Heater blowing cold

Did you flush out the radiator?

How fast did you add coolant? You need to fill it very slowly, and with little amounts.
Takes longer, but no trapped air.

 

Replacing the rotor/impeller would be my plan "A". Pull out your existing water pump and check how hard it is to rotate the impeller. If there is resistance to it being rotated, pull out the impeller and look at the white plastic that covers the magnet end. Do you see splits or swelling in the white plastic. If so, I would try just replacing the impeller. If not, I would replace the complete water pump (plan "B").

 

Hi again, Thanks for your advice. I ordered the rotor, but the original one was seized and didn't come out from the shaft; I replaced the whole water pump, and the problem was solved!!

 

Did you remove the little "O" ring on the shaft to remove the empeller?
At least you found the issue!.

 

Yes, I did. But the rotor was just locked!

 

That does not surprise me since the previous owner put stop leak in the coolant.

 

Now there is a small issue, my engine temperature won't go more than 136 f or 55 c usually in the city. I use to drive 5-6 hours a day and heater is really hot in med fan, and still a bit hot on high but normal temperature in normal mode is that.

 

NewNow there is a small issue, my engine temperature won't go more than 136 f or 55 c usually in the city. I use to drive 5-6 hours a day and heater is really hot in med fan, and still a bit hot on high but normal temperature in normal mode is that.

 

It had the fake stop leak. It clogs everything except the leak.
So your radiator, heater core, thermostad, coolant pump, and every little
passage for the head and more are clogged.
Using white vinegar and water mix might clean it out.....

Everyone that has gone through this has had a nightmare of a problem trying
to get it all cleared out.