First things first, what's an EGR valve?
The EGR valve helps your car more efficiently and completely burn fuel by recirculating a portion of your exhaust and running it through the combustion process again. This results in a cooler, more complete burn of the fuel which decreases you car's noxious emissions by prohibiting the formation of some harmful gases.
The benefit of the EGR is just to meet emission targets, nothing more. The problem is that with most emissions devices, you end up with losing power and economy as a result.
The benefits of blocking the EGR are less black smoke, increased power, less crud (carbon particles) being passed back through the system, and a slight increase in fuel economy. Some would also argue it adds to head problems as it gives uneven temperature across the head. It makes sense to do it.
When I used this process, I was rebuilding my engine at the time so everything is easily accessible. You can do it if you aren't rebuilding your engine, but the inlet and exhaust manifolds need to be removed to perform this procedure the way I did it. I would only recommend it if you have at least basic engine knowledge, otherwise use this process here - Blocking Off Toyota Surf EGR Valve.
If you end up using this procedure, when you remove the inlet manifold you'll see all of the shit that has accumulated in the manifold and you'll understand why your diesel chugs out more smoke than Puffing Billy.
Here's what I did.
1: Remove the inlet manifold EGR studs.
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2: Use a core (welsh) plug to block off the manifold bypass tube opening.
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3: Silicon the opening for the insertion of the core plug.
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4: Silicon the core plug.
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5: Position the core plug in the EGR bypass opening.
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6: Bed the core plug. I used a hammer and a gympie, to ensure equal diametric pressure. The last thing you want to do is to insert it on a skew as it will compromise the seal.
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7: Clean of any excess silicon and viola! The core plug in-situ.
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8: Remove the exhaust manifold EGR studs.
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9: My studs wouldn't budge so I had to use a hacksaw to remove them.
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10: The studs after they've been cut.
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11: As with the inlet manifold, use a silicon on both the core plug and the EGR bypass opening.
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12: Clean of any excess silicon and viola! The core plug in-situ. The process is now complete. All you have to do now is finish rebuilding your engine or put everything back together.
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Here are the silicons I used. The copper mix is for the exhaust side and the black is for the inlet side.
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The core plugs I used were purchased from Veale and the part numbers are CPA71205 and CPA67205.
Now you can throw this shit out!
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I have been using the car now for six months and I can attest to an improvement in fuel economy and power, and also less black smoke from the exhaust.
It also makes working around the engine easier because it's no longer in the way.
DO IT!