help!!help!!no heat in 90 silv.

sorry for being a computer dolt.finally found correct site.I have a 1990 silverado.the heater is not very warm.I have replaced the waterpump(leaking).2 thermostats.1st one a dud.It seems the circulation is poor.the temp guage is running at aprox.65 celcius.please dont ask what that is in farenheight.all i can tell you is the guage sits at about 1/4.halfway being 100celcius.when i open the rad cap i can see that the coolant comming back from the heater core is just a little trickle.when i rev the engine it increases only slightly.i have also replaced the water restricter nipple which is located at the back of the intake manifold and connects by a metal pipe to the heater core inlet.some folks remove the restricter and replace with hose connector and new rubber heater hose.any ideas??
also when i remove the rad cap while engine hot and running,the coolant seems to rise to the top and then falls back down almost out of sight.this is happening about every 20 seconds.sometimes the coolant overflows while it rises to the top.could this be an air lock?Also does anybody know if the heater controls on this truck are run by vacuum.when i rev the engine,the heat gets warmer.but never hot.help please.........its getting darn cold up in canada

Do you have to always add water to the engine? Does the cooling system hold pressure while running? 65 degrees celsius is only 149 fahrenheit. you should be around 200 fahrenheit when fully warmed up.

Do you have to always add water to the engine? Does the cooling system hold pressure while running? 65 degrees celsius is only 149 fahrenheit. you should be around 200 fahrenheit when fully warmed up.
well i gambled....took the heater hoses off at the core,drove over to the car wash and used high pressure to blow core out of both pipes.llyou want to see crap come out!!!! before i did this we were very cold going to my daughters high school and back.(-10celcius in saskatchewan right now)Now the darn thing will cook you out.Yet the rest of the cooling system is relatively clean.what gives.It has an aluminum core...so im told.could the aluminum be making the debri stick to the core?anyway thanks for the response.glad ive got heat and the job is done!!!

If someone used that Alumiseal crap (or equivlent), that's exactly what it does cloggs small leaks in core passes. Problem is it sticks to everything else. I used to use chili powder to fix radiator leaks.Don't ask me how but it works on small holes.