I've been running plain water for two weeks now. I've replaced my radiator, and am trying to flush my engine. I've used two bottles of radiator flush stuff (sodium citrate), and I'm still getting rusty water. Hopefully someday, before winter, when the water drains clear I can put coolant back in. But no harm running water so far (no aluminum), and the car is starting to run cooler as more crap comes out.

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'83 240D with 617.952 and 2.88
'01 VW Beetle TDI
'05 Jeep Liberty CRD
'89 Toyota 4x4, needs 2L-T
'78 280Z with L28ET - 12.86@110
Oil Burner Kartel #35

http://i16.photobucket.com/albums/b1...oD/bioclip.jpg

1984 300d turbo 147k
take the top radiator hose off, and check for oil spots in water
maybe the transmission line in the radiator is leaking, replace
radiator and change trans and torque converter oil and filter you may notice your trans slips

You could block one side of the radiator cooling loop for the transmission and apply air pressure to the other side. Should be able to stand 60 lbs pressure but check elsewhere.

Bubbles in the radiator the unit is shot. Also better than changing the rad out on speculation. You might or might not also see something unusual on the transmision dipstick.