Lexus LS400 overheating quickly, heater doesn't work.
 

Hello! I have a beautiful bronze 1993 Lexus LS400 that overheats within 10 minutes of engine on. It boils over and have had to put red antifreeze/coolant everytime I go somewhere. Very annoying. I've had a new computer replaced in 2010 and TPS replaced. These are just a few of the symptoms I'm experiencing now:

*Heater does not blow hot air.
*Engine overheats within 10 minutes of igintion.
*Tempurature guage jumps when A/C is engaged.
*(of course) the orange raditator light is on the dash.

One mechanic says it's the radiator sensor, my dad says it's the water pump. The black cap on top of the coolant resivor appears to have endured extreme temperature conditions and shows white oxidation around the seal. PLEASE HELP.

Get a different mechanic (a bad sensor would not overheat.)

Is the fan running. Can you see the water moving when you take the cap is off with the engine is running (cold)? Is it overheating just because its so low? No heat usually means coolant is low.

Actually yes, the water flows through when the bolt is removed. Fan is running. It seems to be drinking coolant. I fill it up, go 5 miles, turn it off, check under the hood and the reservoir is empty.

If the water is running, doesn't that mean the water pump is working correctly?

Yes, pump is ok. Overheating because its empty.

Fix the bigass leak and it might be ok!

If you get someone to rev the engine, and get a bright flashlight and shine it around, you might be able to see it squirting out. Mind that damn fan and stuff though when you're poking around.

Course, it might be leaking around the pump and hard to see. Take a look at where its dripping out.

There is no large leak. I don't know...

Are you revving the engine high? Like 4000rpm? It must leak something if its emptying the reservoir in 5 miles.

Nope. Normal RPM 1500-2500. Within 7 minutes, it begins to heat up and boil.

You don't have a large wetspot on the passenger side of the cabin do you?

check ur oil and see if its mixed with water (very liquidy) blown head gasket :(

Heater core isn't shot. No blown head yet. I'm about to change the oil soon, so we'll see what it looks like. Any more suggestions? Keep 'em rolling.

not very many other likely issues, the coolant has to be going to somewhere, its either inside the engine, dumping on the ground, or inside the cabin. fill it up, leave it stationary, and wait for it to start overheating... its it not on the ground, or in the cabin, it MUST be inside the engine edit: meaning to say, its one of those three options

And have you determined if the thermostat is still functioning? that would cause backpressure and expelling of the coolent through the bottle... but again, you'd see the coolent on the ground, inside the engine compartment, etc...

u dont even have to let it over heat... attach the hose to the radiator obviously at a slow enough speed where its not spewing everywhere and wait till u find the leak. just sit there and chill ull see it eventually if its not a blown head gasket

leaking head gasket....