Cracked manifold

I just had the manifold replaced last year and somehow it's already cracked. Engine seems to get incredibly hot, even though temperature register remains in the normal range. Could the heat have caused the crack? And if so what might be going on in the engine to cause the excess heat? Seems to be part of a set of cascading problems related to the heat, including an electrical one that makes the ignition fail to work intermittently (bypassing the neutral safety switch seems to have *mostly* fixed this problem).

Thanks!

 

Did you torque the nuts/bolts to the proper spec? I've heard you don't want to overtighten them. You want the head and manifold to be able to expand at different rates and allow a little wiggle room along the gasket.

I guess excess heat could contribute, but I don't know why you'd have so much heat unless you are burning more fuel than usual or the thermostat and cooling system aren't working. You could monitor the actual coolant temperature by the OBD live data.

 

Quality might be your first issue if you're replacing it with lesser quality and cheaper product. Second, I would make sure the entire exhaust system hangers are in use and not just hanging on to dear life under there.

 

If you have a 2.7 then replace the cast manifold for the OEM 4Runner mini header (

$374 17141-75080 Exhaust Manifold

17141-75080). I've had mine for at least 8 years and no cracks.

 

I would check the engine mounts for excessive play.

 

Comes down to quality!!

#2 is the exhaust system supported as it should be??

Heat how hot is it glowing Red??

If it is thermal cycling normally it should not be a problem .

If it is hot and you hit cold water puddles on a constant basis that could cause problems.

Pictures of the crack would help.

 

Mini header upgrade.

What tends to cause it is the engine torquing (twisting when you press the throttle) and not having the exhaust bracket on your down pipe to hold it to the transmission. If it is not there, the exhaust pipe doesn't move with the engine when it twists but tries to stay stationary so it tends to crack the exhaust manifold due to it getting weaker from the HOT/COLD cycle and added pressure