Coolant Change
Thread Starter
Instructor
Joined: Nov 2014
Posts: 239
Likes: 116
From: Wilmington, NC
Coolant Change
I've never changed coolant in a C3. The previous owner put in a valve to shut off flow of coolant to the heater core. When I change coolant, should I open the valve in the event there is any in there? Is there another way to check if there is coolant in the heater core? Does it have a separate drain? Anything else I should do other than drain and refill? Thanks
Pro
Joined: May 2017
Posts: 583
Likes: 196
From: Wisconsin
Question: Do you know why the previous owner put in the bypass valve? - Reduce heat in cabin or maybe heater core was leaking? ?
There is no separate drain for the heater core. If known that the core is not leaking I would open and flush with the system.
There is no separate drain for the heater core. If known that the core is not leaking I would open and flush with the system.
Pro
Joined: Aug 2010
Posts: 648
Likes: 452
From: Napa, CA
No drain in th heater core that I’m aware of. Open the shutoff valve to allow the fluid in there to drain as well. I’d recommend flushing the entire system thoroughly with water then let it all drain then refill with your selected coolant H2O mix.
Last edited by 210ken; Aug 27, 2022 at 07:07 PM.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Yes, open the heat core valve. No drain, no way to check unless you want to disconnect the hoses.
Some people elect to do a reverse flush of the system.
Some people elect to open the block drains. If they are NPT plugs, they should come out. But be leery. Not a god place to strip or damage threads.
Mine are petcocks somebody put in. I would not touch those with a 11 ft pole.
Just flushed mine last Thur. Installed a Anode Rod in place of the radiator drain plug. Also known as a sacrificial rod. Same thing that is in your houses hot water heater, but shorter. The rod deters electrolysis corrosion with aluminum engine parts. I think it was $25 at Summit.
Some tips:
Front tires up on ramps or small concrete blocks helps burp the system.
Never tighten the Rad Cap until done. . . . . to help burp the system.
Always use distilled water w/ the old-style green coolant.
Fill the Rad well below the neck until burping is done. Then top it off 15-20 mins later.
Don't forget to remove the old nasty stuff in the over-flow tank with a turkey baster.
And I always add a bottle of Water Wetter. That stuff really works.
Some people elect to do a reverse flush of the system.
Some people elect to open the block drains. If they are NPT plugs, they should come out. But be leery. Not a god place to strip or damage threads.
Mine are petcocks somebody put in. I would not touch those with a 11 ft pole.
Just flushed mine last Thur. Installed a Anode Rod in place of the radiator drain plug. Also known as a sacrificial rod. Same thing that is in your houses hot water heater, but shorter. The rod deters electrolysis corrosion with aluminum engine parts. I think it was $25 at Summit.
Some tips:
Front tires up on ramps or small concrete blocks helps burp the system.
Never tighten the Rad Cap until done. . . . . to help burp the system.
Always use distilled water w/ the old-style green coolant.
Fill the Rad well below the neck until burping is done. Then top it off 15-20 mins later.
Don't forget to remove the old nasty stuff in the over-flow tank with a turkey baster.
And I always add a bottle of Water Wetter. That stuff really works.
Race Director
Joined: Nov 2006
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From: Sunshine Coast, Queensland, Australia
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Cruise-In VIII Veteran
All of above sounds good. I have found when working on my engine, getting all the old coolant to drain out is near impossible. if you can get to the block drains, about in the center, just above oil pan gasket and if you have the factory plug wire boomerang covers, under those. Pull those plugs if you can. Otherwise Flush it really well. Drain what you can.
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,051
Likes: 4,193
From: US-PNW
This bears repeating: DO NOT ATTEMPT TO OPEN A PETCOCK OR A SOLDERED RADIATOR DRAIN PLUG. 117 out of 100 times it will break off or not reseal. Better to remove the lower radiator hose and flush in both directions from the top radiator hose. Consider about a gallon of fresh flush water remains trapped in the nooks and crannies and match that with a gallon of antifreeze. Then start blending the two after that - and do use distilled for the added water after the flush.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
My Rad Drain is a short bolt / plug that the O.P. installed. 1/4" NPT. Very lucky it comes out so easily with socket / ratchet. (hate petcocks)
Easy access with front on ramps. A dab of thread sealant on the plug and good to go.
I used to pull the lower Rad hose. What a sticky mess, everywhere. I see no benefit in doing that anymore.
Easy access with front on ramps. A dab of thread sealant on the plug and good to go.
I used to pull the lower Rad hose. What a sticky mess, everywhere. I see no benefit in doing that anymore.
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