2003 Escort ZX2 - Burning smell, now heater doesn't work

[PumpinIron]

Okay, so the car in question is a 2003 Escort ZX2 with roughly 110k on the clock. It's run like a champ up until now. My wife was driving it home from work the other day and said that there was a burning smell coming through the vents, then the coolant temp gauge on the dash went all the way to hot and stayed there, and the heat simultaneously stopped working.

She got it home and I quickly found out that the car IS NOT overheating. Something screwy is going on with the gauge and it will sit at cold for 10 minutes, then go all the way to hot, then sit in the middle, and it's just all over the place. However, the engine fan works fine and comes on at the appropriate time, the engine does not overheat at all, and other than the gauge acting weird and the heat not working, the car runs as it always has.

So, just a as a measure of preventative maintenance I replaced the thermostat, thermostat housing, and both clip-in coolant temp sensors on the thermostat housing. This seems to have fixed nothing, but oh well.

Next, I let the car heat up and checked the two hoses going to the heater core in the firewall. One hose is just slightly warm (even at full operating temperature) and the other is completely cold.

When you get in the car and attempt to turn the heat on, all the blower motor speeds work. When you turn the dial from cold to hot you can see under the dash that the cable that opens the blend doors is working fine as well. However, no heat at all, it's just cold air that comes from the vents even on the hottest setting.

The heater core isn't leaking at all, this has been confirmed.

So, I'm unsure where to go from here. The wacky coolant temp gauge seems like maybe it's the actual gauge itself that's gone south (in which case I'd need a new gauge cluster I suspect). The heat though perplexes me. Sure, the heater core could be plugged but that seems rather unlikely considering the coolant has always been regularly flushed and when you open up the radiator there's no gunk or rust or anything in the system at all.

Any thoughts guys?

[PumpinIron]

Just got back from the garage. I unplugged both of the heater core hoses at the firewall. I then ran water through the heater core with the hose and it clearly came out the other side with no effort at all so I can confirm for 100% certain that the heater core is NOT clogged.

The odd part is that both of the hoses going to the heater core (including the one coming directly from the thermostat housing) aren't even hot when the car is at operating temperature. The one coming from the thermostat housing going to the heater core is barely even warm when the car is at full operating temp.

[TooManyProjects]

Possibly the water pump is bad. The coolant is being heated in the block, but isn't going anywhere.

[hakachukai]

Check your coolant flow to see if the water pump is pumping it properly.

1. Drain and store your original coolant ( assuming that you're not using straight water )

2. Remove the thermostat housing and the thermostat

3. Assemble the empty thermostat housing without the thermostat

4. Fill up the cooling system with plan water

5. Leave the upper radiator hose disconnected

6. Start the car ( when it's fully cooled down ) for a SHORT period of time ( no more than 15 seconds ). You DON'T want the engine heating up!

Water should shoot out of the upper radiator hose with a good bit of force and volume. If it does not, there are only a few things that can cause it:

A. Bad water pump ( or maybe it has an air pocket trapped in it )
B. Clogged radiator or lower radiator hose restricting water to the pump
C. Clogged block restricting the properly pumped water from exiting the engine.

Since you'll already have the cooling system mostly apart, you can also pretty easily check it for proper coolant flow.

1. Disconnect the upper and lower radiator hose from the radiator and make sure that the thermostat has been removed.

2. Stick a garden hose in the upper radiator hose (which is still connected to the engine with no thermostat ) and carefully turn the water on all that way. Don't spill the water and soak everything.

The water should pour out the disconnected lower radiator hose just as fast as you put it in there! If it doesn't, you have a clogged block, clogged water pump... or some other random thing between point A and point B.

3. Disconnect the upper radiator hose from the engine and connect one end to the upper radiator. Make sure the cap is on the radiator. Carefully turn the water on all that way. Don't spill the water and soak everything.

The water should pour out of the lower radiator hose connector just as fast as your put it in there. If it doesn't, you have a clogged radiator.


How to read the results------------------------------------

A: If the pump test shows weak or no flow, but the engine flow test shows that nothing is clogged, then you can say for sure that the water pump isn't doing its job! So either the pump is bad, or is full of air pockets and can't pump properly.

B: If the pump test shows weak or no flow, but you also find restricted flow through the engine block, then remove the water pump and test again ( because the water pump could be clogged ). If you get the same result after removing the water pump, you have a clogged head. You'll have to look into getting that repaired or replaced.

C: If you find restricted flow through the radiator, you need a new radiator regardless of the rest of the test results.