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Flushing Coolant System

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bocoogto

New member
Conditions inside my coolant system are horrible. I believe the original Dexcool is still in there. There is slime the consistency of jelly. Today, I decided I'd drain the system, flush it, and put regular anti-freeze in it. Serious problem--I cannot reach the radiator drain cock on the passenger side. I cannot reach the lower radiator hose where it attaches to the radiator---not even close.

Is there an easier way to drain the coolant system than disassembling the front end of the car? This is the first time in my 76 year life that I've seen such a ridiculous engineering debacle.
 

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Just wait till you attempt the thermostat. Like you I was frustrated, needed it done and didn't have the time to remove half the car. I cut the lower hose in the middle, drained and flushed the system and reattached using a hose coupler. I have since replaced the hose, and you will need the clamp tool like this.

Sears.com

Good luck with whatever you do.
 
When I drained my radiator I removed the splash guard, and was able to remove the lower hose on the driver side using a pair of long needle nose pliers to reach the clamp. It's not fun, and I have replaced my clamp with a worm gear clamp to make it easier for removing later.
 
Yeah screw those factory hose clamps. I've lost count of how many blood blisters I've gotten from pliers trying to get those off.
 
wont say how to drain, but it would be wise to pull the heater core hoses and flush the heater core out through the hoses. run water through them in both directions a few times.
 
you don't need to pull the lower radiator hose.

- remove thermostat
- disconnect top hose from radiator
- put your garden hose with clean water in the top radiator neck where you just took the hose off (not the capped neck)
- point the top hose somewhere safe (into a bucket). turn heater controls on high.
- turn the garden hose on and start car. flush that **** out until it runs clear
- turn off the hose and run the car until the radiator is empty then shut off the car (don't overheat it)
- connect top radiator hose
- replace thermostat and open the bleeder on the t-stat housing
- put a couple gallons of green in the radiator through the neck.
- fill the radiator with clean water and start the car again (heater on high)
- keep filling the radiator and watch for water to come out of the bleeder screw.
- shut off the car. top off the radiator and put on the cap. Fill the reservoir halfway with clean water.
 


ScottyDOg's write up is good too

how to flush coolant.

remove the t stat, put the t stat housing back on, take the upper hose off the radiator, then push it down to the ground to a bucket or let it fly.

get your garden hose out, put it in the rad turn it on, then fire up the car, let it run till clear water pumps out the top hose.

then turn the hose off, run the car till no more water comes out the upper hose. then turn it off.

put your t stat back in, with new gasket, the upper hose back on.



now take 1 gallon of full strength green antifreeze, not the 50/50 crap. ( parts store cheap green is fine to use) dump the whole gallon in the radiator, fire up the car, fill the rad with hose water till its full. top as needed till its ready to be bled of air. it will burp and take coolant as the water in the block warms up the t stat opens up for a few seconds till cold coolant hits it and it shuts again.

now to bleed the air out, let it idle rad cap off till the fans turn on, (when the fans are on the temp is over 195 deg, the t stat is wide open) then open the bleeder screw on top the t stat housing a few turns till a steady stream of coolant comes out the hole, shut the screw, top off the rad. cap it.

done.
 
pretty sure the 5.3 has the t stat in the timing cover at the lower rad hose. i could be wrong tho. thats where it was in my 03 gmc truck with a 6.0.
 
bocoogto said:
Where is the thermostat? Near the Coolant filler?
Click to expand...

The thermostat is buried underneath to the left of the front exhaust manifold, if you see the top of the lower hose, that's the thermostat housing. Pretty sure the book calls for removal of manifold to change thermostat. Back bolt is a real issue. These cars have zero space, hence the heat soaking. This motor has its own serpentine belt removal tool designed for it, although it can be done without it(search YouTube). Everything you do in this engine compartment you will lose skin over.
 
Today, I flushed the system. Removed both heater hoses from the alum. tubes on the engine. Stuffed a hose nozzle into a short length of rubber hose and slipped it onto one of the alum. tubes. Put a longer piece of hose on the other alum. tube. Blew water through the system until the discharge was clear. Flushed out the overflow plastic tank. Blew air through the hoses until no more liquid came out. Refilled with two gallons of antifreeze and water. All seems good. Antifreeze is clean, thermostat works fine,\. No reason to change the thermostat. changing it.

I had begun by removing the battery, thinking I could then reach the passenger side radiator hose clamp. That did not work, so two hours wasted pulling and reinstalling the battery. Changing the radiator or water pump on these cars would be major!!
 


I was talking to a retired GM tech , he asked what I drive and I told him. He was actually a fan of the cars, but said for these vehicles they had to basically make/modify many tools to work on these cars. Glad you got it done.
 
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