If I'm Going to Flush the Radiator AND Change the Thermostat...

[Dabblingman]

What order would I do that in? Or when in the process would I change the thermostat? Old truck (99) new to me, trying to both troubleshoot and do maintenance on a coolant issue. TIA!

1999 Ford Ranger V6 3.0

 

[19Walt93]

I'd do the thermostat after you've drained the system because it would be less messy. If the coolant is rusty and discolored make sure to pull the block drains so you can do a complete flush. And remove the heater hoses and flush through the core, too. If you aren't refilling with premixed coolant use distilled water to dilute concentrated antifreexe.

 

[ekrampitzjr]

You'll have to drain the coolant anyway. You should also siphon out the coolant in the overflow tank and replace it with fresh mixture. After draining the coolant, then change the thermostat, get that resealed, then flush the radiator. Leave the step of adding the new antifreeze mixture until last to make sure you have no leaks.

You probably know how to refill a radiator with coolant, but here's a refresher. Just did this myself a few months ago. Fill the system as much as possible through the radiator, start the engine with heat on (fan low), and top the coolant as the system purges itself of air. Expect this to take at least half an hour of run time, and keep a funnel in place in the radiator-cap neck. After you put as much coolant in as possible and the coolant level in the radiator stops going down, drive the truck as usual, but expect more purging over the next several days. As this happens, the replacement coolant will come from the overflow tank. Keep an eye on the tank and top it as necessary with antifreeze mixture. After a week or so, the level in the tank should stabilize, meaning that the air has been purged.

Hope this helps.

 

[ekrampitzjr]

What I wrote above assumes you don't have a lot of rust and gunk in the system, as 19Walt93 warns. If (here I go again about these products) someone has used a stop-leak in the coolant such as Bar's Leaks, you would be better off to plan to replace the radiator and probably the heater core.

 

[RobbieD]

Old truck (99) new to me, trying to both troubleshoot and do maintenance on a coolant issue. TIA!

This would also be a perfect time to examine all of the coolant system hoses, and replace any that have cracks, splits or internal separation.

It's also a good time to inspect the AC condenser, and the radiator behind it, for bugs, leaves and trash lodged in the cooling fins, and clean them as needed.

 

[Dabblingman]

Completed, with much mess and much drama. The ChrisFix videos were sort of good, but left out opening the lower radiator hose, which would have been excellent to know beforehand. Will post my next coolant related question in a new post.