How do you completely drain cooling system?

[Peter_Reinhard]

Hello

I have a 97 ETC, with 64K Miles. Because of its age, people have said to change the cooling system fluid. This last weekend I did, but I screwed up. Apparently I didn't drain all the fluid; I only was able to add 7 quarts (dexCool, Bars Leaks, distilled H2O). I was told to open the drain plug on the bottom of the radiator, which I did with some difficulty. I had to remove the lower hose first just to get my had in there. Very tight.

I recall that some cars I used to work on had block drain plugs.

1) How do you guys drain all of the fluid?

I plan to re-do the whole thing again because there must be 5.5 quarts of tap water in there. (I ran a garden hose into the top tank, and had the lower drain open, and ran the car for 1/2 hour, with heater on, to circulate new water through the system. )

2) Do I need to add the Bars Leaks again, or did enough circulate to do what ever it does? I plan to drive a few hundred miles before I can get some time to re-do this job.

FYI: I replaced the lower hose because it bumps against a 1" round cylinder (looks like it joins two pipes together). The edge of the cylinder made quite an indentation into the hose and looked like it would be a weak spot. Is this normal?

Thanks for the feedback.

I will buy a shop manual.

[JimD]

Driving a few hundred miles and draining again is what I would do. Leave the garden hose on the other side of the house!

And then I would drive another several hundred miles and repeat the above.

You have lost control of the 50/50 mix ratio. By draining - filling several times you will get very close to the recommended ratio.

Yes, I would add a little of the Bars Leaks each time.

Good luck with it...

[KHE]

There are not any block drains on the Northstar engine. All you really need to do is drain the system, add bars leaks to the lower hose and refill with new DexCool mixed 50/50 with distilled water. Don't use tap water as you will introduce minerals into the system.

You can repeat the sequence as JimD suggests as well.

[Peter_Reinhard]

Hello. Thanks for the replies.

Let me see if I understand.

The way you all replace the cooling system fluid is to drain the radiator and refill? As I have found out, this only replaces 60-65% of the fluid. This is OK??

Did I not wait long enough, and eventually, it all would have drained out?

Please advise. Any Cadillac mechanics out there? Is there possibly another way to purge all of the coolant before adding new stuff?

I have the added problem of needing to flush out the tap water, one way of doing this as you suggest is to continuously change the fluid. That sounds a bit odd.

I appreciate your advice.

Thanks

Peter Reinhard

[Oldgamer]

It doesn't matter how long you'll wait. Some old coolant (the bigger part) still will be in the system. So, the best you can do is what Jim told you: to change it more often.

[bobnsue2]

I park on a slight grade nose down hill. Also remove the thermostat housing to let the engine drain a lot better.

This is a 4.9 not a N*.

Bob B

[sal.carceller@cox.net]

1) I remove the thermostat, disconnect upper and lower hoses from radiator, disconnect heater core hoses at the firewall.

2) purchase about 8 gals of distilled water (cheap enough - Walmart 0.60 cents each) now poor 2 gal in Radiator to really flush out. Poor another 3 gal into the thermostat housing to flush. take another gal and poor into heater core with short length of hose. Repeat above till clear.

Some folks will run a garden hose as above for a while then flush out the tap water with distilled, I have done trhis as well but it does introduce tap water into the system and then you flush that out with the distilled. All depends how dirty things are.

That's if you really want things cleared out.

[KHE]

Flushing is not necessary. Just drain as much coolant as you can and refill with fresh DexCool mixed 50/50 with distilled water.

If you flush with distilled water, you will have a tough time getting the coolant concentration to the proper 50/50 mix. If you use a cheap anti-freeze tester, check it against a known concentration of 50/50 as those things are notoriously inaccurate.

[sal.carceller@cox.net]

If you flush with distilled water, you will have a tough time getting the coolant concentration to the proper 50/50 mix.

I agree getting the 50/50 mix right is the tough part if you decide to flush. I ussually would use 100% antifreeze (not the 50/50 mix) and add about a gal, fill and test. Then add or remove antifreeze or water as necessary.

[Ranger]

After you remove the hose or open the drain, get a shop vac or your wifes vacuum cleaner and reverse the air flow. Stick the nozzle in the surge tank and use your hand to seal it. That will blow out most of the residual coolant. What little remains will be irrelavent. If you flush it, what remaines is water. If you then addd a 50/50 mix what you will end up with is 60/40 or less. Then you'll have to drain some, add straight coolant, test it, adjust it, etc, etc, well you get the idea. It is not that crittical to get every last oz. out of it.

[Peter_Reinhard]

Thanks.

Is the thermostat housing at the junction where the lower (short) hose meets the engine? Do you need Permatex (or similar) gasket sealer and and new gasket when you remove it?

Thanks Ranger. I like the shop vac approach. I'll have to try it. Does the surge tank connect to the engine so I can be sure that the pressure will push out engine block coolant and not take the least resistance path (e.g. out of the lower drain)?

It sounds like most people just replace most of the fluid and let it mix with some percentage of the old. (....could this be a headgasket factor??)

I wonder how the Caddy dealer does it??

Thanks again to all.

[Scotty]

The thermostat housing is at where the lower hose attaches. You do not need permatex, there is a rubber seal (#7 below) that goes around the permeter of the thermostat (#6 below). I guess a little RTV on the seal wouldnt hurt, I coated it with my fingers. Here is a photo/drawing, Mike

[Ranger]

Yes, I think the surge tank goes to both the engine, heater core and the radiator. I suppose it will take the path of least resisitance but you can always fix that by pluging the path of least resistence.

There will always be some residual left but I don't think it is a big deal.

[Peter_Reinhard]

Thanks Ranger and Scotty for the replies.

I obviously need a manual. Where did you get that soft-copy diagram? Does the shop manual come on CD?

[Scotty]

Peter I have 96 manual and scan a lot of different components, I had that picture in a folder on my harddrive. If you need any other views let me know, Mike

[Peter_Reinhard]

Ok, thanks Mike.