DIY - How to save your oil cooler

[Mɐʇʇ]

I've just been pricing up gettings parts to make a replacement hardline+hose across the top of the cooler.

It is very doable - but needs quite a number of fittings. At the moment, it's too expensive - the number of fittings (150 degree fittings, 90 degrees, hardline fittings, adaptors, hose and so forth) makes it not viable. I also think to many fittings makes it all look a bit heath robinson.

My recomendation today is to start with the dremel and a nut splitter to save the thread on your cooler and replace with the audi hose 4B3317815B. It's still listed as available.

I'm brewing 2x alternative ways of doing the hardline in future:
1. Replacing entirely with hose. Not such a fan of this since the run across the top is 600mm long and doesn't have much support - but might be able to do something to improve that.
This keeps the number of fittings down to a minimum though - just not sure about the routing on the RHS
2. Using 15mm copper for the hardline (and spraying it satin black obvs). I think I can reproduce the correct shape just fine, reduce the number of fittings and the amount of hose.

Needs a bit more thought and I kinda need my car back together, so I'll revisit this in the spring.

[Classik]

Following with great interest

[Shoppinit]

1. Replacing entirely with hose. Not such a fan of this since the run across the top is 600mm long and doesn't have much support - but might be able to do something to improve that.

I did this on the Saab. Long hose from rad to gearbox diametrically opposed. Worked well. The hose is not unattractive so if you fix it in place it works aesthetically. Not that I care on the Saab.

[Mɐʇʇ]

Yeah, it's easy to do something that just joins the hoses together, but I was trying to make it look a bit more professional - it might be hidden from sight, but you know it's there.......

And by the time I priced all the bits up, you'd be better off giving audi 200 quid. Even for the short hose, it's actually 100 quids worth of bits - of course, the win is it repairs the oil cooler threads too, thereby saving 1700 or so.
Now it's a "known" that you'll always knacker the thread, the cheapest & best answer for the time being is dremel, nut splitter and OEM pipework, IMVHO.

[Mɐʇʇ]

So this is why I won't be doing a How To for the other pipe in the short term:

As you can see, the 90 degree bend is really tight coming out of the cooler against the LHS intercooler duct. If and when it comes to it, I could make a custom union instead of the the M22 adaptor that would take care of this - but it's not really a DIY then since it'd be a bunch of custom work to make. Maybe one day.

In the meantime, I have replaced this pipe with new OEM. Audi do still have stock.
As expected, the nut was locked on hard and I didn't even attempt to remove it.
So what you need is one of these:

And a dremel with a cutting disk.
In addition, the bolts on the p-clips holding it in place are guaranteed to sheer off as well - if they haven't already.
So you start off with this (air ram removed):

Set to with the dremel. Try not to cut into the thread of the cooler at all - but you do want to go a bit deeper in the area I've circled to make it easier to split the nut.
Cut both the front face - and also 180 degrees apart on the back face too.

Then put the nut splitter in. You'll need to bend the old pipe to get it to clear - but I made sure not to cut the pipe since I didn't want to risk any swarf getting into the oil system.

GENTLY use the nut splitter. You want the minimum amount of force you can get away with to part the nut - which is also why we prep with the dremel.
Too much force with the nut splitter could deform the cooler union and you're back to square one.
Just split:

You can see, that even after all that, I did still have a little bit of thread damage to clean up:

So a little bit of effort with the needle files and we were OK.
VERY IMPORTANT - DO NOT USE RAGS IN THE END OF THE COOLER
Any thread off the rag won't break down and could block an oilway in the engine.


ONLY use Scott Shop towels since they'll break down in the oil system and not block anything. I never use rags in the garage any more - I just bulk buy these.


To try and keep things a little bit "sealed" to prevent corrosion in future, I coated the thread in Permatex 35572 Aviation Form-A-Gasket No. 3:

I almost only use Permatex 35572 for any gasket sealing needs these days. For specific jobs, silicone and various loctite products have a role, but for general purpose stuff, I like this. It smells great too.

And then finally put it all back together, including a couple of new 15mm stainless p clips.

Obviously I did go back and straighten up that p-clip.

[IchBautAuto]

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I almost only use Permatex 35572 for any gasket sealing needs these days. For specific jobs, silicone and various loctite products have a role, but for general purpose stuff, I like this. It smells great too.

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Amazing how all the "old" brands are re-surfacing. They actually worked but got temporarily pushed aside by the newer formulations / brands. Read an old trade book from the 50's / 60's and you'll recognize a lot of the stuff being used.

[Classik]

Make sure they save the old bits please - the cooler, that is. Not fussed about the hoses
If nothing else, we could do an RS246 refurb kit on any old ones with a pre-modded cooler and premade hoses for the next person....on an exchange basis or sommat. I dunno.

Hey Matt,

My oil cooler threads need some love so I was wondering if the offer (exchange procedure) has already started? Unfortunately mine will be available after the exchange so I can't propose the 'first' one to activate the process.

[Mɐʇʇ]

I'm afraid not - there was no spare available to get things started. It's no biggie - the critical tool is a dremel & cutting disc, so you should not only be able to do it in situ, but you can more than likely do it saving the thread entirely - which means, if you choose, you can go with OEM hose too.

[Classik]

I'm no expert, but the thread (engine oil) on the right side of my cooler is kind of 'shaved' so I'd say there's not enough 'matter' to recreate a proper thread strong enough to withstand the constraints there. Or am I missing something?
This guy on eBay wants more than 550€ for a refurb one which I find very highly priced for the state of the cooler : https://www.ebay.fr/itm/Audi-RS6-C5-4-2 ... 3442532232, so I'm currently looking for options....

Did anyone try to contact Setrab to see what they could offer, as they seem to be the manufacturer for the oem part? If I read correctly, the model is "Setrab 484 comT 8", or something approaching..

[Mɐʇʇ]

Yes - that is the issue that prevents using OEM hoses - and that's where this DIY hopefully can help.

There should still be a couple of turns on the thread so you can get the brass socket to engage snugly- and then I epoxied it in place with JB Weld.
Mine's been in place for 5 years now (I did it late 2014) - still working fine.

[Mɐʇʇ]

Anyway - I just checked back - you've already done your RHS one? So I assume you mean the LHS one - which is trickier and I don't think the original DIY will work - hence the importance of dremeling the nut off.

[Classik]

Your perfectly correct, the RHS has already been done and the LHS has kind of been done the same way but leading to a very inelegant setup (braided hose running in front of the cooler..), hence my question. Well noted the dremeling approach, I'll ask my mechanic if he's confident to achieve this correctly.

Thanks again!

[Mɐʇʇ]

Certainly the only neat way I could think of doing the LHS pipe thread repair would have entailed making a custom fitting on the thread that has a 90 degree turn built into it. I did consider this, but with the extra fittings it would have needed, would have cost as much as an OEM pipe. So I'd only have done it if the RHS thread was knackered.

[Classik]

I've read your former posts far too quickly and we were not talking about the same thing Your dremeling approach is about preserving the cooler thread at the cost of buying a new pipe, whereas in my case the pipe is ok but the cooler's thread is already damaged...

[sweegie]

I've read your former posts far too quickly and we were not talking about the same thing Your dremeling approach is about preserving the cooler thread at the cost of buying a new pipe, whereas in my case the pipe is ok but the cooler's thread is already damaged...

I'd wager that the middle of a pandemic is a great time to learn to TIG weld....