irax

The sensor at the bottom of the radiator then is a temp switch sensor for the fans or is that for something else?

3UZFTE

Correct. That is the engine fan temp switch, once it hits a certain temp, likely higher than the thermostat's rated for so 200+ degrees F. The picture I posted was just a picture that has the bleed screw in the center of the picture. I would go with whatever Toyota recommends as OE as far as thermostat opening temp. If you lower the temp at which the motor operates, you have varying effects. This might be an extreme, but if you went with the TRD 160F* stat, your LS would likely stay in open loop and run a little rich. From what I can recall, running in permanate open loop is a sure way to take out a pair or dated cats.

Have the system pressure tested, it will show if you are actually loosing coolant and if it's in or outside of the motor, it'll give you a better theory to work with. If the pressure tester holds the amount of pressure on the cap, usually 13-16 psi, for 10 mins, your good to go. It is normal to lose a few psi after a few pumps because it's likely there might be a faint amount of air left in the system.

BlueLS

had similiar problem and then started to progress and get hotter and started to leak at the overfill then i changed the waterpump and no problem since

ROLEXUS400

iTrader: (2)

This will sound absolutely ridiculous,but please try it. Take the car and warm it up then drive it down the road like a maniac and lock the brakes up while nose diving the car watch the gauge. If it goes down ive got some really crazy info for you only seen it once tho. Also how well does the heat work? when you do the nose dive the the heat temp icrease at the vent substatialy?

LS4Lalonde

SO what happened? I'm having overheating problems as well. Replaced fans and thermostat with no resolve. I don't want to change the water pump but sounds like that's the culprit.

NTRUDA

I changed the thermastat, anti-freeze and also changed the radiator cap and my overheating problem was solved...I agree that you should get the system pressure checked as well....

caliLS400

Im my experience with over-heating if you get top the 4th line and don't shut it down, it will stay pegged on red until something blows. From the sound of it your guage is not accurate.

Replace all coolant temp senors, drain and flush, note to do a full flush, not just the radiator, the 1st gen LS has three coolant bleeders. the one on the radiator, then one on each lower bank of the block. They are a 10mm bolt. Hard as hell to get to. Refill from the top of the thermostat housing, not the reservoir. Make sure you are on level ground too. Refill with toyota red or expect your cooling system to give you more problems than you need. If you still have problems, have the radiator removed and taken to a specialist. It could be clogged. I had mine unclogged in a day for $79, made a huge difference.