94.lexus ls400- keeps pushing radiator coolant out of overflow,

Front of intake on the drivers side see link

DIY Coolant Temperature Sensor change PICS Club Lexus Forums

Check the oil dip stick if it is a milky white this is really bad being cracked engine head or blown head gasket.
More than likely and best out come it will be the radiator or a radiator hose.
If you can see water stain some where around the radiator it does not need to be a big amount.
Or a radiator hose that may have water around it or coming out when hot then that is your leak.
Maybe a good idea to take to a radiator place or a mechanic ask them to put a pressure test on the radiator.
Also only fill radiator when cold or if you need to do when hot make shore the car is running to avoid cracking the engine head as this will make any grown person cry $$$$
And do on a hill with engine facing up running and cap off little bubbles will come out keep filling when bubbles stop put cap on fill reservoir ( a little container next to the radiator).
Let me know if this helps.
Regards Craig

May be its low on coolant or radiator hoses clogged or its thermostat issue,its remaining closed or it can be issue with coolant leaking from somewhere.Or cooling fan not running when when engine gets warm.
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There are many other possibilities causing these issues.:----
To troubleshoot the issue yourself,i provide you few very helpful links with solutions:-----
Click the link below:----

Dodge Dakota stalls, stumbles at idle. Has low fuel flow and runs hot?

http://schematicsdiagram.blogspot.in/2012/03/dodge-dakota-stallsstumbles-at-idlehas.html

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1991 Toyota Trecel: Engine Starts fine but dies when gets Warm?

http://whatisbyme.blogspot.in/2012/05/1991-toyota-trecel-engine-starts-fine.html

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1995 Lexus LS400: Running Hot?

http://whatisbyme.blogspot.in/2012/05/1995-lexus-ls400-running-hot.html

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Multiple problems on car: Car runs hot, A/C blows hot and car starts surging?
http://schematicsdiagram.blogspot.in/2012/04/multiple-problems-on-car-car-runs-hotac.html


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There are many possibilities for car overheating.

Faulty thermostat clogged radiator/plugged radiator, radiator hose worn out. Coolant running low. Low coolant pressure. Faulty temperate sensor.

I suggest you to go through the troubleshooting details mentioned in the link below:-----

All types of car overheating problems and troubleshooting?

http://technoanswers.blogspot.com/2011/11/all-types-of-car-overheating-problems.html

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These will help.

Thanks.

replace thermostat.then bleed coolant system, this is how you do it.fill the cooling coolant system with 50 / 50 dexcool and water to raise boiling point,straight water will evaporate boil away cause engine to overheat catch fire thats why you need 50 / 50 mixture antifreeze and water.to bleed coolant system first fill coolant system until coolant stay at the full cold mark on the the coolant overflow jug,then you start engine allow it to idle,place the heater and ac control in any ac setting except max and the temperature control to the highest setting,run engine until lower hose to water pump is hot. with the engine hot run the engine speed up to 3000 rpm and allow it return to idle, repeat this 5 times. slowly open the bleed valve on the thermostat housing or look for bleed valve at the water pump heater hose.open bleed valve for 15 seconds to expel any trapped air.then top off the coolant as necessary,and when top radiator hose hot thermostat open up.keep adding cooling to overflow until coolant level stop at full cold mark dont over fill coolant.if engine seem like overheating while looking at cooling gauge turn off engine wait a while until cool off add more coolant until coolant level stay stable and dont drop any.when open radiator overflow cap use large rag over the radiator cap to keep from getting scald open radiator cap a little at a time but dont open radiator cap until engine cool down first.replace the radiator overflow cap, thermostat,and engine coolant temperature sensor and check the cooling fans fuses and relays see what happens.

REPLACE THERMOSTAT IF TOP COOLANT COOLANT HOSE GOING TO RADIATOR IS HOT TO TOUCH THERMOSTAT OPEN. TO BLEED COOLANT SYSTEM FIRST YOU NEED TO ADD COOLANT TO THE COOLANT OVER FLOW JUG UNTIL COOLANT LEVEL STOP DROPPING AND STAY AT FULL COLD MARK.WAIT 3 MINUTES IF COOLANT DROPS ADD MORE COOLANT UNTIL COOLANT STAY AT FULL COLD MARK.WITH RADIATOR OVER CAP OFF CRANK ENGINE FOR MINUTE WATCH COOLANT LEVEL AT OVERFLOW JUG.IF COOLANT DROPS ADD MORE COOLANT IN THE OVERFLOW JUG.WHEN COOLANT LEVEL STOP DROPPING IN OVERFLOW JUG.SCREW BACK ON THE RADIATOR CAP TO OVERFLOW JUG.WHILE ENGINE IDLING WATCH TEMPERATURE GAUGE WHEN TEMPERATURE START CLIMBING TURN OFF ENGINE WAIT A WHILE KEEP FROM GETTING SCALDED.WHEN COOLANT COOL DOWN SOME. PLACE A LARGE RAG OVER THE COOLANT OVERFLOW JUG OPEN CAP LITTLE AT A TIME UNTIL PRESSURE RELEASED, THEN REMOVE CAP ADD MORE COOLANT IN THE OVERFLOW JUG TO THE FULL COLD MARK.THEN REPEAT THE PROCESS SCREW BACK ON THE COOLANT OVERFLOW RADIATOR PRESSURE CAP.THEN START ENGINE WATCH TEMPERATURE GAUGE WATCH COOLANT TEMPERATURE GAUGE WHEN COOLANT TEMPERATURE START RISING TURN OFF ENGINE AGAIN WAIT UNTIL ENGINE COOL DOWN ENOUGH TO KEEP FROM GETTING SCALDED TAKE PLACE LARGE RAG OVER RADIATOR CAP WHICH IS THE COOLANT OVERFLOW JUG CAP OPEN CAP LITTLE AT A TIME UNTIL PRESSURE RELEASED ADD COOLANT UNTIL AT FULL COLD MARK. WHEN YOUR COOLANT LEVEL STOP DROPPING.AND TOP RADIATOR HOSE VERY HOT THERMOSTAT OPEN AND AIR IS OUT THE COOLANT SYSTEM. MAKE SURE YOUR COOLANT OVERFLOW JUG HAS COOLANT IN IT,WHEN ENGINE COOL DOWN CHECK COOLANT OVERFLOW JUG KEEP COOLANT LEVEL AT FULL COLD MARK.BECAUSE IF OVERFLOW JUG IS EMPTY THATS A SIGN RADIATOR COOLANT LEVEL LOW.WHEN OVERFLOW JUG EMPTY IT WILL ALLOW AIR GET IN THE COOLANT SYSTEM AND CAUSE CAR TO OVERHEAT.WHEN REPLACING THERMOSTAT ALSO REPLACE THE RADIATOR CAP ON THE COOLANT OVERFLOW JUG.

OVERHEATING CAN BE CAUSE BY MANY THINGS LIKE FAULTY THERMOSTAT AND FAULTY RADIATOR PRESSURE CAP,TOO MUCH WATER IN COOLANT SYSTEM NEED 50 / 50 WATER AND ANTIFREEZE.LOOK FOR WATER PUMP WEEP HOLE LEAK, IF COOLANT LEAKING OUT WEEP HOLE WATER PUMP BAD NEED REPLACING.CHECK FOR LOW COOLANT LEVEL, YOUR RADIATOR OVERFLOW JUG SHOULD HAVE COOLANT AT THE FULL COLD MARK IF NOT KEEP ADDING COOLANT INTO COOLANT OVERFLOW JUG UNTIL COOLANT STOP DROPPING AND FULL COLD MARK, IF OVERFLOW COOLANT JUG WAS EMPTY RADIATOR IS LOW ON COOLANT.WHICH CAUSE AIR IN COOLANT SYSTEM KEEPING THE ENGINE COOLANT TEMPERATURE SENSOR FROM BEING SUBMERGE IN HOT COOLANT WHICH TURN ON THE COOLANT FANS.WHEN ENGINE COOLANT TEMPERATURE GET CERTAIN SET TEMPERATURE LIKE 190 DEGREES THE PCM AND COOLANT SENSOR WILL TURN ON COOLANT FANS, IF VECHICLE OVERHEATING COOLANT FANS NOT WORKING EITHER YOU HAVE FAULTY ENGINE COOLANT TEMPERATURE SENSOR CHECK COOLANT FANS FUSE AND RELAYS. YOU CAN CODE SCAN CAR TO SEE IF YOU HAVE FAULTY PCM, FAULTY ENGINE COOLANT TEMPERATURE SENSOR OR FAULTY COOLANT FAN RELAY.IF COOLANT FAN AND ENGINE COOLANT TEMPERATURE SENSOR OKAY,YOU HAVE CORRECT COOLANT LEVEL IN COOLANT SYSTEM, THERMOSTAT AND RADIATOR PRESSURE CAP BEEN REPLACED, YOU COULD HAVE BLOWN HEAD GASKET CHECK ENGINE OIL LOOKS LIKE MILK SHAKE HEAD GASKET BLOWED ALSO WHEN HEAD GASKET BLOWED YOU CAN DRIVE CAR SHORT DISTANCE START OVERHEATING AND YOU LOOSE ENGINE POWER SUSPECT BLOWED HEAD GASKET.

REPLACE THE THERMOSTAT AND RADIATOR PRESSURE CAP.IF COOLANT LOW, ADD MORE COOLANT THROUGH COOLANT OVERFLOW UNTIL COOLANT LEVEL IN THE COOLANT OVERFLOW STAY AT FULL COLD MARK.REASON POUR COOLANT THROUGH COOLANT OVERFLOW MOST GM CARS DONT HAVE RADIATOR CAP.WHEN YOU GET COOLANT LEVEL OKAY, CRANK CAR LET IT IDLE UNTIL ENGINE GET HOT BUILD UP PRESSURE THEN TURN OFF CAR.CHECK FOR COOLANTS LEAKS AT THE RADIATOR HOSES,CHECK FOR LEAKS AT THE RADIATOR, CHECK FOR LEAKS AT WATER PUMP WEEP HOLE IF YOU SEE COOLANT LEAKING FROM WEEP HOLE REPLACE WATER PUMP. IF CAR OVERHEATING WHILE IDLING YOUR COOLING FANS NOT WORKING CHECK COOLING FANS FUSE AND RELAYS.IF FUSE AND RELAYS OKAY THE ENGINECOOLANT TEMPERATURE SENSOR BAD.

CHECK COOLANT LEVEL STILL LOW.ADD MORE COOLANT.UNTIL RADIATOR OVERFLOW FULL AT COLD MARK.THEN CRANK ENGINE UP LET IDLE FEW MINUTES LOOK DOWN COOLANT OVER FLOW JUG ADD MORE COOLANT IF LEVEL DROPPED.WHILE ENGINE RUNNING KEEP EYE ON TEMPERATURE GAUGE.WHEN THERMOSTAT HOSE GET HOT.TURN OFF ENGINE WAIT A LITTLE WHILE TO KEEP FROM GETTING SCALD TAKE LARGE RAG PLACE OVER OVERFLOW JUG RADIATOR CAP.OPEN CAP A LITTLE A TIME.IF COOLANT TRIES BOIL OUT.LET VECHICLE SET A WHILE LONGER.ADD MORE COOLANT.WHEN COOLANT LEVEL CORRECT AND ALL AIR OUT THE COOLANT SYSTEM.IT WILL STOP OVERHEATING.LONG AS ENGINE RUNNING HOT TURN OFF THE ENGINE POUR IN MORE COOLANT UNTIL COOLANT LEVEL STOP DROPPING IN RADIATOR.KEEP COOLANT LEVEL IN OVERFLOW AT COLD MARK.DONT OVER FILL OVERFLOW JUG.

Have you changed the water pump ?

Yes, a non-certified person could replace something on the car. The person has to understand what he/she's doing, though.
Best way: open the radiator cap and drain the coolant. Leave the radiator cap off until done.
Place a container under the radiator to catch the coolant.
Replace the thermostat, and refill the radiator.