Have a 2003 Honda Pilot that was purchased new. The vehicle has been exclusively serviced by a certified Honda dealership for ALL service. At 3 years and 55K of service, coolant was flushed by the dealer. Then, at 5 years and 76K miles started having problems with low heater output. Dealer flushed the heater cores and stated "heater core has restriction, may need to be replaced". The heat was somewhat better until this winter, then became unusable. Took back to dealer and they reflushed the core and stated the core needed to be replaced. By the way, the coolant was also flushed at the 100K timing belt service.

Dealer rep also pulled the radiator cap and pointed out visible corrosion on the inner passages of the radiator. I then asked for a review of the service records. How can 7 Yr, 120K coolant that was changed twice the recommended interval have a corrosion problem? At this point the dealer wanted 1300 just to change the front core, and mentioned the back core and radiator needed to be changed as well. I was looking at potential a 2K plus bill. I called Honda customer service, but they mentioned I was "out of warranty. I kept asking them why their coolant was defective?

I suspect several possible things here: defective honda coolant, poor honda coolant design, or bad metalurgy in the honda heater cores. This situation is completely unsat.

 

the heater in my 04 is shot too.
blows air colder than the a/c. lol

 

I'm having the same problem with my 04 civic 1.7 also

 

here's a possibility... sure, they used a long life coolant

but, did they also used distilled water?

i use distilled water to flush out the old (2x) instead of regular water from the tap/hose.

before

refilling with OEM or similar (prestone long life) fluid & distilled water mixture

 

Shops don't generally use distalled water even though that would be ideal. Also, not sure if anyone has mentioned this to you but if you have combusion gasses getting into the coolant (from a blown headgasket) you will end up with corrosion like that. I've seen several times where Hondas will blow headgaskets with very few typical symptoms; no mixing of oil and coolant, no power lose, no white smoke, etc. It's easy enough to check with a block tester. I really wouldn't jump on the coolant.

 

In agree with 94EG8 Do the leak down test. I cant imagine Honda coolant doing that to the system. Maybe they didn't do all the maintenance that they claimed to do. I use ony Honda coolant in all my Hondas, from my daily driven Odyssey with 201000 miles to my 493whp GSR and never ever had a problem. Check the compression.