Re: Cylinder Head Cracking
- From: "Ray O" <rokigawaATtristarassociatesDOTcom>
- Date: Tue, 6 May 2008 23:54:14 -0500
"Nick Bourne" <"nabourne at tpg.com.au"> wrote in message
news:481feb11@xxxxxxxxxxxxxxxxxxxx
Nick Bourne wrote:
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
Thanks for the ideas guys and we'll try to source a factory header but
last time we tried they were all cracked or not available. Didn't try
toyota but we might be able to get one for a different later model car. I
don;t know if they still support cars from 1986 for things like that.
Just to update you with a couple of details i missed.
1. When the engine was replaced it was with a long motor(Full motor minus
manifolds), this is the last one to crack. it wasn't new but came out of a
low k'm rear hit fount cut from japan and had never been opened.
2. The cold air feed is directed into the factory air intake to make sure
water was not ingested by the motor and is feed from behind the grill to
keep it high for the same reason. But I'm sure this can be ruled out.
3. The factory cast iron header went into the bin years ago as it was full
of cracks. Second hand one were not available due to cracking and the
after market headers were the only option. the head design does put the
pipes for 2 & 3 cylinder close together though, and i had thought it might
be to much heat in the pipes.
4. When mounted in the car the motor is angled back at about 10 degrees
making the exhaust side of the head the highest and what i would think to
be the most prone to vapor locks.
5. we have always used the same head bolts on the car and they have been
tightened to what was said in our workshop manual. No one ever mentioned
or any manual that the head bolts stretched and we would need new ones. We
also have a haynes manual and the factory manual for the motor/body.
6. When we replaced the head we check the head and block for warping /
high spots etc and we have never found any. ( It's something i consider a
must when working with an alloy head on a cast iron block)and we have
tried the factory head gasket, as when it occurred for the second time we
thought it might be a gasket fault so we compared the after market type to
the factory and the gaskets were the same. I had thought that the water
gallery holes in the head were not opened up enough and most of them are
blocked not allowing water to flow through the gasket but the factory was
the same.
Don't know if any f this was useful but it might shed more light on it for
you.
OK, you should use new head bolts whenever you replace the head, but I don't
think that is the cause of the cracks. Re-using head bolts can cause head
gasket leaks down the road.
Looking at your additional information, I'm thinking that the aftermarket
header is causing the cracks, either through some kind of heat problem or
more likely because of difference in the way the header mounts to the head
from the way a cast iron exhaust manifold mounts. The cast iron manifold
has more mass to dissipate heat, and the stress from the exhaust pipe and
catalytic converter flexing is spread over a larger contact area on the head
than from headers, which less contact area.
If you can't find a factory exhaust manifold, check TRD. Also check to make
sure that the exhaust system doesn't flex too much by using the factory
hangers.
--
Ray O
(correct punctuation to reply)
.
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