Re: Cylinder Head Cracking

Hi,

> >I was hopeful that someone might be able to give me a different insight >into a problem that occurs with my dads celica. >The car has an issue where that around every 150000kms it cracks the >head into either the number 2 or 3 exhaust port. the engine is a 3S-GE >with TVIS. The only mods are a cold air intake to feed the factory air >box and a set of tri-Y long primary exhaust headers. >The car has done it to 3 heads so far and always the same problem. The >engine runs fine when the head cracks and still produces full power it >just pumps the radiator into the exhaust with a cloud of steam. >It has also has had the engine changed the last time it happened to a >jap spec motor. The car has had the water pump, the thermostat and the >radiator replaced that the car never has any heating problems. >It usually has the oil changed every 5000kms with the longest it's been >being 7000kms. The car does a lot of highway driving occasionally towing >a lightly loaded trailer. On average it does about 800kms per week. >About the only thing that has happened to the car other than normal wear >and tear is that the heat from the exhaust warped the blades on one of >the radiator fans. >The only thing I can think of is that the head gasket it not allowing >correct water flow to the head and causing a hot spot which causes the >cracking, But I'm not convinced this is the cause and the head gaskets >used are identical in water flow holes to the factory Toyota one. > >If anyone has any ideas as to what could be the cause I'd be grateful to >fix this problem as my dad would like to keep using the car for work for >as long as possible. > >Nick

A little detective work is needed on this one.

  1. It must not be a problem with the head, you've replaced the head three times. I'm assuming you replaced them with new, known good, heads.

  1. It must not be a problem with the engine block, you've replaced the engine. Again I assume you used a new engine or short block.

  2. I don't see how feeding cold air into the factory air filter box could cause the head to crack, unless you use a blower to feed in the air. So your mod to the air filter box shouldn't be the cause of the problem.

  1. Heads usually crack because of either over-pressure or uneven heat distribution. If it always cracks at the exhaust port, then the problem might be the after-market headers you've installed.

Go back to the OEM headers and see if the heads still crack.

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