This process is for those who wish to drill and tap the cast iron exhaust manifold for an Exhaust Gas Temperature (EGT) thermocouple in a DURAMAX.
A thermocouple is a sensor that, when heated, generates a very small electrical signal. The signal is then amplified and used to drive a temperature display gauge (EGT Gauge)
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Some have expressed their concern over metal chips falling in to the exhaust stream and damaging the turbocharger. Although this is concievably possible (damage), it is highly unlikely. Cast iron is a relatively soft metal and the chip thicknesses and sizes produced in the operation are most likely insignificant. The chips cannot enter the combustion chamber because the exhaust side is post-ignition and leads through the turbo and out the tailpipe. Also, the drilling and tapping is done with the engine at idle, when turbo speed is at it's lowest working rpm.
For those that are concerned, you may elect to remove the exhaust manifold.
Determine the thread size per the instructions supplied with your gauge/thermocouple.
Obtain the proper size drill bit(s) and tap.
Do not hesitate to purchase high quality tools. The extra few dollars is worth it in the long run. Stay away from the black "high carbon steel". Look for cobalt.
1/8-27 NPT use "R" (.339) dia. drill
1/4-18 NPT use 7/16" (.4375) dia. drill
3/8-18 NPT use 37/64" (.578) dia. drill
All of the thermocouples I have seen are National Pipe Tap (NPT). This means it has a tapered thread that seals by interference when tightened.
The wheel well liner must be removed but if I remember correctly, I did not have to remove the tire/wheel. This will depend on the drill motor you use and the tap handle size. You can raise the truck some with a jack under the frame, not the control arm, to provide extra clearance. A JACKSTAND IS A MUST.
The technique I used has sometimes been referred to as the "hoot" method
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I do all the drilling and tapping with the engine running. Contrary to what you might think, once you break through with the drill bit, the exhaust exiting the hole in relatively cool and is exiting at a very low pressure.
***************** CAUTION ******************
SAFETY GLASSES MUST BE WORN to prevent metal chips from blowing into your eyes.
The location I chose is on the passenger side at the rear of the manifold on a flat area of the casting.....
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In order help control location and ease the drilling pressure, I used a smaller diameter drill to create a "pilot" hole. This is a smaller hole that is easy to drill and acts as a guide for the full size drill. I believe I used something around 3/16".
Use a slow rpm when drilling and a little cutting fluid. Kerosene or diesel fuel will work fine but tapping fluid works best.
Drill the pilot hole first, taking care that you restrain your pressure so that as the drill begins to break through it doesn't plunge into the manifold, hitting the other side or worse, breaking the drill bit.
Change to the full size drill bit and repeat. Remember... slow rpm. Push just hard enough to draw chips. The exhaust will blow them in your face.
Tapping the whole takes a little more finesse if you've never tapped a hole or never tapped a pipe style thread. NPT pipe taps are made to partially enter the whole when first inserted. As you turn the tap, it cuts the threads and makes the hole larger to create the taper. Get in a comfortable position and use plenty of fluid. Keep the tap perpendicular to the manifold at all times. While applying inward pressure, turn the tap until you feel a stopping resistance. Now turn the tap backwards to "break" the chip you just cut. Repeat this clockwise/counterclockwise process until the tapped hole is deep enough to begin to accept the fitting. What I do here is keep tapping and testing the fitting for depth.
Care must be taken when re-inserting the tap. Turn it lightly to restart it, making sure you don't cross cut the existing threads.
Check how far the fitting screws into the hole. Once the fitting gets in about half way, you should be pretty close. Remember, you will also be tightening it a bit more with a wrench. Too shallow can always be opened up.
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Apply a good high heat antisieze dressing to the fitting and install it. DO NOT OVERTIGHTEN! Use a small wrench to avoid leverage. Tighten it to the point of reasonable resistance.
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Complete the installation of your thermocouple per YOUR instructions....
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The DieselPlace hopes you found this article helpful. Please feel free to reply with comments and suggestions.
The DieselPlace is not responsible for the content and it's usage. It is for reference only.
In the event that you would like to present this information on another website, you may do so only by hyperlinking to this post.
A thermocouple is a sensor that, when heated, generates a very small electrical signal. The signal is then amplified and used to drive a temperature display gauge (EGT Gauge)
Some have expressed their concern over metal chips falling in to the exhaust stream and damaging the turbocharger. Although this is concievably possible (damage), it is highly unlikely. Cast iron is a relatively soft metal and the chip thicknesses and sizes produced in the operation are most likely insignificant. The chips cannot enter the combustion chamber because the exhaust side is post-ignition and leads through the turbo and out the tailpipe. Also, the drilling and tapping is done with the engine at idle, when turbo speed is at it's lowest working rpm.
For those that are concerned, you may elect to remove the exhaust manifold.
Determine the thread size per the instructions supplied with your gauge/thermocouple.
Obtain the proper size drill bit(s) and tap.
Do not hesitate to purchase high quality tools. The extra few dollars is worth it in the long run. Stay away from the black "high carbon steel". Look for cobalt.
1/8-27 NPT use "R" (.339) dia. drill
1/4-18 NPT use 7/16" (.4375) dia. drill
3/8-18 NPT use 37/64" (.578) dia. drill
All of the thermocouples I have seen are National Pipe Tap (NPT). This means it has a tapered thread that seals by interference when tightened.
The wheel well liner must be removed but if I remember correctly, I did not have to remove the tire/wheel. This will depend on the drill motor you use and the tap handle size. You can raise the truck some with a jack under the frame, not the control arm, to provide extra clearance. A JACKSTAND IS A MUST.
The technique I used has sometimes been referred to as the "hoot" method
I do all the drilling and tapping with the engine running. Contrary to what you might think, once you break through with the drill bit, the exhaust exiting the hole in relatively cool and is exiting at a very low pressure.
***************** CAUTION ******************
SAFETY GLASSES MUST BE WORN to prevent metal chips from blowing into your eyes.
The location I chose is on the passenger side at the rear of the manifold on a flat area of the casting.....
In order help control location and ease the drilling pressure, I used a smaller diameter drill to create a "pilot" hole. This is a smaller hole that is easy to drill and acts as a guide for the full size drill. I believe I used something around 3/16".
Use a slow rpm when drilling and a little cutting fluid. Kerosene or diesel fuel will work fine but tapping fluid works best.
Drill the pilot hole first, taking care that you restrain your pressure so that as the drill begins to break through it doesn't plunge into the manifold, hitting the other side or worse, breaking the drill bit.
Change to the full size drill bit and repeat. Remember... slow rpm. Push just hard enough to draw chips. The exhaust will blow them in your face.
Tapping the whole takes a little more finesse if you've never tapped a hole or never tapped a pipe style thread. NPT pipe taps are made to partially enter the whole when first inserted. As you turn the tap, it cuts the threads and makes the hole larger to create the taper. Get in a comfortable position and use plenty of fluid. Keep the tap perpendicular to the manifold at all times. While applying inward pressure, turn the tap until you feel a stopping resistance. Now turn the tap backwards to "break" the chip you just cut. Repeat this clockwise/counterclockwise process until the tapped hole is deep enough to begin to accept the fitting. What I do here is keep tapping and testing the fitting for depth.
Care must be taken when re-inserting the tap. Turn it lightly to restart it, making sure you don't cross cut the existing threads.
Check how far the fitting screws into the hole. Once the fitting gets in about half way, you should be pretty close. Remember, you will also be tightening it a bit more with a wrench. Too shallow can always be opened up.
Apply a good high heat antisieze dressing to the fitting and install it. DO NOT OVERTIGHTEN! Use a small wrench to avoid leverage. Tighten it to the point of reasonable resistance.
Complete the installation of your thermocouple per YOUR instructions....
The DieselPlace hopes you found this article helpful. Please feel free to reply with comments and suggestions.
The DieselPlace is not responsible for the content and it's usage. It is for reference only.
In the event that you would like to present this information on another website, you may do so only by hyperlinking to this post.
