Sc400 tries to overheat while stopped with ac on

[918soarer]

hey guys this is the only mechanical problem i've ever had with my sc, it only happens when im sitting at a red light with my AC on and the temp guage starts climbing and it will get really hot untill i start going and it will slowly cool back off. i replaced the water pump and thermostat about 15k ago and it is full on coolant. im not sure about the fan though it spins but never spins really fast. its my first time ever seeing a fan that runs off ATF. any help is appriciated guys.

also i've been thinking of going to dual electric fans. will this fix my problem?

 

[xspsi6]

Could be a bad hydro fan, air in the cooling system,bad head gasket etc

 

[918soarer]

i know its not a bad HG. it never goes over half way when the ac isnt on and also it never uses any water/coolant.

 

[lexicon]

Soarer,

When was the last time that you had your coolant system flushed? Have you cleaned out your radiator grille to ensure that there are no obstructions present? Another possibility is that your radiator needs a new cap and/or fans. I've had experience swapping out fans in SC400s before and here is the procedure that I usually follow:

1. Disconnect the negative battery cable to the battery.
2. Loosen the four (4) nuts holding the fluid coupling to the water pump.
3. Loosen the drive belt tension by turning the tensioner clockwise; remove the drive belt.
4. Remove the four (4) cooling fan pulley nuts. Remove the fan assembly (see SC400 fan diagram.)
5. Remove the clutch from the fan.

To install:
1. Install the clutch to the fan.
2. Install the fan assembly to the engine and install the four (4) bolts. Do not torque the nuts at this time.
3. Install the drive belt by turning the drive tensioner clockwise.
4. Tighten the four (4) fan nuts to 12 ft. lbs. (16 Nm).
5. Connect the negative battery cable to the battery.


As for upgrading to a system that incorporates two fans, I would most definitely approve of going down this route. This will dramatically reduce temperatures in your engine bay and will most likely reduce the risk you run of overheating

 

[spf_lexus]

As long as the car wont overheat on the freeway, you can rule out a clogged/scaled radiator. Electric fans will be more efficient than the hydro setup and can be done very cheaply as well. I picked up two 14" fans at kragen for about $100 and they cool better than stock. This is without a stock fan shoud as well.

You can clean the system up a bit by throwing away from fan/pump bracket with a stock ls400 fan bracket. Same part, just w/o the hydro pump being built in. Hope this helps some.

 

[918soarer]

Soarer,

When was the last time that you had your coolant system flushed? Have you cleaned out your radiator grille to ensure that there are no obstructions present? Another possibility is that your radiator needs a new cap and/or fans. I've had experience swapping out fans in SC400s before and here is the procedure that I usually follow:

1. Disconnect the negative battery cable to the battery.
2. Loosen the four (4) nuts holding the fluid coupling to the water pump.
3. Loosen the drive belt tension by turning the tensioner clockwise; remove the drive belt.
4. Remove the four (4) cooling fan pulley nuts. Remove the fan assembly (see SC400 fan diagram.)
5. Remove the clutch from the fan.

To install:
1. Install the clutch to the fan.
2. Install the fan assembly to the engine and install the four (4) bolts. Do not torque the nuts at this time.
3. Install the drive belt by turning the drive tensioner clockwise.
4. Tighten the four (4) fan nuts to 12 ft. lbs. (16 Nm).
5. Connect the negative battery cable to the battery.


As for upgrading to a system that incorporates two fans, I would most definitely approve of going down this route. This will dramatically reduce temperatures in your engine bay and will most likely reduce the risk you run of overheating

the car has a hydro fan not a clutch fan.

 

[918soarer]

As long as the car wont overheat on the freeway, you can rule out a clogged/scaled radiator. Electric fans will be more efficient than the hydro setup and can be done very cheaply as well. I picked up two 14" fans at kragen for about $100 and they cool better than stock. This is without a stock fan shoud as well.

You can clean the system up a bit by throwing away from fan/pump bracket with a stock ls400 fan bracket. Same part, just w/o the hydro pump being built in. Hope this helps some.

ya it only does it when im stopped so im thinking it has to be something with that fan, it just seems like it never spins any faster. and i have never messed with a hydro fan before but i know its no like a clutch fan because it doesnt connect to the drive pulley. i have a guy wanting to trade me a slick 97 es300 for my sc so i may just do that and let it be someone elses problem

 

[sideshow]

since when do electric fans work better than hydro or clutch fans
i would never choose electric fans if clutch or hydro can fit

anyway leave yr engine idling for few minutes
unplug the hydro fan water temp sensor on drivers side of radiator if car is left hand drive
in afew seconds u should hear the fan speed up and it should be noisy like flowing alot of air
if it doesnt speed up then u might have faulty hydro fan ecu
or no power to hydo ecu
u maybe the hydro solenoid is stuck closed or wiring unplugged to it which will make fan run on slow speed all the times

another thing the hydro ecu knows when yr ac is on so this should make fan speed up aswell when ac is turned on
these are easy tests if u know how soarers work hehehehe

 

[spf_lexus]

since when do electric fans work better than hydro or clutch fans
i would never choose electric fans if clutch or hydro can fit

Im not referring to hydro setups in general, just the UZ setup. I had different reasons for electric fans = weight savings + simplicity + extra clearance for the blower. My coolant gauge dropped about the width of 2 needles after the swap. I know that OEM sensors are not 100% accurate but this is with a non intercooler blower and I know for a fact that the system deals with more heat.

Anyway, with a quick fan mount kit I had some good flow for about $120 and 2 hours of work. Just my $.02.

 

[918soarer]

since when do electric fans work better than hydro or clutch fans
i would never choose electric fans if clutch or hydro can fit

anyway leave yr engine idling for few minutes
unplug the hydro fan water temp sensor on drivers side of radiator if car is left hand drive
in afew seconds u should hear the fan speed up and it should be noisy like flowing alot of air
if it doesnt speed up then u might have faulty hydro fan ecu
or no power to hydo ecu
u maybe the hydro solenoid is stuck closed or wiring unplugged to it which will make fan run on slow speed all the times

another thing the hydro ecu knows when yr ac is on so this should make fan speed up aswell when ac is turned on
these are easy tests if u know how soarers work hehehehe

i will definetly look into this. and if this does not resolve the issue then im just going to replace the hydro fan with electric fans