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?


Asked by Nov 26, 2014 at 01:47 PM about the 1998 Ford Ranger XLT Extended Cab SB

Question type: Maintenance & Repair

New thermostat, new antifreeze, cardboard still in front of radiator, and temperature indicator still doesn't come up!

20 Answers


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

10 people found this helpful.

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?

9 people found this helpful.

Geez ... Usually just the opposite is true ... The engine gets too hot. Read this thread and good luck ~~ 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

6 people found this helpful.

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 ?

10 people found this helpful.

have you replaced your thermostat?

1 people found this helpful.

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!

12 people found this helpful.

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

1 people found this helpful.

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.

4 people found this helpful.

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

3 people found this helpful.

New radiator cap

3 people found this helpful.

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.

11 people found this helpful.

Here is the O-ring

3 people found this helpful.

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

3 people found this helpful.

Here is how to test it, With the photo

4 people found this helpful.

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.

2 people found this helpful.

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

3 people found this helpful.

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


Your Answer:


Looking for a Used Ranger in your area?

CarGurus has 41,372 nationwide Ranger listings starting at $900.


Ford Ranger Experts

  • #1
    G A Arne
  • #2
  • #3
    Bob Beaman
View All

Find great deals from top-rated dealersTM


Related Models For Sale

Used Ford F-150
4,720 Great Deals out of 251,184 listings starting at $990
Used Toyota Tacoma
955 Great Deals out of 55,091 listings starting at $800
Used Nissan Frontier
587 Great Deals out of 26,582 listings starting at $1,987
Used Chevrolet Silverado 1500
4,112 Great Deals out of 157,443 listings starting at $1,490
Used GMC Sierra 1500
1,765 Great Deals out of 66,708 listings starting at $1,787
Used Chevrolet S-10
3 Great Deals out of 551 listings starting at $1,995
Used Jeep Wrangler
567 Great Deals out of 17,910 listings starting at $2,990
Used Dodge Ram 1500
262 Great Deals out of 6,641 listings starting at $1,000
Used Ford F-250 Super Duty
1,003 Great Deals out of 47,707 listings starting at $2,400
Used Ford Mustang
899 Great Deals out of 39,801 listings starting at $750
Used Dodge Dakota
56 Great Deals out of 1,935 listings starting at $1,900

Used Cars for Sale

2019 Ford Ranger For Sale
77 Great Deals out of 35,126 listings starting at $18,280
2011 Ford Ranger For Sale
22 Great Deals out of 690 listings starting at $3,800
2010 Ford Ranger For Sale
12 Great Deals out of 324 listings starting at $3,495
2009 Ford Ranger For Sale
5 Great Deals out of 198 listings starting at $3,200
2008 Ford Ranger For Sale
18 Great Deals out of 309 listings starting at $2,590

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use. Content will be removed if CarGurus becomes aware that it violates our policies.