eurovanrescue
Samba Member
Joined: April 08, 2018
Posts: 6
Location: San Diego, CA, USA
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 Posted: Fri Sep 21, 2018 9:54 pm Post subject: Another manifold thread |
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Wondering what effects a cracked manifold has on a 1993 Eurovan?
I'm not a real mechanic... I just think I am.
Can anybody elaborate on what symptoms my 1993 Eurovan would exhibit? A recent trip to have the exhaust worked on to pass smog revealed that my manifold has a crack.
Also, if I were to source a replacement manifold, how difficult is it to replace? And/or if I were to pay a shop to install the manifold, what would be your best guess on cost? Assuming that they also have to connect the downpipe (I just said that to sound like I know what I'm talking about, even though I don't) |
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Thoragaverung
Samba Member
Joined: September 15, 2018
Posts: 81
Location: Saint Paul
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| Posted: Sat Sep 22, 2018 9:16 am Post subject: Re: Another manifold thread |
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I don't have direct experience with Eurovans (yet) but from my generalized knowledge, which includes cracked manifolds on multiple vehicle types...
Modern fuel delivery systems rely on Mass Air Flow sensors to computer control the air-fuel mixture. The air passes through a chamber that measures the amount of air based on how it cools a heated wire in the stream. Once the air volume has been measured, the computer decides how much atomized fuel can be efficiently burnt.
The problem that arises from a cracked manifold on a normally aspirated car is that extra air enters the stream post-measurement. The computer thinks there's LESS air in there that is actually there. So it's adding LESS fuel than would be appropriate to the volume of the air that's actually entering the engine.
This is a 'lean' condition, and can lead the engine to idle poorly, or stall, and maybe even cause the cylinders to run hot to the point you get some stuff melting in there.
On a turbocharged engine, a cracked manifold leads to pressurized air escaping from the stream after it's been measured. This leads the computer to think it should be adding MORE fuel (a RICH condition) than it actually should. That can screw things up as well -- flooding, stalling, refusing to start, run-on after shutdown, gas in the oil.
Sometimes intake manifolds can be repaired, so they don't leak, but usually the high-heat environment makes the patch temporary. I wouldn't do it unless its on a beater vehicle that I'm just trying to make last a few weeks or months longer before scrapping it.
Replacing the manifold is usually the best course of action.
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Happy to help, but my advice comes with no guarantees. Use at own risk. |
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