No heat. Temp gauge barely moves, but hoses to/from core are hot
I have replaced the coolant, thermostat, and radiator cap. Still no heat inside the car. Thought I might have to replace the heater core, but I don't understand why the temp. gauge (which I believe is okay) reads cold. Hoses to and from the core are relatively hot. There are no external coolant leaks, nor any apparent internal problems with the head gasket. I heard replacing the heater core is a nasty job, so before I do that, I was wondering if there could be some other cause for no heat. Any suggestions?
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Re: No heat. Temp gauge barely moves, but hoses to/from...
Did you run engine from cold, with heater (not defrost) on , rad cap off & wait for rad fan to come on 2 or 3 times before you put rad cap back on? Rev engine slightly and hold it there for 30sec. to 1 min. every once in a while while doing this to aid in increasing flow & remove air locks. If both hoses in & out are hot to touch, then you should be getting heat, and I would start looking at blend/air door etc on heater to make sure it's going to it's proper position.
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Remove the thermostat temporarily just for a diagnostic strategy. Put the thermostat housing back on with a new gasket and then drive it for a time to confirm that it is no longer doing that same thing. You will be running too cool to leave the thermostat out and you will have little or no heat. I just want to know if removing the stat helps before I continue. let me know.
While it doesn't seem likely, if you've changed, or had the thermostat changed.... I'd say you got a faulty thermostat. I am curious as to what your temperature gauge says the temperature of the engine and coolant is.. If your gauge is showing hot, I can think of two more possibilities... the water pump isn't pumping right... and, if the water pump isn't working right, the problem can be a cracked head or block, which can cause an airlock in the coolant system. Check the coolant or radiator cap.
It would appear your thermostat is stuck in the closed position , find where it is on your engine, drain coolant and remove thermostat housing and stat, replace housing(liquid gasket OK) and coolant. now run engine, turn heater controls to hot leaving filler cap off, top up any water to max and replace cap now warm up to temp until fan comes on. if all ok replace thermostat with a new one and new gasket, you could also flush the sytem out at the same time with a hose pipe by loosening one of coolent pipes and flush radiator.
disconnect the heat hoses going into fire wall , put hose into one with pressure and flush as it sounds like it could be bloked in the heater core,the other thing that could be the problem be the hot ,cold switch as it restricts the flow to makes the heater hoter or colder , it might need tlc or replacing as it is manaul not elec
Before assuming the heater core is blown check the following.
1. Check coolant level while engine is cold. 2. Leave the radiator cap off and let the engine run. See if you can see the coolant circulate when the engine is brought up to temperature. 3. Check the temperature gauge inside and note if the engine temp is correct. 4 Does the engine overheat? 5. Feel the heater hoses and check if they get hot. 6. Can you smell antifreeze inside the cab?
I believe your thermostat is beginning to fail, although the truck really isn't all that old. Still, it is 5 years old, and has been through many heat cycles, so I would change the thermostat. Change--drain completely and replace--the anti-freeze at the same time, and use Dexcool anti-freeze. Check the heater hoses, and make sure neither of them has a collapsed area in it. Lastly, check the water pump--with radiator cap off on a cold engine--start it and warm to driving temperature (takes a long time with the cap off), and look at the coolant at the top off the radiator...is it swirling around the neck (if full), or gushing across the top of the core (if low on coolant)? If you squeeze the upper hose together with your hand while the thermostat is open, can you feel/hear the coolant rushing through it? These things mean the pump is pumping.
Why was radiator replaced?Did it have heat before ? If it was plugged, the heater core may also be plugged. Try flushing it with a water hose in both directions. I dont know why the botton radiator hose would be cold, the radiator should be a uniform temp and the air coming through the radiator should be HOT, when the engine is at operating temp. What condition was the old coolant? if it was rusty, the water pump may have lower flow than normal.
Does your temp gauge read normal? if it does then the thremostat is ok,but sadly the water pump is going bad this is typical of jeeps at an idle the heater cools off because the water pump fins are worn enough to not circulate through the heater core and when you step on the gas the increased rpm move the water fast enough to circulate through the heater,it is possible that the heater core is plugged but I doubt it as a plugged heater core would not get hot either it would be cold or just luke warm all the time.