Oli Pressure Light

[John Lang]

After an oil and filter change the oil pressure warning light stays on. I drained the oil again, removed, cleaned and tested the switch, refilled the crankcase and started it up once more. The engine ran long enough to fill the new filter but the light stays on. When I unplug the switch it goes off, as it should.

I tested the switch by poking its pressure plate while a multimeter was connected. The circuit breaks when the plate is pressed. There was never a prior indication that oil pressure was low.

Now what?

[Laitch]

Did the filter you removed still have its gasket on it? If its gasket was stuck onto the mounting flange during removal, the additional gasket of the replacement filter would create conditions for leakage and a resultant drop in oil pressure.

[John Lang]

Aha! I did not check whether the old gasket came off. You might have solved the puzzle, Laitch. Tomorrow I will drain, inspect and report. 

[John Lang]

Alas I had not doubled the filter gasket and the low pressure light is still on. But I suspect the problem does relate to the filter change. Well, I cannot think of anything else. Perhaps the new one does not seat correctly. I cannot recall which it is, a Mobil-1 or something ending with 3614 probably. All I can think to do is swap it for a filter that definitely worked in the past. I'm grasping at straws.

[Laitch]

Alas I had not doubled the filter gasket and the low pressure light is still on. But I suspect the problem does relate to the filter change. Well, I cannot think of anything else.

There's always coincidence, John. However, it can't hurt to revert to using your usual filter model.

First, The mounting flange should be clean and the replacement filter must be firmly attached but not over-torqued. To me that's quarter-turn to half-turn after contact.
Next, the oil pressure relief valve in the pump could be stuck in the Open position and not allowing sufficient pressure to build. Remove it, clean the orifice, inspect the spring and piston, then reassemble it and test by running the engine briefly.

[Chaos]

Were you testing it by just letting it idle?  Maybe it needs some RPMs.

[John Lang]

Yes, Chaos, I revved hell out of it to no avail. But...

Happy ending folks!

I could not follow Laitch's suggestion to look at the possibly stuck open pressure relief valve because the bolt for that seems to have welded itself to the oil/water pump. Before bringing in reinforcements -- heat, wrench extender, monks -- I decided to try a filter that definitely worked in the past, WIX 57936, in the hope the Mobil-1 filter was somehow gasket incompatible. My heart sank when I saw the two filters were almost identical. Just before I began installing the Wix, A local Brick buddy called to say that I should pre-fill the filter with oil before installing it. I obeyed and the warning light went out after about 2 seconds. I cannot imagine why that made a difference when it has been unnecessary in the past, but I'll take the success. Now, should I throw out the Mobil-1 or would the same trick work with it? I'm gonna throw it out.

Thanks for  your responses.

[Laitch]

 

[daveson]

Just before I began installing the Wix, A local Brick buddy called to say that I should pre-fill the filter with oil before installing it. I obeyed and the warning light went out after about 2 seconds. I cannot imagine why that made a difference when it has been unnecessary in the past, but I'll take the success.

Hey John, here's a dollop of being pedantic with extra helpings of guesswork. Most of us do a thing the non pedantic way, so we get away with it 999 times out of 1,000. So if we do our own services once a year, we usually won't have a problem over a lifetime.

Do you put a thin smear of oil on the seal before you install the filter? I'ma Gunna guess you don't. If the seal is in dry contact in some places, it could bind earlier in a spot and cause the seal to kink, so not seal properly, therefore leak. A good habit is to smear a thin film of oil on the seal before installing the filter. When you topped up the filter, I'll guess it got some oil on it so there was even pressure all around the seal, or it was evenly dry.

Now to get even more pedantic, it's better to get a smear of the old oil, rather than the new oil.

This is just my guess.

[John Lang]

That's a very good guess daveson and thanks but I did smear oil on the gasket before twisting it on.

It's a mystery to me. When I started the engine, revved it a little, and when the light failed to extinguish after about 8 seconds I turned it off. I did that  twice more, hoping for a different result, and then took the filter out to check whether I had failed to remove the old gasket. I had not, so I refilled and started up again a couple of times but never for longer than 10 seconds owing to the reproachful glare of the red light. When I pre-filled a different filter the light went out in less than 2 seconds. The filters side by side seemed identical but perhaps the first filter was jinxed with an invisible fault.

[Chaos]

It might be interesting to dissect the misbehaving filter. I’m curious to know how that could happen.

[frankenduck]

I always get my oil filters from ACME, just like Wile E. Coyote.

[John Lang]

Yes, Duck, using the Mothership's recommended filter(s) would have avoided this. As I buy whichever filter on the shelf fits a K-75 (and my cup socket), I have used a variety of them. I am prejudiced against Fram.

I think I now know what happened. The gasket on the 'failed' filter sits nicely on the housing flange -- which is all I looked at -- but, rather than lying flat against the filter base it sits in a circular groove, stands a few mm proud and wants to be compressed. My 'snug plus half a turn max' ritual was probably insufficient to make a seal. I simply did not tighten it enough!

If this is the case, my situational awareness and readiness to adapt are again kicking in after the need. As Sherlock said, "the last possibility, however unlikely, must be the solution". I'll see next oil change when I crank it down. Thanks all for trying to help.

By the way, even Wile E. Coyote succeeded eventually.

[daveson]

Guess what? some more guesses, once again not very confident though. It's been stinking hot on this end of the planet, so I guess very cold on that end, especially in the morning.

With the fresh cold oil poured in, the filter bypass valve might have opened (to protect the paper filter element from getting damaged) This allows unfiltered oil to circulate. Some crap coated in a thick dollop of oil could have blocked the pressure relief valve, which eventually loosened up. Maybe even blocked with pieces of the paper filter element.

The filter should have had a plastic protective seal (without splits) which is removed before installation, not all of them do.

[John Lang]

Thank you, daveson. You have a gift for abstruse diagnostic. If ever I have to look at the pressure relief valve, which I am unable to open, I might prevail upon you all for suggestions. Until then it will remain unmolested. I might revisit the 'failed' filter (Mobil1-101) next oil change to determine whether cranking it down more is the answer. But, do I need 'closure' on this and risk re-entering the filter twilight zone or should I just toss it out and move forward?  A weighty issue on which I will try not to obsess.

[daveson]

My first thought after reading your last post was; where's the dictionary? I don't think my guesses are likely, just possible explanations.

Your oil pressure problem has disappeared, so it's happy days. Once I got a no name oil filter and cut it open after use, the paper filter element had three holes in it. Maybe I over worry about filters for that reason.

[John Lang]

Your guesses are good, daveson. Diagnosis of unusual occurrences requires knowledge and imagination. I have looked at a few of the many YouTube videos on oil filters and am not much wiser as a result -- so many variables. Bosch and K&N seem good; cheaper Fram filters not so much; most engine wear comes from particles in the oil that are too small to be seen and which cheap filters using a paper element might not capture. It is a highly competitive market so I suppose you get what you pay for.

[Chaos]

haha, any search of filters will always generate negative results for Fram oil and K&N air filters!  Possibly justified, but I had a K&N air filter on my K75s for 200,000 miles with no ill effect and have used Fram oil filters on my VW 1.8t for the last 23 years and it's still running strong.  I wouldn't use the KN air filter on newer cars because of oil contamination of the air flow sensor or the oil filter on a K because the grippy stuff they put on it could dissolve in the sump.  But I have defied internet advice and lived to tell the tail!