Heater Core Flush

[blueglide88]

My 2001 Blazer has had some poor heat so before resorting to an expensive heater core replacement, I decided to flush it. I bought a cheap transfer pump off Amazon and a gallon of CLR.

I started with tap water and the first 5 minutes flushed ouit some black junk. I ditched the bucket and refilled it haf way with water, then added 1/2 gallon CLR. I changed hoses a few times, flushing forward, and back flushing. I also stopped/started the pump many times to shock the core. In the first pic you see the cheap transfer pump. It failed in less than and hour and a half. My neighbor gave me a submersible pump that saved the day. When the 1st pump failed I ditched that bucket of solution and refilled the same way. In total I ran it about 3 hours, then close to another hour flushing with several clean buckets of water. I now have blast furnace type heat!!!!!

 

[JHZR2]

No reason a 2001 blazer should have poor heat if the right dexcool and cap were used. Recommend verifying that you don’t have Dex-sludge in the rest of your system due to a mistaken addition of a silicated coolant…

 

[JohnnyG]

Back in those years GM was also quite fond of using Bar's leak right from the factory. This was a precautionary thing due to occasional porosity in the casting of aluminum blocks and heads. I think that casting issue was solved right around 2003 or so.
The Bar's leak usually never caused issues, but tended to hang around for the life of the cooling system.

 

[Fordiesel69]

Begin saving now for a heater core replacement. No doubt this will begin to leak anywhere from right now to 1 year from now.

 

[JTK]

I've seen South Main Auto use this same method on heater cores. It's worth a shot for sure.

 

[blueglide88]

Begin saving now for a heater core replacement. No doubt this will begin to leak anywhere from right now to 1 year from now.

Thanks for the positive vibes

 

[blueglide88]

I've seen South Main Auto use this same method on heater cores. It's worth a shot for sure.

That's where I got the idea from. He says in the video he has done lots of them like this and hasn't had any customer complaints or failures.

 

[blueglide88]

Another thing to note about this method is that Honda has a Service Bulletin 14-063 that uses this exact same method. That's where South Main Auto got the idea. As he says in his video, "if it's good enough for Honda, it's good enough for me"

 

[KrisZ]

That’s how you flush tankless water heaters.
It’s a good method for sure and thanks for sharing.
You can also try with hot water solution, that usually helps as well.

 

[blueglide88]

So about a week ago, my heat suddenly starting getting cold again. I refuse to tear apart the dash to change that heater core so since I am off for two weeks over the holidays, I started to flush it again. This time using full strength CLR Pro. The Pro stuff is safe to use with aluminum. I have it on a timer. It runs for 3 hours and shuts off for 1 hr. I ran it like that the past 3 days and I will run it until Friday when I change out new fluid. So far it’s been just a Backflush but I will at some point reverse the flow. I’ll probably run it until next week sometime. Hopefully this gets it done. I have noticed the fluid started clear green and now it’s kind is a milky green. Fingers crossed

 

[Chris142]

The heater isn't the problem. It's the victim of a dirty cooling system. You need to get the block and radiator clean.

 

[blueglide88]

You may be right but I am confused. I recently had the intake manifold gasket replaced and at that point they flushed the system. I think when I’m done I’ll add some cooling system cleaner then have it flushed again

 

[blueglide88]

The system was also flushed about 5 years and about 25k ago

 

[GON]

Your heater core will soon start leaking. You are off for two weeks. Might be a good time to pull apart the dash and replace the heater core.

I did the heater core on my youngest son's 1998 S10. Hard on my back, but overall a lengthy but simple job. Just have a dozen lock bags to store and label all the removed nuts and bolts.

 

[Chris142]

You may be right but I am confused. I recently had the intake manifold gasket replaced and at that point they flushed the system. I think when I’m done I’ll add some cooling system cleaner then have it flushed again

The only way to get the junk out of the water passages in the sides of the block is to remove the drain plugs or a freeze plug on each side then flush it with pressurized air and water.

If you don't do this it's going to keep coming back. A stop gap is to put a filter on the heater hose that feeds the heater.

 

[Coolant Kid]

Begin saving now for a heater core replacement. No doubt this will begin to leak anywhere from right now to 1 year from now.

This. Absolutely this.

 

[Langanobob]

I did something similar to a Subaru years ago when I discovered that their factory recommended “Cooling System Conditioner” is a heater core clogger.

 

[f355spider]

Begin saving now for a heater core replacement. No doubt this will begin to leak anywhere from right now to 1 year from now.

He may be just fine. I was having issues on my BMW with no heat on the passenger side and low heat on the drivers side. Shop flushed the heater core with just a garden hose and gunk came out and it was good for a year, but then problem returned.

The shop recommended I put Liqui Moly radiator flush in the car before driving to their shop (an hour away), then when I got there, they used this tool they had recently purchased:

Its been over two years, still heats fine. No leaks, no issue. Car is 24 years old and 371k miles.
The annoying thing is I only use factory BMW G48 coolant and get it changed every 3 to 4 years since new. Not sure why this black gunk was forming in the heater core.

 

[Tempest1]

I bought that Lisle tool earlier this year to flush my heater core and it worked very well. Just have to take it easy and not hit it full blast unless you have regulated water / air pressure.

 

[johnmyster]

So about a week ago, my heat suddenly starting getting cold again. I refuse to tear apart the dash to change that heater core so since I am off for two weeks over the holidays, I started to flush it again. This time using full strength CLR Pro. The Pro stuff is safe to use with aluminum. I have it on a timer. It runs for 3 hours and shuts off for 1 hr. I ran it like that the past 3 days and I will run it until Friday when I change out new fluid. So far it’s been just a Backflush but I will at some point reverse the flow. I’ll probably run it until next week sometime. Hopefully this gets it done. I have noticed the fluid started clear green and now it’s kind is a milky green. Fingers crossed

How much of your heater core did you dissolve away?