My 2005 Tahoe with 165K miles on it has a issue with the heater recently. I set temp up to like 80 and hit AUTO and it just blows cold air even after the engine is warmed up. This goes on for 30 to 45 minute sand then it starts to work sometimes. I took it to the local Chevy dealership and they told me the hoses from the engine to the firewall/heater core were leaking and the water pump show signs of leaking. Cost to repair is around $1400 I think this diagnosis is suspect! What is your opinion and any recommendations? Thanks in Advance!