mvbls400

97 ls400 when I turn the heater on it just stays the same temperature. Is it the heater core? Any other possibilities? How much to fix heater core?

Kansas

A common cause of limited or no heat from a heater is a thermostat stuck in the open position. Thermostats sometimes fail in warmer climates (e.g. California, southern states) where owners neglect to use adequate antifreeze -- antifreeze contains anticorrosion additives which help keep thermostats functioning.

Of course, it could be a bad heater valve, servo that controls the heater valve, heater core or a number of other expensive components.

You could remove the thermostat and test it in a pot of boiling water to see if it closes or just go ahead and replace it -- it is an inexpensive part.

PureDrifter

iTrader: (10)

air bubble. search for it.

LiCelsior

iTrader: (32)

thermo stuck open or yep an air pocket...

spazzy67

Thanks for replies!

I took out thermostat and tested in pot of boiling water and it is functioning properly, as was the old one I replaced!

What is the best way to bleed the system to remove an air pocket? Could the reservoir cap have anything to do with it??

Thanks!

Amskeptic

Not likely to have anything to do with it.

The best way to bleed the system to remove an air pocket is to make sure engine is stone cold with the car level or on a slight upgrade. Crack loose the big bolt on top of the thermostat housing and if it does not weep coolant, take it off entirely so that you can carefully install coolant. Let it trickle in as slowly as it wants to. Once full, tighten that bolt to 14 ft/lbs or so (snug with a little yank), start the engine with heater on 85 fan on high with sunroof open, and run the revs from idle to 3,000 rpm or so. Keep an eye on the coolant level in the reservoir. It will draw down under high rpms (it will start to shoot upwards when you go back to idle as the thermostat opens if you dally). Get your coolant level to "cold" middle area at the higher rpm, and put the cap on securely. Drive the car in lower gears on surface streets with heater on around 3,000 rpm or so. Allow to cool and check reservoir level stone cold. These systems self-bleed, but you have to get some velocity in the water jackets and heater core.
Colin