2000 Boxster transmission fluid...

So, I was at the track this weekend with my 2000 Boxster 5-speed, and noticed some light, amber fluid on the floor of the track garage; very small drips. Seemed like motor oil, but just a bit lighter. Came home, crawled underneath and found this stuff in a lot of places, droplets coming off the bottom of the engine/transmission mating point. Took the engine cover off, and poked around. There is a small, vertical port coming off the right side of the top of the tranny (if you are facing the back of the car), with a small black cap. The cap is not tight on the port; I can move it and spin it, but I cannot take it off without more force. The area around this port was wet with a coat of fluid. I also noticed that my axle air guide on this same side was missing. I did not check the clutch slave cylinder, but my clutch performed perfectly. Don't believe its brake fluid. Someone else suggested power steering fluid.

So, now I am wondering:
1) Is that port on the transmission a relief port for transmission fluid, in case it expands from overheating, so as to prevent pressure buildup inside the transmission?
2) Is the axle air guide that critical to cooling the transmission? Could it have overheated then, without that axle air guide?
3) perhaps most importantly, is transmission fluid for this model Porsche a fairly thin fluid? I've looked around and get varying opinions on gear oil, it's consistency and what is inside a Boxster transmission. Have never replaced it myself.

Quote
Pbastian
So, I was at the track this weekend with my 2000 Boxster 5-speed, and noticed some light, amber fluid on the floor of the track garage; very small drips. Seemed like motor oil, but just a bit lighter. Came home, crawled underneath and found this stuff in a lot of places, droplets coming off the bottom of the engine/transmission mating point. Took the engine cover off, and poked around. There is a small, vertical port coming off the right side of the top of the tranny (if you are facing the back of the car), with a small black cap. The cap is not tight on the port; I can move it and spin it, but I cannot take it off without more force. The area around this port was wet with a coat of fluid. I also noticed that my axle air guide on this same side was missing. I did not check the clutch slave cylinder, but my clutch performed perfectly. Don't believe its brake fluid. Someone else suggested power steering fluid.

So, now I am wondering:
1) Is that port on the transmission a relief port for transmission fluid, in case it expands from overheating, so as to prevent pressure buildup inside the transmission?
2) Is the axle air guide that critical to cooling the transmission? Could it have overheated then, without that axle air guide?
3) perhaps most importantly, is transmission fluid for this model Porsche a fairly thin fluid? I've looked around and get varying opinions on gear oil, it's consistency and what is inside a Boxster transmission. Have never replaced it myself.

The transmission is vented. That is the small vertical port with the cap. The vent is there to let the transmission breath that is maintain air pressure balance between the inside and outside of the transmission. If this wasn't done as the transmission and fluid got hot pressure build up could force fluid out the seals. Do not force the cap off or you may be facing an expensive transmission repair to replace it.

The fluid is not transmission fluid. That is thick (75w-90) and nasty smelling stuff.

The fluid is probably power steering fluid. Often times on the track the power steering system gets hot and the fluid can be forced out the vent at the top of the tank (cap). Some install a power steering fluid cooler. Or just keep your sessions shorter.

Be sure the power steering fluid level is correct. Do not over fill but do not under fill either. Check the system for any leaks and check the steering rack boots for any fluid build up. They'll feel like breast implants. The Boxster can experience a power steering high pressure bypass valve failure that routes too high pressure fluid to the rack. This forces the fluid out the seals but it is caught by the dust boots. One often doesn't know there's a problem until the power steering pump gets noisy due to low fluid level but by this time it can be too late.

I am not sure what axle air guide you are referring to. The little rubber scoops that hang down from the leading edge of the under engine stiffener tray are I believe there to cool the rear brakes. These get torn away once in a while and you want to replace them when this happens. While maybe not that critical for just every day street driving they are I think pretty important if one is engaging in some canyon carving or spending some time on the track.

The 5-speed (and 6-speed) fluid is some Shell fluid or Mobil fluid with a 75w-90 viscosity. I get my 2002 Boxster 5-speed transmsision fluid changed at the dealer. While the fluid is a bit pricey the labor is just 3 tenths of an hour. And often the dealer gives me a price break on the fluid. One time it charged me just $5/liter as it had some left over from warranty work. The fluid is pretty good. My Boxster's tranny is going on 298K miles and all I've ever had in it is Porsche transmission fluid, changed every 60K to 90K miles.



Edited 1 time(s). Last edit at 02/09/2016 09:39PM by MarcW. (view changes)

... , which can seep from the motor/trans junction if it was to leak at the RMS or IMS seals.

New motor oil would also be amber. OTOH Marc's suggestion is very possible.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

I also left out one thing...when I had the engine cover off, I did discover what I believe is a leaking oil fill tube. There was a good bit of mess up there because of this, I think. I found a little pocket on the top of the engine compartment that was full of motor oil. Haven't proved it yet. I do change the oil frequently, as in pretty much every other track session, or more. So, if the leak is bad enough, it could mean a lot of oil is getting on the engine, and this time, there was enough to work it's way down and show up on the garage floor. I just find it hard to believe that the oil could make it's way from there to the base of the engine and on to the tranny. But it might. I'm not that experienced, so I wouldn't really know. I'd love to clean that stuff up, and then watch it next time i do an oil change. Any suggestions on cleaning the engine compartment? I saw a post with a small steam cleaning unit with a wand...seemed like a good idea.

Could be oil then. Oil vs. Pentosin should not be that tough to determine but I say this based on an assumption not experience as I've never had to do this.

If you think the oil filler tube is leaking why not just replace it? It is an intake air leak that doesn't help the engine any even if it is not severe, yet.

To clean the engine I like Gunk, the stuff that comes in an aerosol can and is water soluble. I use a couple of cans of this to really soak the engine then let it sit a while then rinse thoroughly. If you can arrange it connect the hose to a hot water faucet and use warm water to rinse the engine. Afterwards I start the engine and after letting it idle a bit to ensure it runs with no untoward behavior I take the car out and drive it around until the engine is good and warm and I keep it warm a while to thoroughly dry the engine.

I've only washed the Boxster engine once this way. But I used to wash other car engines, and motorcycle engines using the above technique. My preference is to not wash the Boxster engine but in your case with the oil leak I can understand the desire to clean this off the engine.

… by MarcW that fluid is not tranny oil. Tranny oil is dark colored (blue or green) and very heavy weight.
The amber fluid most likely is power steering fluid which if overfilled tends to overflow when overheated at the track or AX.
You can install an under drive pulley which helps tremendously in keeping down the overheating of the fluid.
The two rubber scoops are spoilers to cool down the CV Joints. They force air up and around the joints as well as to the rear part of the transaxle.
If you are missing one or both you should replace them especially if the car is being tracked.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

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