TrailMedic
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- Jan 11, 2023
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Question for the brain trust.... I have an 2012 3500 6.7L diesel. A while ago it started overheating momentarily and loosing cabin heat. Sounds like low fluid? filled radiator and reservoir, bled properly, and it kept doing it. I took it in to my local shop who has a Cummings 'expert' who ran a lot of testing...compression, head gasket, pressure test...all good. They replaced the thermostat and called it good. Drove well for about a month before it started doing it again. Took it in again, more of same testing all good again, replaced the radiator cap...'that should fix the problem'...well it got to 220 on the way home WITHOUT cabin heat, but then back to 190-200 and cabin heat came on (is this the point where the new thermostat failed, and now stuck open?)
They did mention a 'pinhole' leak in the reservoir...but that would not cause it to overheat/no cabin heat on the way home from the shop. Since then, it has been driving fine but taking a while to warm up , and likes to run 180-190 (too low? new thermostat stuck open?), but I do have cabin heat. Ran well until yesterday...on the highway at steady 65 mph, cabin heat warm...started noticing cold air, then temp went from 190 to RED within 60 sec, by the time I pulled over, went back to 200 and ran the rest of the short drive at 200 with cabin heat. couldn't have been more than 2 min of terror, but UGH. Coolant reservoir now way past the Full mark at cold...not returning to radiator
Questions:
1. there seems to be a connection between no cabin heat and the overheating. While this would indicate low fluid, it has done this with freshly bled system. Does the hot water to the heater core need the thermostat open? before the problem started, I seem to recall getting a little hot air while the engine warmed up. And it seems that in all other vehicles, you get a little warm air while heating up to the thermostat opening.
2. On the drive yesterday..up to RED and back loosing cabin heat within 2 minutes. I have always thought of this being a mechanical system, but water isn't going to heat up and cool down that fast...can there be an electrical but in the system? However, there was radiator blow off from the radiator cap when I got to my destination...so I will assume that there was extra pressure in the cap for those 2 minutes, but what about the rapid spike?
3. With the reservoir coolant seemingly not returning, other posts would indicate a bad head gasket....They have tested for this twice!
I'm going to replace the reservoir myself, as the pinhole leak that doesn't cause it to fail a pressure test, might be loosing more while driving.
But , there have been enough problems when fully bled and topped off it can't be just the reservoir.
If you've made it this far through a long post...BLESS YOU and thanks. Any input will be greatly appreciated before returning to the local shop.
They did mention a 'pinhole' leak in the reservoir...but that would not cause it to overheat/no cabin heat on the way home from the shop. Since then, it has been driving fine but taking a while to warm up , and likes to run 180-190 (too low? new thermostat stuck open?), but I do have cabin heat. Ran well until yesterday...on the highway at steady 65 mph, cabin heat warm...started noticing cold air, then temp went from 190 to RED within 60 sec, by the time I pulled over, went back to 200 and ran the rest of the short drive at 200 with cabin heat. couldn't have been more than 2 min of terror, but UGH. Coolant reservoir now way past the Full mark at cold...not returning to radiator
Questions:
1. there seems to be a connection between no cabin heat and the overheating. While this would indicate low fluid, it has done this with freshly bled system. Does the hot water to the heater core need the thermostat open? before the problem started, I seem to recall getting a little hot air while the engine warmed up. And it seems that in all other vehicles, you get a little warm air while heating up to the thermostat opening.
2. On the drive yesterday..up to RED and back loosing cabin heat within 2 minutes. I have always thought of this being a mechanical system, but water isn't going to heat up and cool down that fast...can there be an electrical but in the system? However, there was radiator blow off from the radiator cap when I got to my destination...so I will assume that there was extra pressure in the cap for those 2 minutes, but what about the rapid spike?
3. With the reservoir coolant seemingly not returning, other posts would indicate a bad head gasket....They have tested for this twice!
I'm going to replace the reservoir myself, as the pinhole leak that doesn't cause it to fail a pressure test, might be loosing more while driving.
But , there have been enough problems when fully bled and topped off it can't be just the reservoir.
If you've made it this far through a long post...BLESS YOU and thanks. Any input will be greatly appreciated before returning to the local shop.
