Aircon O-ring replacement

Problem: My R12 aircon system was leaky when I got the car. Upon converting it to R134a I decided that the best way to go was to replace all of the O-rings in the system.

Models: All E32 and E34s with aircon systems.

Replacing the O-rings:

Expansion valve O-rings:

To get to the expansion valve you have to undo the nut under the bulkhead panel otherwise you can't slide the evaporator where the expansion valve is mounted to out of the car. To remove the bulkhead access panel have a look at the "Center vents" section.

Next you have to take the passengerside glovebox, the piece of carpet trim and the footwell airducts out of the car. How to do this is described in the "dashboard removal" procedure.

Now undo the screws of the plastic cover that goes over the evaperator/expansion valve.

To remove the upper pipes from the expansion valve remove the hex nut on top.

After removing the hex screw you can remove the plate on top of the valve. Tou will now see two more hex screws holding the expansion valve to the evaporator.

Fit the new O-rings to the evaporator pipes. In my case a 602 and a 603 ring.

Put the expansion valve back on the pipes.

Put new rings on the pipe from the heatingbox to the expansion valve. In my case a 604 and a 601 ring.

Pipe in bulkhead:
To get to the bulkhead pipes you at least have to remove the bulkhead panel behind the coolant expansion reservoir. Have a look at page 2 of the "center vents" section.
Fit the new rings to the pipe from the bulkhead to the heaterbox:


On my car a 604 and a 601 ring. This image was taken with the heaterbox out of the car.

Filling lines

Now fit new rings to the pipes with the filling valves.


On my car a 604 and a 601 where fitted.

Dryer O-rings The easiest way to get to the dryer on a 6 cylinder E32 is to remove the airfilterbox and put the windschield washerfluid tank in it's place.

The rings to the dryer are 2 601s.

Condensor seals

The seals to the condensor can be reached by removing the bumper of the car. To do this remove the chrome trim by pulling it forward and pressing in all tabs in the trim. Be carefull not to break them.

Then undo the 2 hexagonal bolts holding the bumper.

Now you can pull the bumper off. It's advisable to do this with 2 people to avoid damaging the bumper.

The rings you'll need here are a 601 and a 602. I was to much of a chicken replacing these rings. Upon undoing the nuts the pipes bended way too much and being a student I don't have the cash to get a new condenser if things go wrong.

Compressor O-rings

You can just replace the rings on the compressor without jacking the car up. The tricky part here is to get the large connector nuts off in the limited space that you have. But it can be done !

The seals used here are a 602 and a 604.

Used parts:
BMW partnrdescriptionprice (1 piece)used amounti
82 31 9 067 396R134a retrofit kit111.061
64 50 8 390 601O-Ring D=7.651.016
64 50 8 390 602O-Ring D=110.773
64 50 8 390 603O-Ring D=140.801
64 50 8 390 604O-Ring D=17.171.074

There are two pipe systems used in the E32. One set for R12 and one set for R12/R134a. Offcourse both can be used with R134a gas, but they use different O-rings in several places. Where the R12 uses the 604 o-rings the R12/R134a system uses the 605 rings. The rings are not that expensive so best get enough of both the 604 and 605 rings to avoid those nasty surprises.

Skills needed/difficulty level: Be sure you know what you are doing. Always have the system evacuated by a proffesional before removing any component. Even if you think the system empty. R12 and R134a gas is poisenous and can cause nasty cold burns.

Story by Johan735.

If you would like to add any comments, remarks and/or corrections to this procedure, feel free to email Mike Oswald and we'll put it on our site. Share your experiences with us so others may benefit from it.