My 1990 Ls400 Keeps Over Heating Any Suggestions?

[90 LS400]

i have a 1990 ls400 is has about 212,000 miles on it, i dont kno wat maitenance has been done to it ever and this ismy first lexus. ever since i purchased the car about 2months ago the car tends to gets really hot after about 20 minutes of driving, not to the point where its smoking but the temp. gauge is almost touching the 'H' , jus the other day while i wasz driving the needle went all the way 2 the 'H' ! and started nsmoking from the engine coolant..i didnt have anti-freeze i had water inside the coolant

any tips or suggestions pleeeaase this is my first car !

[E910]

Take it to a mechanic & get it checked out asap. You shouldn't be letting it get that hot. It could cause permanent damage to the engine.

Your problem could be something as simple as the radiator cap needs replacing or more involved like water pump or radiator etc.

[Mybikesacx500]

Could be a sticking thermostat

[steve2006]

Hello and welcome to the LOC.

Sorry to hear of the problem you are having with the Lexus.

I have to agree with the other replies regarding possible causes but do something now otherwise you will have a wrecked engine.

Topping up with plain tap water will also cause damage as it should be approved Lexus/Toyota Coolant mixed with distilled water.

If you have a good local garage ask them to "Pressure Test" the cooling system basically this is done by feeding compressed air into the expansion bottle with a suitable seal adaptor then seeing if the pressure drops indicating a leak.

The thermostat is probably the favourite as mentioned previously, access is fairly easy and testing off the car is also straightforward, in fact for the minimal cost replace it anyway.

Another thing to check is the operation of the radiator cooling fan is it kicking in when the engine overheats as there have been known problems with the fan brackets.

Let us know how you get on.

[ROYT]

As above,thermostat first and check the engine cooling fan, these have fluid coupling

and this may be faulty, not lifting the fan speed.

[90 LS400]

Thanks for the help

I'm going to change the thermostat first and see what happens will deff keep the club posted.

I did notice that my fans haven't turned on is there a way 2 check if its bad and is it a easy fix ?

[ROYT]

If you have 2 fans visible at the front, these rarely come on unless the aircon is on, stuck in traffic etc.,

look in front of the engine for the big fluid coupled ,not electric fan.

[90 LS400]

The fan in front of the motor, behind. The radiator..the big fan is spinning wen the car is seems 2 be spinning fine but the 2 fans in front of the radiator I never have seen move..my a/c. Has a problem also it blows hot so I haven't had it on for those fans 2 turn on ?...but which fan should I be checking...

Do yu or any1 kno why my car could be running soo funny cuz wen it ober heated it steamed out all the water inda motor thru the coolant box..now its running real tired and slow

Wat could this be ?

[simontaylor]

Just go to the garage and get it pressure tested, this will tell you if you have any serious problems.

Does the rad get hot whan the car is running, if it does, maybe it is not the therostat stuck closed?

[E910]

Do yu or any1 kno why my car could be running soo funny cuz wen it ober heated it steamed out all the water inda motor thru the coolant box..now its running real tired and slow

Wat could this be ?

Sounds like you've cooked it mate. I'd suspect a blown head gasket at minimum

[90 LS400]

soo if the radiaTOR gets hott its probably the radiator not the thermostat ?

[90 LS400]

i'll deff check the head and gasket...could it be the spark plugs by any chance cuz it sounds like its running on less cylinders

[simontaylor]

mate, you sound a bit confused by the suggestions. I think it is best that you take it to a garage for advise and then tells us what they find, what they recomend and why they recomend that action?

Good Luck.

[Manc]

Might not be the head gasket yet....mine went on a peugot (but it was the 205gti B) )

it overheated and cut out on a slip road but immediatly all the stop lights appeared on the dash.

If you r gasket went you should of had warning lights on the dash.

It does sound like it was already a problem, maybe a word with the previous owner would tell you more he sounds like a pirate to me :arrrggg-matey:

[Steviegeeza]

Might not be the head gasket yet....mine went on a peugot (but it was the 205gti B) )

it overheated and cut out on a slip road but immediatly all the stop lights appeared on the dash.

If you r gasket went you should of had warning lights on the dash.

It does sound like it was already a problem, maybe a word with the previous owner would tell you more he sounds like a pirate to me :arrrggg-matey:

If the head gasket goes you either get oil in the water, water in the oil , pressure in the coolant system when the car is running but still cold.

My Mk2 overheats if you thrash it, which is down to a blocked radiator, if you fill the coolant system with tap water ( I had a leaky expansion tank)

the system gets lots of gunk and corrosion in it. I discovered this when changing the thermostat.

I'm going to try chemical cleaning and backwashing, maybe I'll get away with out changing the radiator :^O