Rebuilding BMW Transmission Oil Cooler Hose Quick Connect Fittings

I pulled the BMW E61 into the garage last week to sort out a few issues - rear axle CV boots leaking, oil leak, and low boost pressure. On inspection, I found a leaking transmission oil cooler quick connect fitting, which was spraying oil on the charge air duct from the intercooler to the intake manifold.

The upper (pressure side) tranmission oil cooler quick connect fitting is leaking

I did some research on the internet, could not find any articles about people rebuilding these fittings. This hose costs $170 - expensive to replace for a simple leak. I figured since it was leaking anyway, I would try to take it apart and see if there were replaceable seals. The part numbers of the hoses affected are: 17227570973, 17227571978 and 17227571985.

Once the connection is separated, I took a pick and very easily removed two regular o-rings from the female side of the fitting.

It was easy to remove two standard o-rings from the fitting using a pick. I was careful not to scratch the inside of the connector shell. Once I had the o-rings removed, I noted there were two spacers made from plastic - one green spacer deep in the fitting, and one gray spacer just above the green spacer.

O-rings removed from the fitting, see the green spacer and gray spacer just above. 

The old o-rings were squared off, and not very pliable. They held their out of round shape upon removal. I measured the old o-rings and then estimated what the original uncompressed size would be. They appeared to be standard metric o-rings, and a quick trip to the local o-ring supplier yielded some potential replacements. 

Old o-rings above, new o-rings below. Two per fitting. 

Next step was to stuff the new o-rings into the fitting.  To start with, I used a pick to push the green spacer to the bottom of the fitting, and lift the gray spacer to the top of the fitting. This leaves a groove the width of two o-rings to fit the first replacement o-ring. I stuffed the o-ring into the fitting using some needlenose pliers. 

Start by pushing the green spacer to the bottom of the fitting.

Then - insert the replacement o-ring using needlenose pliers. 

I used the needenose pliers to insert the o-ring into the fitting just above the green spacer, and then to hold one side of the o-ring in the correct position while I used a screwdriver to massage the o-ring into position. With the first o-ring in place between the green and gray spacers, use your pick to push down the gray spacer (and the first o-ring) against the green spacer. 

First o-ring inserted above the green spacer. 

Next step, insert the second o-ring just above the gray ring just as before. With both o-rings inserted, I closed the fittings, cleaned them carefully to remove all traces of oil, so that any new leaks would be apparent. Following a run-up - the two fittings I repaired were both well sealed. I created this simple schematic showing how the o-rings stack in the fitting. 

I've purchased spare O-Rings - if you would like to purchase O-Rings to repair your own fittings, click this link.

If you're careful with the plastic ring and don't break it when disassembling the connection, you may be able to repair it. One other tip - if possible, before disassembling, wash the hoses with soap and water, and get into the release clip side of the fitting with a toothbrush to get as much grit and sand out of the fitting. Blow water out of the release clips using compressed air, and this will make the disconnection a bit easier. Comment below if you have any questions.