VERY strange EGT's

[Lathe Guy]

I have just gone over 11K miles. All of the sudden my EGT's come down as fast as they go up. I live Phoenix. We are at 113 degrees today! Before when I would get anywhere I would sit for 3 or 4 min. and wait for the temp to come down to 300. Now it only takes 10-15 seconds. Whats going on here? Is this something that changes with millage? I checked my probe fittings. All tight. No vacume or turbo or exauhst leaks. The truck still gets it on. No noises, nothing.

 

[rbattelle]

Where's the probe mounted? 3-4 minutes to cool sounds too long to me, 15 seconds seems much more normal (for unloaded driving).



-Ryan

 

[Lathe Guy]

The probe is mounted just before the turbo. But it has always been there.

 

[Blue2002]

EGT Probe: negative temperature co-efficent

My EGT probe acts like yours. When the outside temp is warmer, the gauge seems to reach 250 deg easier. When it's cooler outside, it seems to take longer to reach 250 degrees. I thought I remembered reading something about a negative co-efficient on these probes (compares outside temperature with exhaust temp?). AHA here we go - calibrated at 70 deg F: read the section on thermocouples http://www.westach.com/repair.htm#THE PRINCIPLE OF A THERMOCOUPLE

 

[Lathe Guy]

Thanks, I will.

 

[DIESELMAN]

Its 115 Degrees outside, where is the end of your probe wire leads? The output is usually temp compensated at 70 or 77 degrees, ie, the output is correct only if the cold junction is at 70 degrees. Now if the leads end in the A-Pilar, and the air in there, tucked behind the guage wrapped in steel sitting in the sun, or under the carpet behind the engine, is at 110 degrees, the indicated temperature will show 50 degrees in error, colder, than it really is.



This is part of the summer/winter EGT difference.



DM on the Road

 

[Lathe Guy]

It all makes sense... Thanks All!



I just wanted to solve this before summer hits!!

 

[Lathe Guy]

Well I guess I spoke prematurely. It was 88 degrees this morning and I'm idling at '0', but I can still hit 1400 quickly if I'm not paying attention.

 

[Lightman]

Somthing else to look at is are you running your A/C it makes the air over the inter cooler about 200* hoter so there for cool down will be longer. Try turning off your A/C and see if it doesnt cool down faster

 

[rbattelle]

Try turning off your A/C and see if it doesnt cool down faster

Mine certainly seems to!



-Ryan

 

[claymike]

Yup with the AC on it seems to take longer to cool down.

 

[Lathe Guy]

A/C always off on cool down. I sent the gage, wires and probe back to Dipricol. I'll post thier comments.



p. s. It's amazing how naked I feel without an EGT gage... ... .

 

[MMeier]

Soinds like the probe took a dump, let us know !!

 

[Lathe Guy]

I sent the gage, wires and probe back to Danin Inc. in Huntington Beach. I'll keep you posted.



Thanks for all the help.

 

[Lathe Guy]

Well I just got off the phone with the gage Mfg. (Danin - DiPricol) they said I melted the gage and the connector! They are replacing it for free. I guess I need to use the sun shade.



Phoenix SUN: 1

Dash gage pod: 0

 

[puebla]

Same thing here, my pre turbo EGT gage displays rapid cooling within 20 seconds idling... I don't know about 3 minutes.