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thomastractorsvc

1992 E7 400 Shutdown Light comes on

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Been working " Big Ugly " a lot and had it in to the Mack dealer as they were doing overhead specials for$475.   While it was there I had them check the "jake" as it was starting to cut out and do a service.

With in 700 miles of having it in I had started losing power and EGT went up to about 1000.  I pressure tested system found leak at the air compressor inlet separator/filter valve.  Got that fixed and installed a boost gauge.  Hard pull 90 to 100K I am getting 30 psi boost egt is 900 to 950 no smoke, temp gauge shows about 190.  If I let up and baby it egt about 850 to 900 boost about the same temp stays around 185.  Oil pressure around 60psi both ways hard or babying.

If I baby it the shut down light does not come on, if I pull hard it will.

the lighting bolt does not come on, truck does not lose power, does not shut off.  If i turn truck off it will reset.

I have checked coolant as Superdog thought they may be the issue, I checked wiring to the sensors and unplugged the pin plug on the pump and checked the wires all seem good same with the ecovance.

What other sensors would make the light come on without shutting the truck off or throwing a code?

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If it's the red shut down light, I'm pretty sure only 3 sensors will activate it, high coolant temp, low coolant level and low oil pressure. 

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I think it is the high coolant temp sensor.  It only comes on when I am pulling heavy and hard and the temp works it way towards 200.  I watched it yesterday and when it was just above 195 degree mark the light came on.  It stays on even after the temp settles back down.

My jake quit working again so I am going to pull the valve covers today and check the valves myself and the jake wires.  I am glad I spent so much money at Westfall Mack in Kansas City to get this issue fixed.  I check my miles less than 1200 and since they put there hands on it been one thing after another.

 

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We had so many problems with the coolant sensors in some of the later series 60’s we started putting jumper wires on all of the trucks to remedy the problem instead of leaving us stranded on the highway. Get to our destination and and take the jumper wires off and plug the sensor back in and truck would run fine for a long time. Maybe you’re running into a similar problem as I have described? 

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