These units wear out over time and are exposed to quite a bit of muck and grunge over their life so its no surprise they will fail at some stage. Mine presented as a steady leak after parking up one day which eventually tapered off until I started the engine again – but Ive heard of them letting go altogether and didn’t fancy that occurring which would be a lot more dramatic!! On a 3B at least they are relatively easy and cheap to repair.
I thought it might be useful to give a quick run through of how I changed my 3B oil cooler, as I couldn’t find such a guide. This is how I did it and by no means a proper mechanics guide!! Also this ”how to” doesn’t apply to the ABY unit which has significant differences in design. The oil pipes are larger with different sized unions and are located differently (either side of the “front” of the cooler as you look at it rather than on the top as here). The housing and air guide / intake are also quite different.
For the 3B unit its pretty straightforward stuff just made difficult by the amount of corrosion the unit has unavoidably picked up during 15 years or so of life under the car. So the hardest part of the job is releasing bolts / nuts that will undoubtedly be pretty corroded and tight. That being said I found non of them too much of a problem, but I may have been lucky!! All the nuts cracked off remarkably easy, even the ones securing the cooler to the mounting bracket which looked well rusted.
The oil cooler is located behind the front bumper, basically in a space in front of the drivers front wheel so not bad to get at. First off remove the undertray if fitted. The drivers front wheel needs to come off for access so I then jacked the drivers side of the car up on an axle stand. The wheel arch liner on mine has been chopped (perhaps to get at the oil cooler at an earlier date) but under normal circumstances I think would need to be removed.
Once all this is done access to the oil cooer isn’t bad at all. I started with the first oil pipe nearest to me. It’s a 22mm nut on the pipe and I used an18mm spanner on the housing joint to help leverage. This integrated nut at the base of the joint was badly corroded and getting a good grip with a spanner wasn’t that easy. The union nut was certainly on tight, but with a little application of effort using the two spanners it cracked off not too badly at all.
Being careful to catch any spillage! I moved the pipe out of the way and tackled the second bolt in the same fashion. Not much problem there either fortunately - so that’s the pipes off!
Both pipes removed and a hand latex glove to stop the residual oil!!
The two domed 13mm nuts that secure the oil cooler housing to the mounting bracket looked badly corroded but actually released quite easily
With the nuts off its only the housing bolts and the air guide keeping the cooler unit in place.
Now its just a case of manoeuvring the cooler unit out – dropping it out from the bracket and away. As you do so the air guide (which is attached to the oil cooler housing) will detach from the air guide which is attached to the front bumper behind the lower left hand grill. These are just sleeved and not secured together so pull apart quite easily. There’s no need really to move the air intake. The air guide is secured to the oil cooler housing by two Phillips screws which on mine were rusted solid to the metal retainer. Fortunately, there’s no need to remove the air guide either.
Once the air guide and intake are separated the unit can be withdrawn for inspection.
Leaving this hole!
The oil cooler is actually two parts (three if you include the plastic air guide) Typically, the problems / leak will be down to the core failing, as it is here with mine. I had a steady ooze out the bottom of the core. The core is a separate part (117 113 021). As of late Feb 08 it was still technically available from Audi (though when I checked they had no stock) Up until April 07 it was possible to exchange units and at half the cost – but this option is for some reason no longer available. Also NLA is the housing so I had to reuse this part. It was pretty corroded on the surface as you would expect but still serviceable
This left I four possible options for repair:
• Buy a new core from Audi at £96 +vat but with the uncertainty of availability
• Get the existing core repaired or recored at a local specialist for around £30-£45
• Source a second hand unit with no guarantee of how much life it would have left in it
• Buy a new core from VW Heritage Parts Centre (no 41) at £37 all in
I went for the latter option which I can highly recommend! It’s the same unit as used on a few VWs such as earlier Golfs so I was in luck – many thanks to Mike Dewer for the link and contact there!!
This meant I had to separate the old core from the housing. The securing bolts at first inspection looked badly corroded so looked like it could be a problem!
Remarkably, underneath the surface rust the 10mm bolt heads themselves were not too badly corroded and I managed to get a socket and spanner on either end. To my relief they cracked off with a bit of persuasion . One of the longer bolts was corroded to the surface of the housing but a little gentle persuasion tapping it through from the bolt end released it!!
With the three bolts withdrawn the housing can finally be separated from the core, ready to take the new replacement. Be careful not to lose the two rubber grommets which seal the oil path between the units. These are NLA (though possibly available from the suppliers of the core) As mine still looked ok I decided to re-use them.
New against old!
I did manage to get replacement bolts which are still available from Audi: part no: N 010 349 5 (M6x45mm) and N 010 311 4 (M6x75mm)
Cleaned up the underside of the housing/retainer as best I could but to be honest didn’t really bother with anything like a refurb. You can see where the grommets fit into the underside of the pipes to seal the cooler core to the housing and the joining pipes
And from above
Seals in place
Then it’s a case of matching the cooler back up to the retainer, taking care to ensure the grommits sit in the right place (the corresponding dimples on the core) and then replacing the 3 x 10mm securing blots – the shorter 45mm long bolt obviously goes at the “front”.
Tightened up and from the side you can see the grommet nice and snug providing the necessary seal between the two parts.
Complete oil cooler unit is ready to go back on the car!
In the best tradition, re-fitting is a reversal of removal! Firstly line up the air guide which is attached to the unit to fit over the oval mouth of the air intake which can be seen here and was left in situ bolted to the front bumper behind the grill. Apologies for what look like two oil filled condoms in the front!!
With the air guide and intake sleeved together its easy enough to guide the two securing bolts on the housing through the locating holes in the mounting bracket and replace the 13mm domed nuts. Then its just a case of replacing the two oil feed lines, gently finger tightening the 22mm nuts at first (furthest one first for ease of access) so as not to cross thread. Getting the 18mm spanner on the join on the housing still was a bit tricky so as to get enough leverage with the 22mm spanner to tighten the union bolt sufficiently - yet taking care not to twist the mounting bracket in the process! All in all through, not really a problem and voila!! Oil cooler replaced!!!
I thought it might be useful to give a quick run through of how I changed my 3B oil cooler, as I couldn’t find such a guide. This is how I did it and by no means a proper mechanics guide!! Also this ”how to” doesn’t apply to the ABY unit which has significant differences in design. The oil pipes are larger with different sized unions and are located differently (either side of the “front” of the cooler as you look at it rather than on the top as here). The housing and air guide / intake are also quite different.
For the 3B unit its pretty straightforward stuff just made difficult by the amount of corrosion the unit has unavoidably picked up during 15 years or so of life under the car. So the hardest part of the job is releasing bolts / nuts that will undoubtedly be pretty corroded and tight. That being said I found non of them too much of a problem, but I may have been lucky!! All the nuts cracked off remarkably easy, even the ones securing the cooler to the mounting bracket which looked well rusted.
The oil cooler is located behind the front bumper, basically in a space in front of the drivers front wheel so not bad to get at. First off remove the undertray if fitted. The drivers front wheel needs to come off for access so I then jacked the drivers side of the car up on an axle stand. The wheel arch liner on mine has been chopped (perhaps to get at the oil cooler at an earlier date) but under normal circumstances I think would need to be removed.
Once all this is done access to the oil cooer isn’t bad at all. I started with the first oil pipe nearest to me. It’s a 22mm nut on the pipe and I used an18mm spanner on the housing joint to help leverage. This integrated nut at the base of the joint was badly corroded and getting a good grip with a spanner wasn’t that easy. The union nut was certainly on tight, but with a little application of effort using the two spanners it cracked off not too badly at all.
Being careful to catch any spillage! I moved the pipe out of the way and tackled the second bolt in the same fashion. Not much problem there either fortunately - so that’s the pipes off!
Both pipes removed and a hand latex glove to stop the residual oil!!
The two domed 13mm nuts that secure the oil cooler housing to the mounting bracket looked badly corroded but actually released quite easily
With the nuts off its only the housing bolts and the air guide keeping the cooler unit in place.
Now its just a case of manoeuvring the cooler unit out – dropping it out from the bracket and away. As you do so the air guide (which is attached to the oil cooler housing) will detach from the air guide which is attached to the front bumper behind the lower left hand grill. These are just sleeved and not secured together so pull apart quite easily. There’s no need really to move the air intake. The air guide is secured to the oil cooler housing by two Phillips screws which on mine were rusted solid to the metal retainer. Fortunately, there’s no need to remove the air guide either.
Once the air guide and intake are separated the unit can be withdrawn for inspection.
Leaving this hole!
The oil cooler is actually two parts (three if you include the plastic air guide) Typically, the problems / leak will be down to the core failing, as it is here with mine. I had a steady ooze out the bottom of the core. The core is a separate part (117 113 021). As of late Feb 08 it was still technically available from Audi (though when I checked they had no stock) Up until April 07 it was possible to exchange units and at half the cost – but this option is for some reason no longer available. Also NLA is the housing so I had to reuse this part. It was pretty corroded on the surface as you would expect but still serviceable
This left I four possible options for repair:
• Buy a new core from Audi at £96 +vat but with the uncertainty of availability
• Get the existing core repaired or recored at a local specialist for around £30-£45
• Source a second hand unit with no guarantee of how much life it would have left in it
• Buy a new core from VW Heritage Parts Centre (no 41) at £37 all in
I went for the latter option which I can highly recommend! It’s the same unit as used on a few VWs such as earlier Golfs so I was in luck – many thanks to Mike Dewer for the link and contact there!!
This meant I had to separate the old core from the housing. The securing bolts at first inspection looked badly corroded so looked like it could be a problem!
Remarkably, underneath the surface rust the 10mm bolt heads themselves were not too badly corroded and I managed to get a socket and spanner on either end. To my relief they cracked off with a bit of persuasion . One of the longer bolts was corroded to the surface of the housing but a little gentle persuasion tapping it through from the bolt end released it!!
With the three bolts withdrawn the housing can finally be separated from the core, ready to take the new replacement. Be careful not to lose the two rubber grommets which seal the oil path between the units. These are NLA (though possibly available from the suppliers of the core) As mine still looked ok I decided to re-use them.
New against old!
I did manage to get replacement bolts which are still available from Audi: part no: N 010 349 5 (M6x45mm) and N 010 311 4 (M6x75mm)
Cleaned up the underside of the housing/retainer as best I could but to be honest didn’t really bother with anything like a refurb. You can see where the grommets fit into the underside of the pipes to seal the cooler core to the housing and the joining pipes
And from above
Seals in place
Then it’s a case of matching the cooler back up to the retainer, taking care to ensure the grommits sit in the right place (the corresponding dimples on the core) and then replacing the 3 x 10mm securing blots – the shorter 45mm long bolt obviously goes at the “front”.
Tightened up and from the side you can see the grommet nice and snug providing the necessary seal between the two parts.
Complete oil cooler unit is ready to go back on the car!
In the best tradition, re-fitting is a reversal of removal! Firstly line up the air guide which is attached to the unit to fit over the oval mouth of the air intake which can be seen here and was left in situ bolted to the front bumper behind the grill. Apologies for what look like two oil filled condoms in the front!!
With the air guide and intake sleeved together its easy enough to guide the two securing bolts on the housing through the locating holes in the mounting bracket and replace the 13mm domed nuts. Then its just a case of replacing the two oil feed lines, gently finger tightening the 22mm nuts at first (furthest one first for ease of access) so as not to cross thread. Getting the 18mm spanner on the join on the housing still was a bit tricky so as to get enough leverage with the 22mm spanner to tighten the union bolt sufficiently - yet taking care not to twist the mounting bracket in the process! All in all through, not really a problem and voila!! Oil cooler replaced!!!
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