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I have a 2001 Hyundai Elantra and the vents blow cold air when the heat is turned on. I took the car for an hour long drive and then parked it, felt the 2 hoses going to the heater core and both were cold. I read that if one hose is hot and the other is cold, then the heater core can be clogged. What could be the issue if both hoses are cold?
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The three possibilities are stuck open thermostat, stuck closed heater hose valve (if there is one) or plugged core.
heater hoses stone cold….radiator hoses HOT….
I do not think they used a heater valve……I could be wrong… But it sounds like a bunged up heater core…..or a massive air pocket blocking coolant flow into the heater core.
S-
With the engine cold and you’ve got reasonable access to safely disconnect your heater core hoses one at a time, disconnect one or the other and have a friend start the engine. I’d personally try to find the heater core return hose and disconnect it at the engine. Start the engine and look for coolant flow. Have the friend shut down the engine after you see some reasonable coolant flow. It’s a messy method, but it’s usually effective in purging trapped air if the heater core is air locked.
Hi and thanks for the replies. I saw where the heater core hoses were connected to the engine, both to the thermostat housing. I disconnected one of them and there was pretty steady flow coming from the housing from where it was disconnected. I put that one back on and did the same thing for the other hose but the flow wasn’t as steady coming out of the housing from where it was disconnected. I am not sure which one was the return hose though.
Assuming one of the two times was the return hose, should there have been coolant coming out of the thermostat housing when the return hose was disconnected? I figured the coolant would go into the heater core then out the return hose, not out of the thermostat housing.
Usually, the return hose is connected to the water pump or metal tubing at the lower part of the engine. If both hoses are connected to the thermostat housing it could explain your problem.
The thermostat housing can be seen here> http://www.rockauto.com/catalog/moreinfo.php?pk=2405010&cc=1373385
The hoses were disconnected from the side with the thinner hoses. I may not be experienced much in mechanic work but what do you mean when you say “If both hoses are connected to the thermostat housing it could explain your problem”?
Does that mean that I can rule out a problem with the heater core and that there’s some type of problem with or before the thermostat housing? What should I check for next?
I think what we would need is to see your current setup and how the heater hoses are run. Without having the car in front of most of us–we can only guess using prior knowledge of how it normally works for most cars. Of course nothing is ever 100% normal on any of these cars.
S-
I can’t find any pictures of the way the heater hoses are set up but here’s a diagram of what’s in my car:
The lower diagram shows the thermostat housing (part 25620) and those 2 smaller hoses on the end of it on the right side (25615A and 25617B) are where the hoses to the heater core hook up.
Looking at that same housing, note that one pipe on the left side is straight and the other pipe is angled down. The straight pipe is connected to the upper radiator hose and the angled down pipe is connected to the water pump hose.
Still looking at same diagram, the housing cover (25631B) is connected to the lower radiator hose.
It does appear that both heater hoses are connected to the thermostat housing. However one hose has to connect to the suction side of the water pump and the other side to the pressure side of the water pump. Otherwise no flow.
This is a curious and unusual design. Anyway, the above is still true meaning that there must be twin passageways for coolant internal to the thermostat housing.
Step 1 in a any situation like this is to check the cooling system for trapped air. The most common place for air to get trapped is in the heater core.
If that doesn’t yield any results the next place I would look is to the heater control valve.
Always start with the simple stuff and then work the more complex theories.
Keep us posted.
Ok so today I disconnected those 2 hoses that go to the heater core from the thermostat housing and backflushed with water from a garden hose and sure enough, a steady stream of brownish gunk game out for about 2 minutes straight. I reversed this and flushed from the other hose and the same result just not as bad. I alternated both ways a few times and the backflush way definitely yielded more brown liquid that the natural flowing way. So my car has heat now and will drive the car with the heat on later to make sure.
Now that I do have heat, I let the car cool a few hours and went to refill the system with water. I am actually running 100% water right now because I drained the antifreeze a few times before today. When I took the radiator cap off there was a white soapy foam coming out. I let the car run as it was boiling over and then filled with more water as it came to operating temperature.
Can this just be to air being in the system?
[quote=”joeycava” post=114501]Ok so today I disconnected those 2 hoses that go to the heater core from the thermostat housing and backflushed with water from a garden hose and sure enough, a steady stream of brownish gunk game out for about 2 minutes straight. I reversed this and flushed from the other hose and the same result just not as bad. I alternated both ways a few times and the backflush way definitely yielded more brown liquid that the natural flowing way. So my car has heat now and will drive the car with the heat on later to make sure.
Now that I do have heat, I let the car cool a few hours and went to refill the system with water. I am actually running 100% water right now because I drained the antifreeze a few times before today. When I took the radiator cap off there was a white soapy foam coming out. I let the car run as it was boiling over and then filled with more water as it came to operating temperature.
Can this just be to air being in the system?[/quote]
That’s great that you got the heat working by flushing out the heater core. I had to do that also with my truck. The fluid stays stagnant in the heater core in the summer and can cause gunk to build up. After I flushed out my heater core I run the heat once a week in the summer to circulate the coolant through the heater core to keep it moving. I haven’t had a problem since.
As far as the boiling issue, water alone has a lower operating temperature than using 50/50 coolant. Also, the coolant system, under normal operating conditions, is pressurized which increases the boiling point of the fluid by 2 degrees for every pound per square inch of pressure.
So running strait water and running the car with out a radiator cap would allow the fluid to boil at a much lower boiling point.
Check your owners manual but running 50/50 coolant is the way to go for most vehicles.
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