jh48

Hello All,

My name is Joe and I am from New Jersey. I have been lucky enough to inherit a 1971 Olds 442 that belonged to my grandparents back in the day. It has been restored about 5 years ago and I am slowly learning how to take care of the car by myself. I was wondering what are the proper steps on how to flush the coolant system? Can you use tap water to flush out the system and if so, does it have to be hot or cold? Also, when flushing do you keep the radiator cap on or off? Learning all this is new to me and any help would be appreciated! Thanks!

oldcutlass

Welcome to the site, buy whats referenced below at your auto parts store and just follow the directions.

I use one of these:



And this:

jh48

Thanks so much!! Will do!!

76olds

Can't beat the advice Oldcutlass provided above with embedded photo's of the product to use ! Let us know how it worked out Jh48 .

Allan R

When you're finished flushing the system and have run the engine enough to circulate the new coolant throughout the block, make sure you hydrometer test it to ensure it has the proper level of protection. A recent thread I read about a flush done at a shop by a so called pro and it left the engine with next to no protection. IF you need to ensure the block gets drained as much as possible before you fill with new coolant, simply disconnect the lower rad hose and let it drain. Make sure you have a good sized catch bucket though.

Dave26

oldcutlass

I never mess with the block plugs. I buy 3 gallons of antifreeze and pour in 2 gallons to start. Check with a hydrometer, should be around -21*ish, which is fine for a car stored in a garage in winter. If the coolant gets a bit low I'll add straight coolant until I hit -34* on the hydrometer then 50/50 after that.

My442

I use the Prestone Flush Kit, and do the following:

1. Be sure the heater is on
2. I put in a bottle of Prestone Radiator Flush, and let it circulate for 10 minutes (car running)
3. CAREFULLY remove the radiator cap (car turned off)
4. Hook up a hose to the Prestone flush tee
5. Use hot water
6. Start car and let the hot water flush the system for 5 -10 minutes. Water will be clear when the flush is done
7. Turn off car, shut off hot water, and drain radiator
8. Add 2 gallons of 100% green anti freeze, and water to fill
9. Run car for 5 minutes to mix coolant, radiator cap off to "burp" the system (thermostat open) Add coolant as needed
10. Check freeze protection with a hydrometer, adjust antifreeze as needed

jh48

Hello All,

Thanks for the great feedback from my question! I really appreciate it! I have two other questions. First, this maybe a stupid question but when draining the coolant system, do I just take the radiator overflow reservoir off and dump the coolant out? Also, when I'm done flushing and filling up the coolant system, would it be wise to pressure test the system? I definitely will due a hydrometer test after, but wasn't sure if a pressure test would be beneficial...still learning how to do all this.

Allan R

No, you need to also drain the radiator. Use the petcock on the bottom right side. Take the rad cap off to do the draining. I would also suggest removing the lower rad hose to get some of the coolant out of the block too. Pressure testing the system is best done when the rad is out of the car at a radiator shop. A pressure test isn't a bad idea, but the flush and getting rid of crud on the cross tubes is going to be a big payoff.

jh48

Thanks Allan R for responding! I will drain the radiator and remove the lower rad hose to get the coolant out of the block. After I do those two things, do I take off the overflow reservoir and dump the coolant in there out? There is no way to drain it from what I can see. Sorry for all the questions...

oldcutlass

Pressure testing is best done when the cooling system is all together, that ensures the head and all other gaskets are sealing and there are no other leaks. However, if the system was not losing coolant before then I doubt its necessary.

Yes, remove the coolant over flow, drain, clean, and reinstall. Fill it with a 50/50 mix of coolant.

jh48

Thanks so much!! I really appreciate all the help and advice!!

jh48

Hi all,

I finally got the time to complete the flush for the coolant system. I drained all the coolant and filled the radiator with Prestone Radiator flush and water. However, I turned the car on and found that no heat is coming through the vents....I even tried the AC and it is not working either. As I toggle through the choices of AC, heat, vent, defroster, I hear mechanisms moving around but nothing seems to be happening. Is this possibly a fuse issue? Any ideas and advice would be greatly appreciated!!!! Thanks!

Allan R

No heat condition usually is a heater core problem. Was the heat function working before you had all this work done? You do have air flow through the vents?

EDIT: On AC cars you may have a water valve restriction. It's the valve at the back side of the engine just before the hose going to the heater core.

Allan R

Heater valve (AC car with 455)

jh48

Yea the heat was working before. I dont drive the car often bc I'm in school. The heat was working in the floor vents but now no longer works in either the dash and floor vents. 😑

jh48

Hey,

So I finally finished the coolant job and I tested the coolant temp and the freezing point is +10 F. I used prediluted coolant. To get the correct in the correct temp range, do I drain some of the prediluted coolant and add undiluted coolant?

Dave26

Eric,
Where I live the domestic water supply has an unusually high mineral content. Ever since the 1960's I have tried to flush and drain the system completely, draining the block plugs.(I also have used the Prestone kit since it first came out.) Two gallons of anti-freeze then topped off with distilled water, close to another two gallons. I have done it that way because I was concerned about too high of mineral (calcium & iron) in the system. Should I not have this concern?

Fun71

Yes, if +10º isn't sufficient for your location. I'm in Phoenix so that would be fine for me.

jh48

Yea I live in NJ so I would need to get the coolant freezing point less. Especially that the car sits in garage all winter.

oldcutlass

Yes, you want drain some of your premixed and add straight until your down to at least -20ish. Add some run the engine for a bit to mix and chck when its cool.

Texas has very hard water, I use tap with no issues. I do change mine at probably 7 year intervals.

Allan R

The default position for AC cars is Defrost.

76olds

Did you install a new T-stat? You should get heat once you run the engine (at high idle until you see flow through the rad. Usually takes 15min or so, once you see coolant flow, turn the heat on full defrost and it should be working.
Top up the rad on high idle and cap it, should be good to go

Eric

76olds

I wouldn't pull the block plugs either, no concern's IMO. The Prestone Flush will clean the system out very well leaving the blocks plugs alone.

jh48

Thanks so much for all the helpful advice!!

droldsmorland

Another tip is to pull the heater hoses and gently flush the heater core separately. Use low pressure water be fairly gentle... on/off with the garden hose. Followed by a shop vac or low psi compressed air to evacuate the H2O , The water pump doesn't move the heater core contents as aggressively as it should (by design) to dislodge the sediment.
Note if you have a weak core this will find it. Better to find it in driveway vs going down the road.