I was thinking about flushing the heater core again, because I think I rushed it the first time.

So I was wondering if this is a good plan:

1) run water through both hoses 3 times
2) blow the water out and add vinegar and let it sit for 24 hours
3) run water through both hoses again 3 times
4) blow the water out
5) add coolant and get all the air out of the system
6) test drive

Does this sound good to do?

I would really appreciate the feedback thanks!

 

Be careful using shop air to blow it out; the system never sees much over the 16 psi radiator cap relief pressure...

I used a pond pump in a 5 gallon bucket to circulate stronger-than-instructions-state coolant flush and deionized water through the core; worked great... I rinsed it out by pouring deionized water into the hose and then just hooked it up. That extra bit of water isn't going to affect anything...

 

I'd be very careful with air pressure. I've never felt the need to use it at all. I have two 4' lengths of heater hose, one 3/4" and one 11/16". I clamp one end of each to the heater core and hang them over the fender. I alternate running the garden hose through each end for about 20 minutes or so. Household water pressure is about 60 p.s.i. (around here anyway) and I only run it about 75% of that while flushing the core out.

I picked up a heater core flushing tool like the one below about 40 years ago and still have it. I'd make one now before I'd pay for this one. They've gone up in price! The most simple of garden hose nozzles would work just as well.

Lisle HEATER CORE BACKFLUSH TOOL | lis60900 | ohcanadasupply.ca

 

I haven’t done this, but I’ve considered using something like Coca Cola to clean out a heater core. The acids and carbonation should do a good job of getting sediments out of it without damage, and would rinse out with water as easily as anything else.