1994 Ls 400 Overheating Problem

[KeithLS400]

Hi all

i have recently purchased a 1994 LS400 all has been well with the car until this evening

I was driving and noticed the temp guage started rising above the halfway mark heading towards the red line i stopped the car and as i went round to the nearside i noticed water steadily dripping on the floor (from the overflow in the expansion tank) i let the car cool down for a few mins and decided to gently loosen the cap on the expansion tank as soon as i had turned the cap slightly boiling water and steam started to pour out i let the engine cool down and totaly removed the cap added some fresh water to top it up then ran the engine up after it had been running for a few mins it started boiling over and both hoses from and to the thermostat housing where rock hard and very hot !!!

there seems to be too much pressure or an airlock in the cooling system ???? anyone else had a simular problem and have a simple cheap cure ???

thanks

Keith

[ROYT]

Might just be a faulty thermostat, try it without one and see if the same fault recurs.....

[ColinBarber]

may be worth getting a compression test done on the engine in case a head gasket has blown.

[KeithLS400]

Might just be a faulty thermostat, try it without one and see if the same fault recurs.....

Hi Royt

I will try that suddestion as it seems simple and cheap to start with

Keith

[KeithLS400]

Hi all

i have just replaced the thermostat on my car and it doesn't seem to overheat anymore the temp guage stays just under halfway but the water system still seems to be pressurised ???? after a ten minuite run sticking my right foot down the temps ok but the pipe on the right of the thermostat housing seems quite hard and warm and when i losen the expansion tank cap the water rises and starts flowing from the overflow pipe ??? not as bad as it was and before though.

should the water system be pressurised as much as it is ??? anyone shed some light on the problem ????

any ideas would be greatly appreciated before i scrap it or sell it for spares lol

Keith

[terry moore]

Hi all

i have just replaced the thermostat on my car and it doesn't seem to overheat anymore the temp guage stays just under halfway but the water system still seems to be pressurised ???? after a ten minuite run sticking my right foot down the temps ok but the pipe on the right of the thermostat housing seems quite hard and warm and when i losen the expansion tank cap the water rises and starts flowing from the overflow pipe ??? not as bad as it was and before though.

should the water system be pressurised as much as it is ??? anyone shed some light on the problem ????

any ideas would be greatly appreciated before i scrap it or sell it for spares lol

Keith

Hi ,once your car has reached normal temp,don't open or loosen the pressure cap,the pressure cap,if OK will control the coolant level.if it is over fill,it will dump,until it reaches the correct level.all cooling systems build up pressure as the coolant expands and gets hot.quick way to see if the thermostat is working correct,is to feel both ,top and bottom rad hoses .if the bottom hose is cold,and the top ones hot ,u have a problem.if they are about the same ,then it is OK.i think u have sorted it out,just check the coolant level first thing in the morning,before running the motor. B) then add if u need to.cheers

[ROYT]

...............and check your heater works Ok and is not airlocked!

[steve2006]

If you are still unsure if the system is presurising too much,which could indicate head gasket failure and you have a friendly MOT station you could ask them to stick the exhaust gas tester probe into the expansion tank ( but not into the water) when the engine is running which would indicate or not whether exhaust gases are present in the coolant thus confirming or hopefully eliminating this possibility.