2005 Silverado heater

Truck heats up fine while it is in park and idling. When you put it in drive, the temperature gauge starts dropping and blows only cold air in drive. I replaced the thermostat but it continues to do the same thing.

If this is a Silverado pick up this is the wrong forum, seems so. I am moving this to the Sil. forum above in the trucks.

Truck heats up fine while it is in park and idling. When you put it in drive, the temperature gauge starts dropping and blows only cold air in drive. I replaced the thermostat but it continues to do the same thing.

my guess is the coolant system needs to be burped.

start cold engine . remove coolant cap add coolant to the cold fill mark . rev engine to 2,ooo rpm every 2 min . repeat until engine is at normal operating temp. this is how the coolant system is purged of air.


whenever coolant is replaced/changed you remove the heater core hoses from the engine. then you flush out the heater core in both directions until the flow is clear and unrestricted.

always use dexcool at 60% to 40% distilled water. 2 to 1 ratio will give max protection and with these engines you need it.

replace every 3-4 yrs not 5 years.

my guess is the coolant system needs to be burped.

start cold engine . remove coolant cap add coolant to the cold fill mark . rev engine to 2,ooo rpm every 2 min . repeat until engine is at normal operating temp. this is how the coolant system is purged of air.


whenever coolant is replaced/changed you remove the heater core hoses from the engine. then you flush out the heater core in both directions until the flow is clear and unrestricted.

always use dexcool at 60% to 40% distilled water. 2 to 1 ratio will give max protection and with these engines you need it.

replace every 3-4 yrs not 5 years.

Thanks. I will give it a try.

Thanks. I will give it a try.

post back how it went. if air is in the system you will need to add coolant for sure. air bubble is usually in the heater core.

if this is not correcting this, it may mean some expensive repair work is required.

post back how it went. if air is in the system you will need to add coolant for sure. air bubble is usually in the heater core.

if this is not correcting this, it may mean some expensive repair work is required.

It worked! Thanks again for the help.

It worked! Thanks again for the help.



thanks for the feed back . goodluck.