Tips for replacing oil pressure switch?

autojack · 12-06-2016, 02:31 PM

I'm 99% certain that the source of my car's slow oil leak is the oil pressure switch. The mechanic who did the PPI told me it leaked a little at the "oil pressure" something. I thought he had said "sender," but that is visibly dry. The drip is coming from the back of the engine, and today I poked my borescope back there and there is definitely fresh oil in the area, seemingly concentrated around the switch. Attached is a grainy picture of the area...

I've heard that the switch can be replaced, with liberal contortions and cursing, without even a partial drop of the engine. I'd really rather not have to drain the oil and take on the partial drop to do this. Can I get away with just removing the air box and, maybe, the AFM?

I've read that some people put some Loctite 574 flange sealant on the switch when they replace it, but to me it seems like that wouldn't seal against the pressure of the oil system there. Thoughts?

Thanks in advance

merlinfe · 12-06-2016, 02:38 PM

I'm pretty sure there a lot of people here who will tell you to drop the engine and address the "triangle of death" and the other while you are in there stuff while you're at it.

Might be easier than you think.

-Steve

Arne2 · Arne2's Garage

Can be done on a 3.2 without the partial drop. I did it. Like you said, pull the airbox and AFM. Still hard to see and get to, trained fingers are very helpful.

I'd recommend doing the breather gasket and oil thermostat o-ring at the same time. On my '84 both of those items were quite crispy. If you do them, be careful when removing so as not to drop pieces of them into the motor. Also take a good look at your breather hoses (the big hoses going to the oil filler and airbox). Mine were getting badly weather checked.

JohnJL · 12-06-2016, 04:03 PM

Whatever you do, the best tip I can offer is to clean everything 100%. You dont want any crusties falling in the sensor fitting.

Flat6pac · 12-06-2016, 04:22 PM

88 911, It's easier to remove the airflow sensor, air cleaner and if necessary, pull the right bank if the injection, but that's a lot more complicated than just the sensor and air cleaner.
Bruce

Joe Bob · Joe Bob's Garage

The TOD is a traditional repair/rite of passage item for the air cooled crowd. Time to join the club, bud....someone should make a tee shirt documenting passage like cross the international date line or the equator.

autojack · 12-28-2016, 09:15 PM

I started to pull the air box and AFM tonight. I unbolted them from their brackets and popped the AFM off the air hose, but I can't figure out how to move the assembly to get it completely out. I had to head in for the night. What's the trick?

wrxnofx · wrxnofx's Garage

Did you remove the nut inside the airbox holding it to the manifold? See the rubber buffer in the front that you removed the nut off of? There is another one inside the airbox.

autojack · 12-28-2016, 09:27 PM

Quote:

Originally Posted by wrxnofx

Did you remove the nut inside the airbox holding it to the manifold? See the rubber buffer in the front that you removed the nut off of? There is another one inside the airbox.

Oops, no! When someone earlier said to remove it as one assembly I assumed I didn't need to open it. Thanks!

wrxnofx · wrxnofx's Garage

Aha, then that's your problem. Just unlatch the right side of the airbox and remove it, pull out the filter, and you should be able to feel the nut on the bottom of the part of the airbox still attached to the manifold. It's the same size as the front one (M10?). You'll have to lift the box up to get it over the two studs while at the same time pulling it to the right to get the AFM out of the rubber elbow. Just a little fiddly. You'll do fine. Oops - I see you've already freed it from the elbow. You're almost home.

GregT2000 · 12-29-2016, 06:24 PM

I did the full triangle without the partial drop.

My best tip is to raise the rear of the car on jackstands. It's a much more comfortable angle to lean over the engine for the work.

Couple other things: the sending unit had a very low torque spec if I remember right, basically finger tight.

My 3.2 had a bracket I think for hoisting the engine that had to be loosened to get the breather cover off.

Double check all the vacuum hose connections when you're done. I missed one and had a hard time it tracking down after the fact.

autojack · 12-29-2016, 06:40 PM

Damn, why didn't anyone tell me the air box has clips at the back?! That was confusing, Bentley to the rescue though. Finally got everything removed, put the borescope back there again, and confirmed for sure that the switch is the source of the leak. Hopefully I'll get it replaced this weekend.

A horse with no name · A horse with no name's Garage

Like Joe Bob referred to...'Its a pig of a job' and it just takes lots of patience... Just a suggestion - If you would like a 'safety alert light', purchase the sensor with the twin terminals. The stock one is only wired for oil pressure.

BTW, the fun starts when you 'try to' put the bottom rear air filter box clip back on. Make sure to take the oil filter off, and make up a wire hook so as to pull the clip shut...Unless you have very tiny hands like 'the donald' that is.

autojack · 01-03-2017, 01:10 PM

Switch replaced, I just need to get the air box and AFM back in. Hopefully this week. To be honest, actually working back there where the sensor is was no big deal. With my head in the right spot I could see it, and my $20 Android borescope camera helped me clean up the surrounding area. A deep socket at 6" extension was all it took to get it out, and my small torque wrench had no problem tightening the new one.

The old switch looks like it was leaking from the red plastic part of the housing, not actually at the metal surface where the crush washer is. My replacement is a different brand, from Pelican, hopefully better quality.

A horse with no name · A horse with no name's Garage

Hi...On your heading - Quote: "Tips for replacing oil pressure switch? my info seems not to have been applicable to you as I thought you were replacing the engine oil temp sender, including the oil presure sending unit.

Our car is a '86 and I see that yours is a '88...As a matter of interest, what "oil pressure switch" did you end up replacing?.. I ask, as I was not aware that there was a need for second one - Thanks in advance!

autojack · 01-05-2017, 10:42 PM

Quote:

Originally Posted by A horse with no name

Hi...On your heading - Quote: "Tips for replacing oil pressure switch? my info seems not to have been applicable to you as I thought you were replacing the engine oil temp sender, including the oil presure sending unit.

Our car is a '86 and I see that yours is a '88...As a matter of interest, what "oil pressure switch" did you end up replacing?.. I ask, as I was not aware that there was a need for second one - Thanks in advance!

I thought your comment was relevant... There is an oil pressure SENDER, which sends the voltage signal to move your oil pressure needle up and down. That's at the very back of the engine/car, near the fan. Then there's the oil pressure SWITCH, which turns the oil pressure idiot light on if pressure drops way too low. That's at the back of the motor, behind/below the air flow meter. That's what I replaced.

A horse with no name · A horse with no name's Garage

Hi...Thanks for your reply; unfortunately I still cant' seem to picture it.

Re back and front - Quote: "That's at the very back of the engine/car, near the fan."

When I open the engine hood, I consider this to be the front of the motor where there is both a oil temp sensor, including the oil pressure sending unit... 'Back,' to me that is, is towards the transmission.

If you still have it, would you mind posting the part #? - Again... Thanks in advance!

autojack · 01-05-2017, 11:26 PM

It's nearer the transmission, above the bell housing, next to the breather and the thermostat. The PN is 911-606-230-00-OEM.

A horse with no name · A horse with no name's Garage

Thanks 'autojack' for informing me of 'where' and 'what' the sensor/switch did that you replaced!..I never knew that our car even had one. I have replaced the two on the front of the engine for the oil temp and pressure; I likely should now replace this one also ay. I wonder if there is a way of testing them?.. (I don't have any oil leaks whatsoever)

autojack · 01-06-2017, 07:37 AM

Quote:

Originally Posted by A horse with no name

Thanks 'autojack' for informing me of 'where' and 'what' the sensor/switch did that you replaced!..I never knew that our car even had one. I have replaced the two on the front of the engine for the oil temp and pressure; I likely should now replace this one also ay. I wonder if there is a way of testing them?.. (I don't have any oil leaks whatsoever)

I wouldn't replace it unless there is a leak. The switch has a crush washer to seal it, and it only takes 20 ft lbs to torque it. From what I've read, it is easy to under or over torque it, and either way you'll have a leak. If it ain't broke...