EGR Cooler "Nightmare Nut" Removal

You can check @Mendel Leisk posts as he has links on how to do that job in the signature line of all his comments. His suggestion for that nightmare nut is to work on getting that one loose prior to the day of doing the job. I'm about to dive down into the Gen3 EGR rabbit hole and start doing them regularly and my plan is to have a clean EGR and cooler ready to go so I just swap them rather than having to soak and wait for them to be clean... Seems like that's the strategy of more than just me, lol...

 

As I recall, it is an external torx net, either an E8 or an E10.

External torx nuts are commonly used in German cars like BMW and Mercedes.

 

It's a run-of-the-mill hex nut.

The stud it goes on has an external Torx end, so that you also have a way of removing the stud.

 

You take the nut off first and then remove the threaded stud with an E8 external torx socket on a 1/4" drive. Pulling the orange cables out of the way is reported to help gain access.




The hex nut has to come off first. Recently one guy managed to break the stud off trying to use the torx socket without loosening the nut.

 

You could get the nut loose by a turn or two and then remove the stud with the nut still on it using the E8 bit.

You just shouldn't try turning the stud when the nut is jammed down tight.

 

I would leave both the nut and stud off, permanently. If selling or trading in the car, “maybe” reinstall. With them off, the cooler can be extracted without removing the two studs at exhaust manifold, which keeps the gasket there from falling, and makes alignment during reinstall dead simple. You do need to loosen the mounting bracket of a tube running above, channeling gas tank vapour back to intake manifold iirc. It slightly obstructs the cooler as you pull it forward.

I’ve cleaned the EGR system on our ‘10 a couple of times now (with relatively low miles, so not that bad), opted to just clean the existing cooler. It’s good to get it out, one end corked (smaller end is ~21 mm ID), filled with cleaner and propped up in corner of laundry sink ASAP.

Let it soak about an hour, rinse and repeat-till-clean, while dealing with the rest of the system. Both times I used a concentrated solution Oxi-Clean Stain Remover (powdered laundry additive. Next time I’m considering to use a comparable approach but with 20~30% (by weight) potassium hydroxide (KOH) solution, see how that goes.

Sodium Hydroxide (NaOH) would be comparable, but harder to obtain these days, due to its use in methamphetamine production I believe. Potassium Hydroxide has similar efficacy, and is commonly used in soap making. Sodium hydroxide is present in readily available oven cleaner sprays, albeit relatively dilute I think.

Do use appropriate safety precautions with either; they’re strong caustics. Also, only use such caustics on the cooler: it’ll react with anything other than stainless steel or plastic, ie regular steel (such as the embedments on the intake manifold) or aluminum (the body of the EGR valve). It could be used on the stainless steel EGR pipe (between EGR valve and intake manifold) but it’s overkill. Brake cleaner, brushes and rags will suffice for those.

there’s more EGR cleaning information in my signature (on a phone turn it landscape to see signatures)

 

I'm getting ready to do my first one on my junk Gen3 and then a steady flow of Gen3 owners who need this job done. And I have a couple questions on the cleaning part:

1) How many times do you have to soak and rinse with Oxyclean to get your barely gunked up EGR cooler and valve cleaned? How long total does it take to clean? I'm actually working on aquiring a spare cooler to go with my spare EGR valve so customer only has to wait for me to swap parts out rather than what I suspect would be an overnight soak.

2) Jack told me that most shops use an ultrasonic cleaner on these and I've been researching a cleaner large enough to hold the cooler. I'm eager to know the measurements so I can figure the smallest size that will work for this job. Also wondering what your thoughts on ultrasonic cleaning compared to soaking are?