Scott oil temp gauge replacement--warning

zero.one.victor · Post by **zero.one.victor** » Fri Oct 15, 2004 5:08 am

I just replaced my Scott p/n RN-2100 oil temp gauge (went gunnysack after only 7 years!) with another. It was listed in the Spruce & Chief catalogs as p/n RN-2100, but the box showed up marked as p/n 13340-00. It came with a new adapter bushing for the probe. I installed the new gauge, but used the old adapter bushing, mainly because I had modified it by grinding the 1" hex back on the inboard end so a 1" wrench could fit on the oil screen after the bushing was in place.
Anyway, after it was installed, I happened to look at the Scott Aviation website, investigating the label Scott put on the box:
"FAA-PMA eligibility per Scott document no. 3900038". What I happened to find was "SIL 7701" (service/installation letter?) which stated that starting in 1998, the temp probe was made with a bevelled flange, instead of the flat flange as on the earlier versions. It said to be sure & use the adapter bushing that came with the gauge, as it has a tapered seat instead of the flat seat of the earlier bushing. The two styles of flange & adapter-seat are NOT compatible. Shame on me for not looking closer at the new part(s).
So, I got to drain the all oil back out and change out the bushing. Luckily, after only one tightening, the probe flange was not damaged, but I can see where tightening the bevelled flange against the flat adapter seat sure wouldn't do it any good. I did grind back the new adapter bushing, like the one I replaced, so the 1" wrench would fit on the screen.
I'm posting this little saga because there was no instructions or anything in the box with the gauge regarding this change in flange & bushing-seat configuration. So be careful! Like I said, the flange was not damaged,YET, but after several installations it might distort enough to cause a catastrophic oil leak while in flight.

Eric

N170BP · Post by **N170BP** » Fri Oct 15, 2004 5:28 am

The big guy upstairs must really look after fools (like me) 'cause I also
replaced the same gauge, but at the time, I thought "ah hell, for $12.50
more (or whatever it was), I'll buy their new adapter/bushing too".

You're right, in that they really ought to state on the item that you
must use their new adapter with this replacement gauge. I'd
call & complain, but they (AS&S) already probably view me as
one of their "problem customers" as it is....

In any event, serendipty is kind of a cool thing, eh?

Post by **GAHorn** » Fri Oct 15, 2004 1:56 pm

Eric, am I reading your msg correctly? Did the new style adapter come already packaged with the new gauge? Or did you have to purchase it additionally as Bela indicated was necessary in his case?
Can you post the SIL text in the Mx Library also?

zero.one.victor · Post by **zero.one.victor** » Fri Oct 15, 2004 3:04 pm

The Scott gauge came with a mounting bracket, 2 nuts, and the new adapter bushing. I bought it from Chief Aircraft for $74.50, it was listed as p/n RN-2100 but is actually p/n 13340-00.
I don't know how to post the text of the SIL on our website. Maybe you can do it for me,George, here's the address:
http://www.scottaviation.com/TechPubs/A ... IL7701.pdf

Eric

simatos · Post by **simatos** » Fri Mar 11, 2005 4:40 am

RE Scott oil gauge. Is there supposed to be a gasket or crush washer between the probe and the adapter.?? i also bought one new outta the box and it leaks like a sieve. G

Post by **GAHorn** » Fri Mar 11, 2005 5:12 pm

No gasket between the probe and adaptor. Make certain to click on the link provided by Eric in his last post, and examine the Figures 1 and 2.

zero.one.victor · Post by **zero.one.victor** » Fri Mar 11, 2005 6:26 pm

I use teflon tape on the "adapter nut" (for lack of a better term). Haven't had any problem with leakage there. And no, I got no basis for approval.

Eric

Post by **GAHorn** » Fri Mar 11, 2005 6:42 pm

zero.one.victor wrote:I use teflon tape on the "adapter nut" (for lack of a better term). Haven't had any problem with leakage there. And no, I got no basis for approval.

Eric

Eric, do you mean between the adaptor and the engine? Or between the compression nut and the adaptor? (Those are the terms Scott uses.)

zero.one.victor · Post by **zero.one.victor** » Sat Mar 12, 2005 4:43 am

Teflon tape on threads of compression nut.

Eric

Post by **Bruce Fenstermacher** » Sat Mar 12, 2005 1:52 pm

You will also note in the Scott instructions that there are at least 2 styles of compression nuts and adapters. One stye being flat and the other being conical to fit the flange of the bulb. There may be more adapters with other differences.

I ran across this problem when installing my F&M filter adapter. Can't remember why but I couldn't or decided not to use the adapter which had been working with my old screen. Perhaps the threads where different. In any case I was digging through a box of spare adapters a friend had and had to find several before I found one that would work.

simatos · Post by **simatos** » Sat Mar 12, 2005 3:41 pm

Guys can you tell me the part number for the gasket used between the Scott adaptor and the engine. I think I can locate the teflon tape. Sure sounds like alot of goofing around for such a critical fitting. Thanks G

N2865C · Post by **N2865C** » Sat Mar 12, 2005 5:25 pm

zero.one.victor wrote:I use teflon tape on the "adapter nut" (for lack of a better term). Haven't had any problem with leakage there. And no, I got no basis for approval.
Eric

Teflon tape on threads of compression nut.

Eric

I might be missing something here, but why would you use Teflon tape on the compression nut. It seems to me that the Teflon tape would only make it easier for that nut to back out on it's own as it is not safety wired. I know of a C-140 that went down when that nut backed out.
jc

johneeb · Post by **johneeb** » Sat Mar 12, 2005 8:26 pm

This thread badly needs a visual aid. This picture is not real sharp as it is a scaned copy of a printout of a pdf file. It does show the difference between the tapered and flat flanged sensors.
Johneb

Post by **GAHorn** » Sat Mar 12, 2005 8:33 pm

Without critiqueing anyone's decision to use Teflon tape on the compression nut (Scott does not specify anything in that location and specifically illustrates nothing is used in that location)...
The critical sealing surface is between the probe "skirt" and the adaptor. This is clearly Scott's concern in their Service Information Letter, and why they warn against using a temp probe with an adaptor not matched in shape to itself. Be certain that nothing interferes or gets between the copper skirt of the thermocouple and the adaptor or the skirt and the compression nut. The nose of the compression nut must bear directly upon the thermocouple skirt and hold it against the adaptor's internal flare/flange.
The "gasket" which fits between the adaptor and the engine or oil filter set up is a common AN900 copper "crush" gasket. I believe it's the AN900-10 size (but I'd appreciate someone's confirmation on that.)

zero.one.victor · Post by **zero.one.victor** » Sun Mar 13, 2005 1:20 am

I don't know why I used the teflon tape, just to make you guys wonder I guess.

As I recall, the AN900 crush rings are sized #28 (1-3/4") for the (pressure) oilscreen, #16 (1") for the suctiion screen, and #10 (5/8") for the adapter. The one for the adapter is a goofy fit as I recall, due to the undersized configuration at the base of the threads.
I'm kinda unhappy with Scott, as the instruction sheet that points out the new probe flange & compression nut configuration (tapered versus flat) did NOT come with the oil temp gauge. I happened to look it up on their website quite by chance. You'd think something this critical would be prominently included with the gauge. After all, the sheet says "WARNING: FAILURE TO INSTALL THE GAUGE SENSOR AS INSTRUCTED HEREIN MAY RESULT IN DAMAGE TO THE GAUGE ASSEMBLY AND/OR LEAKAGE OF OIL WHICH COULD RESULT IN INJURY OR DEATH TO PERSONS." Maybe they just slipped up only on my gauge package?

Eric