6.7 Liter - Draining Coolant Question

[Loren]

Okay. I did my due diligence and searched these forums several times and can’t find where this has been asked previously.



I’m trying to drain the coolant from my 2008, 6. 7 liter engine and radiator.



I drained it once already and the system took only about 3 gallons of water, even after several heat-cool cycles. I added just water because I want to flush the system. My understanding is that this system holds about 6 gallons. If that’s true then I’m not getting nearly enough coolant out of the system.



Is there another drain, besides the one at the bottom of the radiator, that I need to open? I seem to remember that the 5. 9 liter engine had another drain on the block that I had to open. Does the 6. 7 liter engine have the same thing? If so, where is it?



I know about the vent at the top of the engine, and opening that doesn’t get any more water into the system.



Any help with this would be very much appreciated. Thanks in advance.



– Loren

 

[AH64ID]

There is supposed to be another drain, but from what I gather there isn't a lot that comes out when you drain it.

Here is a writeup I did, the 6. 7 capacity is lower than my 5. 9, and is 6. 5 gallons.

https://www.turbodieselregister.com/forums/showthread.php?218402-Coolant-flush-on-a-3rd-Gen/page3

 

[Loren]

AH64ID,



Thanks for the input. I found your post when I did my original searches for the 6. 7 liter. It was a very nice posting, by the way. With the trouble I've had, I thought that the 6. 7 procedures must be different.



I'm just baffled about draining the 6. 7. I have owned two trucks with the 5. 9 and never had any problem (that I can remember) with draining the coolant on those trucks. The new 2008 truck, however, is giving me fits. If I can't get all the coolant out, I won't know what the anti-freeze/water proportions are when I refill it.



Also, the less coolant I drain, the more times I have to run the truck with water to flush the system. I notice that you ran through four flush cycles before you were satisfied with the result. I am hoping to do this just once or twice.



Your post got me to re-read the stuff I could find in the service manual. (The service manual for the 2008 trucks is an 8-volume set. ) The procedure in the manual says just to open the radiator drain plug. There is no mention of an engine drain. I'm doing this procedure again as I type this. This time, I've parked the truck so it's pointed downhill. Maybe that will be enough to make the difference. I hope.



Thanks again.



-- Loren

 

[Bob4x4]

Why are you flushing with water!

 

[AH64ID]

The block just holds a lot of coolant that won't drain out.

I thought about it after I did mine, but 3 flushes is probably plenty and here a rough breakdown assuming you get 3 gallons out each time.

Original: 50:50 (3. 25g coolant)
1st Flush: 27:73 (1. 75g coolant)
2nd Flush: 15:85 (. 95g coolant)
3rd Flush: 08:92 (. 51g coolant)
4th Flush 04:96 (. 27g coolant)

 

[Loren]

Why are you flushing with water!

Because that's what is used to flush a cooling system. Is there something more that you want to say?



-- Loren

 

[Bob4x4]

There is no reason to flush with water. All that is needed is to change out the old for new. Water will do nothing special. If your cooling syst is contaminated that is another matter

 

[NIsaacs]

A 5 year old cooling system will always be contaminated. Sediment will build up and accumulate in all the little nooks and crannies and settle there on shutdown. Draining the system will not cause enough flow volume disturbance to pull all this yuck out, especially the back of the block, it sits lower than the front. I always flush forward and back all the orifices that I have open with a garden hose, especially the heater core, it will not drain due to the fill tubes mounted in the top of the core. When all is clean, I blow the heater core and block out with compressed air.



Nick

 

[Bob4x4]

I am not an enviro nut but doing this at home you are creating many gallons of hazardous waste. Sediment doesn't happen because coolant is 5 yrs old. It was there because of the mfg process. The flush process is so easy with a machine that is designed to do it and contain all the waste

 

[Loren]

Nick,



Thanks for the good idea about blowing the system out with compressed air. I'll take a look at the hoses and see where I might be able to do that. That will surely get more coolant, and sediment, out of the system.



I found that parking the truck downhill helped. Last evening I was able to drain about four gallons through the radiator drain. I'm guessing that it was about four gallons because that's how much I've put back in so far. It took a long time to drain through that little hole, but I'm patient, sometimes.



-- Loren