How to replace a oil tank level sending unit?

john4061 · john4061's Garage

Gentlemen:On a 1985 Porsche 911, Does anyone know how to replace the oil tank sending unit.? So far I took of the two wires and the 5 nuts off the studs,from the unit on the side of the oil tank. The unit seems like it won't fit through the hole in the tank to get it out. I bought the part from Pelican and did a search on the forums but could not find the steps of replacing the unit.

Please Help

Jim Sims · 03-24-2006, 08:27 PM

One has to turn and articulate it in several directions to get it out but it will come out. Experiment with the old one and pay close attention to the moves you are making and do the reverse to install the new one. Don't forget to slip on the new gasket before installing the new sender and don't over tighten the nuts.

EdT82SC · 03-24-2006, 09:28 PM

Notice where the lever arm bends. You need to turn the whole sender to follow the bend as you thread it out. Make sure you have a new cork gasket, or it will leak.

RoninLB · 03-24-2006, 10:54 PM

I used the optional/up-graded rubber gasket.

rw7810 · rw7810's Garage

What Jim said about several articulations. Much easier to do with oil tank out of the car. Just don't force it.

john4061 · john4061's Garage

Thankyou, everyone I got it out ,like Jim said.I kept turning it around till I could maneuver it out of the hole.

moneymanager · 03-26-2006, 06:44 AM

Now you're ready to put it back in. Do this. Cut a hole in a piece of cardboard whcih is the same size as the one into the tank. Use this to practice the moves you'll use to install the new unit to the tank, in its proper orientation. This will help you visualize what you need to do when working blind under the fender edge.

Chuck Jones · 11-03-2006, 08:08 PM

moneymanager: What a guy!!...I did exactly what you suggested, cut out a hole in a piece of cardboard the size of the hole for the oil sending unit access point, and spent about 3 minutes familiarizing myself with the way the unit had to go in and come out. It only took me about 20 seconds to get the old one out....but about two minutes to get the new one in....however all in all, a great suggestion that undoubtedly saved me a lot of time, some money, and a bunch of unprintable vocabulary. The archive search paid for itself that time. This was my first DIY and Pelican was there to help...Chuck

moneymanager · 11-04-2006, 05:44 AM

Glad you could make use of it Chuck. It took me about twenty minutes of cursing before the idea came to me!

Bob's Project · 11-04-2006, 09:33 AM

There really should be a vault for these classic threads. I bet every first time oil sending unit changer goes through this.

Chuck Jones · 11-04-2006, 09:57 AM

Well....I got the sending unit in with practically no trouble at all...but the damn gauge won't register. I guess I saved all my cuss words for after I got in the car, all pumped up with enthusiasm over the ease and success of my first DIY and how smoothly it went....and fired up the engine and NOTHING HAPPENED!. The gauge needle still lies dead at the bottom of the gauge....

I did do the check before I ordered the gauge...and that was to disconnect the ground wire and see that the needle pegged at the top of the gauge. According to those in the know, this is supposed to tell you that it's the sending unit that's bad and not the gauge. I cleaned up the entire area, took all the gook off the tank, cleaned all the contacts and even sprayed them with contact cleaner....and after all that...I'm right back where I started except that I have a new sending unit in there.

I'm open to suggestions...which will probably be something like I now need to change the gauge?

moneymanager · 11-04-2006, 10:17 AM

I saved the following note by Walt Fricke some time ago... it may be useful.
"Oil pressure & level gauges not working. These gauges are configured so that infinite resistance in the sender pegs the gauge. That's how you know the wire has come off the sender - turn on the key and the gauge immediately pegs. Zero resistance (grounding) is apt to produce no movement, at least not more than happens when you turn on the key and the instrument gets its 12 or so volts.
Since yours don't move, you probably don't have an "open" in the system. But you can use this feature to do some checking: Remove the wire at the sender and see if the gauge pegs. If it does, then maybe the sender is bad. Luckily they aren't that expensive (standard VDO parts)... If it doesn't, I'd then pull the sender wire off the gauge (the one which doesn't have 12V when you turn the key). If the gauge doesn't peg, I'd start suspecting the gauge. If the gauge pegs, at that point I'd be looking for a ground in the sender wire somewhere between gauge and sensor...
Oil pressure & level gauges not working.

Chuck Jones · 11-04-2006, 04:02 PM

Well, I found one of the problems....it didn't measure any oil level because the level was below the dipstick....that's probably what you might call a clue. I added more oil, but did so before the engine hit normal operating temps so I ended up adding a bit too much. In spite of that, even though the gauge is now indicating an oil level about 1/4 inch above the red bar at the bottom, the dipstick is showing full all the way to the full line...According to the best information I've gleaned from the guys in this forum who know, you're only supposed to add oil midway between the bottom and full. Going by that criteria, I've overfilled the tank, even though the gauge only indicates 1/4. The good news through all this is that it's working....maybe not as accurately as I'd like, but it's working.

Is there any sort of calibration you need to do to the sending unit? I would hate to think that I have to overfill it to get it to register anything.

Bottom line...check the dipstick.

moneymanager · 11-04-2006, 04:40 PM

The gauges are usually charitably described as only modestly accurate and you have discovered what everyone recommends: check the dipstick. Having said this, mine reads perfectly...IF the motor is warm, and IF it has been idling for 30 seconds or so and IF I am on level pavement. I've never heard of calibrating these things...perhaps someone has. I suppose you could bend the arm one direction or another but you know what installing and removing is like. My best advice would be to use the gauge as a guide, observe its behavior and rely on it only when you understand that it consistently under or over estimates real conditions. Overfilling won't do any damage, though you may find a bit of oil in the aircleaner or around the engine compartment that shouldn't be there but, yes, best to set the oil at the half way point on the di[stick.

randywebb · 11-04-2006, 05:42 PM

are you sure the gauge and sender match?

Chuck Jones · 11-04-2006, 05:52 PM

Yes the gauge and sending unit match...I got it from ********AZ and they matched it up by the part number from Porsche....it looks exactly like the one that came out. I think it's just like MoneyManager said...."modestly accurate" is a good description....To me its virtually useless, unreliable, and inaccurate. Given the built in unreliability, I don't know why Porsche even bothered to put it in. German engineering is usually better than this.

Quicksilver · 11-04-2006, 05:54 PM

Are you sure that the gauge is in at the correct orientation? It has 5 bolts holding it on. Is it possible that it is in turned 1/5th of the way around?

Chuck Jones · 11-04-2006, 06:22 PM

I used the orientation of the spade connector that was facing down and slightly to the right to position the sending unit so I think it's in the right position. I may have a bad unit...how do you test them anyway? Id hate to have to take it in and out.

Howard M · 11-04-2006, 06:55 PM

Don't assume it's bad until you check the gauge with a fully warmed up engine. It is quite temp sensitive.

moneymanager · 11-05-2006, 06:21 AM

I believe the sending unit can only be installed in one position...the reason the several bolts on the cover are irregularly placed. So I doubt if you have it wrong. The "fully warmed up motor" advice is good...and remember to have the car on level ground when you measure.