for some reason i cant post the process in the right forum but if anyone has no heat reply and ill walk you through what seriously worked for me $7 fix!

 

I have no heat, but it is on a 90, so I am unsure if same thing will work or not.

 

1 disconnected heatercore hoses near tstat.
2 used air hose to clear coolant.
3 dumped in CLR with hoses raised till full
4 let sit for 20 mins
5 air through top hose to puch out clr
6 through same hose ran garden hose to flush (10mins)
7 connected hoses
8 inclined front of car to raise radiator
9 open radiator cap
10 start car with heat on high
11 add fluid to top of cap and to fill line in resevior
12 squeeze top hose to release air through radiator cap
(repeat steps 11 and 12 till no more bubbles, took me 15 mins)

replace cap and drive with heat

***see pic of my setup (white hose is from garden hose to top core hose, red is from lower core hose to bucket)

p.s. i used electrical tape to hold/seal pex pipes to extend hoses to drain and flush properly

please dispose of coolant properly

thanks to TJWALKER (serior member) for the CLR idea

 

Same method applies for your 90. I did it on my 88 about a month ago. But, I flushed everything. block, radiator and heater core. Previous owner put bars leak in and I wanted it out.

only difference is if you have a closed system like mine, you need to disconnect the heater hoses at the heater core, attach different hoses and flush that way. I just used an old piece of heater hose I had laying around.