egt probe [Archive] - Diesel Place : Chevrolet and GMC Diesel Truck Forums

Hotwater

11-30-2006, 11:18 PM

Here you go

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- - Duramax Pre-Turbo Thermocouple Installation (http://www.dieselplace.com/forum/showthread.php?t=892)

hoot 10-02-2003 06:59 AM
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)

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.
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Phil_to_DMAX 10-04-2003 12:32 PM
Hoot, Great article, I followed your procedure a while back and it worked great. What happened to you over at TDP? Last I heard you were complaining about updating the forum and then you were gone

Phil B.

hoot 10-04-2003 12:46 PM
Quote:
Originally Posted by Phil_to_DMAX
Hoot, Great article, I followed your procedure a while back and it worked great. What happened to you over at TDP? Last I heard you were complaining about updating the forum and then you were gone

Phil B.
Thanks Phil.

I am no longer allowed to post on TDP.
Edited by: hoot

Zip from Tenn 10-05-2003 01:38 PM

Thanks Hoot. Good article for those of us who haven't done this yet. But I disagree with you on the drill speed. (Real big deal,huh?) Cast iron is a relatively soft metal and really doesn't require a cobalt drill at a slow speed, as long as the drill bit is sharp. But of course, I agree with you on being careful when you break thru the casting. I'll be following the Hoot method when I do mine.

zip

hoot 10-05-2003 08:14 PM
Quote:
Originally Posted by Zip from Tenn

Thanks Hoot. Good article for those of us who haven't done this yet. But I disagree with you on the drill speed. (Real big deal,huh?) Cast iron is a relatively soft metal and really doesn't require a cobalt drill at a slow speed, as long as the drill bit is sharp. But of course, I agree with you on being careful when you break thru the casting. I'll be following the Hoot method when I do mine.

zip
Zip,

It's just more of a precautionary thing. You are absolutely right but it doesn't hurt to do the slow thing with a drill bit that only costs a few bucks more on a $40,000 truck.

I've been in the machining business for about 28 years. I've found that on one piece jobs it pays to take too long.

seatec 10-06-2003 11:35 AM
Wow, i've seen several stp throughs over the years on how to drill the probe hole but i never felt coformtable enough to it but this step through really make me think i can do it myself. thanx

Max Power 10-06-2003 02:47 PM
Thanks hoot. I just did mine today. I must say it was a bit hard on the nerves but all went smoothly. Thanks for breaking the ice for us.

egirardin 10-10-2003 10:14 PM
Hoot,

Thank you very much for that installation walkthough.

I was getting ready to install my my EGT this weekend and this page makes it all possible.

Much appreciated.

[10/11/03 5:00 pm EDT] UPDATE.

And it came out Flawlessly. Time for a beer.

P.S. I removed the tire anyway, it gave me a lot of
extra workroom to manuver. But I guess you could
do it w/o removing the sneaker. Cheers.

Edited by: egirardin

Mitchagain 10-20-2003 04:15 PM
Hoot, I followed your tips when you posted them some time ago on TDP. I just found this forum today and was glad that you are here. Because of guys like you, John Kennedy and many others, I now have the truck that I always wanted! Thanks for all the tips, and keep 'm coming!

hoot 10-20-2003 08:45 PM
You're welcome Ken. It's a pleasure doing it. I've learned tons on these forums. How did you find us?

wkbrd2damax 12-28-2003 10:26 PM
I am interested in installing a egt gauge but unsure of where to drill the manifold. I was directed by a manufacturer to install the sensor on the left manifold at the upper side on the front. Does it matter on the location? Have noticed int he past that some a/m exhaust come with a hole already tabed and plugged, but this after the turbo. Is it not better to be in the manifold for more precise reading? Thanks for the help, i'm new the site.

Mackin 12-29-2003 06:22 AM
Yes, pre turbo (manifold) is the best reading to achieve .... You can drill either manifold .... The rear of the manifold would be the optimum place for probe so it would be directly in the flow of the exhaust gases ....

The right side (passenger) is far more accessible to work on with the wheel liner removed ....

Good luck

Mac

hoot 12-29-2003 06:30 AM
Quote:
Originally Posted by wkbrd2damax
I am interested in installing a egt gauge but unsure of where to drill the manifold. I was directed by a manufacturer to install the sensor on the left manifold at the upper side on the front. Does it matter on the location? Have noticed int he past that some a/m exhaust come with a hole already tabed and plugged, but this after the turbo. Is it not better to be in the manifold for more precise reading? Thanks for the help, i'm new the site.
Was the direction you recieved from that manufacturer specifically addressing the Duramax engine?

If so Iwould be curious what their reasoning would be. Not that I think it's wrong. By putting the thermocouple up front, you would be reading egt of the front cylinder only. By installing it in the rear you get a combined reading of all the cylinders on that side.

As far as exhaust manifold or at the turbo is concerned, there are some that like to know the temps going through the turbo so they can protect it. They install a thermocouple there but you have to add a guesstimate amount of degrees (somewhere around 300 has been mentioned) to know what egt's are coming out the cylinders.

I prefer the rear of the exhaust manifold. Pretty easy to get to and give a good reading of what the engine is up to. For those concerned about the turbo, I would install a second thermocouple. It can be linked to the same gauge and switched or a second gauge can be added.

16gaSxS 01-12-2004 02:35 PM
When we drilled & tapped my 6.5TD we did it pre turbo also. just before you break through put your drill bit in heavy grease and most of the chips will stick to the grease and the few that fall into the turbo will not hurt anything. Same with the tap.

HD-Nate 01-14-2004 04:12 PM
Hoot,

Great article, but since I have already done mine may I add a couple hints…

1) Prior to starting your engine, use a center punch to help start your pilot bit.
2) I drilled down just a smidge, (technical term for 1/16th of an inch) just to have a good start.
3) Started the engine
4) Coated the drill bits with a heavy grease to help capture the shavings.
5) Tapped using 1/8th NPT, (Edge/Attitude) turned the tap ½ turn then back ¼ turn to clear the flutes in the tap. (No heavy grease on the tap as it would clog the flutes).
6) Run your NPT fitting in while the engine is still running to clear out the final few chips.
ARM 10-13-2006 10:41 PM
where would you drill for a post turbo sensor ??

arm

Fredrick 10-14-2006 01:42 PM
I followed the same instructions a while back and they worked great!! Thanks Hoot.

Idle_Chatter 10-14-2006 02:18 PM
Quote:
Originally Posted by Fredrick (Post 1351779)
I followed the same instructions a while back and they worked great!! Thanks Hoot.
Hoot doesn't live here anymore. He bought a Dodge almost two years ago now, his last post here was Nov of 2005.

ghost69_98 10-15-2006 05:18 PM
After I drilled my hole, I put a magnet on the end of a nail and put it in the hole. I was suprised at the amount of shavings that were inside. I kept cleaning the nail off and reinserting until no shaveings. It worked very well.

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