sha4000

iTrader: (1)

Forgive my ignorance since I'm new to the 460 and It's a totally different animal than my 400 and 430 for that fact. I searched for days with lots of different word combinations on my no heat problem and I still can't figure out what the issue is exactly. My heater on high blows cool to luke warm air at times. I might of had some good heat once in the 2 weeks I've owned the car. I see the previous owner complained about this same issue back in 2013 and it was stated it was low on coolant from a leak in the radiator. Lexus installed a new radiator and the PO was back a week later complaining about the same issue. The tech checked the water pump and thermostat and did not see any issues but then said the HVAC box was faulty and the PO declined the repair. We all know that the dealership does not really diagnose lots of issues and when they get stumped they tend to change parts until the find the problem. I'm assuming the tech flushed and bled the system correctly prior to returning the car. Also the PO serviced this car religiously at the dealer up to 80k so I would think they would do whatever to accommodate him. This car basically sat idle from 2014 till i purchased it. I specifically asked if the HVAC issue was addressed and was told it was through emails and phones calls since I had to fly to Chicago to purchased it. If it does turn out to be the HVAC I might be on the hook but I'm ok with that since everything else is almost perfect other than the ML amp which I'm keeping an eye on. I'm the ultimate DIY guy so I have no problem doing whatever work I have to do within reason. I am in contact with the dealer about these issues but I don't have high hopes since it's so far away.

My first thought was that there was air in the system so I did my universal bleed procedure which did not help. After a couple of days I ran the car up on ramps to get the reservoir higher than the rest of the system and followed the instruction on the label of the reservoir to a T. I squeezed both hoses repeatedly Idled for 20 minutes, closed the cap and then ran the car for 10 minutes at 2500 rpm and still no success. All the while I saw no air bubbles and the coolant level NEVER dropped. When checking hoses the lower hose which is connected to the Thermostat did seem to take a little longer to heat up when I was waiting for it to open up but I did have the heat on high the whole time that might account for that though. I see no crystallized coolant in the engine that would lead to water pump issues either. I felt the 2 hoses coming out of the heater core and the felt warm which leads me to believe coolant is getting in there. I can't see any heater control valve like on the 400 to let me know it's opening and closing. AC is working properly and there are no codes. I'm getting air from all the ducts and at different speeds.

Now I'm a bit stumped and about to take it to the dealer because I need this addressed before it gets cold. Now to my question. Does the thermostat and housing come as one unit or can I just get a new one and place it in the housing? What brand of thermostat and water pump if necessary do you guys recommend beside Aisin?

213374U

Bleed the system again without the heat running (at first) as even a small bubble in the line can prevent the thermostat from operating as it should. If coolant is being run through the heater core with a fan running it will take much longer for everything to come up to temp and for the thermostat to open. Once engine is fully warmed up and you don't see bubbles at idle, turn on the heat and run it at 2K rpm for 5 minutes, then turn the heat off and go back to watch for more bubbles at idle. When 4-5 minutes pass with no bubbles, put the cap back on the overflow tank and then run it at 2K rpm for 5 more minutes. Turn the car off, let it cool, and top off the overflow tank if needed.

I had the same issue with mine since I bought it in February, but since it warmed up shortly after purchase I never bothered with it. Topped everything off and bled it last night and have great heat even when sitting at idle today. Gonna keep an eye on the level but, just like you, I was unable to see any signs of a bad water pump. If the problem returns I'll likely be replacing the pump and rad hoses, along with the serpentine belt and tensioner pulley.

Doublebase

If it's not an actual coolant issue then unfortunately it's probably a stuck actuator in the hvac box, most likely a blend door is not opening all the way. So the dealer is probably correct. You could try to find someone that can diagnose those actuators, see if they move when commanded by a scan tool, then at least you'd know. But I wouldn't be thinking it's the thermostat at this point, especially if your engine temp gauge is where it's supposed to be.

sha4000

iTrader: (1)

Thanks for the replies. It's a little warmer out today so I turned on the heat and I got some hot air so I'm a bit perplexed. I contacted the dealer in Chicago and he indicated that he would try to work with me through this issue. I will try to bleed it without the heat on and see what happens. I wonder if Techstream will allow me to test the actuators?

sha4000

iTrader: (1)

This is what I'm leaning towards. I had slight heat until I got on the highway and then it turned cool.

213374U

Oh, I doubt it's anything to do with the cooling system then if the heat went cold while in motion. Air in the system or thermostat not operating properly will see you losing heat when sitting idle and then heat returning when you being to move, not the other way around.

sha4000

iTrader: (1)

Does anyone know the heater control valve is located? I've scanned the firewall and can't seem to find it.

roadfrog

Hopefully this will help:

sha4000

iTrader: (1)

Thanks that diagram will come in handy if I have to pull the HVAC. I want to make sure sure the heater control valve is opening and closing. Everything seems to be electronically controlled on this car. There does not seem to be a throttle cable to rev the car from under the hood either.

213374U

Drive by wire. As you said, everything is electronic.

We're all gonna be in a bad way when the EMP hits :P

Doublebase

This does help but holy crap! Usually it's just a few mode doors and a blend door, this isn't very complicated because there's a number of things that could cause it.

First thing I don't do is go to the dash control head on the car and determine which side is the problem, if it's nothin sides - both sides are blowing the same temp despite what you command it to do? I think you can narrow it down to three servos that could be the culprit. Tough repair.

sha4000

iTrader: (1)

All the vents are blowing at the same temp. What an EMP?

roadfrog

Electromagnetic pulse. All unshielded electronics will be fried when it hits - either by natural cause (solar flares), or nuclear explosion (in which case, not having a working car will be the least of your worries).

sha4000

iTrader: (1)

No kidding. I thought it might hanger been some new car tech.

sktn77a

iTrader: (2)

Holy cow! And I thought my '99 RX was a pain with only 3 HVAC servos!