2001 slow to heat
 

My 2001 RCSB with the 5.3 just does not build heat fast in the colder months even if its just in the 40s let alone when we get to the sub zero temps that are around the corner.
Takes forever to get up to just under the 210 mark
Replaced the T stat once and the water pump got replaced when it started leaking neither one made any difference

Any ideas?
Thanks!

Re: 2001 slow to heat
 

Are you sure the thermostat is the correct temp and it's opening when it's supposed to?

Do you have an air pocket in the cooling system or low coolant level?

Are you getting heat or is the heater blowing colder than it should with the engine warmed up?
I've had heater cores rot out internally between the intake and outflow ports on 1978 Dodge W200 Power Wagon and one of my mid 80's Subaru Brats. There's a separator panel in some heater cores to force the coolant to flow through half of the heat exchanger and back through the other half that rotted through in those rigs. The coolant was almost completely bypassing the failed heat exchangers through the rusted out separator panel. A replacement heater core made them heat too well.

Last but not least is the temp gauge actually reflecting the real engine temp?
Failing Engine Coolant Temp senders can read lower than actual and react slowly to temp changes.

Re: 2001 slow to heat
 

Thanks...
I put a standard thermostat in it about a year before the water pump started leaking and also played around with the coolant level without any change
The gauge is pretty much saying what the heater is putting out.
This truck has been like this since I bought it three years ago.
City driving this thing takes forever to get close to 210

It is a Ca. truck I guess they don't need much heat anyway..

Re: 2001 slow to heat
 

You can get 165°, 180°, & 195° thermostats.
I always specify the temperature. I've had the parts guys hand me 180° stats because they didn't have the 195
I believe the stock stat in the 2001 4.8/5.3L is 195°.

Vacuum cooling system fillers are almost a must have tool anymore.

Re: 2001 slow to heat
 

These trucks tend to plug the water side of the heater core. I am not sure why it happens but it does. Just helped my friend do his, night and day difference in the cab heat.
Just pull the heater hoses and back flush with a hose. No high pressured needed.
Hook it back up and enjoy. Be careful as the plastic quick disconnects get fragile with age. It takes a special tool to get them off.
Stainless steel replacement are available but not necessary. Just be aware of the possibility of them braking one off. I recommend replacing them to avoid issues later.
I had to do mine about once a year till three years ago I flushed the system and replaced the antifreeze. Been good since then.