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Problem With Heat in 98 Taurus

Well Sanjuro has some trouble shooting help so I figured I'd give mine a shot.

One of our cars is a 98 Ford Taurus. The heat doesn't work very well. Never had the heater core melt down with the collant leaking onto the cabin floor.

The engine doesn't get overheated. But warm air will not blow through the cabin vents no matter which setting is used. AC works just fine.

With the engine running, warm, and heat selected to hot on the cabin controls, the heater core hoses are warm, but not hot. You can squeeze them and they feel a little spongy.

Thermostat was replaced and put in the proper direction. No change.

Things I can figure that might be worng:

-The heater core is plugged or otherwise broke. $500 fix if it has to be replaced.
-There is a heat/cooling blend door on the 90's era Tauruses that is known to get fouled up.
-There is some valve between the water pump and heater core that is plugged up. But I get see where there would be one.
-Perhaps the water pump is not working so good? (But then why am I not overheating?)

When the system was flushed a few months ago, I got decent heat, but not fantastic. It eventually went away. That's why I'm thinking there's some valve the is not opening. But I'm not sure.


I think the heater core is clogged. This happened to a Jeep I had.. same issue. All having the system flushed did was...well nothing. I eventually flushed it myself (properly by waiting till the thermo kicked in) and it did fix it for a while, but went back to not heating very well.
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That's what I'm leaning toward. I read about a shade-tree-mechanic method of using Draino.... disconnecting hoses from engine and pouring into core, waiting a bit, and then flushing with a garden hose.

But damn it cold to be doing that.

TELL me about it! This stuff only seems to happen when its cold! I remember vividly changing out a radiator and freezing my ass off in 30 degree weather one night a couple of years ago.
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Some vehicles have a vacumn heater control solenoid. It's generally connected in one of the heater hoses along the path and occasionally go bad. The purpose of this little device is to dissallow the heater core to get hot when the heat isn't on. Remember the old days when even on "vent" the air would blow warm?

Autozone Part # 5867

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I'd start there. Not to say heater cores don't get blocked, but that would be last on my list.
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That's worth checking into.

Also, remember to check for vacuum going to all the heater controls and valves. It could be as simple as a vacuum hose is rotted, pinched or fallen off somewhere. It might be you could get an extra piece of vacuum hose and jury rig the valves and controls long enough to test them.

I have on some occasions used flush and fill kits to force water and chemicals backwards through the heater core with varying degrees of success. If both heater hoses happen to be the same size you might be able to swap the hoses to back flush the core but then you'll need to flush the entire cooling system. When I was a lot younger we used some really strong chemicals to flush cooling systems but as with so many things those chemicals turned out to be really dangerous and have been removed from the market. They were mostly acids and if left in the car too long they would dissolve the radiator and heater core.

You know, come to think of it in over 30 years of driving I've never had to replace a heater core when the weather was nice and personally I'd rather pull and engine than replace most heater cores.
Billy The Blogging Poet

Thanks for the input.

Changing that heater core would be a bear. You have to disasseble the dash to get to it. I've read where some guys have managed to get it out and new one without taking the dash apart but from what I can tell, that's a job for someone extremely thin and flexible with small hands.

I don't know too many female russian gymnasts with mechanical aptitude.

That vehicle can have two different systems installed, one with the knobs and one with electronic control. In both cases, the blend door (Hot/Cold) is controlled by an electronic blend door actuator. Air distribution doors (Defrost/Floor/Face) are controlled by engine vacuum. Here are the Procedures for removal of the blend door.
1. Disconnect battery ground cable.
2. Disengage console panel from instrument panel reinforcement and remove from instrument panel.
3. Disengage console panel from RH side of center console finish panel if equipped.
4. Working from under the passenger side of the instrument panel, remove A/C electronic blend door actuator electrical connector from A/C electronic blend door actuator.
5. Remove four screws retaining A/C electronic blend door actuator to the A/C evaporator housing and remove A/C electronic blend door actuator from A/C air temperature control door.

Here are the Procedures for removal of the heater core.
1. Remove instrument panel NOTE: If a heater core leak is suspected, the heater core must be leak tested before it is removed from the vehicle.
2. Drain coolant from radiator into a clean container.
3. Disconnect heater water hoses from heater core. Plug heater core tubes or blow any coolant from heater core with low pressure air.
4. Remove four retaining screws and A/C electronic blend door actuator from A/C evaporator housing.
5. Remove metal cover, disengage spring from heater core cover and remove spring from lever.
6. Gently depress locking ramp and remove lever from secondary A/C air temperature control door end. NOTE: Do not attempt to bend any part of the lever. It is brittle and will break.
7. Rotate primary A/C air temperature control door shaft down, then swing metal link and remove from pin.
8. Remove three heater core cover retaining screws and remove heater core cover and heater core cover seal from A/C evaporator housing.
9. Remove heater core and seal from A/C evaporator housing by pushing on heater core tubes.

A scan tool will tell you if the blend door has set a Diagnostic Trouble Code if you have the electronic system. If you have the manual system, visual confirmation of the bend door actuator movement is the only way to verify operation.
Yes, a lot of guys just loosen things enough to get it out of the way so the best thing to do is just look at it as you go and decide if something really needs to come off or not.
Make sure the coolant is topped off, and the heater core hoses are HOT. 120 degrees at least, after the thermostat has opened (top rad hose hot). Don’t use draino! If it wasn’t leaking before, it may after. Just use the garden hose in the outlet side and run it until you see clear water running out of the inlet. After that, hook the hoses back up. That is a self bleeding system so you can just top off the coolant and run the engine until the thermostat opens with the heater in full heat position. Keep adding coolant as it warms up as trapped air is purged. Man, that was long.
Jack Aubrey

I will tell you this... Worst comes to worst, Pepboys sells DC electric heaters that plug into your cig lighter. They suck monkey nuts, but it's a "little"bit of heat, when you're freezing you butt off. I had to buy one with the Cavalier, because the heater core leaked...

But... I'd check that valve... My dad's ranger (which I'm driving right now) has a problem with that.... and "it" basically has the taurus 3.0... so uh... yeah.... check it.
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These nothing between the water pump and heat core inlet except hose. Nothing between the heater core outlet and the engine return/inlet except hose.

I did some yoga, removed a cowling on the cabin interior by the front passengers feet, and turned the cabin air temp valve from hot to cold. I verified the actuator that moves the blend door was operating. Now I didn't actually see the blend door opening and closing, but I gotta assume it was.

Damn. I was hoping it was some sort of vacuum valve or something.

so I think I'm down to the heat core or water pump. Mostly likely heater core.

The heater core hoses look pretty easy to access. I might try disconnecting them from the water pump an engine return/inlet and seeing if I can force water through to flush it out.

The plot thickens.

Started the car up, let it get up to operating temperature. The top radiator hose was hot, but spongy. I could squeeze it to almost pinch the walls together and felt no coolant flow.

So that's water pump or thermostat. I'm going to try changing out the thermostat. Maybe I'll just leave it out, put the hose/housing back on, and see if the hose gets hard.

Do they make viagra for cars?

The system pressurizes as the coolant heats up. If the tank cap pressure releases too soon or is stuck open the system will never pressurize. If the thermostat is stuck open, or opens too soon the system again will not pressurize and the hoses would never stiffen and the engine will never reach operating temperature. Coolant flow is caused by the water pump. If the water pump wasn't flowing like it should an overheated engine would probably present itself very quickly. Sometimes, if it hasn’t become too cloudy , you can see if it is flowing by looking in the tank. There should be coolant flowing out of the small hose into the tank. The Taruses with the 3.0L in the mid 90s had a cooling system problem where the systems would clog and Ford had a TSB where they replaced one of the heater hoses and placed a restriction in the small bled tube leading from the intake coolant passage to the tank, then they would knock out some of the casting plugs in the block and flush the entire system. I thought that they may have corrected it by 98. Here's what I'd do, remove the thermostat, pull the large hoses on the block, run clean fresh water through the block and see how dirty the water is. If it's bad, flush the rad and the heater core at their respective inlet/outlet. Replace the thermostat with a good one, NAPA, or Motorcraft is what I'd recommend. Fill it up with a 50/50 mixture of antifreeze and water. There are different types of antifreeze so use what the owners manual calls for. Then run it and see if that made a difference. Don't you love cars? They're the greatest physics project ever invented!
Jack Aubrey

Nope. You'd be overheating if the thermostat stuck close. Also there should be a bypass to the heater core anyhow. Either A) it didn't get hot enough, or B) it's just partially open (which is likely with the colder temps)

Remember it's just a spring, not an on and off switch. It could let through a couple of cups of water through before shutting again.

As Jack says... Check a) your levels, b) your radiator cap

This also suggests be careful where you check your level. If your driveway, street, etc. is on a hill, you'll never get the proper check. Some cars where the engine is higher then the reservoir require using a bleed valve in the head to purge air from the system in order to completely fill the the cooling system.

But have you checked that valve (heater control valve)?

Does the hose before it in the path fill with water?

Also if you've never done a Ford thermostat... Um.. get silicone to hold it in place, or you might regret it, if it's a vertical one.
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There is no valve between the water pump and the inlet to the heater core. Just a hose coming from the water pump, goes into the bypass T, then to the heater core.

I've done the thermostat on this one before. It is a bit of a pain.

I have had problems with the plastic reservoir over pressurizing and splitting open. Changed it once and have a small crack near the top on the current one. It's not a bad one but I do have to keep an eye on the coolant level, especially in the summer because it will leak some.

It's a 3.0 right? If so it "has" to have one, unless someone removed it.

Are you sure, The T isn't the valve?
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it seems to be just a T fitting. No vacuum line or other control going into it. I flipped it over to make sure there wasn't supposed to be some sort of input. Nothing.

Okay, I did a bit of checking.... so here ya go...

Check the diverter door in the cabin first... if we're okay there... then....

It sounds like the T might be a pressure valve. Which diverts water away from the core if pressure builds too much.
As in a case of a clogged core. Which, my undertanding, never happens.... except in the case of third gen Tauruses.

Supposedly, it's defect in the design of the car, and to correct it you knock out one of the engine plugs (as jack was saying) and back flush the engine....

or do some variant thereof, to partially restore heat for a temporary amount of time.

This is assuming the coolant is brownish... if not. Who knows.

One guy replaced just the metal hoses with rubber ones and solved his problem. Other people are replacing the core, which Ironically isn't so bad in this vehicle.
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I have a 1998 Taurus with (2 years) the same problem. Had the radiator flushed, heater core flushed and replaced the thermostat. Still very little heat. Did you ever find a fix? hattenw2@hughes.net

Ford mechanic here just wanted to let you know that flushing the heater core itself by disconnecting it on the firewall is probably going to fix your problem at least for one season. There is a thing called electrolysis where water turns to deposits on the inside of the heater core due to a small amount of voltage in the ground circuit of the car. The only other option is to replace the heater core. My full recomendation is to flush the heater core itself at the firewall using two hoses. One hose on either side of heater core, new hoses from a part store at least four feet long each. Flush with pressurized hose nozzle you know the garden hose type, moving from inlet and outlet until all color is gone. then have cooling system flushed.

I know this thread is wayyyyyyy out of date but I just noticed the Draino suggestion and I didn't want to leave it unchallenged in case someone tried it. This is a bad idea for two reasons.

Draino is mostly sodium hydroxide (caustic soda, lye) it is mixed with aluminum and/or zinc flakes as the reaction of NaOH with the aluminum produces heat plus hydrogen gas and helps stir up a drain clog. The NaOH works in a drain clogged with grease (as it turns it to soap) and organic stuff like hair (which it dissolves)

Since a clogged coolant system is not likely to be caused by grease or hair Draino would be ineffective and the bit about dissolving aluminum flakes should provide a hint as to why it would be a bad idea to put it into a car coolant system.

If anything use an acid flush. There are several available that contain Sodium Citrate or Oxalic acid, so don't try a home brew and follow the instructions.
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A Person

I know that this is too late but maybe someone else can use this info. Your problem is your heat bypass door. There is a solenoid under the dash directly under the radio. It is electric not vacum driven. The solenoid works off the temperature knob. Turn your temperature knob to hot. Go under the dash and look for the solenoid it is a square white plastic box with a few wires and a plug . Attatched Below the solenoid the is the actuator arm (silver) that is hooked to the bypass door. You can only see about a 1/2 inch of it. There is a metal housing that covers the rest of the arm. There is a small gap at the bottom of this housing about 3/16 of an inch and you should see the end of the actuator arm through this gap. Stick a screw driver in there and push the end of the arm up. You should see the arm go back up and warm air will start to flow. If the arm continues to stick you will need to replace it.

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