My wife’s cousin has a 2006 Fusion with about 110,000 miles on it. Recently, she complained that the heater doesn’t blow hot air when she’s stopped, only when the car is moving. The coolant was due to be changed at 100,000 miles, but I don’t think she ever got that done. I dropped it off at Firestone an hour ago and asked them to flush the coolant. When they asked me what was wrong and I said the heater wasn’t working, they said the coolant flush definitely wouldn’t fix the problem, and they’d have to do a diagnostic.
Assuming it’s not just low on coolant, what else could the problem be? A bad thermostat or bad water pump? She said she hasn’t noticed the temperature rising at all, but she mostly drives short distances to and from work. I’d like to know what to expect when the car’s ready to pick up.
“Just low on coolant” is the most likely cause of the symptom, and is the first thing that should be checked. And while a coolant flush per se won’t fix that, getting the cooling system full of liquid with no air pockets, which is part of a proper flush, will.
If it is indeed low on coolant, the thing to do is find out why. Most often it’s a leak that will show up with a pressure test and visual inspection, though occasionally it’s more involved than that.
If the symptom occurs when the cooling system is full, then a faulty water pump and restricted flow through the heater core are the next things to check. But it’s premature to investigate these until it’s KNOWN (not assumed, but known) that there’s no air in the cooling system.
Firestone called - “We flushed the heater core and now the heat’s working fine. You’re good to go.”
Could evaporation be the problem if the coolant was never topped off? My wife’s cousin is a poor waitress who uses the services of the occasional mechanically inclined boyfriend to maintain her car, so it’s entirely likely that the coolant hasn’t been touched since she bought it.
It’s not impossible. The choice is to do nothing, hope it was evaporation, and run the risk that it does have a leak and might exhibit a worse symptom next time it gets low; or have it pressure tested and find out whether or not it has a leak.
The potential consequences of its losing coolant and overheating can cost a heck of a lot more than the fee for a pressure test. “You’ve got to ask yourself one question, ‘Do I feel lucky?’ Well, do ya, punk?”
ETA: The question about evaporation suggested the system was low. If it was NOT low, there’s no need for a pressure test. If they specifically said they flushed the heater core (rather than did a whole system flush), that suggests the core was partially clogged. It would be nice to know for certain whether or not the system was low, and whether or not there was restricted flow through the core.
Well, when I dropped it off, they charged me 69.99 for a diagnostic on top of the 89.99 for the coolant flush, so I will ask my wife to make sure that diagnostic included a pressure test.
Remember, they have Christmas presents to buy too. Hopefully the repair order shows evidence of a diagnostic pressure test. If the system was low, something is leaking. Antifreeze is not going to evaporate from a sealed system. It has to either leak out or be pushed out by pressure as from a bad head gasket. Now if the boyfriend had drained and refilled the system, he could easily have left air in it. Otherwise, the air got there when the coolant leaked out and you will have a repeat problem. This system needs to be monitored closely. Even if you keep topping off a leaky system, eventually it will damage a head gasket from the hot spots created when it is low. With 110K on it that water pump is very suspect. Hoses can also get hardened and leak at the clamps.
One way a system can go low is if the overflow tank has a crack in it. The fluid goes into it when it heats and expands, and since the fluid leaks out the bottom, the cooling system sucks in air when it cools. The overflow tank is not part of the pressurized system.
So when she went to pick it up, they told her that the heater core was full of crud, and once they cleaned it out and flushed it, the heat worked perfectly. She asked about the diagnostics, though, and they hemmed and hawed before finally taking $50 off the bill, not having any actual results of these “diagnostics” to show. But apparently, the coolant wasn’t low, just dirty. I’ll tell her to keep a close eye on the coolant level and the temp gauge, though.
the remaining question is “did they / did you have them flush the entire cooling system and renew the coolant?” The car’s got 110,000 on it and that stuff doesn’t last forever.
The invoice includes 2 gallons of coolant, so I hope they actually put fresh coolant in. I didn’t check under the hood before I brought it in, though, so I wouldn’t know for sure. She left this morning on a 400-mile road trip and hasn’t called to say she’s stuck on the side of the road, so I’ll take that as a good sign.
The answer on an older vehicle would directly point to either an extremely odd functioning thermostat, or simply a valve malfunction.
Unfortunately, on newer cars, this will be so labor intensive that she might just want to drive to heat the car, rather than pay the hundreds of dollars to remove the emissions controls from above the engine…
