12.7 Detroit pushing coolant out of overflow

I think you are stressing a little (understandable, I would be too)

Get the motor to cool down, then open the filler cap. If there's pressure, even after cooling, I think your system is not venting properly (filler cap is suspect)

Too much coolant is bad for you...

 

1998 Detroit should be a Horton fan clutch. Sounds like a bad relay, or resistor. Or possibly the clutch selonid $150 ish. Or your clutch hub going $1100 for whole thing or
$350ish for rebuild kit.

 

sounds like you blow your head gasket or cracked an injector cup. before you get into changing your gasket check your heater control valve in the bunk.

 

If I'm following the blown HG rationale, then you should be able to test for combustion in the overflow coolant.

I'm not sure if the kit is readily available to you.

High pressure from crankcase will leak out via HG, and thereby push the Lower pressure (coolant side) out of the overflow. These exhaust gasses will be present in the coolant (may even show as a oily film in the reservour).

 

99 and older bunk heater valves are electric and air operated. When they go bad it pumps 110 lb air into coolant system causing many an unnecessary head gasket or overhaul$$$$$$$. Shut off the water valve to bunk.Fill antifreeze to proper level leave cap off and run for at least an hour to get all air pockets out of system. Open bleeder on coolant tube if so equipped.Then figure out why fans not engaging.Probably selinoid on firewall.My 01 is kicking on too often even in winter. Had same problem on my 99 opposite of your problem but still I suspect selinoid.Maybe get fan switch wired into cab so you can turn on manually that way you can lock it in when it’s cycling a lot like when your parked saves on fan clutch wear.I think you just overheated antifreeze expanded filling tank then you topped it off actually overfilling it or had air pockets in system either way wreaking havoc and ofcourse worst case scenario thinking. All backed up by every mechanic telling you you need a head gasket or overhaul.I would spend the money on a selinoid since they are a known problem on older Freightliners.Meanwhile I would lock in fan and run it full time engaged. Till I had a chance to fix it avoiding costly downtime

 

Just a note water boils at 212f. Antifreeze I believe 234f Some claim up to 265f or so I don’t believe that myself but my guess is 50/50 boils around 221f either way it expands before it boils

 

The fan is working with the A/C according to OP. That eliminates the solenoid. If it has a manual switch that eliminates the solenoid. There are 2 ECT sending units and 1 sensor. Sensor is for ECM. 1 sending unit for the gauge 1 for the fan

 

So Not to hijack the thread but why does mine come on at anytime even below 180 with a/c off?Where do you find these 2sensors ?