Dee_seal

Hey guys

My faithful sc400 is showing its age at 194K on the odometer, she is overheating my guess its the waterpump but I was doing some research and I found this link:

https://www.clublexus.com/forums/sho...pling+assembly

It spoke of the fluid coupling assembly?? Basically a few post down states tha if you can stop the fan with your hand then it is the fluid coupling assembly?? I called lexus and they never heard of that part, I called Toyota and they needed a part number, can anyone else stop their fan with their hand?? and does anyone have any additional information on the fluid coupling assembly??

On the highway with the heater on blazing at 65 mph it will not overheat

I swaped the thermostat with a NAPA thermostat part and I still get the overheating

what about this part

http://replacement.***************/par...art=Water+Pump

$97.00 this is definitely my price range any advice? I am pretty mechanically inclined done quit a bit of wrenching, I am guessing if this is bolt of and bolt on make sure no leaks I can pull this of

I wanna start pulling out the bad part today sunday Jun 05 and expect to be down for a couple days next week so if anyone has any ideas please let me know

Thanks

DN

PERRYinLA

There are lots of reasons cars overheat so be sure you are checking everything before the open-heart surgery of replacing the water pump (although they certainly fail, too).

You've provided limited info to go on, but it could be blockage in the system. Make sure radiator fins are not clogged with debris. If it won't overheat on freeway, then whatever blockage exists is being overcome by the extra pressure provided by the fast-spinning water pump.

Dee_seal

I would have guessed the no overheating on the highway was caused by the fact that the car was moving at 60 mph and that air was being forced to the radiator


Later today I will remove the thermostat completely, what should I expect to happen?

what about the fan, fan clutch, fluid coupling assembly thing rember I can stop the fan with my hand, can anyone else do that?

The radiator is brand new, and I did a flush about 8000 miles ago when I installed it, the rubber from the thermostat is still all together.

Thanks

DN

PERRYinLA

That might be true as well, but in either case it is "blockage" of either air or coolant at lower speeds.

If temporarily removing the thermostat prevents overheating, it's not likely to be a restriction in the coolant passages, and you get to drive your car again without worrying about overheating.

The long-term fix may indeed be the water pump, but I'd want to be certain before taking the front half of the engine off. If you end up doing all that, you may as well change the timing belt, too (if not done recently). You'll find plenty more info on this with a search.

Dee_seal

I removed the thermostat, ran the car in the garage for 30 minutes no overheating it actually ran cooler than ever just a nudge below 3:00 I ran the AC full blast and it just went up a smiggin still no overheating, I guess its the thermostat, that crappy thermostat from NAPA was probably a bad idea,

Question;
1: can I run the car without a thermostat, I drive 40miles to and 40 miles from work, eventually I will get a Lexus thermostat sometime this week. What are the disadvantages of running the car without a thermostat?

2. What about that fluid coupling assembly thingy I can stop the fan with my hands no problem?

3. And from this exercise can I conclusively say its the thermostat?

Thanks

PERRYinLA

1) In the winter, your car may not get hot enough for the heater to work
1a) It takes longer for car to warm up to proper operating temperature

2) Dunno, but my hands stop mine, too.

3) Guess we'll find out later this week, once you get an OEM thermostat!

JspecSC3

iTrader: (4)

Nope, If you can stop the fan with your hand it is the fan clutch. I have never heard of a fluid coupling assembly Also, if your car is near redline on the temp meter it could be your water pump if you have already replaced your thermostat. If your fan clutch is out your car should only be overheating by a little bit. Like half a notch maybe. Because the fan is still spinning but not with the RPM's. Check your pump.

Dee_seal

Well I finally got me that $30.00 lexus thermostat and that $10.00 seal and all is well in my SC400 194K heading for 250K miles land. I guess the problem was the thermostat so after I replaced it no overheating runs like a happy baby. Good thing I did not jump and replace the waterpump.

One way You can check the waterpump is to squeeze the hose wile the car runs without a thermostat, if you can feel the coolant gushing through the hose the waterpump is OK

Thanks for all the help everyone I guess I can put of on getting that 300C for another 6 months

vaki2

Funny,

I have the same problem. When on highway it does not overheat, but as soon as you stop, there is goes. Mine has 191K on it.
I did what you did and replaced the thermostat with a lexus one hoping that would fix it.
But it didn't

I think the other problem that it could be is the radiator having a blockage or waterpump.

Being a sc400 it has the hydraulic fan. I tested the fan by turning on the AC, it turns the fan to high RPM. So I assuming the fan and hydraulics are fine

I guess its time for a new timing belt and waterpump.

I will keep you posted, thanks for all the information you posted in this thread

vaki2

PERRYinLA

Of course it is possible you need a new pump, but like I said above, be sure you've eliminated every other possibility before embarking on such a major job.

Test that new thermostat in boiling water, and try the same test Dee_seal tried with no thermostat at all.

vaki2

Well tried the no thermostat and still overheating

The car is due for a mayor job, I am planning to go ahead and change the timing belt, waterpump, crank seal, cam seal, serpentine belt, new front struts, probably new rack, tie rod ends, lower and upper control arm bushings, steering bushings. Depending on how much $$ I have left I may go ahead and put the supra brakes on and also new 18" staggered wheels..
It has 191K on it and it needs some work as you can see

I will keep you all posted on what I ding once we start taking this puppy apart

vaki2

Nomis

The SC3 guys always miss this: The SC4 has a hydraulic fan unit. There is no belt connected to the fan, and no clutch - at least not a mechanical clutch.

Dee_seal

I have a 95 sc400 and I can stop my fan with my hand, can you stop your fan with your hand? However, my car works fine and does not overheat

vaki2

Yea,

what I noticed is that on the sc400 you can. The fan will go to 1100 RPM when the AC turns on. You can also speed up the fan when you short the pins in diagnostic. Please do not try to stop it with your hands then

Vaki2

vaki2

Quick update,

the problem with overheating was the radiator. We found it by moving the plastic on top of the radiator. Found it was seeping at the seems. Installed:

-New radiator
-Timing belt
-water pump
-tensioner
-serpintine belt
-fuel filter
-Rear TT brake calipers

To be installed:

-new LS400 or TT front brakes (have not decided yet)
-NGK spark plugs
-Wire set
-Cap
-Rotors
-probably need new set of 18's to clear new front brakes
-ss lines
-lower control arm busings
-upper control arm
-new front struts

Well thats it for now. Also have a new 97 front, but that wont go on untill I get the whole car painted. Long list

vaki2