What is my car heater up to?

Factual Questions
1

I have a beater, aka a 1993 Taurus.

Since the temperature dropped this year, it has been behaving…oddly.

This fall, I had the serpentine belt and idle timer (at least I think that is what it was called…that or the idle timer belt) replaced.

Regardless of the temperature outside, the engine temperature spends a good bit of time in the red. No engine or oil lights ever come on, just the temperature gauge needle in or close to the red. Coolant and oil are full, though it is overdue for an oil change. The temperature issues started around the time that the serpentine belt went bad. I had hoped that had something to do with the engine temp, but the temp problem didn’t go away once the belt(s) were replaced.

When it is cold outside, the heater takes waaaay to long to start working, while it worked just fine last winter. The fan is blowing air, but that air doesn’t get warm untill at least 20 minutes of highway driving. Also, as I’ve noticed many times, the warm air only comes in occasional bursts, which happen to coincide precisely with the engine temp droping down from hot to normal.

If it is not cold enough to turn the fan on, the temperature will warm up to high normal/low hot and pretty much stay there.

I don’t know crap about how heating/cooling works on this car, but it seems almost as if whatever mechanism is supposed to be drawing hot air away from the engine, whether to heat the interior or just cool the engine, isn’t drawing properly. Or something.

I don’t drive it all that much, but I want it to stay in good working order, and I like being able to drive without my teeth chattering out of my head. I’m on the cusp of taking it in for a once-over at the dealer, but I always prefer to be more informed than not when talking with mechanics.

Thanks in advance for any “IANA mechanic” WAGs or other hypotheses.

2

IANAMechanic.

Bad thermostat?

Clogged lines in the coolant system?

When was the last time you had the coolant system flushed?

3

IANAM but I’ve owned two cars with bad thermostats. I will be astounded if you do not have a bad thermostat.

If I were you, I wouldn’t bother to ask a mechanic to test anything. I’d just ask her to replace the thermostat.

4

The Taurus had a history of bad head gaskets. If the head gasket blew, you could have an air bubble in the coolant, which would cause the heater and temp gauge to behave badly, even while the coolant tank seems full.

Pray that it’s a bad thermostat.

5

You have a potentially major problem. Don’t drive the car with the temp gauge reading that high.

Regardless of the temperature outside, the engine temperature spends a good bit of time in the red.

This is not good. It’s overheating, and serious engine damage can be (or perhaps already is) the result.

No engine or oil lights ever come on, just the temperature gauge needle in or close to the red.

Oil warning light is irrelevant to the problem. The car almost certainly does not have a temperature warning light, because it has a temperature gauge instead. The needle in the red is the equivalent of a warning light. Needle in the red means shut off the engine NOW.

Coolant [is] full…Also, as I’ve noticed many times, the warm air only comes in occasional bursts, which happen to coincide precisely with the engine temp droping down from hot to normal.

I seriously doubt the engine is full of coolant. What you’ve described is the textbook symptom of a major air pocket in the cooling system. That means there’s not enough liquid (coolant) to keep the engine temperature down where it needs to be, and not enough liquid to consistently flow through the heater core.

I venture that the coolant level in the overflow reservoir is full. That doesn’t mean that the level in the engine and radiator is full*. Take off the radiator cap (cold engine only!) and I bet you’ll see no sign of coolant. It should be up to the brim.

This is the kind of thing that causes blown head gaskets, and possibly other even worse problems. Head gasket repairs are major jobs and quite expensive, probably at least a thousand on this car, possibly quite a bit more depending on what damage has been done. If you’re really lucky, it might not have gotten that far yet. Fill it up before driving again (with a 50/50 mix of antifreeze and water). Get it to a qualified repair shop ASAP.

*When everything is perfect, the radiator and engine are full, and the reservoir is roughly half full. As the engine heats up, expansion pushes some coolant from the engine into the reservoir, then when the engine cools down it sucks it back in. But with some coolant leaks, instead of sucking liquid coolant from the reservoir, it sucks air in through the leak. The result is a reservoir that maintains its level while the engine and radiator get progressively lower on coolant. Reservoir level is not a reliable guide to engine coolant level.

6

Thanks everyone.

Just out of curiosity, which is more likely? A blown head gasket due to an air pocket in the cooling system, or an air in the cooling system due to a blown head gasket?

Will flushing the cooling system remove any air pockets as well as indicate whether or not the head gasket is blown?

7

Also, having grown up with duct-tape/shoe-string volkswagens, I’m meticulous about checking under any car I drive for any leakage while parked, and I have seen no signs of any leakage…for what it’s worth.

8

Just out of curiosity, which is more likely? A blown head gasket due to an air pocket in the cooling system, or an air in the cooling system due to a blown head gasket?

It’s often hard to know the root cause as it’s a “chicken and the egg” scenario, but it’s more likely that an air pocket will precede a head gasket failure. This is because anything that causes coolant loss can lead to an air pocket.

Will flushing the cooling system remove any air pockets as well as indicate whether or not the head gasket is blown?

A proper flush & fill will get the air out, but it won’t find or fix the reason air was in there, and it won’t indicate the presence or absence of a head gasket problem.

…I’m meticulous about checking under any car I drive for any leakage while parked, and I have seen no signs of any leakage…

Not all leaks leave drips under the car when parked. Sometimes the leakage will evaporate before hitting the ground. Sometimes a head gasket gives way first and sucks coolant out of the engine, emitting it through the exhaust as vapor. I’ve even seen a faulty radiator cap cause coolant loss without leaving drips.

If you do indeed find the coolant level low in the radiator, that verifies some form of leakage, and the first thing to do servicewise is to find the leak(s). This is most commonly done with a pressure test. If there’s any question of head gasket failure, a combustion leak test is the thing to do. I’d get the leakage and overheating issues resolved before considering a flush.

9

Just being a 1993 Taurus with the 3.8 liter V6 will cause head gasket failure. (And whatever recall campaigns were in effect are long since expired.) By the time all the incidentals were taken care of, mine cost $2500 to fix five years ago.

Air is worthless in a cooling system as it’s occupying volume that should be occupied with coolant.

When the gasket goes, if it’s cylinder to water jacket, (seems to be the most common failure mode) you’ll have a big pressure shock of steam in the cooling system that will try to find its way out. In my car, the way out was through the water pump and timing cover gasket. A cylinder-to-cylinder breach will at first, just make the engine run badly as the two cyliders won’t make proper compression.

By “incidentals” I mean sending the heads off to a machine shop to be fluoroscoped to ensure they’re not cracked, and checked for flatness to ensure they’re not warped. Evacuating and eventually re-charging the air conditioning - plus retrofitting for R-134a as the '93s had R-12. Plus all of the “While most of your engine is out, you might as well pre-emptively replace this doo-dad that’s on its last legs underneath it” and “it’s already out - not much sense in putting the old one back in” stuff like spark plugs, ignition wires, hoses, water pump and on and on.

Take your car to a good radiator and cooling system shop and have them run tests like what Gary T described. Another quicky check for a bad head gasket is to pop a smog tester probe into the tailpipe - a blown gasket will put huge amounts of water vapor into the exhaust.

10

I bought it about 2 and a half years ago for $1000, then put about $600 getting it drivable, that was for the first of the 2 serpentine belts I’ve replaced and a new water pump. All the work was done at a Ford dealer.

I don’t know anything about the history of the car, or whether or not either of the two previous owners complied with any recalls.

I did just get it smogged in October though, and it passed. Would a lot of water vapor in the exhaust have caused a failure of the test? Or at least prompt the technician to point it out? He just said “You passed.” and sent me on my merry way.

But since I have had both water pump and timing issues…sigh

I’m taking it in for the local dealer’s radiator treatment package. We’ll see how it goes from there.

11

Actually, the trick here is to put the probe at the radiator neck with the cap off. The smog tester doesn’t test for water vapor, it tests for other combustion gasses. Since water is a normal byproduct of combustion, there is always some water vapor in the exhaust (though there can be a lot more with a blown head gasket). But combustion gasses are not normally present in the cooling system. If they are detected at the radiator neck, there’s clearly a breach, which is almost always a head gasket and/or cracked head.

12

No, it’s not indicated in that test. If you had big billowing clouds of “white smoke” (steam) coming out the tailpipe, I would expect him to say something – but if you had that, I would have expected you to have mentioned it here already.

Be sure to mention the symptoms you’ve described to us. While one would hope they would notice things aren’t right and recommend further investigation, sometimes people just don’t see things they aren’t looking for. It would not serve you well to have the root cause of your problem undetected and unfixed.

13

Welp…it was fun while it lasted.

The Service Center at my local Ford dealership says I need a new engine. $4400. Not gonna happen.

Suck.

14

Sorry to hear that. Thanks for letting us know what was found.

15

Why? What did they say is wrong with the engine?

(BTW, in addition to two cars with bad thermostats, I have had two cars with blown head gaskets. My money is still on the thermostat. And it’s <<<<$4400 to replace.)

16

It was the head gasket(s). And due to the problems with the 1993 Taurus that have already been mentioned, replacing them isn’t an option. They won’t take. So the whole engine needs to be replaced.

17

Sounds like the dealership has a rack full of engines they want to get rid of. Unless your engine overheated so badly that the heads warped beyond machinable tolerances or cracked, or the block itself is broken, there should be no good reason a competent mechanic can’t replace the gaskets, re-assemble the engine and have you back on the road for a lot less.

The head gaskets for this engine were re-engineered and substantially updated about 12 years ago.

18

I believe the heads are indeed cracked, and while I appreciate your suspicions, truly, nothing about me or this car screams “easy mark” for talking into an arguably unecessary new engine at a price of $4400.

One look at it, and me, and knowing that I only purchased it 2 years ago (from my ex…problem #1) it is pretty obvious that I didn’t pay very much for it and I would never agree to repair it for that much.

They would’ve increased their chances of my spending more at their shop by offering an intermediate option, which they didn’t do, imho, because there is no intermediate option.

It has over 100,000 miles on it, and though I did not drive it more than occasionally over very short distances since it has been getting hot, I have no idea how well it was treated prior to me.

19

Total suck. Get a second opinion.

20

Based on some quick shopping, you could probably get a rebuilt engine delivered locally for slightly under $2000. Always a cheaper option out there than the dealer…
But yeah. You’re getting a new car unless the dealer was completely scamming you, or you wanna spend more fixing that thing than it’s worth. I’m showing a RETAIL value on this car of $1500 and $700 private party.