i have a 1989 honda civic hatchback SI, im having trouble with my heater, it was working untill my blower motor went out on me but then i replaced it and now it WONT blow out heat. i replaced the thermistat and that wasnt it, its getting coolant to the "IN" side but not the "OUT" side. im out of ideas, can someone please help me out????? im so tired of freezing my balls off everytime i drive my car.


update... now it will blow heat for like 20 seconds and then it will cool back down. could it be the water pump not pressurizing the system enough????

 

did you change the vtec oil?

 

HUH??????

 

Now it computes.

 

So you're getting coolant to the input of the heater core, but not the output of the heater core? Sounds like a problem with the heater core.

 

update

 

Yes?

 

If coolant is going into the heater core, but not coming out, I would think the system would start building a lot of pressure. are you loosing any coolant? does the temp change at all when you turn the blower motor on and with from recirc to outside? does it get even colder when you put the temp switch on cold? is coolant spilling out into the pass floor, or underneath the carpet? if your not leaking coolant, and your sure coolant is going into the heater core but not coming out, then the core is clogged somehow. thats my guess. I havent messed with ef's interior much but is the heater core able to be taken out without removing the entire dash? if it is, take it out and see if its clogged.

 

The heater core is in parallel with other parts of the cooling system, and is much lower flow. Blocking something that won't cause a flow obstruction won't cause a difference in pressure.

 

thanks guys