My drain plug has become stuck and I have not been able to get it out. At some point I will need to deal with that but in the meantime I'd like to change my oil. Rather than risking damage to the pan threads I decided to try an oil siphon pump that is intended to be used to siphon oil out through the dipstick tube. A simple approach which is used already by some fast oil change places.

. Multiple online videos show it working fine.

I know for sure there is oil in there, all I have to do is look at the dipstick. So to start I marked the siphon hose with a sharpie at the point where it would be in as far as the dipstick for a reference to tell if it was in far as the dipstick to start..

I can insert the siphon hose to the length of the dipstick, and beyond by as much as maybe 6 inches. Sometimes it goes in pretty easy, other times it seems to catch and I have to wiggle it around some to get it to go in farther. Regardless of how far I insert it, I get little to no oil to siphon out.

I confirmed the pump actually will siphon by putting some oil in a cup and it siphons that up just fine.

The only things I can come up with are:

- the siphon hose is getting pinched shut. Generally I can move the hose back and forth without that much resistance, although across multiple attempt sometimes it got a little stuck and other time it didn't (see bullet 2). I am looking around for a smaller siphon hose to see what happens.

- there are more that one place the hose is going. I would thing that the dipstick access goes just into the oil pan and nowhere else, but I can't actually see down there to prove there are not more that one path it could follow. And as noted above, across multiple attempt the effort needed to insert the hose was not consistent.

Can anyone confirm the dipstick access just goes to the oil pan and not to some other mystery places?

Has anyone used a siphon of some kind to pull out the oil through the dipstick pipe, and if so, what did you use that worked?

Also, I looked down the oil inlet for adding oil which is much bigger, but I was never able to get the siphon hose any deeper than to the depth I can actually see. So that path must be blocked somehow just beyond that point.

TIA

 

Did you try removing the oil fill cap?

I recently used one of those siphons for the first time on my newish minivan - which has filter up top, so perfect for a topside oil change without even having to lift the car...

Anyway, they do create plenty of suction... but the hose can end up being quite a tight fit in the dipstick tube, and could seal enough inadvertently to close it off and prevent sucking the oil out?

 

Yeah I loosened the fill cap. I have not gotten my hand on a smaller suction side tube yet to test the "mine is getting squeezed" theory.

I called the local Porsche shop and they said they have one of the siphons that they use sometimes, I am planning to stop by there to look at what they have to see how much different it is, or isn't.....

 

I've used something like this with other cars:



Note that the smaller tubes are quite stiff, not like the hoses pictured with your pump. Might (or might not) be the difference.

I've never used it with my 944, though.

 

Yeah, that hand pump is the style I got too...

 

Have you used it on your Porsche without issue? If so can you tell me the outer diameter of the tube that worked?

 

No, I haven't - but mine are all 2.0L anyway, not 3.0!! LOL

 

I stopped by the Porsche service center and ask to see theirs. Tech said he had not used it on 968 or 944, which is not all that surprising since those probably seldom show up there anyway. From what I have learn, or think I have learned at least, what they have would not work any better than mine, the smallest siphon hose they had was a 6mm OD which is what I have. I just ordered a 4mm OD hose from Amazon and will attempt to adapt to that, cross all fingers and toes, and maybe it will work. Will post success or failure...

 

Is your engine warmed up when you are trying this? My boating experience is that it moves very very slowly if the engine is cold.

 

Yes I warmed it up some, didn't really know how much is "the right amount" to warm it. I basically let the temp gauge get to the first mark.

 

Oil warms slower than coolant, keep in mind... any warming is better than none, but if the coolant just got to the first mark, the oil was probably barely above ambient, maybe 80F or so...

For future reference - in a car without an oil temp gauge I find the idle oil pressure to be a very convenient indicator of oil temp... different motors will vary, but in my 2.0L turbo (924) the cold idle pressure after starting will be between 6-8 bar depending on ambients... I stay out of any serious boost until the oil will be at least 4bar max idle pressure, and she's fully up to temp and ready to play once she's at around 2 bar idle pressure...

 

Ah OK. I didn't think of that. I'll let it warm up a bit longer next time. Next time might be later today since I have ordered a 4mm OD hose from Amazon to see if that will work since the 6mm that came with the siphon is pretty snug and might be getting pinched off.

 

My E36 M3 has an oil temp gauge. The water is nearly up to operating temp by the time the oil temp gauge gets off the peg. My driveway is a slow 1/2 mile (dodging potholes), and it takes about another 1/2 mile after that.

The M3 has an iron block, but the 944 has slightly more oil volume. So probably roughly comparable?

 

Got the 4mm OD hose and as expected it easily fits down the dip stick pipe for 5 maybe 6 inches beyond the max length of the dipstick, then hits a wall, or maybe a floor. Without being able to actually see in there, my guess is illustrated below. I think I know the general shape of the oil pan, so my guess is the dipstick is hitting the bottom of the pan in the narrow part somewhere in the crosshatch area. If this assumption is correct, there is no way a tube from the top will be successful draining the oil. Without access to an actual to scale drawing showing where this stuff is, I am assuming this is the reason this plan is a failure!

 

No, the dipstick tube is over the deep part of the sump. Maybe there's a baffle i there that you're hitting?