficult to get good mechanics. This forum helped me a lot to fix my old Ranger 98 2.5 l xl.

I put new radiator and thermostate'+heat selective switch/still no heat.