Oil cooler questions

[Fastguy]

On disassembly I broke my front oil/trans cooler male threaded compression fitting on the radiator itself. I no longer need a trans cooler section as I will have a manual. I want to eliminate the stock radiator and get a replacement with a single core for oil only.

Any suggestions on what to purchase? Does anyone know the size of the oe cooler compression fittings so I can get a universal that fits directly to the existing oe stainless lines? I was thinking of something like this: http://www.ecstuning.com/Audi-RS6--4.2T/Engine/Cooling/Oil_Cooler/ES2855412/

[SteveKen]

Maybe I'm mistaken, but I thought you asked this before. Might have been someone else.

As far as I know, you can't get an OEM V8 radiator without the trans cooling circuit. Even the S6 manual car uses the trans cooling similar to the allroad. I just thoroughtly clean it out and plug the ends.

As for the oil cooler, I think you are best keeping it in teh stock location. This hten severely limits your choices. Setrab makes on e that's close but is a fortune once all the lines are fabricated and all the fittings are spec'd out. On my car, I used an oil cooler from an E30 BMW M3. It required some fabrication to mount bout no more than what would be required in your ECS link.

Here's one for sale but you can also geat a used one if you look hard enough: http://www.ebay.com/itm/BMW-Engine-Oil-Cooler-seals-e30-325i-325ix-coupe-sedan-convertible-oem-/291469517484?fits=Make%3ABMW&hash=item43dcefe2ac&vxp=mtr

Here are the used lines that you can use for attaching the custom flex lines: http://www.ebay.com/itm/BMW-E30-Oil-Cooler-Fluid-Lines-Hose-Late-Model-88-89-90-91-325ix-325is-325iC-/221174179431?hash=item337f022667&vxp=mtr

[Fastguy]

I think I may be missing something...

As I understand it the main coolant radiator is closest to the engine. As far as I can see there is only one main coolant section in this core? I see a larger (around 1.5" line) in the top and coming out the bottom. Next is the condenser coil for the AC. Finally, there is the small combination cooler for both the trans and oil. It's the small one that spans the length of the bottom of the stack of radiators and it's only about 3-4" tall?

Oh, and there is a second oil cooler that I did all the seals on and the bufkin pipe at the block.

[Fastguy]

went out and took a little better look. I must be thinking of the flow incorrectly. I thought the smaller cooler up front is split into two circuits. One has trans fluid and the other has engine oil? I must be incorrect in this? I broke only one fitting. I have only two options; replace with an oe/aftermarket cooler, or somehow find a person who can remove the broken fitting and reattach it to the cooler?

1647916480

[bethridg]

went out and took a little better look. I must be thinking of the flow incorrectly. I thought the smaller cooler up front is split into two circuits. One has trans fluid and the other has engine oil? I must be incorrect in this? I broke only one fitting. I have only two options; replace with an oe/aftermarket cooler, or somehow find a person who can remove the broken fitting and reattach it to the cooler?

1647916480

No, you are correct regarding the cooler you broke the fitting off of. It's a combination oil/trans cooler. SteveKen is also referring to the in-tank trans cooler in the radiator; hard lines located on the driver side of the tank.

He is saying plug the in-tank radiator cooler and repair or replace the small combination cooler.

His solution was to use the E30 BMW cooler linked above. Below is the link to his post in his build thread about the the oil cooler.

http://www.rs6.com/showthread.php/25661-S6-conversion-to-RS6?p=260496&viewfull=1#post260496

You can just make out the cooler installed in the top pic of this post.

http://www.rs6.com/showthread.php/25661-S6-conversion-to-RS6?p=267167&viewfull=1#post267167

[Fastguy]

Ok, So I pulled the stack of radiators/coolers apart in preparation for cleaning and repair.

The circled ports on the radiator...are these for trans cooling? If so, what do I do about them?

16504

Second, I'm assuming here the top two ports are also for trans cooling (1 and 3) and the bottom two ports lead back to the oil cooler attached to the block (2,4)? I simply need to eliminate the lines at 1 and 3 and cap somehow, and get 2 repaired?

16505

Finally (question for Steve) I am 99% sure the upper and lower lines in these pics get deleted as they are part of the secondary coolers that will now be eliminated (the little radiators behind the intercoolers)

1650616507

[bethridg]

The circled ports on the radiator...are these for trans cooling? If so, what do I do about them?

16504


Yep, that's them. I'm going off of memory and a few pictures I took when I replaced mine. Technically, I don't think you need to plug them as its sealed off from the coolant side. Other radiators I've dealt with had threaded plugs installed. But the RS uses an o-ring and tab/bolt setup. Maybe someone else with experience will chime in as I haven't reached this stage nor have I seen SteveKen's solution.

[P1054]

Yep, you're right on all counts, or at least that's what I determined during my 6-speed swap. I got rid of the upper and lower coolant lines you're pointing out, and capped off all 4 trans cooler ports with rubber stoppers I bought at my local hardware store. The ones on the radiator I held in place with some custom plates I made that used the original trans fluid line attachment bolts, and the ones in the combo oil/trans cooler I just pressed in. They are still there after 10k miles, and I've had no issues with any of the changes I made.

[SteveKen]

The rubber stopper method is preferred. I've tried a few things. If you leave them open and don't thoroughly clean and blow out the passages, they will leak/dribble until they are completely empty. This will probably freak you out, thinking that you have a leak.

I've also merely plugged the holes with absorbent wadding like a piece of a PIG mat.

My hesitation in physically sealing them would be a cyclic change in pressure with heat cycling, but without doing the calculations, it's still probably insignificant, which is probably proved by the rubber stoppers still being in place after 10k miles.

[SteveKen]

Yep, you're right on all counts, or at least that's what I determined during my 6-speed swap. I got rid of the upper and lower coolant lines you're pointing out, and capped off all 4 trans cooler ports with rubber stoppers I bought at my local hardware store. The ones on the radiator I held in place with some custom plates I made that used the original trans fluid line attachment bolts, and the ones in the combo oil/trans cooler I just pressed in. They are still there after 10k miles, and I've had no issues with any of the changes I made.

A bit OT, but can you give a 10k mile report on your clutch? What manufacturer and stage are you using?

[P1054]

Sure. AMD Stage 3, 10k miles, holds the power with no issues, smooth when cold but gets a bit chattery on takeoff once it's warm. I can avoid the chatter by using a bit more revs on takeoff, but it does get old in traffic. Certainly not a deal breaker for the manual, at least not for me, but when it comes time to change I'd be pleased to find someone with a clutch that holds power and stays smooth.

[Fastguy]

Just a little bit of overkill with the questions but I like to understand completely what is taking place. The tran lines on the radiator cool the trans via coolant, and the lines on the combo cooler are additional and cool the trans fluid/oil via air to fluid heat exchange? If this assumption is correct with the main coolant radiator and the two sides are sealed from one another, how is the coolant initially introduced into that side of the radiator?

[SteveKen]

Just a little bit of overkill with the questions but I like to understand completely what is taking place. The tran lines on the radiator cool the trans via coolant, and the lines on the combo cooler are additional and cool the trans fluid/oil via air to fluid heat exchange? If this assumption is correct with the main coolant radiator and the two sides are sealed from one another, how is the coolant initially introduced into that side of the radiator?

Transmission fluid runs through both external coolers.

Therefore, without running the trans cooling circuits through the radiator and oil cooler, they should do a better in keeping the coolant and oil temps down. I essentially have the stock cooling from a UK car, with no afterrun capabilities, etc. and the water ans oil temps have never go out of control on me.

Technically, if you want, you can cool the 01E with the pump assembly that was stock on the allroad and manual S6 01E. It might require custom lines. The S6 manual lines might be available, but would only run through the radiator.

[SteveKen]

Sure. AMD Stage 3, 10k miles, holds the power with no issues, smooth when cold but gets a bit chattery on takeoff once it's warm. I can avoid the chatter by using a bit more revs on takeoff, but it does get old in traffic. Certainly not a deal breaker for the manual, at least not for me, but when it comes time to change I'd be pleased to find someone with a clutch that holds power and stays smooth.

This is good info as I'm running the same clutch. I've got around 2k miles on it. It's very driveable in comparison to the AMD stg 4 that I ran for about 1100 miles. No complaints here.

[bethridg]

Just a little bit of overkill with the questions but I like to understand completely what is taking place. The tran lines on the radiator cool the trans via coolant, and the lines on the combo cooler are additional and cool the trans fluid/oil via air to fluid heat exchange? If this assumption is correct with the main coolant radiator and the two sides are sealed from one another, how is the coolant initially introduced into that side of the radiator?

Think of it like a hard tube, similar to the power steering cooler, that enters and exits the coolant tank. G12/G13 coolant surrounds the tube and transfers heat.


http://i.imgur.com/pMMOSItl.jpg

[bethridg]

This is good info as I'm running the same clutch. I've got around 2k miles on it. It's very driveable in comparison to the AMD stg 4 that I ran for about 1100 miles. No complaints here.

I ordered AMD's stg 3+ clutch last week; will report back when I get that far.

[Fastguy]

Ah. Ok. Forgot I had this.
16509

[Fastguy]

update: Did some calling. No one seems to want to repair that aluminum compression fitting. The one shop I was able to contact (the only one the really seemed competent), said they won't weld aluminum coolers that have had oil flowing through them. The reason being the oil will impregnate the aluminum and a sufficient weld will not be possible. As they heat the aluminum, the oil will release from the pores of the metal and screw up the weld. He suggested that I call a local Napa and ask out a replacement "Hayden" cooler. Not too sure what to do at this point. Going to have my trans back by end of this week or beginning of next and going to try and hustle to get all this complete.

Edit: Wondering if I could just tap and thread a new fitting in there? I'll take a look at the thickness of the metal tonight. Also need to figure out the diameter and thread pitch of that fitting.

[Bigglezworth]

Don't mess with this part. Source a suitable replacement that is guaranteed to hold the pressure. Last thing you want is a blown fitting that quickly depletes the oil from your engine under load.

[Fastguy]

Sorry for keep digging up this thread. Questions I think are almost done.

Are the threads/fittings on the combo cooler a "an-x" standard or are they something metric? I ask because it would be very nice to use the oe part that connects at the oil filter and source some custom length hoses and aftermarket cooler. I'd purchase the mishimoto kit but I don't see how the hoses would be the exact length. This would leave some excess hose, I'd imagine, that would need to be dealt with somehow. IMO this would look sloppy or maybe make the installation of a universal style cooler much more difficult.

I dont think hunk there is anyway the stock cooler is going back on as no one locally will repair it and I'm not about to spend $900 on a new oe one.

[Nkirk99]

In terms of the lower combined cooler. If you were doing a manual conversion andtherefor not using and blocking off the upper core. Would it be feasable to use both the upper and lower for engine oil cooling. Looking at the large picture provided by fastguy. If you had a custom line that moved the supply line into the left hand side, unused upper core (previously the trans cooling return exit) and on the other side a small u shaped line joining bottom and top cores therefor the engine oil would enter in the top left, travel to the right, then down into the bottom core and out the orignal exit. Just a thought.... Do able, or silly?

[SteveKen]

I thought of this when I performed my first conversion and decided against it. The diameter of transmission lines are noticeably smaller and I figured that there might be flow issues.

I still think that the aftermarket Setrab or the M3 stock cooler is the best option provided you find someone competent to fabricate the lines.

[Fastguy]

I was thinking this exact same thing yesterday-combine both cores. My most pressing issue at the moment is to find the size of the oil core ports. My best guess is 22mm 1.5 pitch but this is purely a guess. I need to somehow get sample fittings to test. I was told once again to get it repaired and that a good welder can do the job? Just clean it well?

[Bigglezworth]

I thought of this when I performed my first conversion and decided against it. The diameter of transmission lines are noticeably smaller and I figured that there might be flow issues.

I still think that the aftermarket Setrab or the M3 stock cooler is the best option provided you find someone competent to fabricate the lines.I do believe the OEM unit is made by Setrab... As for the diameter, we should all remember that the size of the oil lines within the block are a lot smaller than the size of the lines feeding the cooler - meaning it will increase the pressure at the cooler. Not being a physics major, I do believe that means the oil won't pass 'through' the cooler as quick which would mean slightly poorer cooling. How much - debatable I guess.

[s8prtotype]

Here is some more info...

http://forum.rs246.com/viewtopic.php?f=2&t=113332

[lswing]

Here is some more info...

http://forum.rs246.com/viewtopic.php?f=2&t=113332

Nice, I just read that also and was thinking of sharing it over here. He's been doing some good writeups...