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.
- 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.
- 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.
- 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.
- 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.