12.7 Detroit pushing coolant out of overflow

I thought there’s just a temp sensor and a sensor that’s part of selinoid

 

I’m curious as to what it is a friend of mine has same prob on 05 Pete w a cat

 

They are in the thermostat housing on a CAT.

 

Overheating with fan on and coolant pressurized. Time for head gasket and possibly a new head. Do injectors as well. At that many miles it would make sense to do whole motor though

 

You can test the fan clutch by draining the air tanks. When you start the truck the fan should be full blast spnning.
For the coolant try a new filler cap. You would be surprised that something as small as that could have such an impact

 

Friend of mine fixed his 05 Pete turned out to be a sensor.

 

It could be a new problem of 1 stuck thermostat along with an existing fan problem for that matter be sure to eliminate simple things.I had a water pump that sheared and worked partially that is tha impeller still turned a bit. Easy check remove hose and pry impeller it shouldn’t turn.I would have never thought of it except it happened on an old slant six dodge.Didnt figure it out till spring when it got hot!!But you can put overflow tube into a bottle of water and look for bubbles. If it’s making pressure from head gasket or liner pinhole or heater valve even isolate air compressor as a bad compressor can put air into the system.

 

For some reason I thought you had a Freightliner.Im not familiar with heater valves on Volvo’s.Sounds like fan is good since it does respond to a/c high pressure switch.Its got to be a sensor as someone else suggested.

 

When my previous Ser 60 Detroit was doing this ( pushing coolant through the overflow) , the problem was, worn out injectors o-rings and the fuel was mixing with the coolant. The coolant got dark in color and oily. Time for new set of injectors with new injector cups and all the seals and o-rings.

 

I believe you have to remove head and press new brass cups in. Very expensive. But an o-ring kit is cheap. It comes with a crush washer that crushes when injector is torqued down. I’ve done 2 injectors so far.The first one was still good just needed O-Rings.I kept original for spare.Its been 4 yrs or more. The second one last summer. It was spraying out of top .I ran 60 miles had 10 gallons of fuel in oil before ecm shut it down !! The only thing is front main seal still seeps oil but it was pushing the fuel out all over. Both cups had visible minor damage from the pounding they take.Just had oil sample come back so good I’m wondering if they just made the report up!!!! It’s the best oil sample I’ve ever gotten on any truck I’ve got over a million on an overhaul.I was expecting to find fuel in oil due to another inj seal.Will overhaul Soon just been running for 9 yrs now doing only bare nessesary repairs.Cant believe the service from this Detroit.Very economical.