Do I need to flush my system before I change the heater core? I've only had the car a few months and the antifreeze looks pretty good. The car was only driven in the summer so I'm not sure how long the heater hasn't work or been clogged. Any thoughts?

By the way that top bolt sucks but it was much easier to reach when I remove the computer and mounting bracket. It allowed me to get one hand in there to hold my socket on the top bolt.

 

AF can turn acidy in 3 to 5 years no matter how many miles is on it.
It really wouldn't hurt to put $20 worth of new AF in it. Corrosion protection in old cars is important along with freeze and boil protection.

That coil is clogged because ??? is there stuff settling, scale etc ?

I would change it.

 

You're going to lose a fair amount of coolant when you take the two hoses that connect to the heater core near the firewall off anyways. A fresh batch of antifreeze/water is recommended. It's a cheap thing to do and once the new heater core is installed, you shouldn't have leaks to worry about for a long time.

 

Given up on heater core for the moment. Before I pulled the core, I tried to unclog the core one more time. It worked heat was kicking! However, it soon clogged again. So I decided to drain everything backflush etc. Spent a few hours flushing filled with prestone cleaner and distilled water. Tried to flush the core again but no luck. I'm going to log a few hours driving with the cleaner in there...drain and flush again. Will also try and flush the core again. There was a lot of gunk in my cooling system so I assume it will take some time to clean it all out. Anyone have any other suggestions/tips?

 

As suspected, I left with clean cleaner and distilled water and came home with an ugly brown mess! Nasty! Anyway, I'm off to get it cleaned at a radiator shop tomorrow. I just don't have time to flush it again like I did the other night!

 

Heater Cores are a pain in the @$$. I would pay more for one that is much better designed just so I wouldnt have to find that rear bolt. You would think they could make one out of stainless or with a coating of somekind.