Question about trans cooler lines and cleanliness
 

My 87 300D is leaking ATF from both sides of the trans cooler lines. It's fairly mild and consists only of a couple drops after the car has been parked. The lines leak out of the connections that sit on either side of the oil pan, and as far as I can see, nowhere else. I haven't driven the car a lot lately so I'm going to see how it progresses once I get it back on the road (needs brakes done). My question is this: I have a spare set of transmission cooler lines that came out of a 1988 300E, and I think they are exactly the same as mine. If I decide to replace them, should I do anything to "sterilize" the replacement lines? I know even the slightest micro-crumb of lint, dirt, etc., can terminate the transmission, so I'm very paranoid about that. These spare lines have been sitting in a dusty shed. It's not something I'm going to do at this time, but I'm just asking as a hypothetical, because having a plan of action for potential future problems helps me overcome my constant worrying (something I'd like to address in 2010). I'm just curious what the path of the ATF through those lines is, i.e., would a particle in one of the lines get caught in the filter. I don't have the FSM for the trans, just the chassis/body.:rolleyes:

I'd hose them out with brake cleaner, then make sure they dry out and dump good clean ATF through them. Then they should be clear of any debris and gunk.

Path of fluid --- one is the pressure from the torque convertor return fluid flow going to be cooled

the other is the of corse the return and it just dumps into the trans pan < the filter in the pan is the catcher of all this sort of debris

if it is a keep you up at night thing and it should not be - its not a human body and we all know they leave screwdrivers in them

i would replace the lines first - run the car 1/2 hour and than change the oil in pan with a new filter and do the convertor -- its the way i would do it -- jz

Could it just be a missing or dammaged washer on the Banjo bolt? do they still use that set up on yours?

I would clean the lines before I installed them. If the lines were so contaminated that a fluid and filter change is in order, they most definitely should not be installed.

That was kind of my thinking ... I'd rather go to the effort of cleaning them, or even shell out for new ones, than create a new, bigger problem.

Those lines are barely a year newer than the old leaky ones. You will be very p*^#* off if you install them and in a couple of weeks they leak too!! New ones are the go!!

My tranny cooler lines weren't leaking at all, then the temps dropped, then I got the same thing you described: a few drops at the connection between the hard line and the nut on the flex hose. I just tighted the line a bit and the leak stopped.

The hard line fitting on my 300CD is some odd size, neither metric nor standard. I ended up using a large crescent wrench.

If you're going to replace, get new lines. 20+ year old used lines wouldn't be worth the labor to re-install them.

X2 --- on what Yak said.

One of my latest orders to Phil included 8 transmission cooler lines. Yes, I said 8. I've owned enough of these old MB diesels to know that the next one I buy is going to need the lines replaced.