Oil pressure sensor & gauge

[mkinne]

I would like to add a VDO oil pressure gauge to my center console.
Can anyone provide part numbers for appropriate gauge and sensor for a '73 2.0?

TIA
Matt

[thesey914]

Don't remember the part numbers, but when I fitted this gauge I used a 911 pressure sender (same M10x1.0 thread and is made by VDO)
Trouble is the sender fouls the distributor body so you'll have to find an appropriate oil hose.
VDO make a "T" piece so you can still run the oil pressure switch to operate the light on your dash.
The gauge I used is from a Golf GTI (VDO -measured in BAR) alternative cars would be the 944/924
Cheers

[mkinne]

I thought I had heard about a pressure sensor / switch that had two terminals; one for the analog signal (sensor), and one for the idiot light (switch).

Also, I thought the stock switch has a 1/8" NPT thread. Can anyone confirm which is correct?

- Matt

[Will98D]

I think if you look right in the Pelican catalog you'll see the dual sender (light/gauge). I have been told it is a 1/8" NPT also, and it's just what it looked like when I changed my sender a few months ago. A straight thread like an M10 x 1.0 would require a shoulder and a washer/gasket/etc. to seal properly, whereas the tapered pipe thread finally gets tight as it goes down into the hole and seals things up.

[Dave at Pelican Parts]

Yup to all of the above.

The sender is too large, so get the "adaptor kit" (a bracket, some hose, and an adaptor) or DIY with some grease-gun hose. Make sure to ground the case of the sender...

--DD

[mkinne]

OK...
Finally found the gauge and sensors in the PP catalog.
Last question: 80 or 150 psi for a stock 2.0L?

- Matt

[Dave at Pelican Parts]

80 PSI. A stock Type IV engine shouldn't get that high when the oil is warmed up. Cold oil can, but the 80 PSI gauge is fine for normal running.

--DD

[thesey914]

Originally posted by Will98D
I have been told it is a 1/8" NPT also, and it's just what it looked like when I changed my sender a few months ago. A straight thread like an M10 x 1.0 would require a shoulder and a washer/gasket/etc. to seal properly

The thread is M10x1.0. ( I'm 99% sure -the VDO "T" piece was labelled M10x1.0 on its packaging too) -NPT is American national pipe thread and is imperially measured. The 914 is built in Germany and therefore uses metric threads.
You are right about the straight thread needing a washer to seal it -the sender on the 911 has a crush washer/shoulder.
Cheers

[Dave at Pelican Parts]

Now for the funny part--
There is no standard for metric tapered (pipe) thread. So they use US standards instead.

The fitting in the 914 case was originally a metric size (M6??), tapered thread. But that is very close to a US size (if M6 is correct, that's 1/4") that the US size works just fine. More than fine enough, in fact--and most or all of the aftermarket VDO senders you can get are actually the US size!

--DD

[thesey914]

Dave, well I learn something new everyday......I looked on all my engineering thread charts and no tapered metric threads were listed.
Now I remember, when I screwed the sending units into the VDO "T" piece, they were tapered (they tightened on insertion) but the male end, that screws into the case I'm (98% sure) was a straight thread.....

Not trying to conduct a p*ssing contest, , and if it fits then problem solved

[Pump]

This thread is already pretty old, but it needs some clarification for those that read it for the first time. Don’t listen to those self-certified internet technicians and their theories. A 1970s German car design is 100% „Deutsche Industrienorm“ (DIN). All threads are metric. I just tried to replace an oil pressure switch on a 2.0L 914 and regretted it the second I turned the wrench. One of these self-certified YouTube Master technicians managed to drive an American standard (⅛*27) pressure switch into the M10*1, totally braking the thread. Meaning for whoever reads this thread:
The sender you are looking for to connect is VDO 360-006 for the 80 PSI VDO gauge. It comes with with a copper washer for sealing the connection. Since there are many „fakes“ with ⅛*27 thread out there get an M10*1 nut for $.50 from your local hardware store. If it binds after 2.5 -3 turns you were fouled. For the 914 I recommend getting an oil pressure hose fitted from you local hose store for $15 with male and female M10*1 thread. Brake hoses might do the job as well, but I don’t know how temperature stable these hoses are on the long run.
Meanwhile I have to find a way how to fix the damaged thread issue without having to take the engine apart.
Btw. The damaged thread might even be the cause of cylinder scaring in the adjacent cylinder.

[Dave at Pelican Parts]

Note that the threads for the oil pressure sensor hole are tapered. Regular straight threads will not seal correctly!

--DD

[Pump]

Dave you are right, I had forgotten about that. Over-tightening the right thread would have had the same effect, which happens relatively quick with a conical/tapered thread. Any ideas/recommendations for how to fix the problem? I’m thinking re-cutting the thread or inserting a helicol or forcing in a thread cutting adapter fitting.
I understand that the switch sits right in front of the oil cooler in the lubrication circuit. Would I be able to reach the area below the switch if I remove the oil cooler? I need to replace it anyways.
What do you think?

For those that are still not sure what thread the oil switch is. The original Porsche switch is a conical/tapered M10 with a 1mm pitch (ISO 724). Conical/tapered relates to a (minimal) change in Diameter of the bolt/nut, not a change in pitch of the thread. 1mm pitch equals roughly 25.4 threads/in. The discussed NPT 27 has 27 threads/in and therefore a lower pitch. It will eventually brake the M10 thread and destroy it. That usually happens after 2.5 - 3 turns.

[Dave at Pelican Parts]

I don't have any really good ideas for fixing in situ. Anything you do runs a significant risk of debris getting into the oil circuit, which obviously will not be good for bearings. Most of the thread repair kits that are out there are for straight threads, not tapered, and of course drilling the hole to the correct oversize and also tapping for the inserts create chips... You can mitigate your risk by doing things like applying compressed air elsewhere in the circuit to blow chips out the hole, or filling the hole with grease to catch the chips, or greasing the flutes of the tap, but none of those are a guarantee.

I know this has been a problem for people before, but I don't know a really good fix for it.

--DD

[Rodsrsr]

I have the dual terminal sender and was able to screw it directly into the block. Its a little tight but it will fit if you carefully enlarge the hole in the tin. I prefer this way so you don't need that extension hose which always gets in the way. It previously had the extension hose but ripped due to age, fortunately it happened in the garage so I was able to shut it down before losing all the oil.

[Pump]

Good point. I thought about that as well. But, I’ve got a 123ignition distributor sitting right next to it which is very temperature sensitive. I’m trying to keep heat sources away.

[GregAmy]

Anonymous new guy comes in, all high and mighty, destined to educate the world with his knowledge.

Starts calling everyone YouTube Master technicians.

Get pantsed by the first reply to his first post.

In a 23-yr-old thread.

Classic Internet.

Welcome...?

[Pump]

@GregAmy, welcome!
Just cleaning up with all the rumors about matching American Standard and Metric fittings. In automotive sizes theses standards just don’t match. There are very few that do. Most of them are bigger sizes and no NPT or NPTF standards.
Outside CONUS most of the ROW is metric and almost totally unaware of SAE, at least all Porsche, BMW, Audi, VW and Opels are metric only. There is only one exception. The rim size is expressed in „Zoll“ (= inch). I‘m not sure about the Fords that were built in Europe and now in China, just because it’s Ford.
…
Besides that I‘m always happy for any advice, since I have only been working on 6-cyl Porsches until now. My knowledge about Type 4 engines goes back to when I was a kid tuning my first VWs for racing and trashing them off-road.

[Pump]

Originally Posted by Rodsrsr

I have the dual terminal sender and was able to screw it directly into the block. Its a little tight but it will fit if you carefully enlarge the hole in the tin. I prefer this way so you don't need that extension hose which always gets in the way. It previously had the extension hose but ripped due to age, fortunately it happened in the garage so I was able to shut it down before losing all the oil.

Did you remove the tin for enlarging the hole? I think I’ll go for mounting the sender to the engine block as well, since there doesn’t seem to be any hose maker in VA that has metric fittings in the right size. Ordering from Germany takes at least 3 weeks.

[Rodsrsr]

Yes, I removed the tin, but was swapping heads anyway so they had to come off either way.

Its not too difficult of a job. The hardest part will be removing the cheese head screws which are a major pain if they've been in for a long time. You'll need liquid wrench, a super large screwdriver, and a hammer. BTW, I have a new extension hose that will screw directly into the block if you need it, but even with that I think you may still need to remove the tin. The issue I had with the hose was that there was no convenient place to mount the sender, it seemed to interfere with the distributor, or the cooling flap arms, so I went directly to the block. As far as threads go, I knew that it would be a metric thread, so took a chance and the sender screwed right in. I used the paste type thread sealer and was careful not to overtighten.