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Flushing the heater core?

15K views 24 replies 11 participants last post by  roadmaster'94 
#1 ·
I have good air coming out of my heater and defrost, but only moderate heat. I'm wondering if perhaps the core could/should be flushed. It is, after all, simply a reverse radiator. Perhaps I could do a radiator flush with the heater turned on and that might do the trick.

And yes, the first thing I'll do is check to see if the hoses are bad or clogged.

Advice anyone?
 
#2 ·
If you are a member of the no heat club, read here. If you search for flush in the heating/cooling/hvac section there are several other threads.
Flushing the heater core may help for awhile, you should flush the entire cooling system through the bottom of the block (knock sensors), these engines have a history of sediment.
 
#3 ·
When I swapped out the LT-1 a few months ago, I had everything flushed completely. But does that automatically flush the radiator, too? Or does it need to be turned on to be included?
 
#4 ·
I don't have an answer for your radiator question, but I had no heat for 2 years. I did the heater core flush a couple weeks ago and have heat. :)

Don't forget to replace your Tee and Restrictor. Also, the enhanced bleeder valve is a must have. :)
 
#5 ·
Anytime you open up the cooling system make sure you properly bleed it. Not doing that will cause you severe grief.

Like others have said, pull the knock sensor to get the gunk out, when you flush the core flush it back and forth in both directions. I find using a piece of tube connected to a garden hose and using the heatercore hoses works pretty well. Just be gentle on the core at first, if it is really clogged taking a full force water pressure out of a hose might be a bit much. Don't want to blow your core out, remember it is at least 15 years old. That being said, if the core is clean it should be able to take it all.
 
#9 ·
Flushing worked! Now it's TOO hot! LOL

I had an hour to spare today, and decided -- what the hey -- I'll try flushing out the heater core since I was under the hood replacing the tensioning pulley anyway. Can't say that I took it all that seriously, either; didn't use radiator flush and didn't have the nerve to use the Lime-Away than another poster suggested.

So, for better or worse, all I did was disconnect the pair of heater bypass hoses at the point where they intersected the water pump (plugging the lines to the block) and ran moderately high water up through the lines first in one direction and then the other. A fair amount of sludge came out, but it was hardly an ah-ha moment.

I re-buttoned everything, turned on the heat (this morning I had it set at 90 degrees and it barely reached room temperature) and POW! I coulda roasted hot dogs on the dash vents, and actually felt uncomfortably warm. What a difference!

This will be a wonderful change when it snows this weekend. No more sitting in the driveway waiting half an hour for a tiny space to defrost so I can see the road.

Next summer I'll do the complete flush and really clean things up. Thanks for all the good advice, guysl
 
#11 · (Edited)
It really doesn't matter. Pull both hoses at the WP and douche it with a hose - do it both ways it makes you feel better.

Did you see the link above in post #2?

Wow - MN in January playing with a garden hose.........I feel for you.
 
#17 ·
No heat club EX

I was having the no heat issue, But Thanks to prestone flusshing cleaner and little bit of karma, My heat is working like it should be after flushing the system 3 times. My advice to anybody having this issue is to do it right the first time. FLUSH FLUSH FLUSH TILL YOU GET CLEAR WATER COMING OUT BOTH WAYS OUT THE HEATER CORE.
 
#20 ·
got in the car today thinking i had heat. nope. 15˚F today driving to work, and 7˚F driving home from school an hour ago. no heat. 20 minute drive. got me thinking it might be the actuator. maybe it isn't opening all the way and letting heat out? i flushed the core out pretty good last night and got wet in the precess. topped off the coolant and bleed out the system. what if it is my actuator? i had a problem with that on my old honda, i had to physically slide it open to get heat. maybe the roady just has a bad/ stuck actuator?
 
#24 ·
I'm not at all familiar with the roadmaster wagons and their intricacies, but I did own (2) Mid 80s Hondas, and rebuild the engine on my brother & father's 1983 Civic.

On my 9C1 as well as my Caprice (Both 96 models) neither had the heater control knob in the cabin mechanically move the 'paddle' in the heater control valve via a cable, directing water either away from or into the heater core.

Pulling the knock sensors isn't difficult; just take your time. I used a bo wrench, and thuroughly SOAKED the threads W/WD-40 or equivalent. Also, a trick to remove pseky stuff that may have be difficult to get out is to loosen the bolt or in this case sensor, a few threads, then soak the threads with WD and turn it back in (Tightenng) it those few threads. Repeat the process 'till you get the knock sensors out. Just take your time, and try and use a box end wrench if they're going to put up a fight, that way you'll have full contact of the hex on the sensors, and be less likely to booger up the hex in the process.

Also be sure to use distilled water when the time comes to fill the cooling system.

Good luck.
 
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