hammer

I have a 96 Sc400 with 180k miles.
My problem is that my temp gauge moves up to H within the first minute I start the car. It first happened when driving and the needle seems to go up and down at will. Now parked and idling it stays at H.
The car does not appear to be overheating. There is no smoke at all. The oil looks as it should, not murky and so does the coolant.

This is what I know:

- I've taken the thermostat out and put it in boiling water and it opened. -
- I have replaced the temperature sensor with a new one.
- I have no leaks of coolant at all.
- Both the upper and lower radiator hoses are hot to the touch after warmup.
- After taking off the radiator cap, the fluid level is full.
- Turning on the heater does not appear to lower the temperature.

Please help! Thanks in advance,
MH

shonuff53

iTrader: (3)

pull out the gauge cluster and check for obvious signs of damage ie burn mark on boards. swap it out with a friends cluster to see if the problem goes away.

turbodremz

iTrader: (18)

^^^I agree. Sounds like the gauge is on the fritz, and said screw it Im doing what I want too...

lLOlRlElN

go ahead and do a dye test just in case. some cars dont give you any other signs of bhg besides overheating

hammer

Pulling out the cluster seems like a lot of work. I dont have a friend with one laying around. Could it be anything else before I go to that extreme?

thx

Nova

iTrader: (21)

have you pressure tested the system just to make sure there are no leaks? i would do that first and if u do pull the cluster and there seems to be signs of damage u can always wire in a aftermarket gauge

Bott63

Also, check the oil... If it looks like chocolate milk, blown head gasket.

MooJohn

With the age of the car and no other symptoms present, I'd suspect a faulty temp sensor. It's on the center of the engine, in front, and is the smaller one with a single wire connection. While you're at it you might as well replace the 2-wire sensor next to it that sends temp data to the ECU.

SC400-V8

iTrader: (1)

Hey there, same problem here... No signs of overheating.... But the temp needle just bolts right up to emergency levels.

What's the temp sensor part number or description?

poorsupra

iTrader: (11)

extreme? its 4 screws. 3 clips.

broda805

iTrader: (6)

any solutions? mines just started doing this, viewing the coolant temp via my aem ems says its normal but the cluster just pegs when it gets warm and wont go down till its totally cold

WadeLovell

iTrader: (5)

First, even though I doubt the cluster diagnosis, pulling the cluster is a piece of cake. Search the forum and, if you don't find it, I will search and post or just write a quick summary.

Second, there are probably two temp gauges on the SC400. I know there are on the SC300. To me, it sounds like either the one that signals the cluster gauge has a short or a bad sending unit (sensor) or there really is an air pocket where there should be coolant.

mak89

iTrader: (6)

Check the engine coolant sensor. Ecs. It's only couple bucks.

DoomLight

iTrader: (3)

the cluster comes out in like 5 mins! the only thing thats going to kick your butt is the harness plugs on the back. the middle and far right are difficult to unplug.

xxtoobsxx

iTrader: (4)

Did you properly bleed the system/fill it correctly?