3.6 swap - Oil temp sensor/gauge

Tremelune · 07-31-2017, 07:33 AM

I have an '84 with a '95 motor, and the temp gauge is inaccurate. I would like to correct this.

I currently have this gauge I have in my car:

I prefer the look of this gauge:

I'm trying to figure out what my options are. Here is what I have in mind:

1) Get custom temp gauge from North Hollywood or someone else that looks the late style gauge, but is matched with my '95 sensor such that the "good" range is marked as 180-210°F. This would be ideal, but I'm not sure it's possible (I've contacted them), and I'm sure it'd be expensive.

2) Get a temp sensor that matches my current gauge and install it in the motor. Are the threads the same?

3) Install a gauge that is compatible with the '95 sender. The 993 gauge has lots of idiot lights and looks a bit goofy as such. I'm not sure I'd want to go through the effort for that final result.

Tremelune · 07-31-2017, 07:34 AM

Some shots of the sensor location (though I can't tell where on the motor this is):

Sensor questions for 3.6 conversion

This thread goes into some detail, but I'm not sure the specs are relevant to my year of gauge and sensor:

Oil temp & pressure gauge / sender operation

Shots of the inside of the temp gauge:

My oil temp gauge repair

Thread about installing a new sensor that I'm leaving here for my own notes:

Molykote Substitute and Temp Sensor Tool

Tremelune · 07-31-2017, 07:35 AM

Am I correct that this is the temp sensor with the green wire? That looks...extremely difficult to get to.

will hung · 07-31-2017, 10:45 AM

The previous owner probably never changed the sending unit. Search around and find the correct one for your gauge. Unfortunately for you, your gauge has been changed from the original, non-numbered gauge to a numbered gauge. Lucky for you, the part number for that sub gauge should be printed on it. A search for that number will locate the sending unit. Our host used to sell them as a pair.

I'm not sure what the thread is for a 3.6 oil temp sender, but I can't imagine Porsche changing it. Even if they did, you could get a thread adapter.

This isn't the first early 911 with a 3.6 swap, what have others done?

uwanna · 07-31-2017, 05:16 PM

I have a 3.6 in my '80SC. Here is the gauge I have, it shows the correct temp with
the 3.6 temp sender. I don't know the "vintage" of this gauge as I found it at a swap meet, but it works. By the way, does your gauge show the correct oil pressure? Most folks who put a 3.6 in an older car show double the real oil pressure on the gauge.
Most just live with it by mentally dividing the pressure shown in half. The problem
is the 3.6 duplex oil sender (oil press+ oil warning light) is a 0-5 ATM sender and the older pressure gauges are 0-10 ATM. There doesn't seem to be a suitable
0-10 ATM duplex sender replacement available.

Tremelune · 07-31-2017, 05:19 PM

Figures my gauge isn't original either. The problem with finding the "correct" sender for it is that I can't confirm the thread size, and I think the 3.6 senders are on the rear of the motor (I believe because they do not use an on-engine oil cooler). It looks like I'd have to remove the intake manifold to get at it, which is intimidating. Much easier to change the gauge, I'd think, but I'm not sure if anything that matches the 3.6 sender will just drop in...

Tremelune · 07-31-2017, 05:22 PM

Oil pressure accuracy doesn't seem important to me. There's either oil in the car (and I check it frequently) or it's dumping out of the motor behind me and the game is over. I dunno. I think an inaccurate gauge functions pretty well as an "oh sh:t" light...The druck press is always pinned on any air-cooled 911 I've ever driven unless at idle.

Jack Olsen · 07-31-2017, 06:10 PM

Getting in there is not a lot of fun, speaking from experience. Both the pressure and temp sender are fitted into a console that comes out with two nuts. I think taking the whole console out is easier than pulling one of the units. Then you just unscrew the one you're replacing on the bench.

You're right that it's easier to change the gauge. I didn't remove the whole manifold, but a few of the pieces had to come off. It's no doubt a lot simpler when the engine is out of the car and you can get to it from the opposite direction.

uwanna · 07-31-2017, 06:31 PM

Quote:

Originally Posted by Tremelune

Oil pressure accuracy doesn't seem important to me. There's either oil in the car (and I check it frequently) or it's dumping out of the motor behind me and the game is over. I dunno. I think an inaccurate gauge functions pretty well as an "oh sh:t" light...The druck press is always pinned on any air-cooled 911 I've ever driven unless at idle.

I agree with you, that's why I just ignore the doubling of my oil pressure on the gauge.
Most folks have noticed the oil pressure problem, but I've never heard of anyone
complaining about their temp being inaccurate with a 3.6 swap, even with older gauges. Could be you have a bad gauge. If you could borrow a known good gauge from someone, you could verify if it's the sender or the gauge. That sender with the green wire you showed would be a beech with the motor in the car! It's located on the plate C
which is installed in place of the thermostat D. See below

Jack Olsen · 07-31-2017, 06:52 PM

The pressure sender/gauge mismatch is a $100 fix. In my case, it was only worth it when my 993 sender failed.

I also haven't heard about a mismatch between the temp sender and gauge.

uwanna · 07:24 PM

Quote:

Originally Posted by Jack Olsen

The pressure sender/gauge mismatch is a $100 fix. In my case, it was only worth it when my 993 sender failed.

I also haven't heard about a mismatch between the temp sender and gauge.

Hey Jack,
What is the pressure sender fix and where did you get it? I had heard PMS had one.
Grant

Busta Rib · 07:38 PM

**Edited as per Jack's correction below**

I went through this with my 3.6 conversion. Use the temp sender that is compatible with your guage.

Re: getting access to the sender, it is a PITA but much easier if you completely remove the passenger-side intake manifold, airbox, and MAF. I've done it so many times that I can do it in less than 15 min. Once you remove the manifold et al, you can access the console. Remove two 10mm nuts to pull the console and as Jack mentions, you can replace the temp sender from your bench before re-installing onto the engine. While you have the console out, replace the rubber O-ring that is on the console. They get flattened over time which contributes to oil leaks in this area. I believe the new ones or green or orange, but I am not certain. Good luck.

Busta Rib · 07-31-2017, 07:25 PM

Yes, the green wire in the photo connects to the temp sender. It is the only lead back there that has that style connector. It slides onto the top of the sender which is shaped like a small coin.

Quote:

Originally Posted by Tremelune

Am I correct that this is the temp sensor with the green wire? That looks...extremely difficult to get to.

Jack Olsen · 07-31-2017, 07:27 PM

Quote:

Originally Posted by Busta Rib

PMS includes a new temp sender with their conversion kit with a threaded adapter that fits into the 964 console. Contact them to get the specs. Remember to put a crush washer between the new sender and the adapter. Use the temp sender that is compatible with your guage and get the adapter from PMS.

Are you sure you're not talking about the pressure sender? PMS sells an adapter paired with an earlier sender for their swaps. I didn't know there was a similar fix needed or available for the temp sender/gauge. But then mine matched, so I've never looked into it.

The older pressure senders are threaded M10 and the newer ones are M18. The older senders us 10-184 ohms of resistance to cover a range of 0-150 psi, and the newer senders use the same 10-184 ohms over 0-75 psi. So when they're mismatched, the old gauge doubles the newer sender's reading.

Busta Rib · 07-31-2017, 07:32 PM

My engine is from a 1990 and has the plate labeled C in this photo. Both the temp and oil pressure senders mount to this plate, which is then secured to the engine by two 10mm nuts.

Quote:

Originally Posted by uwanna

I agree with you, that's why I just ignore the doubling of my oil pressure on the gauge.
Most folks have noticed the oil pressure problem, but I've never heard of anyone
complaining about their temp being inaccurate with a 3.6 swap, even with older gauges. Could be you have a bad gauge. If you could borrow a known good gauge from someone, you could verify if it's the sender or the gauge. That sender with the green wire you showed would be a beech with the motor in the car! It's located on the plate C
which is installed in place of the thermostat D. See below

Jack Olsen · 07-31-2017, 07:34 PM

If you take yours out, I'd get a new o-ring for the console as well. Lousy place to have a leak.

Busta Rib · 07-31-2017, 07:34 PM

Jack, you are right. The adapter is for the pressure sender. The temp sender doesn't need an adapter. I did buy a new temp sender that matches my guage but it is threaded the same as the 964 temp sender. My bad. Sorry for the confusion.

Quote:

Originally Posted by Jack Olsen

Are you sure you're not talking about the pressure sender? PMS sells an adapter paired with an earlier sender for their swaps. I didn't know there was a similar fix needed or available for the temp sender/gauge. But then mine matched, so I've never looked into it.

The older pressure senders are threaded M10 and the newer ones are M18. The older senders us 10-184 ohms of resistance to cover a range of 0-150 psi, and the newer senders use the same 10-184 ohms over 0-75 psi. So when they're mismatched, the old gauge doubles the newer sender's reading.

uwanna · 07:45 PM

Quote:

Originally Posted by Busta Rib

I went through this with my 3.6 conversion. PMS includes a new temp sender with their conversion kit with a threaded adapter that fits into the 964 console. Contact them to get the specs. Remember to put a crush washer between the new sender and the adapter. Use the temp sender that is compatible with your guage and get the adapter from PMS.

.

EDIT: You guys are fast on the trigger, made it all right while I was typing! LOL
Hey Busta Rib,
I think the PMS part you are referring to is the pressure sender fix, not a temp sender. Just looked it up here:
Oil Pressure Sending Unit 3.2L- 3.6L Engine Conversion - Dual Pole By Patrick Motorsports Porsche & Mid Engine Performance Specialists

As Jack and I have both said, never heard of a temp sender mismatch with a 3.6 swap
to an older car.

Tremelune · 08-01-2017, 06:05 AM

Interesting. So, sanity check:

1) My gauge is from before 1978, and is not electrically compatible with the temp senders used from 1978-1998.

2) Temp sender from 1978-1989 was M10. Temp sender from 1989-1998 was M18. Both are electrically compatible.

Which means my solution is to buy both a later gauge that is the style I like and the OEM 993 temp sender that is still electrically compatible with it...

Ah, one snag: Looking at the image above, and my motor, and reading that C is installed in place of D...Does that mean something custom was done and the M10 sender was used, or is this merely a relocation of the 993 M18 sender?

This is all very helpful, folks. It smells like I'll be taking a few things apart one way or the other.

Jack Olsen · 08-01-2017, 06:13 AM

I don't think so. The pressure sender changed threads between the 3.2 and 3.6. The temperature sender was the same from 1977 to 1998. (Part 911-606-112-00, I just looked it up.) So if you're getting inaccurate readings on your gauge, then the problem is not a mismatch of parts, but more likely a faulty sender, gauge, or some other piece in between them.