Wednesday, May 2, 2012

1995 Lexus LS400: Running Hot?

Engine running Hot.Basically in this types o cases the problem can be anything from faulty head-gasket,thermostat, water pump,low coolant or leak in coolant etc etc.

But basic testing troubleshooting is required.

Remove the thermostat and install just a gasket. Top off the coolant start the engine and circulate the coolant and make sure all the air pockets are out of the system. At this time make sure that you have good coolant flow through the top radiator tank. Drive the vehicle for some period of time and see if the vehicle continues to overheat. With the thermostat not installed in the vehicle it should run almost near cold maybe one quarter of the way on the temperature gauge. If it continues to run hot and push the coolant out into the reservoir tank then you still has something going on with the head gaskets or the cylinder head itself. There may be cracks in the cylinder head or the valve guide seats super heating the coolant and pushing it out the system. If it continues to run stone cold and does not overheat anymore you have an air pocket or circulation problem with the thermostat.


Also check the Coolant level.If you have already filled coolant,then also check coolant level.

Coolant should be checked at radiator cap. After replacing of parts, if bleeding was not done correctly, overheating would occur.

When engine is cold, remove radiator cap and check level. Top up if necessary. and run engine and let it idle for 5 mins. Check systems for leaks and allow engine to cool before removing cap to check again. If coolant level is low, repeat above process again.

The reservoir is part of the coolant recovery system and is the level constant or is it overflowing when engine is running?

When AC is turned ON, is the cooling fan working?
Does overheating occurs without the AC turned ON?
When overheating occurs, does turning the AC off allows the temperature to go down?


When coolant is hot, fan should be working at high speed.

If the lower hose seems much cooler than the upper hose when fan is working, you could have a partially clogged radiator, ie if the coolant level is correct.

Coolant should be checked at the highest point and in this case it should be the engine cap.


This details will help.
Thanks.


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