Mechanics

HEAD GASKET??

1991 Lexus ES 250

Engine Mechanical problem
1991 Lexus ES 250 6 cyl Two Wheel Drive Automatic 160, 00 miles

Car was driven while dry with no water in engine, because a hose had been removed, for a period of time which may be as long as 10- 20 minutes. Now, since the hose was replaced and coolant put into engine, the car runs very roughly and it has smoke, some of it is blue, coming out of the exhaust.

Is the problem a blown head gasket and how much will it cost to repair? Will the engine need to be replaced? If so, what will that cost?
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Campbell Johnson
October 19, 2010.




Hi Campbell Johnson. Welcome to the forum. You might be surprised to find your engine has survived. There is still a lot of coolant in the passages of the engine so the engine won't overheat instantly.

Still, overheating can cause a cylinder head to warp, especially if cold water is added quickly, and a leaking head gasket can cause an engine to overheat. Blue smoke is a sign of engine oil being burned. Due to the nature of the cause, it is likely sneaking past the piston rings which have lost their temper from the excessive heat. Oil's lubricating properties will be degraded too at very high temperatures which would promote rapid cylinder wall and piston ring wear.

The first thing to do is to determine the cause of the misfire. You need spark, fuel, and compression. An injector is probably the last thing to be damaged from overheating, and while compression could suffer, it isn't going to totally disappear. An overheated spark plug is a good possibility but so are burned valves. After inspecting the spark plugs, perform a compression test. If one cylinder is low, add a teaspoon of oil to that cylinder and repeat the test. If the reading comes up, suspect piston rings are leaking excessively. If the reading stays the same, suspect a burned valve, typically the exhaust valve. You will hear the " putt-putt" at the tail pipe. A cylinder leakage test will confirm the diagnosis.

If you solve the misfire, change the oil. The blue smoke might diminish on its own over time. Sometimes piston rings stick to the piston after being overheated rather than expanding outward to seal against the cylinder wall. The burning oil can coke up between the rings and piston. New oil with a good detergent will often dissolve that coke and free up the rings.

Caradiodoc

Caradiodoc
Oct 19, 2010.


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