Coolant flush and refill

[Mrprez]

So, I am going to do a flush and refill along with a new thermostat. The issue is the existing coolant. Despite the warning on the reservoir about special coolant, the PO apparently used the green stuff. I've read the discussions about the HOAT coolant and not mixing with the green stuff, but what if you don't know for sure what is truly in the system? Can I do a thorough enough flush and then go back to HOAT or should I stay with the green coolant? I sure don't want to create an issue with the mixing of coolants but it may have already occured.

 

[CodaMan]

During my flush I removed all the HOAT and installed the green stuff. 2 years and no problems.

 

[toximus]

The flush (unless otherwise stated) should be done without coolant in the system. Drain and fill a couple of times with distilled water to get the coolant out. Then you'll be safe to switch to HOAT.

 

[Mrprez]

And you live in CA? The coolant police didn't come and take you away? Good to hear that does work though.

 

[Mrprez]

The flush (unless otherwise stated) should be done without coolant in the system. Drain and fill a couple of times with distilled water to get the coolant out. Then you'll be safe to switch to HOAT.

Do I run the engine in between fills of distilled water to get it circulating and then drain again?

 

[toximus]

Do I run the engine in between fills of distilled water to get it circulating and then drain again?

Yes. You can run the engine like normal with the distilled water. Make sure you burp it each time. Just don't let it freeze or leave it in long term (coolant prevents corrosion). Do them same to get the chemical flush out of the system before putting coolant back in.

 

[CodaMan]

Do I run the engine in between fills of distilled water to get it circulating and then drain again?

Yes, you have to get it out of the block. I drained and filled with distilled water 2 or 3 times without a thermostat installed. That probably diluted the system by 90% or more which is good enough to change fluid types.

 

[PatMc]

Do I run the engine in between fills of distilled water to get it circulating and then drain again?

I have a HECAT pulsating flush gun...so that gets the system pretty clean, but without one I'd do it like this:

Drain what you can, pull the thermostat and put the T-stat housing back on..(if you're too cheap to buy a couple extra gaskets...cut some out of an oil filter box or something with scissors and hole punch). Fill with water and "flush" chemical"...(I've used a Cascade dishwasher pod in a pinch) and run up to temp, then drain again, fill with water, run up to temp, drain again...till it comes out clean. Then mix your new coolant, put in your new T-stat, and fill 'er up.

 

[Mrprez]

OK, I think I got it. Thanks for all the help.

 

[PatMc]

OK, I think I got it. Thanks for all the help.

Also, a small block chevy is much easier to do this with than the 4.0, but before you put the new T-stat in, use a funnel and try and fill as much of the block with coolant through the T-stat hole in the cylinder head as you can, then install the T-stat....makes it a bit easier to get all the air out.

 

[Leinhit]

This fall mine was so dirty that I drove it around about a week and flush it 6 times before it finally stopped looking rusty. Use coolant engine flush, spliced in a hose connector to the heater hose, etc.

It was Brown when I started.

Then went with green coolant. And when I look now it still looks a bit rusty to me so I'm sure this spring I will do it again.

 

[TJ4Jim]

If your in CA and not concerned about freezing temps then I would refill the system with distilled water and drive normally for for a few days then dump and refill with fresh coolant.

 

[eastbloc]

just in case:
https://wranglertjforum.com/threads/how-to-flush-the-cooling-system-on-your-jeep-wrangler-tj.1737/

 

[MountaineerTom]

I recently did mine. Drained and refilled 3 or 4 times (can’t remember which). Drained the block each time too.

bu the last time, the distilled water draining out of the block was a clear as when it went in.