First off, family man w/ kids. I need my heater. Ok, before I thought to bother the forum, I chose to read all threads I could find relevant to my problem. 98 Laredo, inline 6. Blowers are working fine, just blowing cold air. I checked the heater hoses, both are hot so that should rule out a faulty thermostat. The linking rod underneath the dash is attached and working properly. I took off my dash to examine the blend door. It appears to be working fine. In the off position, door is open. when I switch heat to on the door closes, so it appears operational. The only thing left to check that I have read about would be a clogged heater core, or it need flushing or replaced. However, I cannot find step by step directions on how to flush my heater core. Where do I even start? Advice and guidance is greatly appreciated, thanks everyone.
You can get them pretty much anywhere, lowes, HD, HF, Wally world..
take a bucket a can of radiator flush, a piece of rat wire and an old sock.
Make a filter cage out of the sock and rat wire to keep big chuncks from going back into the core. Trace the hose from the water pump to the firewall, that's the one that was your inlet and you want to put a jumper hose from that stub to the bucket. Then run the filterd line to the pump then to the core outlet. turn on the drill and you are backflushing like a pro. odds are you will get some crud out even if your core is clean but if you only get a trickle out of the outlet and a few minutes of running the pump doesn't help you need to replace the core (easy job). If you get flow then you might as well runn the pump for 10 or 15 minutes before a fresh water flush and hooking it back up.
I use the radiator flush and water to back wash the core.
The wire makes a cage and the sock over it creates a filter that doesn't suck in and stop up the works. It seems to work for me at least for smaller radiators and heater cores, the little pump doesn't put out enough GPH to flush engines or multi core radiators.
Sorry man.. just trying to follow what you're saying. The way I have done it in the past is to disconnect both hoses going to the top of the water pump. Using a pointed on/off nozzle on a garden hose in the top hose and the other hose coming from the heater core into a bucket turn on the water and let it go through the core into the bucket. This works well but it is a problem if your outside faucet is frozen.
I envision the same thing here except you use the Bucket for both the supply and waste and the sock as a filter. You would need to connect the pump to a hose on the inlet of the pump and secure the hose coming from the core to the other end to the outlet of the pump. Do you know if the pump has enough pressure to completely flush the heater core?
Just a question, but - when you turn up the fan blower, do you actually feel air blowing out near your feet and/or thru the center dash vents facing you? Or is it only blowing on the windshield/defog? (wondering if you may have the infamous vacuum issue, where your AC & heat permanently blow out only on defog). If I'm mis-reading your post on this, apologies for taking your time.
My motor is directly behind the glovebox. I didn't disconnect it because using the switch it was opening and closing. With my hand I checked for any hot air, and nothing. Maybe semi warm, but its really to cold outside to tell.
If it is like mine pull the two screws out that secure the actuator to the HVAC unit, remove it, and manually move the shaft. You should feel it positively stop in the full open hot and cold position. If it doesn't stop firmly then your doors are probably broken or cracked.
Removing the actuator is required because you need to know if the doors are positively attached to the shaft. If it stops both ways then they are.
Interesting technique, Vadslram. I may look into a pump like the one u describe. Now you suggest my core isn't blocked at all, because I said that the two hoses were hot. What would be my next move?
I set it up after I paid $35 to have a radiator flushed and saw that all they had was basically a pump, hoses and a strainer.
If you have hot going in and hot coming out then the core has to be hot. that only leaves the air interface. At least on my '90 there was a lot of room for air to go around the core and the foam that was used for weatherstripping was pretty deteriorated. It was falling apart and blowing all around, including into the fins of the core. I replaced mine because it was leaking but when I did I was amazed how much more airflow I got with open fins and blend doors that actually closed and sealed. Is there as much force at the vents as normal? maybe the heat is getting to the core but the air isn't flowing through it. It has to be either that or the blend doors are jammed shut/broken.
My vents are blowing just as hard as they ever have. Just because I witnessed the doors operating, opening and closing, by using the temp switch, doesn't mean that they are working properly? The door is closing all the way, but perhaps isn't opening fully?? It was suggested to me that I disconnect it from the motor and try to manually open and close it. If unable to, I guess the door needs replaced? I am really hoping its gonna be a simple solution. I read last night in depth on how to remove the entire heater core. That involved a bit too much for my skill level.