Hello all,

I have a 1991 Accord. I haven't had heat since the day I bought the car, and its damn cold out lol. I've been told the heater core is a huge job, and I honestly don't wanna swap it out if I don't have to. I doubt my core is leaking because I haven't noticed ne coolant loss, or any puddles underneath my car. I read up that if the unit is clogged, one hose will be colder then the other... Or, 1 will be pipping hot, and the other cold. This is the case with my car, so the question is what is the easiest way of unplugging it?

I have heard that Prestone Radiator Cleaner works best, but I can't find it ANYWHERE. I have flushed my system and it hasn't done nothing. Also, when the car is completely warm, I have very very little heat.

 

I understand that some of you may think i should just change it to a new Heater core.. At the moment funds are tight, and if at all possible I'd love to just get thru' the winter.

 

I'm gonna flush the system, and use Prestone Super Flush to clean out the entire cooling system, including the heater core. I'll post back with updates.

 

It's not easy to pull the dash which you have to do to replace the heater core. Do a youtube search for Eric the Car Guy and heater unclog...he has a vid on how to flush it.

 

interested to see what happens with this.

how often did you flush the coolant before the problem? I've seen in one case a clog due to using cheap coolant.

 

I just did it, and nothing better or worse happened. Its the same thing. I did however notice that both of my heater core hoses are piping hot. Could it be a fuse or something holding the heat back?

 

On the CD cars there is a cable controlled valve that prevents coolant flow through the heater core. Maybe that control valve is stuck closed.

 

I moved it back n forth trying to fix this, nothing happened.. It is now closest to the block.. which as far as I know is open.

I forgot to mention, I changed the tstat about 3 months ago (trying to fix this problem).

 

If at all possible, I need a step by step procedure to finally fix this. I have a 5 year old son and I drive him to school every morning, this is getting almost unbearable.

 

If the system was bled correctly, can you verify that the blend door for the heater core is allowing air flow? If so can you verify that there is nothing blocking flow over the core?

I've had a control valve appear to work, but the actual valve inside had disconnected from the linkage and would flutter open or close depending on coolant flow. (non Honda)

 

I don't know about bleeding, but the heater never worked. I didn't know I had to bleed my coolant system? and no I can't verify the blend door is allowing air, how can I do this?

There seems to be a little tension on the line when I move it closed and open, it appears to still be connected.

 

OOMPF!
Yes, this is probably why the heater does not work, you may feel hot hoses but they may just be full of warm air, not coolant.

On the intake manifold, where the thermostat housing connects, there is a nipple/bleeder screw that must be opened if the cooling system is ever opened(radiator cap does not count). With the heater turned to full hot, open the bleeder valve. You want a solid stream of coolant to come out, no air or air bubbles. Once you have a solid stream close and start the car.

 

Mike, I think you just solved my problem!!

I'm gonna do this as soon as I can get to the store to get coolant. I beleive this is my issue, when I first got the car I had coolant leaks all over the place. I corrected those, and I trust that I got air in the system for sure..

Should I fill then open the nipple? Or, open the nipple and fill so the air is pushed out?

 

The heater core actually bypasses the bleeder valve. I don't think that's going to solve the problem.

Check the hose closer to the passender side on the firewall and see if it's getting hot. I'm guessing it is since you said you flushed it but check it yourself after the car warms up.

What's happening when you turn the blower on ? When you press the different buttons does air move to those positions...eg defroster...air vents...floor..etc etc. If not, then the electrical portion of the heater system isn't moving like it should be. You should actually hear it move as you push each button to move air to whatever you are trying to get air to.

 

Crack that sucker open about a half turn and fill er up.
While filling up if you do not see any coolant come out of the bleeder place your finger over the top and see if there is air bleeding out. If not the bleeder may have debris inside, remove and clean it.
IIRC you will need a 12mm box end wrench. If you can try to use a 6 point rather than 12point. Those bleeders can be stuck.

 

Thanks! Definitely gonna try this!

I drained all the coolant and have it sitting at the moment, I need to get coolant and add it in properly this time.

 

When I turn the blower motor on it blows COLD air, If the car is at operating temperature the air gets a little warmer. It does move to different positions, defroster air vents floor it all works.

 

Thanks both you guys for the help & suggestions

 

Make sure that the cable connected to the temperature control is actually working. On mine, I have to manually move the piece that the cable is connected to which is on the passenger side of the vehicle under the dash.


Also, if you changed the thermostat is should ONLY be a Honda OEM Part and make sure the little hole is facing the correct way.

 

I installed the Thermostat the same way it came out.

 

1. Did you check both heater hoses to see if one is getting hot and the other isn't ?
2. When you checked to see if the heater core was clogged was water coming out fairly easily to the other port when you flushed it ?
3. Step 2 above would involve disconnecting the heater control valve hose from the passenger side heater core port, did you physically remove the heater valve and check it's operation ?
4. Do any of the heater control operations give out heat ?
5. When you move the heater control dial in the car does it offer any resistance or does it appear that the cable is broke ?

 

1.) Both heater core hoses didn't always get extremely hot, I changed the thermostat then they did, before none of them did.
2.) I didn't flush through the heater core, I poored a 10 minute flush agent into the rad, figuring it would circulate throughout the system.
3.) No, I am however thinking of doing that.
4.) I get 0 heat except for when the car is hot, I get very little. (Enough to notice, but still unbearable)
5.) There is no resistance like a normal heater control should have. I did however know this, and have been manually closing and openning the valve using the cable in the engine bay.

 

No offense but I wouldn't put anything except coolant or distilled water inside my cooling system.

What I would do first is get the three hoses that you are going to be fooling with since your car is probably old and they haven't been replaced before, unless you did when you did the swap. The three hoses are the one from the water pipe to the driver side heater core port(I pray you replaced this one when you did the swap and the engine was out of the car as this one is a bitch to access the clamp that attaches the hoses to the water pipe. I recently had to replace this as I didn't when I did my swap and it had busted, but I got lucky and needed to replace my driver side axle and luckily I was able to access the hose clamp through the driver side where the axle had been removed), the one from the engine(cylinder head) to the water valve, and the small one from the passenger side heater core port to the water valve...this last one is small, about 5 inches or so. I would get em from the dealer, however it's going to depend on what you want to do here, this is just informational. In order to access the heater ports I needed to remove the throttle body to get enough room to put a pair of 90 degree needle nose pliers to remove the hose clamps. If you don't tear the throttle body gasket you can get away with not replacing it but it's such a cheap part it's going to depend on what you want to do here as well.

Then I would shoot a hose into one port and out of the other and see how good the water travels. Keep in mind that there are minerals inside of tap water so if you have a hand pump it would be best to pump "distilled water" inside the heater core just to be on the safe side. Walmart actually sells a hand pump but you will probably want to put the pump inside the port and put tape around so it's strong enough and tight enough to pump the water throughout the heater core to see if it's blocked or not.

Then check out the water valve. It has I think a couple bolts holding it on and you will need to take off the heater control valve cable.

 

I just did this. Its the nipple on the top of the thermostat? I cracked it loose and had my wife feel for air.. She didn't feel any air, but a steady stream of coolant came out with a little air, I beleive the coolant was added right. Cracked the nipple first, and poored in 5litres of brand new coolant. This did not work, or change anything as far as heat goes. I am ready and willing to try anything to comfort my son on his way to school. Thanks

 

All coolant hoses were replaced shortly after buying the car, including the 2 coming out of the firewall (heater core). I don't leak or lose any coolant.

I am gonna go purchase a hand pump from Walmart later today and a Jug on distilled water. So, remove the 2 hoses off the firewall (heater core) and shoot water (via a hand pump) into 1 end? Expecting of course it will shoot out the other? I seen Eric the car guy on youtube do this. I did try it, and I can't for the life of me (and without the right tools) get them OFF. I may do what you said and remove the throttle body, I'm 6'4 230 pounds and bending over this car to inbehind the TB is a pain in the ***. I'm slammed to the ground too! LOL!

Thanks guys!