Hey guys,
I have a 2007 5.9 with Dipricol gauges that are likely 12 or so years old.

Engine isn't modified at all. Totally stock from a power output perspective. But it does have the pac brake exhaust brake on it, and it has been whistling a bit recently.

Recently, I have been seeing high exhaust temps on the pyrometer when towing uphill. I cannot figure out if its the gauge giving a false reading or if the temps might be real. I can keep the temps under control if I lug the motor well below 2k rpm, but If i downshift and blow a lot of air the temps try to go way past 1400 deg.

There were definitely some events over the last couple years where that dipricol pyrometer was giving false high readings. Like ludricous temps. and if i simply power cycled the gauge, they would immediately drop 500 degrees.

The pyrometer behavior is super sensitive to engine RPM.

What do you guys think I should do? Check the exhaust brake and catalytic converter for blockage? Other problems with the engine I should hunt for? Or do you think its a bad gauge? I think dipricol has been out of business for a decade.

Usually thermocouples do not fail with a false high output, but that gauge could be doing anything with the signal.

 

I have the same gauge, and it is 13 years old. Every now and then when I start it, the gauge doesn't reset to zero. When it does that, if you cycle the key it usually fixes it. The cause is a bad ground, usually at the back of the gauge. I have had to "fix" mine several times.

 

I have a 15 year old DiProcal rail pressure gauge that is still hanging in there!
I've have a couple of minor issues with my 15 year old Autometer gauges over the years but nothing major.

In your case, what are your boost levels? Usually lugging increases EGT's and downshifting, to increase RPM (and boost), will decrease EGT's but you state the opposite.
I would be monitoring the boost levels like a hawk. Have peak boost, high load boost and cruise boost levels changed?

 

Boost levels are totally normal or this truck. It can get up to 30 psi.

I am starting to wonder if the problem could be a bad or dirty probe, if the TC sheath is cracked, and carbon is getting inside, it could be affecting the voltage at the thermocouple junction.

Regardless, I ordered an Autometer pyrometer, and it is sitting on the work bench in the garage, Now I just need to find a few minutes to install it.