smokespeed

Hey guys my 98 ls is overheating when I'm at idle with the ac on. Everything seems fine besides this issue, the air blows cold and I just can't seem to figure it out. I have noticed that I don't hear any fans running though when this happens. Can anyone help me figure this out?

LScowboyLS

most likely possible causes of overheating at idle with A/C on:

worn fan clutch
electric fan not operating due to motor failure
electric fan temp sensor bad
debris in condenser fins (leaves, bugs, plastic bag, etc.)
clogged radiator (replacement is only effective fix)
thermostat
refrigerant overcharge

dc893

and the easy one, low coolant

LScowboyLS

or depleted or incorrect coolant, such as plain water

additional items to verify:

cooling fan relay
A/C pressure switch on top of A/C dryer

RA40

iTrader: (6)

+1, this time of year we'll see plenty of these overheating running hot issues. 30K intervals so get those cooling systems checked. We don't like reading about BHG, chocolate milk coolant problems.

python

iTrader: (4)

if the electric fans aren't working it wont over heat on the freeway but once u exit into city traffic it will
"plain water" wont cause this either..the only time having just water in will cause over heating is if it reaches boiling temps.
not sure how the pressure switch is related to over heating

LScowboyLS

perhaps this chart will help make it more understandable:

Attachment 498722

here is an example, say the head (high) pressure side of an A/C were overcharged, or the condenser was blocked with dead bugs or whatever - the A/C pressure switch, sensing the high pressure, would turn on the electric fan and thereby prevent the overly hot refrigerant in the condenser from overheating the car. If the pressure switch was defective, this turn on of the electric fan would not happen until the coolant temp were over 194F and at that point the cooling of the fan may not be able to catch up with the overall cooling system heat load.

smokespeed

Today I sprayed the off the radiator and the area around it. I drove the car for a bit today and the problem didnt happen. Ill keep u guys posted and let u know whats up.

LScowboyLS

do you mean the condenser? - you cannot see the fins of the radiator from standing in front of the car, what you see is the condenser that is sandwiched up against it

you can only see the back of the radiator, and only then by looking back from the engine area towards the front

did you mean that you sprayed it off with water? compressed air?

smokespeed

I opened the hood and sprayed down what I think is the radiator (the big wavey box behind the front fan) and the area around it. It was really clogged with bugs and debris. I haven't had the issue since.

LScowboyLS

yes, when viewed from the front of the car, you are looking at the A/C condenser, and when viewing from the engine side, you are looking at the radiator, they are sandwiched together and look like the same finned piece!

lexusrolex

my 97 ls400 over heats when I'm going under 30mph or when I'm i traffic, but it starts cooling down when i start picking up speed like 60 or 70mph, I'm trying to figure out whats wrong, I'm new to this forum some help me out

Greg5OH

^that sounds like a fan issue. The high speed air is able to cool the motor once your moving quik, but at low speed you need the fan to pull the air thru the cooling grid. fan cluth may not be engaging.

SynicalVip

iTrader: (2)

Having sort of the same issue with my 96 LS, temp would rise if sit at idle too long but will start to go down when rev it up. I can just sit at idle in neutral or park and just rev it up steady at 1000+ rpm then the temp would go down.

RA40

iTrader: (6)

Not even that hot yet. If you can rev and the temp goes down, the fan is pulling air thought but that still doesn't rule out the fan clutch or other sensor. Doing the basics to have fresh coolant, thermostat and clearing the A/C condenser and radiator fins of debris first. When was the last cooling system maintenance?

DIY is reasonable, ~$20 for the thermostat, $3 gasket, $30 jug of the LL red coolant. $1 for a gallon of distilled water. 20-30 minutes later, it is done. As well if the radiator drain **** is old, replace it. $10 for the drain ****, $3 for the O-ring. Cant remember what a radiator cap goes for. prices are full retail from the dealer. I do a thermostat, radiator cap and coolant drain every 30K.