lexusls430

Hey everyone, i just replaced my timing belt and water pump and i picked up the car and there is just a little heat coming out but when i raise the temp to like 84 there is no heat at all and just cold air comes out. The rear heat works great. What could be the problem??

V8_Fan

I presume this is for a LX? How's your coolant level (check the bottle)? Make sure the two coolant hoses are plugged into their ports in the firewall. If they forgot to install them, you'd certainly get no heat, but you might also get coolant spewing all over the place if you turn the front heater on (there's usually some kind of valve that allows hot coolant to flow through the heater core, which is in the dash). I'm not sure where this valve is on the LX (if it's in the engine compartment (more likely) or in the heater unit in the dash. FYI, the rear heater has its own dedicated two hoses that plug into the heater core, so they will work independently from one another.

Gohawks63

You probably have air in the cooling system which is preventing the coolant from passing through the heater core.

Some engines have a bleeder valve right (don't recall if or where there is one on this engine) on the thermostat housing. As the engine warms, you open the valve until coolant begins to flow. You obviously need to be careful not to burn yourself.

I'm pretty confident that's your issue.

V8_Fan

If you have air in the system, you need to burp it. Park the vehicle on an upwards slope (engine cold), pop the hood and remove the radiator cap. Run engine w/ front & rear heaters full blast, let engine warm up so the thermostat opens (you will see the coolant in the radiator "move" like a flowing river and it'll turn warm). The air bubble can only exit the engine via the thermostat, which is why you need to get the engine hot (you can rev it at 2000 rpm for a minute or two to speed things up). Once the thermo has opened, you should be okay. Cap the radiator and you're good to go. Check the level of coolant in the bottle to make sure it's within the cold-hot range. If not, add some DISTILLED water to the bottle (bottled reverse osmosis water if you have no steam distilled).

lexusls430

Thanks guys, im guessing it was just air. Heat is working great now.

V8_Fan

If it was a pocket of air, it should have exited the block via the thermostat and out the radiator via the bottle the first time you drove the vehicle and got the engine hot enough.