Auto Repair - Roadshow forum

Question

Can cracked exhaust manifold cause engine temperature rise?

I became aware that my exhaust manifold has a small crack in my 2001 Honda Civic. Just recently I have been having problems with the engine temperature rising. Can a cracked exhaust manifold contribute at all to the engine temperature?

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All Answers

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Answer
Can be lethal. I know folk that will dismiss this.

In reply to: Can cracked exhaust manifold cause engine temperature rise?

http://www.aa1car.com/library/overheat.htm lists a lot of issues but if this plus another issue is present, sure.

Now by rise I have to guess you mean beyond the normal rise. I run into folk that run low on cooling fluid and only add water. There's a proper mix to cooling fluid and water alone will eventually dilute to the point you see issues.

How long since you changed the coolant, do you add only water and more questions need to be asked.

But this can be dangerous to operate, read that link.
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Answer
Not likely, but....

In reply to: Can cracked exhaust manifold cause engine temperature rise?

....if there's a cracked block behind it, where it's attached, that might.

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Answer
Most like cause of temp rising

In reply to: Can cracked exhaust manifold cause engine temperature rise?

Is usually sticking thermostat, failed water pump, or some obstruction in a hose or radiator.

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I've only had a few overheating cars to deal with

In reply to: Most like cause of temp rising

In the past decade. They were pretty evenly split over the owner used only water to the other issue they let it run low.

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what I do for a flush

In reply to: I've only had a few overheating cars to deal with

I use vinegar (organic acid) and dishsoap to clean flush a car's water cooling system. The vinegar will remove built up rust without damaging the good metal since it's organic acid. The dish soap helps emulsify any grease or oil that might be in the water covering the rust areas. Works great and better than some of the chemicals they sell in auto store for such flushing.

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Answer
Cracked exhaust manifold

In reply to: Can cracked exhaust manifold cause engine temperature rise?

Hi, John; A couple of things come to mind, here. Depending on where the coolant temp sensor is located, it could be picking up the hot exhaust blowing on it and giving you a false reading? If the crack in the manifold is ahead of the upstream oxygen sensor, could cause a rich fuel condition. These manifolds are 'relatively' inexpensive. It is a very easy test to check for a cracked head or gasket.
I would recommend replacing the manifold, then go from there. As the other guys noted, be certain that the cooling system is in good shape.
Good Luck!
Loren

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