Pressurized cooling system
Have you ever seen temps rise that quickly? I am inclined to believe that either a liner has slipped or the block is cracked. Anyway, I have put so much into the rest of the truck that I will probably do a new long block and call it a day. That way I can tear this one down and really go through it in the fall/winter.
Thank you all for the comments. I think that I may be safe to conclude that I have a blown hg. New water pump flowing nicely, new thermostat, new cap, new hoses, new viscous clutch/ fan. No air in system. Fresh coolant 50/50 mix. 10 minutes of driving from cold, temps fine at first with heat on full blast. Then temps started rising, and rising. Hit 260 before I could get it off the road. 199-265 in less than 60 seconds. Coolant boiling and hoses and expansion tank look like they are going to explode. Coolant changed colors.
Last edited by Extinct; Jul 11, 2023 at 07:59 PM.
What did you observe to determine the system was "overpressurized"? And did the temp spike happen immediately after you did all the other cooling system work?
I know that when I drain, flush, refill and bleed the cooling system every couple years the UltraGauge will initially show a spike to ~230° when I take the truck for a spin, but the temp also drops back pretty quickly (after a minute or so, I recall). Is it possible that's what happened in your case, and that you perhaps overreacted to a quick spike?
I agree with what others have said that if there's no coolant loss it's likely not a failed headgasket or cracked block. My money is on a failed thermostat (stuck closed), or on what I described above.
I'd try what Extinct suggested and try driving it a few miles with the cap fitted loosely (although that shouldn't be necessary with a well-maintained system).
I know that when I drain, flush, refill and bleed the cooling system every couple years the UltraGauge will initially show a spike to ~230° when I take the truck for a spin, but the temp also drops back pretty quickly (after a minute or so, I recall). Is it possible that's what happened in your case, and that you perhaps overreacted to a quick spike?
I agree with what others have said that if there's no coolant loss it's likely not a failed headgasket or cracked block. My money is on a failed thermostat (stuck closed), or on what I described above.
I'd try what Extinct suggested and try driving it a few miles with the cap fitted loosely (although that shouldn't be necessary with a well-maintained system).
I just thought that I would try again after refilling with the coolant that boiled over after the overheating 8 hours ago. Temps spiked again at idle. This time I left the cap loose.
Last edited by DiscoMerlin; Jul 11, 2023 at 10:33 PM.
What did you observe to determine the system was "overpressurized"? And did the temp spike happen immediately after you did all the other cooling system work?
I know that when I drain, flush, refill and bleed the cooling system every couple years the UltraGauge will initially show a spike to ~230° when I take the truck for a spin, but the temp also drops back pretty quickly (after a minute or so, I recall). Is it possible that's what happened in your case, and that you perhaps overreacted to a quick spike?
I agree with what others have said that if there's no coolant loss it's likely not a failed headgasket or cracked block. My money is on a failed thermostat (stuck closed), or on what I described above.
I'd try what Extinct suggested and try driving it a few miles with the cap fitted loosely (although that shouldn't be necessary with a well-maintained system).
I know that when I drain, flush, refill and bleed the cooling system every couple years the UltraGauge will initially show a spike to ~230° when I take the truck for a spin, but the temp also drops back pretty quickly (after a minute or so, I recall). Is it possible that's what happened in your case, and that you perhaps overreacted to a quick spike?
I agree with what others have said that if there's no coolant loss it's likely not a failed headgasket or cracked block. My money is on a failed thermostat (stuck closed), or on what I described above.
I'd try what Extinct suggested and try driving it a few miles with the cap fitted loosely (although that shouldn't be necessary with a well-maintained system).
Super high. Now you know why I have two brand new ones on the shelf I have been offering to give away to anyone who will pay shipping. Experience like you are having is exactly why I converted to inline.
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