Overheating Ls400 At Idle - Tried Everything?

[LS400FAN]

My 1995 Lexus ls400 heats up at idle, I have replaced fan clutch, thermostat, water pump, flushed radiator (and washed fins,condensor) , AC fan is working, gets air above thermostat at filler port, replaced overfill tank.....what the heck? This only occurs at low engine rpm's, typically when idling with ac on. In slow traffic (35) putting the stick in 2nd will raise rpms to 2k and temp will go down. I am not losing any antifreeze anywhere, but after about a week, the filler port above the thermostat will have air and will take about a cup of liquid....What the?

[wwest]

My 1995 Lexus ls400 heats up at idle, I have replaced fan clutch, thermostat, water pump, flushed radiator (and washed fins,condensor) , AC fan is working, gets air above thermostat at filler port, replaced overfill tank.....what the heck? This only occurs at low engine rpm's, typically when idling with ac on. In slow traffic (35) putting the stick in 2nd will raise rpms to 2k and temp will go down. I am not losing any antifreeze anywhere, but after about a week, the filler port above the thermostat will have air and will take about a cup of liquid....What the?

Replace the "plugged up" catalytic converter.

[carlhpretired]

My 1995 Lexus ls400 heats up at idle, I have replaced fan clutch, thermostat, water pump, flushed radiator (and washed fins,condensor) , AC fan is working, gets air above thermostat at filler port, replaced overfill tank.....what the heck? This only occurs at low engine rpm's, typically when idling with ac on. In slow traffic (35) putting the stick in 2nd will raise rpms to 2k and temp will go down. I am not losing any antifreeze anywhere, but after about a week, the filler port above the thermostat will have air and will take about a cup of liquid....What the?

Some of the passages in the radiator may be clogged. I have a 1990 LS400 that had a similar problem, but in my case the electric cooling fans kept coming

on even though the temperature gauge indicated normal. These radiators have an aluminum core with very small passages. If you use the wrong type of coolant or inadvertently top off the coolant with anything except the special long-life (red in color) coolant designed specifically for aluminum radiators, it will have a corrosive effect that will clog the passages in the core. If this is the problem, it can be verified by doing a temperature scan of the radiator that will reveal hot spots (Lexus dealership service departments have the tools and procedures to do this testing).

In my case, the test revealed that this was the problem and replacing the radiator fixed it (after wasting $250.00 on a new fan clutch, and another $76.00 on a new radiator cooling fan temperature switch, of course!)

[legend4life]

My 1995 Lexus ls400 heats up at idle, I have replaced fan clutch, thermostat, water pump, flushed radiator (and washed fins,condensor) , AC fan is working, gets air above thermostat at filler port, replaced overfill tank.....what the heck? This only occurs at low engine rpm's, typically when idling with ac on. In slow traffic (35) putting the stick in 2nd will raise rpms to 2k and temp will go down. I am not losing any antifreeze anywhere, but after about a week, the filler port above the thermostat will have air and will take about a cup of liquid....What the?

Sounds like there could be air in the cooling system.

[Harky]

Yup...could be an air bubble. There is a procedure for refilling the cooling system and purging the air. Don't remember the details...

Have you checked in the "How To's"??

[LS400FAN]

Yup...could be an air bubble. There is a procedure for refilling the cooling system and purging the air. Don't remember the details...

Have you checked in the "How To's"??

Thanks all, I had done the air purge repeatedly, replaced the radiator and that seems to have fixed the problem. I need to get some of the red antifreeze though, had to fill the new rad with the green stuff. I sure wish I had tried the rad first, but I flushed it and did not see any kind of corrosion or 'rust' just the good red stuff, so I figured that was not the problem....256,000 and still going strong!!

[mastertech]

these are a real b-eitch to get to burp.. after cooling down it is common for the overfill to be empty a few times cause as it burps it sucks more in... just check it a few times after...

[OmarG]

i had the same problem with my ls400. I was freakin out! But thankfully my dad told me about the air bubbles trapped in the system. What a relief! i thought my car was toast.