I just replaced the water pump and oil pressure switch about seven weeks and 2,600kms. Everything seamed to be fine and I had a trip planed starting on Thurs and getting back Sunday or Monday. While checking the bike over before the trip, I noticed some oil residue laying in the belly pan. I decided to be optimistic it could have been from the fork oil that bubbled and spit back out as I was changing the fork oil last week. I cleaned it up and decided to watch for any further signs of oil during the trip. half way through the trip I decided to head back home. the trip was excellent, 1,351kms, and didn't have any problems until this morning. I noticed a small amount of oil again, this time I could see it was coming from the weep hole. I plan on emailing Max BMW on Monday, but I remembered reading a comment regarding the ceramic seal may take some time to "break-in" and actually seal. so I decided to run the bike a bit more over the weekend and see how things progress. So, I headed out, got some gas and about 9km from home, the oil light came on. So I limped back home. I pulled the cover off of the oil pressure switch and it was full of water from the torrential downpour Friday afternoon. Not sure why this would only cause a problem now, I cleaned the contact and reattached the switch. Well, the light still comes on and I had a single drop of oil in the pan with no other signs of possible problems. I have a brand new water/oil pump and new oil pressure switch, both of which no longer work? I did do a recent oil change, could the filter have backed off or a kink in the rubber seal cause the oil pressure problem?

I guess on a good note, I did get back home without any issue. two days of riding with a total of 16hrs 30 min moving and 3hrs 30 min getting gas and food covering 1,351kms and I didn't have a problem until this morning 9km from home.

I am going to leave the bike until tomorrow, when I may replace the brand new switch with the old one and see if the light still comes on. If it does, what could be the cause? Maybe a blockage in the engine? The water and oil look fine with both a proper amount of each and no signs of cross contamination.

Did you dismantle the spring loaded pressure release of the oil pump whilst working on it? It might be that it sticks and therefore the pump is not generating sufficient pressure. I would not use the bike until you know what's going on. I assume that you cleaned the drain hole in the pump, so there should not be any cross-contamination as it would drain away through the leakage passage and the channel in the block. Is the light out with a disconnected sensor wire and it comes on when you connect it?

Not quite enough info in your post just yet, but I recommend the following -
1. Take out the oil pressure switch and (temporarily) fit a pressure gauge. Start the engine and check if there is pressure. This will determine that the oil pump is operating. If not there are a few possibilities. Pressure relief valve stuck open, pump drive sheared.
2. Depending on what is determined from point 1, check the pressure switch for correct operation, also check that the wire insulation isn't damaged down near the oil pump.
A couple of other things -
Oil leaking out the tell tale hole indicates leaking seals on the oil pump side. These seals are lip seals, not the ceramic seal, which is on the water side.
Be sure the oil isn't leaking from the pump joint to the engine. This can be determined by inserting your little finger in the hole where the oil pressure switch wire exits. Oil in there means leaking joint. Remove pump, check, clean thoroughly (Loctite primer) and reseal.
If the tell-tale hole is blocked (really blocked) and the oil pump seals leak, it is possible to push oil into the cooing system via the ceramic seal as that seal works in only 1 direction. Oil pressure is about 3 Bar, cooling system pressure is 1 Bar. This happened to me when I took a chance and installed an engine which had been standing foe a long time and I didn't notice the tell tale hole was blocked. Nasty.
Hope this helps.

The pump unit came brand new a couple of month ago, ~2,600km. It came as a whole unit except for the oil pressure switch and face plate. I had a brand new oil pressure switch that I used while installing the pump. No, I did not remove the pressure release valve as it was new. I will see if I can get to the garage tomorrow and have them check the actual oil pressure. I don't have a gauge myself, but had thought about replacing the new oil pressure switch with the old one from the old pump to see if it still lights. I did notice that the outer plastic cover on the wire was cracked when I replaced the pump, but the wire itself looked ok. I'll check it again.

Re working of the pump. Have a look at the tell-tale glass oil level when you start the bike. If the pump works it'll draw the oil and you should loose the oil level from the glass immediately.
Was the block in way of both gearwheels completely clean? If scored the new pump will have a lot of issues to build up sufficient pressure.
Further, on another tack; re the downpoor, could the wire of the pressure switch be shortcircuited to ground elsewhere?

The oil in the sight glass moves slightly, but does not disappear. That
has me concerned. I replaced the new switch with the old one and oil
light does not come on, however after switching back to the new one and
the light still does not come on. Perhaps the was a problem with a
ground wire, but I don't like the minimal oil movement at the start-up.
I will coast down to the local garage tomorrow and have the check the
pressure as well as put in a heli-coil in the oil pump, http://k100rt.aforumfree.com/engine-and-transmission-f10/heli-coil-my-new-cus-word-t1064.htm
I guess I may have to resurrect it after all.

How high is the level initially? With my bike it is at the dot and as soon as I start the bike it disappears from the glass.
An other issue could be the seal of the suction pipe (the one with the bent and the suction filter at the bottom inside the block). If that one is not tight you might be sucking in half air/half oil.

The oil level is on the dot and just seams to flutter ~ 1mm. From what I remember, mine use to suck it below the sight glass as well. I just pulled the pump and things look fine inside. Where exactly is the sear pin and how can I check it. Since the oil seal was leaking anyway, I am going to get a hei-coil put in the old pump and try it. I also have a rebuilt kit, so I could replace the seals at some point, but I have to figure out what's going on first. ReneZ, you mentioned the suction pipe. I can't see how that would have been damage, but what if there is a problem with the filter of if the filter wasn't on tight enough and back off the threads? Going to go dump the oil and check the filter now.

Make sure you didn't leave the old oil filter O-ring stuck inside the engine when you changed the filter. Can happen sometimes and is very easy to overlook.

just ran out to check the old filter and the rubber ring is still there.

With the pump installed and the water cover off, the water prop will not move, but moves freely when the whole unit is removed. I assume from this, the pump must be turning when the engine is running, correct? so there must be a problem getting the oil to the pump or it was an electrical glitch. The outer plastic covering is very brittle on the lead wire, but I still think the wire itself is intact. I'll have to try and check this out, but the oil level not moving is what has me concerned. This oil filter was put on before the trip, 1,351km, but I think I will pick up a new one. Maybe the filter is faulty. It's BMW filter

The oil filter that you normally change is on the pressure side of the pump. There is a separate suction filter.

No pressure can be:
no suction
- because the pump is sucking air (not enough oil or leaking suction filter line)
- because the pump is not getting enough oil (dirty suction filter)
- because the pump can't generate pressure (pump housing scored in way of gears/pressure relief valve sticking in open position/pump is not being driven by the shaft)

Has the little gearwheel the flat part that is supposed to fit in the driving shaft?

Running out of ideas here, sorry.

Well, I am in the process of putting things back together now. I guess I'll just hold my breath and run id down the road and see what happens. For what it's worth, I am starting to believe there was a short caused from the previous days rain. I did stop at a local shop that has been working on BMW 30+ years. I was advised that it is too late when the light goes on, so if it is still running now then there wasn't a problem. hmmm My thought would be "Why have the light then" But, the light was only on Saturday and after swapping out the oil switch Sunday, I couldn't get the light back even during a short 9km trip around the block. If it was a short, I think it was in the joint at the switch. has anyone used some sort of dielectric grease to keep moisture or water from breaking a circuit?

Thanks for all the help ReneZ


Scott

If you clean the contacts good on the switch and the cable and then fit it and cover it with silicone or a big amount of petroleum jelly before fitting the rubber hood. I have the jelly over the contacts and have closed of the hood with some silicone.

From memory, the rubber boot has a small drain hole. I was reluctant to block it so I used silicone grease over and under the contacts, but didn't fill the rubber boot with it before fitting it over the sensor.

BTW there is a temperature gauge sensor next to it with the same issue.

I've decided to "service" both connectors each time I do oil / coolant change so a god smear of waterproofing is all I will do there.

Thanks, I thought about petroleum jelly but thought it might eat the rubber boot. I am going to check a local electronic store and see what they have. I am also going to have a problem where the out plastic covering over the wire os broken. I think I will try and slide a section of heat shrink tubing to keep water from running down the inside along the wire lead. I have a K75S so I don't have the water temp gage. at least not yet. I keep thinking about one, but I think an actual gas gauge could be of more use.

Oh, I took bike out and ran through ~120kms tonight and everything worked great. So with any luck, if I can get the sensor waterproof, I may not have that issue again.

Thanks for the support guys.

If you are going to run heatshrink get the stuff that has an adhesive inside it. I believe it is also called double walled as it should then provide a much better waterproof seal.
Check out: http://www.easternbeaver.com/Main/Elec__Products/Shrinktube/shrinktube.html
to get a better idea.

Well the dilemma continues. Well, I hope not so much with the oil light. After fixing the outer covering over the lead wire, everything worked fine. Today, I took a dive into town. While watching my daughter play soccer, I ran out to the corner store to pick up some extra water for her. While leaving, I turned on the ignition and hit the start button when something caught my eye. I shut down the bike and turn the ignition key back on. My warning light is no longer on for the oil pressure. Nor is the one for the water temp, can't remember if that one is suppose to light or not.

Back at home I went through a number of checks before finally deciding to check the oil pressure switch. Nothing, an open circuit in the switch. This is the new one that I had questioned earlier. So I check the old one and put it back in and I again have an oil light with the ignition key on. I wonder if it has been this new switch the whole time.

So now I am wondering about the water temp light. is it suppose to come on during the ignition check? And how would I hunt down the wiring for it. the 75S doesn't have any gauges and I have to rely on these idiot lights.

When both the water and oil light were out, I swaped out instument clusters and still had the same results. I was curiuos if I had a corrosion issue inside mine. In any case, it does not look like it's just a burned out bulb for the water temp.

Water temp light does not self check I believe. You can simulate an overheat and it should light then. When it is lit the bike will continue to run but will not restart with the over temp light lit if you switch off.
Regards,
K-BIKE

Thanks K-bike, I could not remeber if I had ever seen it lit during start up or not. I all of a suden thought I use to see three light up oil, bat, and temp.

Hi Swells,
I went and checked this on my 1990 K100RS the temp light does self check I mislead you there, sorry about that. So your memory of seeing it lit was probably correct!
Regards,
K-BIKE

On the early K's the water temp light does NOT self check with ignition on and there is a procedure mentioned in one of the posts on how to test the temp warning light and fan.

Ideally we need to know which models it does and does not come on.

It probably changed with the change-over to the Motronic ECU. IIRC the Motronic switches the light and fan, whilst the L-Jetronic doesn't - it has the temperature solenoid that takes care of that, which is a rather simple circuit.