After replacing a section of coolant hose, I flushed my coolant system and filled it up with a 50/50 mix of coolant and water. But then I couldn't get any flow in the system; only one line was heating up.

After trying all sorts of ineffective ways to get the coolant moving I re-flushed the system, but this time afterwards I didn't add any coolant, just 100% water. I then figured out the flow problem--now everything is getting hot and works perfectly.

But my question is: how do I go about adding coolant now (in the proper 50/50 ratio) so that I don't introduce more air into the system while doing so? (trapped air bubbles were what I think was causing the initial problem)

Can I just open the lower radiator drain (to let some water out) and simultaneously add undiluted coolant to the expansion tank? Will this cause air to get trapped again anywhere? How much coolant do I add to get my system around 50/50 again?

Thanks for any help on this one. I know it's probably a no brainer for some of you, but I'm not familiar with the coolant system and all it's complexities.

Point the vehicle uphill and fill it up the block using the upper radiator hose. Run the engine with the heat on full blast to burp it.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Thanks Kerry.

Also, is there any danger in driving it tomorrow the way it is? I don't have time tonight to work on it. It's summer here in California so there's no fear of freezing. Can it overheat with just water?

I have to drive to work (about 30 miles away) and I'd prefer not to have to borrow a car again if I don't have to.

It won't take long. 15 min. Remove radiator cap drive around and leave it parked up hill. A good highway run will get it flowing too. Shouldn't overheat. Just watch gauge and carry coolant.

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What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius

I'm not sure what you mean biopete...do you mean to drive around with the expansion tank cap off? What will that do and how long should I do that?

My question was how do I empty the water half way and fill up with coolant without introducing air into the system? Is that possible or will I have to struggle with burping it again after I fill it with coolant?

Oh. Oops. Didn't see that . The system is sort of self bleeding. But leaving expansion tank cap off and parking up hill and running it lets air bleed out. And driving on highway (revving) gets it pushed through. So yeah, just drain half and add coolant and go.

Ive never seen a 617 get hot when trying to burp system. See a 602 do it though. I had to,stop, remove expansion cap and add coolant. Once the air was purged it didn't have enough coolant.

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What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius

617 will get hot if it has an air lock. Driving with water is not a problem.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Awesome, that's what I needed to know. Thanks a lot guys for your help, I really appreciate it!