KrazyK

Has anyone tried Imre's idea of eliminating the coolant flow through the AOS/OVS? Is the purpose of having coolant flow through the AOS only for frigid climates or does the hot coolant serve another purpose in making the system work better?

If the only purpose is for freezing weather, I would consider this because it would certainly eliminate the risk of intermix and coolant leak due to AOS problems. It would also eliminate the silly plastic coolant fitting that breaks so easy on the front of the engine.

5CHN3LL

I have the same question and haven't seen an answer anywhere yet. If this feature is strictly for cold climates, I would be inclined to bypass the AOS.

alpine003

Coolant is for cold climates. In the case of BMW AOS for example, they use insulating foam around the tubes and such since they don't use coolant.

Capt. Obvious

Sooooo, fill the AOS coolant lines with expanding foam and bypass the water line? LOL

Cuda911

A local indy shop that only works on 911s (of all years) told me that the AOS bypass is fine. But I didn't do it, I replaced my AOS.

KrazyK

I bought a new one as well but it seems this could prevent a future problem or at least eliminate that particular failure.

Macster

Not sure it is for freezing weather only.

The AOS wants to be kept hot so water vapor doesn't condense out to liquid when it comes in contact with the relatively cool AOS. Otherwise, the water vapor returns to liquid form and returns to the crankcase and the build up of water in the oil just accelerates. This could also apply to any unburned fuel, too.

I note the 911 has coolant routed to the AOS while the Boxster (at least my 02) doesn't.

But I also note the Boxster AOS is located on top of the engine which is itself located inside an engine compartment that isn't directly exposed to air flow from outside the car thus the Boxster AOS runs hotter.

I suspect removing the coolant from the AOS would be a case of jumping from the frying pan into the fire. Or trading off the risk of an intermix from a failed AOS to that of a engine with a spun bearing or some other lubrication related issue arising from heavily contaminated and diluted oil.

KrazyK

All good points Macster. The 02 - 04 is mounted different and I wondered if the engine heat would keep it warm enough. Maybe just assume it has a valid purpose and risk the next leak. The original lasted 10 years.

Macster

Maybe in slow traffic on a warm day the engine and engine compartment heat is sufficient. Maybe. At least until the engine compartment fan comes on.

But what about the cooler times? Or when the car is moving down the road. There's a lot of air flowing through the engine compartment to remove the heat. The air flows downward so the AOS is going to get cooled right down and stay cool.

Imo000

Macster, I disagree. The engine will get plenty hot for the AOS to not cause condensation issue. I have no idea where you get these theories but coming up with them has to be time consuming as they are very convincing to those that don't have much experience with engines. I'm fairly certain that line is for extreme colds and short distance drives. I think its worth a shot bypassing it.

Macster

So you think Porsche put the coolant heated AOS there for looks? Geesh. You want to bypass the thing, run a non-heated AOS, have at it. Your car. Your engine. Your theory.

Hurdigurdiman

You disagree with Macster on this point and in doing so disagree with the Porsche Engine designers. So you have more experience with engines than the Porsche Engineers? Then you go on to say that Macster is convincing to people or THOSE that don't have much experience with engines. YET you are only half convinced that you are correct with your reckoning when you say things like :- I am FAIRLY certain and I THINK it's worth a shot bypassing it. You my friend are all bologna. I don't THINK so I know so from your posting. Not that Macster would have told you so, as he is more a gentleman than I am. If you did this MOD, would you return it to the original as you pass on the car to the next owner. I know not. And some poor unaware buyer buys what could be an exploding time bomb especially if it moves from one part of the country to another with a different climate. If I ever had to buy another 996, I would not buy it from an owner who frequents this or any other Porsche Board. You scare me half ****less with your mods.

Quadcammer

You literally appear dumber every...single...time you post.

stick with applying decals to your vehicle, because mechanics are simply not your calling.

KrazyK

Holy s#$%! QC, that was rather harsh. Hurdis starting to perform lots of DIY's which is awesome at any age and he makes interesting posts.

I welcome and respect anyones opinion and can certainly see arguments for keeping the coolant through it or not. Is it common practice for the track guys to bypass the AOS? Seems like it would be less hoses/potential leaks to worry about while tracking.

I have not decided which way to go with this. I was hoping others had tried it and could give opinions.

Adker

Different Pcar engine but I use a catch can between the AOS and the intake. This is a 99% track car and you have to manually drain the catch can. After short runs in cold weather, all that comes out of the catch can is water with a little oil mixed in. Hot weather, very little water and a little oil. My AOS is NOT water heated. From what I find the my catch can, I would agree that the water jacket is there to help speed up the process of vaporizing any water in the AOS in cold weather.

This is a better unit (Motorsports Cup Air -AOS- Oil Separator) that was designed for racing to avoid hydro-locking an expensive race engine...a bit pricey $800.

http://www.suncoastparts.com/product/9XXSEP.html