Question about 1988 Jeep Wrangler

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Not enough heat coming out of the heater of 1988 2.5L Jeep Wrangl

I already changed the coolant and put 195degree thermostat. The heater outlet hose from the engine to the heater core gets hot - after 5 minutes
running. The heater produces not too hot out of the dash board or out to the floor. Found also, the larger hose from the heater core toward back or return heater hose to the engine was more colder. Does it mean I have a problem with heater control valve or I have a partial clogged heater core ? And if I have a partial clogged heater core,.. is it possible I can reverse the flow of coolant to release the clog inside the heater core? Thank you very much for what ever opinion or helping information to me. Oscar

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It sounds to me your heater core is plugged. you can try to back flush it,being this vehicle is twenty yaers old,i would say to replace it

Posted on Dec 15, 2008


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1995 jeep wrangler yj low heat after changing heater core -would reversed heater hoses cause this also- thank u -so much

Not really, the heater core would still get hot enough to produce enough heat and usually the hoses will fall to the right spot making it hard to put them on the wrong ends. Why was the heater core changed? was it clogged? Did you flush the engine out to prevent the new core from clogging up? Have you looked into it being a stuck open thermostat?

Dec 23, 2017 | Jeep Cars & Trucks

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Heat not working

Sounds like the air blend door is not opening to let heat in.

Engine coolant is provided to the heater system by two 16 mm (5/8 inch inside diameter) heater hoses. With the engine idling at normal running temperature, set the heater-A/C controls as follows. Temperature control to full Heat, Mode control to Floor, Blower control to the highest speed setting. Using a test thermometer, check the air temperature coming from the center floor outlets and compare this reading to the Temperature Reference table.

If the floor outlet air temperature is insufficient, check that the cooling system is operating to specifications. Both heater hoses should be HOT to the touch (the coolant return hose should be slightly cooler than the supply hose). If the coolant return hose is much cooler than the supply hose, locate and repair the engine coolant flow obstruction in heater system.

If coolant flow is verified and the heater floor outlet temperature is insufficient, a mechanical problem may exist.

  • Obstructed cowl air intake.
  • Obstructed heater system outlets.
  • Blend-air door not functioning properly.
If heater floor outlet temperature cannot be adjusted with the heater-A/C control temperature control lever, one of the following could require service:

Jan 21, 2014 | Cars & Trucks

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My 1984 grand marquis does not get heat

did everything said to do put new heater core in and a new thermostat instill no heat

Oct 08, 2012 | 1984 Mercury Grand Marquis

1 Answer


  1. Removing the Heater Core
    • Lift the hood and prop it open. Makes sure the engine is cold. Disconnect the negative battery cable with a socket wrench or box wrench. Avoid using open-end wrenches on the battery terminals, as they tend to strip the bolt heads.
    • 2Place a drain pan under the radiator. Open the radiator cap. Open the radiator drain on the bottom of the radiator and the two coolant drains near the oil pan. You can reuse the coolant unless it appears cloudy and contaminated. Close all three drain openings once all the coolant has drained from the system.
    • 3
    • Disconnect the inlet and outlet hoses of the heater core inside the engine compartment using a socket wrench. Be prepared to catch or wipe up any coolant that drips from these hoses. Drain the coolant from inside the heater core.
    • 4Unscrew and remove the lower instrument panel sound insulator from below the dashboard on the passenger side. Use a socket or screwdriver to loosen and remove the screws on the heater flooricon1.png outlet. Remove the clips and take out the duct.
    • 5Loosen and remove the screws holding the heater core cover in place. Remove the cover.
    • 6Remove the retaining bolts holding the heater core in place. Remove the heater core.
    Installing the Heater Core
    • 7Position the replacement heater core and secure the retaining bolts. Put the cover back on the heater core and reattach the screws and clips.
    • 8Reinstall the floor outlet duct with its screws and clips, followed by the lower instrument panel sound insulator.
    • 9Reconnect the inlet and outlet hoses to the heater core In the engine compartment.
    Refilling the Cooling System
    • 10Tighten all of the drains. Fill the radiator up to the base of the radiator neck with antifreeze, reusing the old coolant if it's cleanicon1.png. Fill the coolant overflow tank up to the "FILL" mark.
    • 11Reconnect the negative cable on the battery and start the engine, making sure you leave the radiator cap off. With the engine idling, look into the radiator and notice that the coolant level has dropped. Add coolant until the level is back up to the base of the radiator neck. Add coolant to the "FILL" mark on the overflow tank. Put the radiator cap on, making sure the arrow on it points to the overflow tank.
    • 12Squeeze the large return hose leading to the top of the radiator with the engine still running. The hose should begin to feel hot, indicating that the thermostat has opened and is functioning properly.
    • 13Check for leaks in the cooling system.

Oct 02, 2012 | 2000 Buick Century

3 Answers

1997 Cirrus is still overheating... The heater does not blow out hot air...would the heater core cause the vehicle to overheat? if not, what other problems am I looking for, I was loosing anti freeze...

it appears that you have a large air pocket/low on coolant. The engine is getting hot due to the lack of coolant but there is no heat because nothing is flowing through the core.

Feb 20, 2011 | Chrysler Cirrus Cars & Trucks

2 Answers

I dont have any heat and i need to know how to replace the hearter core, however the windows aren't fogging up so maybe its the thermostat

the only way you should have to replace a heater core is if it leaks or gets plugged up. When motor is hot feel the two hoses that go to the heater core. one should be fairly hot and the other should be the same but if one is just warm then follow hose and locate a flow valve and check for operation. OPening and closing with control hot /cold knob. Check coolant level in radiator while cold as well as fill reservoir to full when cold. Also remove radiator cap when cold and warm truck and check for flow of coolant. if lower radiator hose is hot hot hot and upper hose is cool then thermostat may not be opening properly, or thermostat is stuck open not building heat. You didnt mention if truck was overheating?? If its not i'd check for the flow valve operation, if it is i'd make sure coolant levels are full and waterpump is working.

Feb 03, 2011 | 1994 Chevrolet Astro

3 Answers

My 2004 Jeep Liberty has started losing heat although the temperature gauge has remained normal. Would this most likely be because of the thermostat or something beyond that?

You may be right, but, here are a few things that come to mind.
1. If your coolant level is low, it could cause this, I would check that first, if you haven't already.
2. If you let the vehicle idle for 6 to 8 minutes and then turn the heat temperature and fan on high, you should hear a click when the thermostat opens to circulate the coolant through the heater core. If you do not hear a click, it could be your thermostat.
3. Turn the engine off and, very carefully reach back behing the engine at the fire wall. You should see 2 small hoses, about 1 inch in diameter, feel both of them and see if they're both hot. If they are, your thermostat should be fine, if only 1 of them is hot than you do have a bad thermostat, or your cooling system has some blockage and the system should be flushed.

I hope this helps.

Jan 30, 2011 | 2004 Jeep Liberty

1 Answer

Have no heat in my 1994 Cevrolette Caprice Classic LS. Had radiator leak, used Bardahl Stop Leak. Engine not getting fully warm. Changed thermostat to fix that. Also noticed AC compressor not kicking in on...

A few things you may try before the expense of a heater core, and the labor putting another one in.
First, I just want to mention I have used Bardahl stop leak, and it worked very well for me, It's a good product. Also, you're right, the a/c commpressor is a seperate issue.

Now, you mentioned you changed the thermostat, the following test is just to make sure it's working properly, and to check the coolant circulation.

1. With the heater temp and blower off, start your vehicle and let it run 6 to 8 minutes to allow it to reach normal operating temperature. then;
turn your heat temperature and blower wide open, when you do, listen very closely in the engine compartment, you should hear a small click from the thermostat opening up to allow ciculation of the coolant.

2. Turn the engine off. Carefully reach behind the engine, at the fire wall where your inlet and outlet hose, ( both about 1 inch in diameter ),hook up to your heater core. feel each one of the hoses. If both are hot, then your coolant is circualting through the core. If only one of them are hot, then the coolant is being blocked from circulating through the core, and if that is the case I would probably try flushing the whole cooling system first.

I hope this helps.

Jan 29, 2011 | Chevrolet Caprice Classic Cars & Trucks

1 Answer

Heater fan blows good but only blows cold air. Is it the heater core? The thermostat? How hard are they to replace if i do it myself?

Check the heater core by checking the hotness or coldness of the 2 tubes at the firewall that lead to the heater core.

If both tubes are hot, the heater core is fine. If both tubes are cold, then the heater core is plugged up and will have to be flushed out or replaced.

The thermostat, if stuck open, will delay the heating up of the heater core. It's not hard to replace the thermostat.

Thermostat Removal & Installation 4.2L Engine To Remove:
  1. Before servicing the vehicle refer to the precautions at the beginning of this section.
  2. Remove or disconnect the following:
    • Some of the coolant
    • The upper radiator hose f150_42_thermostat.gif

    • The bolts (A).
    • The water outlet connection (B)
    • The water thermostat and paper gasket assembly (C)
To Install:
NOTE: The water thermostat is indexed and must be installed correctly.
  1. Install or connect the following:
    • The water thermostat
    • The thermostat
    • The water outlet adapter
    • The bolts
      1. Torque to: 80 inch-lbs (9 Nm)
    • The upper radiator hose
    • The coolant
4.6L/5.4L Engines To Remove:
  1. Before servicing the vehicle refer to the precautions at the beginning of this section.
  2. Remove or disconnect the following:
    • Some of the coolant
    • The upper radiator hose f150_46-54_thermostat.gif

    • The bolts (A)
    • The water outlet connection (B)
    • The water thermostat
    • The O-ring (discard)
To Install:
  1. Install or connect the following:
    • A new O-ring to position the water thermostat in the upper intake manifold
    • The water outlet connection onto the upper intake manifold
    • The bolts
      1. Torque to: 18 ft-lbs (25 Nm)
    • The upper radiator hose
    • The coolant
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Jan 28, 2011 | 1997 Ford F150 Regular Cab

1 Answer

The heater gives a little heat but, not hot air. F-150 4x4 4.6 L engine After warm-up the heater puts out a little warmth but, that is it. It will not get hot like normal during daily operation. I have...

Flushing the system and adding new antifreeze would have been my first suggestion, so, thanks for mentioning that.

We should check a couple of other things.

1. Start the engine, let it run for 6 to 8 minutes, ( with the heater off ), to allow the engine to reach normal operating temperature. Then, turn your heat and fan wide open, then listen to the engine to see if you hear a click, you should be able to hear the thermostat open up to circulate the coolant. If you do not hear a click, you may have a stuck, or partially stuck thermostat.

If the thermostat doesn't open, the hot water/coolant will not flow in to the heater core.

2. In the back of the engine, on the fire wall, locate the inlet and outlet hoses to the heater core. They are both usually about 1 inch in diameter. Carefully feel each hose. Both should be hot. If only one is hot it's because you have blockage somewhere preventing the circulation of coolant to the heater core.

The most common area for blockage is in the heater core itself. Sometimes flushing doesn't clear it out.

I hope this will help you resolve the problem.

Jan 28, 2011 | 1998 Ford F150 Regular Cab

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