Cooling System/Hoses DII
 

I'll try to make this short. I have had cooling issues the last two months, truck running hot. I noticed one day that the hose running from the T-Stat to the plastic T junction was expanding like a balloon, and when I would squeeze it, the overfill would slosh around. I knew the hose would need to be replaced, but did not do it, I replaced the T-Stat instead and did a complete flush of system, water flowed nicely through the system. Well that hose finally blew, and replaced it with a non OEM hose. I refilled the system with nearly two gallons of Dex, ran good for a day and then the T junction broke off, like it exploded from pressure on the side where I attached the new hose. Any ideas on what is causing this apparent pressure build up with that hose?

Sounds like your coolant system is blocked up somewhere and you should not operate truck until fixed. Dex sucks and is harder to maintain so you need to flush all that out and go back with peak 50/50. Some of the other guys will chime in with a more direct place to start looking but i would like to think your water pump is not pumping correctly.

Would suspect clogged radiator from Dexcool. IMHO you would be wise to check rad fins top to bottom after truck has warmed up. If more than 10F difference, with bottom being colder, it can be a sign that coolant has sludged inside rad. Many references to Dexcool problems. See pix of sludge. Also replace the coolant reserve container cap, it is supposed to vent at 18 PSI, but Dexcool eats those up as well. As for why too hot, could be other issues as well. Link to common issues in my signature.

Also, factory gauge is not very precise, consider an Ultra Gauge so you can see it climbing before the gauge does.

your year and milage would help to know. you say your truck was runnning hot, did it over heat? did the red warning light come on. are both your fans working? (clutch & condenser)
why would you replace the t-stat and not replace the hose that you knew was bad? and why would you refill using DEXCOOL?
your truck could be building up preasure from exhaust gases (headgashet or sleeve) or the new t-stat could blocked with trash from the inside of the radiator hose that blew.

When ever you squeeze a hot coolant hose, that extra pressure of your squeeze will cause the pressure cap to vent any pressure over 18 pounds.
Are you hose all new or original.
Get rid of the Dexcool. Consider replacing your t/stat with a cooler soft spring t/stat.

Original hoses and pressure cap

You should replace your cap and hoses also what bleeder do you have on top of fan shroud or where the T is?

'99 144k. It began to over heat, but never got to redline - I shut the truck down before that. Appears that I need to get off Dex. How do you check for exhaust pressure? Any additives to clean out potential DEX sludge in radiator when I do a flush?

you can buy a test kit at most of the large auto parts store to check for CO2 in the coolant

Interestingly enough, there is no bleeder screw. I noticed threads about it, but did not worry about it, because the original owner did not seem to have problems with cooling, and I did not either until now, 81k miles later. How important is that bleeder?