Lately I have been noticing my heater lacked any heat. In the summer it wasn't an issue, but for these cold mornings with condensation on the windows it is becoming necessary. And with fall around the corner, it will be a must.

 

So tonight I decided to tackle this annoyance. Basically I did the reverse flow trick but instead of pulling the thermostat and reversing the hoses (and pushing the crud into the radiator or block), I took off the hoses where the pipes come from the engine and meet the rubber hoses. Then I fashioned an adapter out of clear tubing. One end onto my air gun nozzle and the other into the return line (firewall to engine). I put an empty gallon jug over the other line to contain the crud that came out.

 

Then I gave a blast of air until all the liquid was out. Filled with water twice and blew it out until clear.  No toxic chemicals necessary.  It now gets hot like it is supposed to. Originally got the idea from eric the Car Guy:

 

Great tip. How much gunk were you able to remove? How many miles does all that crud represent?

   My 88 GL 10 T doesn't make heat for nothin'.  It blows and flows clear as can be thru the core, but still doesn't make much heat.  I'm thinkin' my problem is air flow thru the core, but still quite a chore to get it out to clear it.  I ran across a thread some years ago, where the guy cut the side of the htr. box out with a dremmel to avoid dismanteling the dash.  Any thots?  S.