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View Full Version : TR2/3/3A TR3 Water Temp Sensor Installation Problem



luke44
05-28-2012, 06:47 PM
Has anyone run into a problem installing the sensor into the thermostat housing on the TR3? The threads just don't want to catch. Yet the threads are from a brand new/rebuilt gauge and seem fine. Ive at least figured out it is 5/8 x 18 thread and not pipe thread, so, do I try a 5/8 x 18 bottoming tap which will cost me $26.00 to buy for a once in a lifetime use, or do I try a grade 8 bolt and may be cut a couple of slots in it with my die grinder and try to make a pseudo home made tap? Or a $49.00 new housing...Or, does anyone else have another other ideas? Frustrating. What should have been a 2 minute job to button it up has blown my whole afternoon :confuse: ... All comments welcome.

https://farm8.staticflickr.com/7237/7290773824_c6d76f9d37_c.jpg

https://farm8.staticflickr.com/7233/7290804198_38f6e4ddfd_c.jpg

sp53
05-28-2012, 09:26 PM
Yeh your housing is screwy. You should be able to buy a cheap tap and chase it clean. I usually use grease when I fit something like that, but clean it out before you damage the gauge. Or yeh just run a bolt in there and see if you can clean it out.

mallard
05-28-2012, 10:09 PM
You should be able to get a tap on ebay for around $3.00 plus freight. I just got one for the head water jacket plug 1"x 12 for $5.00 bucks. Or as mentioned above try a bolt to clean it out.

jwolff
05-29-2012, 09:48 AM
I've bought several taps from McMaster-Carr: https://www.mcmaster.com/#standard-taps/=hqupvm

shipping is always cheap and arrives the next day.

JerryVV
05-29-2012, 11:23 AM
I thought there was an adapter that threaded into the housing and then you'd insert the temp probe into that adapter fitting. The new gauge that I bought came that way.

TR3driver
05-29-2012, 11:36 AM
It depends on the gauge, probably. I've bought several aftermarket gauges that came with an assortment of adapters; but no adapter was needed for the TR.

https://i258.photobucket.com/albums/hh260/TR3driver/TS13571L/TS13571LInstrumentPanelcropped.jpg

TFB
05-29-2012, 11:58 AM
Looking at he picture,even if I had the correct tap on hand,I would clean that first cross thread area with a small scraper or pic.I have an assortment of little boring bar tool bits,but you could quickly make a good tool,out of even a bent over and groung file tang or screw driver.Start about 1 thread in and scrape , following the grove back to the begining.Should be easy in the soft housing.
Tom

dklawson
05-29-2012, 12:10 PM
Is the length of the expansion bulb for the new gauge the same as the one you are replacing? On A-series engines there is an adapter used to move the expansion bulb out further in the head casting. This same adapter is mentioned on Tegler's web site when you want to fit a mechanical temp gauge to a Spitfire. (Mini Mania part 11K2846).

If you are convinced that it is just that the threads need chasing, do not use a 5/16-18 bolt in your die grinder. Go to the hardware store (ACE or Tru-Value) and buy a 5/8-18 bolt. Use a cut-off wheel in your die grinder and cut some slots axially down the length of the threads. That will become a home made tap for the sole purpose of cleaning the old threads.

Geo Hahn
05-29-2012, 05:07 PM
When I put mine back in (had soaked it in PBlaster everytime I was under the bonnet for about a year) I wrapped it with teflon tape. Not for the sealing effect but just to improve the chance of removing next time w/o fuss.

luke44
05-29-2012, 06:13 PM
Thanks for the input guys. All fixed! First of all I went to my local Ace Hardware and bought a 5/8 X 18 nut and and a grade 8 bolt.

Step one was to check the fitting on the temp line - no problem there - spun on easily using fingers.
https://farm8.staticflickr.com/7083/7298077202_1a2f383eed_c.jpg

Then I tried the grade 8 bolt in the casting - if this didn't work I was going to go to plan B and cut a few slots in it to make pseudo tap. (Plan C was a tap.) Anyway, the good news was the bolt, while a bit tight, did go...

https://farm8.staticflickr.com/7243/7298076904_cf31498b5a_c.jpg

Then insert a rag and clean out the gunk...
https://farm9.staticflickr.com/8023/7298076604_8d13db97a1_c.jpg

https://farm8.staticflickr.com/7237/7298076292_3a5db2cb31_c.jpg

A light oiling of the fitting...by the way, I stayed away from teflon, as this is normally used with pipe thread (as George points out, it won't help with the sealing). What's interesting about this fitting, is it gets it's seal by compressing the tapered end of the brass fitting, not the threads themselves...

https://farm8.staticflickr.com/7086/7298075724_7f5b73c41d_c.jpg

And voila! Good to go. It may not look like its in all the way, but she's tight. As long as the taper on the fitting is seated tight and being compressed, you get a seal.
https://farm8.staticflickr.com/7075/7298075194_0d2e032ccf_c.jpg

Hopefully this posting helps those who come after. It was puzzler at first, because normally you <span style="font-style: italic">would</span> expect a pipe thread fitting here. Not the case though. And pipe thread also has +-18 threads per inch, but, completely different and not interchangeable.

Geo Hahn
05-29-2012, 06:23 PM
I don't know how you work on that thing with all that blinding chrome and shiny clean metal.

Geo Hahn
05-29-2012, 06:32 PM
BTW -- It looks like you don't have a lock tab (Moss p/n 838-560) on the bolt that holds the generator link:

https://i1214.photobucket.com/albums/cc499/Ahwahnee18/TR3/LukesTR.jpg

I drove for years w/o one -- until the day the bolt fell out (somewhere in New Mexico).

luke44
05-29-2012, 06:34 PM
I don't know how you work on that thing with all that blinding chrome and shiny clean metal.

Hah! It's funny you should say that - check out the posting 850518 I just made in this thread here (https://www.britishcarforum.com/bcforum/ubbthreads.php/topics/850376/Home_on_a_wing_and_a_prayer#Post850376). I keep telling myself if I keep at it, one of these days I may actually drive this beast.

luke44
05-29-2012, 06:39 PM
BTW -- It looks like you don't have a lock tab (Moss p/n 838-560) on the bolt that holds the generator link:
I drove for years w/o one -- until the day the bolt fell out (somewhere in New Mexico).

You are probably right. My biggest problem was I inherited a disassembled and poorly labeled box of parts that had been started but abandoned - a big challenge when you don't do the disassembly. It has often felt like building a jig saw puzzle without the picture. Half the job was figuring out what I had, and what was what, let alone how it went together. This board has been invaluable - that's why I try to post my issues as they come up. I know others are coming along behind. I'll check out the lock tab. Thanks.

luke44
05-29-2012, 06:46 PM
Ouch! 838-560 - $7.75!!

Geo Hahn
05-29-2012, 08:16 PM
Ouch! 838-560 - $7.75!!

My reaction too. I made one from a fender washer in a few minutes at the grinder. I had one on the other TR to look at -- I can send you a pic.

Later...

An original locktab:

https://i1214.photobucket.com/albums/cc499/Ahwahnee18/TR3/LockTab1.jpg

And the one I made:

https://i1214.photobucket.com/albums/cc499/Ahwahnee18/TR3/LockTab2.jpg

I see I also used a lockwasher, guess I didn't trust my own work.

TR3driver
05-29-2012, 08:42 PM
A light oiling of the fitting...by the way, I stayed away from teflon, as this is normally used with pipe thread (as George points out, it won't help with the sealing).
Right, won't help with sealing. But I use teflon paste on mine, because it DOES help with getting it apart next time. And I once ruined an otherwise working original gauge, trying to dig the sender bulb out of the Tstat housing. I smear the tapered section of the bulb with it, as well as the threads on the nut.

martx-5
05-30-2012, 06:14 AM
... And I once ruined an otherwise working original gauge, trying to dig the sender bulb out of the Tstat housing.

Had this problem once, and wound up removing the t-stat housing and gently tapped and pushed from the inside. Saved the bulb and gauge.

dklawson
05-30-2012, 07:11 AM
I'm glad you got this sorted and for only a small financial investment.

Geo mentioned Teflon tape to keep the threads from seizing. That's a good idea. I have always used anti-seize paste for that purpose but I think the Teflon tape would do a better job.

As for the thread type... for whatever reason 5/8-18 taps are on most LBC engines I have seen. It's a common size for almost every Smiths temperature sending unit, it is used on intake manifolds for barbed fittings, on A-series engines it was used for banjo bolts for external oil feed pipes. I'm not sure why that was chosen over pipe threads but I eventually broke down and bought both a tap and die in that size.

JimTR3B
12-05-2016, 08:03 PM
Where do you get the whole Temp line and sensor. I had the gauges restored at N.Hollywood Speedo but they didn't install the temp sensor or oil line.Help would be greatly appreciated. Jim

Geo Hahn
12-05-2016, 08:49 PM
Not sure how someone could claim to have restored a temp gauge w/o having included a functioning capillary tube. Unlike the oil gauge, the line for the temp gauge is an integral part of the gauge as it is sealed and contains ether.

Some have grafted a replacement capillary tube using a donor from a auto parts store gauge. There is a web page describing this (I will look for it).

But really, if you paid money to N Hollywood for restoration then perhaps you should chat with them about what they did (and did not) do.

Here is the web page I was thinking of. I have not done this but it looks intriguing:

https://www.ply33.com/Repair/tempgauge

dklawson
12-05-2016, 11:19 PM
I have used the temp gauge repair method shown in Geo's link above to fix a half dozen gauges. It works well. However, the last time I did this repair I used dry ice for the cold bath instead of the salt/ice bath mentioned in the link. (Dry ice is both colder and cleaner).

However, as Geo said, if they charged you for repairing the gauge then you shouldn't need to add the capillary tube and expansion bulb.

mrv8q
12-06-2016, 03:17 AM
Morris Mintz refurnished my temp gauge on my TR3 over 10 years ago. No problems since. He worked on
my TR6 speedo as well...

https://westvalleyinstruments.com/

CJD
12-06-2016, 03:29 PM
I can't imagine them restoring a gage without soldering the bulb and tube to it. I'd give them a call!

Geo Hahn
12-06-2016, 05:00 PM
I can't imagine them restoring a gage without soldering the bulb and tube to it...

Me too but... I see that Jim has a TR3B. As I recall a few of the very last 3s got an electronic temp gauge (like a TR4). I suppose we might talking at cross-purposes here.

6TTR3A
12-09-2016, 07:27 PM
JimTR3B,
Geo. Hahn may be right...You may very well have an very early TR4 temp gauge. Take a look at your gauge face. If the high temperature figure is 250 F and he model number (above the needle hole) is BT2300/00 you have the TR4 unit.
That unit doesn't need a capillary line and an ether filled sending bulb, since it is electrical.
The TR4 sending bulb looks a little like the TR3 one and fits in the same hole, but it's an electrical part (sort of).
The connector to the gauge is simply a length of wire.
FRank

charleyf
12-10-2016, 12:33 AM
Me too but... I see that Jim has a TR3B. As I recall a few of the very last 3s got an electronic temp gauge (like a TR4). I suppose we might talking at cross-purposes here.

My TR3B was 130 from the last one and it had the regular TR3 temperature set up. So I would disagree with your assumption. The TR4 items included the transmission and front brakes.
Charley
p.s. On the TR4 gauge you would also need a voltage stabilizer, which the TR3 never had.

TR3driver
12-10-2016, 06:39 PM
My TR3B was 130 from the last one and it had the regular TR3 temperature set up. So I would disagree with your assumption. The TR4 items included the transmission and front brakes.
Charley
p.s. On the TR4 gauge you would also need a voltage stabilizer, which the TR3 never had.
Many of the change points were not "clean", meaning some earlier cars got built the later way, and some later cars got built the earlier way. I have no knowledge about temp gauges, but there were a lot of other things that were fitted to some cars and not others for months or even years.

Or the OP may have been deceived by an ad on eBay. I see a lot of mislabeled Triumph parts, and a neophyte might not recognize the difference.

At any rate, N. Hollywood Speedometer has an excellent reputation around here; I am quite confident they would never deliver a mechanical gauge without the capillary tube & bulb.

Also FWIW, although the TR4 gauge does need it, Smiths/Jaeger did make some temp gauges at that time that did not require the voltage stabilizer. Hard to tell for sure unless you check the part number.