12.7 tough spin when cold

I’ve been through the exact same thing twice. First time, it suddenly got worse. Went from adding one-two gallons of coolant a week to 3 gallons in 24 hrs. Head gasket blew, Engine hydro locked, dropped a liner, 500 miles from home. Second time, different Truck. One year ago.Adding coolant, running water. Coolant making pressure. Ran it home, 1500 miles. Had it overhauled. My guess is it’s pushing coolant. You can do a bubble test using the overflow tube. Or use a pressure test kit. Borrow one from the auto zone, or O Reilly’s. Put 10lbs in it, see if it holds. Start it up, see if it builds pressure. Sounds like the fuel issue is just worn rings. Judging by excessive blow by. Head gasket is leaking, due to corrosion, or a low liner. It’s only a matter of time till it blows and hydro locks. Might be a pin hole in the top of a liner, and it’s burning off, either way it’s going out the stacks. An overhaul kit and head are about $4000. Labor $3500. Bull gear $850, Labor around $2000. So for around $11000 plus oil, coolant, filters, you’ll be good to go. Question is if the Trucks worth it or not. It’s inevitable. You can isolate the compressor, by looping the coolant hoses together, and taking the air line off it, while doing the pressure test. Might get lucky. But coolant is going somewhere. The ground, the oil, or the exhaust.

 

Hopefully you don’t wake up like I did with a locked up engine.

 

That is true, forgot about that I did have coolant in air tank. But that’s been over 20 years. Good point

 

What does exhaust smell like when it does fire? Have you tried to manual bar motor when it is cold? Do oil samples? Coolant additives will show up in oil before you ever see it on the dipstick.

 

You can also buy water indicating paste to see if coolant present

 

My guess is that the head gasket is leaking. I’ve done all the same things as you. Ran with cap loose, buying time. Changing thermostats. Hoping for the best. Changed a Leaking oil cooler, on one engine. Waterpump on this one. Before realizing it was building pressure, causing the failures. If it’s building pressure, any weak point will leak. A lot of things leak when cold. Fluid, air lines. Brake chambers. Cold weather always shows up the leaks. My guess is the head gasket doing the same. You need to do a pressure test. At least put the cap on good, and put the overflow tube in a bottle of water. Any pressure will show up right away. A radiator pressure kit, borrowed from autozone or Oreillys will tell for sure. You need to rule out all other points. Hoses, Waterpump weep hole, heater cores and water valves. Any shop can do one for you. Minimal charge. You never mentioned what year make of Truck you have.

 

Ok my mistake. I see it’s a 93. You need to rule out any air over electric water valves, for heater cores. A lot of Trucks had them prior to 2000. Freightliners had them on the bunk. Look for the valve near the heater core. Look for a small airline running to it. If so, it may be bad. When bad they work fine, while open and coolants circulating. Once they’re closed, either by adjusting the thermostat on heater control, or turning the key off, they’ll put 100+ lbs of pressure into the coolant. Since the problem started when it’s cold, maybe since you turned the water valves on? So if you have one, and it’s bad. You can run the Truck, with heat on, cap off, and when you turn the hot/ cold dial to cold, or turn Truck off, coolant will shoot out of the surge tank. Check it out. Might be your problem. Check both valves near both heater cores. Some Trucks had them on the Cabs too. Mimics a blown head gasket symptoms.