im wondering if you can change the coolant or convert the coolant on my 1997 express from the green to the pink? the reason im asking is i keep loosing coolant out of my overflow tank from the cap drain hose and the coolant on the pink is a closed system.. when the truck runs it builds pressure to around 15 pounds but i lose coolant when i drive the van down the highway for more than 20 miles but doesnt do it when im driving 30+ miles in the city. anybody got any ideas?

 

color of antifreeze has no bearing on consumption on open or closed system, problem with green in your truck depending who/when the switch was made, did they do a proper flush, your van came with Dex-cool orange from GM if mixed with standard green or improperly flushed they are not compatable. I suspect a mechanical issue causing the loss, have you checked for water in oil? External leaks from heater connections, or weep hole in waterpump? if no mechanical external leaks foum possibly a leaking head gasket from improper mixing of coolant types in the past.

 

the truck has green in it and it being a titled 1997 but build in 1996 it would have came with green, it has a new water pump new thermostates new bypass hose for heater and im not seeing a leak other than the hose from the overflow tube from the tank, i have replaced the caps twice in 2 weeks and still lose it from tank. when i put a pressure test on system i just hook it up and let the truck run and it builds up between 15 and 17 pounds after runing for about 15 min

 

May have had green but I suspect Dex was what it would have had as last quarter 95 is when I think the swap to Dex started be that as it may, color of the coolant is not a contributor to your lost coolant, more questions than answers rite now.

Did you get a Diesel cap?

you say 15-17 psi @ idle ? what is your ECT at this time.

That high a psi in such a short time is odd to me, possibly on verge of overheating ?, I struggle to get mine to 170+F in 15 minutes of idle when setting up for a TDCO learn which requires temps above 170F.

 

the temp is around 190 i have removed the factory cooling fan and switched to an electric fan along with the oil and trans no longer run thru the radiator and as for the cap i got the one recommended by the parts store

 

You are seeing 190F @ idle ??? what temps are you seeing while driving ?

Bad idea electric fan, also bad idea no cooling of trans & engine oil through rad if not rad how are you cooling those ?

AC Delco for 6.5 Diesel is only rad cap you should be running.

 

im seeing 190 at idle after sitting for 30 min and i have a 16 inch 2500 cfm electric fan for the radiator that has a 200 temp switch in the waterpump plug that turns it on and off. i have a 10 inch electric 600cfm fan for the oil and a 12 inch 750 cfm fan for the trans . the oil fan comes on at 180 and the trans comes on at 180 and why is an electric fan a bad idea?

 

Electric fans can't move enough air to effectively cool a 6.5.

Even with the very best mechanical fans/clutches/waterpumps the cooling of a 6.5 is marginal.

As said coolant loss due to over pressure is has no bearing on coolant type,compression in the cooling system from a blown head gasket,cracked head or cracked block,or a stuck shut thermostat(s) is the most likely cause of the problem or a bad rad cap.

 

i havent had my temp go over 2 lines below the 210 line ever. i installed the electric fans over the summer and installed the remote coolers on the trans and oil then as well and the truck is curb weighted at around 14.780 pound. we also pull a 16 foot trailer with it that holds a kabota bx25 . i had the injector pump replaced around 2 months ago and have been adding a little coolant ever since then. i replaced the water pump and thermostates on thanksgiving day as the waterpump starting making noise and didnt want to wait till winter was full blown to have the waterpump go out. the tailpipe blows no white smoke and theres no bubbles in the overflow tank so can see it being a head gasket,block or head problem but at the same time im not seeing any coolant anywhere

 

What did you use for thermostats?
AC Delco or Robert Shaw are the only reliable stats available-all others do not operate properly in these engines-Delco are the first choice for all parts for these trucks.