ahhhh...another possibility for sure. This also means that there's coolant in the transmission. Jeez.

Is there a creative way of double checking if the ATF is contaminated? Maybe a blot test of fresh versus suspect atf?

__________________
Ben
1987 190d 2.5Turbo

how does the atf in the tranny look? solid red or darker is OK water wise.
if it's got any pink in it or frothy look... bad news.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

but if the system is properly filled, it should not create vacuum, right?...... or perhaps very little

---assuming all other factors = 0

(sorry for the tangent, OP)

If you have a leak into the trans fluid you will have a pink milkshake in your trans. When the motor is running, trans fluid goes into the coolant. When you first shut a warm motor down the coolant will go into the trans fluid.
Best you drain the C##P out of your cooling system & flush with clean water until it is clear. Then fill it with proper coolant at the correct mix & see what happens.
If you have a pink milkshake in your trans it will need cleaning out. There was a thread recently about pink milkshakes in the trans.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving