1990 GMC SL1500 4.3L 133k miles.
On a recent all day haul, at the end of the day the temp gauge moved towards the Hot zone a little farther than usual. About 3/4 between Cool/Hot. Never reached the red zone. Pulled over, cooled off a little. Checked coolant and it was nasty. Pure mud water. Wish I took a picture.
Anyways, today I decided to change it. And also thought that I'm gonna use whatever I have on hand, instead of going shopping for the "right" coolant. Hopefully that decision won't bite me in the arse later.
What I had on hand was Pentofrost E.
Started by draining all the mud coolant from the radiator. Then refilled with garden hose water and a bottle of this.
Ran the engine until it got to full operating temperature, and let it run at full temp with this cleaner for roughly about an hour. Heater was set on full blast, so I watched the temp gauge from the truck bed. All was good, so I proceeded to next step.
Since I had it on hand - I went ahead and installed Prestone flush kit on the heater core hose, while coolant with cleaner was draining.
Then connected the garden hose to the "T" from the kit, and ran the engine until water coming out of the yellow gooseneck was as clean as it can be. This step took over an hour.
Then drained the radiator again, and refilled with 3qts of Pentofrost E concentrate. Took it for a five mile drive, no issues. Drained radiator again and refilled with another 3qts of Pentofrost E. If my math is correct, then all things considered - I should be pretty close to a 50/50 mix.
Took it for a ~20 mile ride. Tried to overheat it, but temp gauge stayed nice and cool. So I'm gonna call this operation a success. Let's see how long this success lasts. Figured that new "incorrect" coolant is still better than who-knows-how-old mud water that was in there... Or regular garden hose water by itself... Was I wrong? Any potential issues with using Phosphate-free G13 coolant in this vintage GM V6? Given how easy it is to change - I can always do it again if the threat is real. But if no huge red flags are present, then I may just run this coolant for next couple years.
On a recent all day haul, at the end of the day the temp gauge moved towards the Hot zone a little farther than usual. About 3/4 between Cool/Hot. Never reached the red zone. Pulled over, cooled off a little. Checked coolant and it was nasty. Pure mud water. Wish I took a picture.
Anyways, today I decided to change it. And also thought that I'm gonna use whatever I have on hand, instead of going shopping for the "right" coolant. Hopefully that decision won't bite me in the arse later.
What I had on hand was Pentofrost E.
Started by draining all the mud coolant from the radiator. Then refilled with garden hose water and a bottle of this.
Ran the engine until it got to full operating temperature, and let it run at full temp with this cleaner for roughly about an hour. Heater was set on full blast, so I watched the temp gauge from the truck bed. All was good, so I proceeded to next step.
Since I had it on hand - I went ahead and installed Prestone flush kit on the heater core hose, while coolant with cleaner was draining.
Then connected the garden hose to the "T" from the kit, and ran the engine until water coming out of the yellow gooseneck was as clean as it can be. This step took over an hour.
Then drained the radiator again, and refilled with 3qts of Pentofrost E concentrate. Took it for a five mile drive, no issues. Drained radiator again and refilled with another 3qts of Pentofrost E. If my math is correct, then all things considered - I should be pretty close to a 50/50 mix.
Took it for a ~20 mile ride. Tried to overheat it, but temp gauge stayed nice and cool. So I'm gonna call this operation a success. Let's see how long this success lasts. Figured that new "incorrect" coolant is still better than who-knows-how-old mud water that was in there... Or regular garden hose water by itself... Was I wrong? Any potential issues with using Phosphate-free G13 coolant in this vintage GM V6? Given how easy it is to change - I can always do it again if the threat is real. But if no huge red flags are present, then I may just run this coolant for next couple years.