JamesB94

Hi,

The heater will start to get warm and then will suddenly go cold. I just replaced the coolant and nothing else seems to be wrong. Speed/acceleratiom doesn't appear to affect it.

Anything else I need to check? I'm making sure it isn't something simple that I can fix myself before taking it in for service.

Tom57

Since you just replaced the coolant, it's very likely that you have air in the system all the way at the heater core. You'll need to check the coolant level, and add more coolant when the engine reaches operating temperature. Also check the overflow reservoir and add to the "full" mark.

rkw77080

And after you are certain that you have purged all the air out of the system, the next thing to check is the water valve. It is located on the firewall immediately to the right of the battery (viewing from front of the car). The heater temperature is controlled by regulating coolant flow into the heater radiator inside the cabin. The water valve is operated with a cable driven by a servomotor (hidden).

With the engine running and up to temperature, turn your A/C temperature to the lowest setting and observe the position of the water valve lever. At the lowest temperature, I believe the cable should be fully retracted (see photo below). Then repeat with the temperature at the highest setting to move the water valve lever. This will confirm that the water valve is functioning properly to allow hot coolant into the heater radiator to heat your car. In fact, if the water valve is working as described above, then we can be fairly certain that not enough hot coolant is available - either caused by air gap, or some sort of blockage.



The LS430 cabin heater design is very simple - it heats your cabin by using engine coolant exclusively, no electric heating. When you first start up your engine, the engine coolant circulates around the engine until it reaches the temperature setting of the thermostat. At which time, engine coolant is allow to flow through the coolant radiator to remove heat. Meanwhile, the hot coolant is available to be diverted into the cabin heat radiator. The water valve pictured above regulates coolant flow to maintain your temperature setting.

arcteryx

When you flushed the coolant, did you also remove the block plugs? this would ensure that you performed a proper flush and no solids were left behind, possibly creating a (partial) blockage.

randal

Great pics and explanation, rkw! The heater valve position is the first place to look.

I would agree with air being in the system except that the poster states that RPM has no affect on the heat level. Usually, heat comes with higher RPM and goes away at idle when an air bubble exists. That is not the case here.

One thing I wanted to ask James was whether or not the heat worked fine BEFORE the coolant change. If so, then it would appear to be lack of purging. As long as that is all that was done (coolant change). Sometimes other things were also changed that could explain the issue.

sushiboiii

iTrader: (1)

also invest in one of these it will help alot when it comes to bleeding a system.