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Over Heating 2003 Elantra

Hey Guys,
Looking for advice- Few weeks back my engine overheated and steam came from under the hood. Turns out the water bypass hose needed to be replaced as I was replacing the coolant I could see it pouring right out onto the street. We replaced the bypass hose and the radiator seems to hold coolant now, but the needle still rides a little high (just under halfway) and if I don’t have the heater on full blast it begins to creep up past the halfway point.

I was going to try the thermostat next, but I’m not 100% sure where to go from here. Thoughts?


If the needle on the temp gauge doesn’t go into the H red zone, the engine isn’t overheating.


I suppose it would be more accurate to say if I don’t run the heater on full blast, the engine would overheat.

Have you tried running the engine without the heater at full blast to see if the gauge goes into the red zone?


I turned the heat off and saw it begin to climb past the half way mark, at which point I tuned the heat back on to prevent that. It did slowly go back down once the heat was running again…

So what you’re saying is, you don’t actually know if the engine will overheat without the heater at full blast.

How do expect to figure it out unless you try that test?


I guess I assume if the needle climbs past a comfortable level I’d like to have it fixed. The temperature gauge, before this incident with the hose always registered about a third of the way up, regardless of driving conditions. Now, it just a hair and the halfway mark and starts climbing without the heat on.

I need the car and thought it best not to push it to the red for the sake of testing how bad it would get.

Maybe that’s wrong, I just know what it used to do versus what it does now.

Run the engine without the heater to see if the gauge climbs into the red zone ,while someone watches to see if the radiator fan kicks on.


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I’ll do that and report back.

Okay so yeah, Thee radiator is not losing coolant- the radiator fans are spinning. The temperature started to climb driving on the parkway. As I slowed down it cooled slightly… at idle (after a 15 minute drive) I turned the heat off and waited a bit and sure enough, the needle started climbing.

Maybe the thermostat?

The thermostat may have been damaged when the engine overheated.

The next step is to replace the thermostat.


That’s what I was thinking! But I’m no mechanic

Before replacing the thermostat, you could try to bleed the cooling system of air again. There may be an air pocket remaining in there someplace. That can cause this symptom. On my Corolla that’s very easy to do, just drive the front wheels onto ramps, remove the radiator cap and idle the engine until the radiator fan turns on, then replace the radiator cap. The procedure might be more complicated on your car. Pressure testing the cooling system and the radiator cap is worth a try too.