TR2/3/3A Oil pressure gauge indicator needle sticking?

[karls59tr]

What's the fix for a sticking oil pressure gauge needle? A tap on the glass dome settles the needle but what's the cause?

 

[Geo Hahn]

I suppose you could have a bit of something in the oil line &/or works. I'd be tempted to undo the line and let some oil pump through it and possibly (gently) flush out the innards of the gauge while it is undone.

Sorry, that is the one gauge I have never opened up so I have no idea how serviceable the works are.

 

[CJD]

I would imagine it works going up, but sticks going back down?

If that's the case, it's likely an accumulation of dust in the mechanism. These gages are not sealed, and the return spring for the needle is almost hair thin. It does not take much dust to cause it to stick. The fix is to remove the bezel, glass, and face and clean it out with low pressure air or a soft paint brush.

 

[karls59tr]

CJD Good advice. Made a discovery when doing the cleaning: You have to gently bend the needle up to slide the faceplate past it to get to the works. When reassembling it's possible that the needle will bind in it's slot and will stick. The trick is to gently fiddle the needle back into position. There is also a ferrel on the threaded male oil pipe connection that has two little slots in it. It seems that that this ferrel can come loose and the needle along with it. A small screwdriver or 90 degree pliers can be used to tighten the ferrel to the case. THen test the needle for free range of adjustment and fine tune as needed.

 

[karls59tr]

Almost forgot. I've lost the gauge hold down screw retainer nuts and cant find anything to fit. Do you know what the thread size is? Not Whitworth I hope!

 

[martx-5]

Almost forgot. I've lost the gauge hold down screw retainer nuts and cant find anything to fit. Do you know what the thread size is? Not Whitworth I hope!

Probably a 2BA or 4BA. You'll have to measure the OD of the threads. Here's some info on BA (British Association) threads.

https://www.britishfasteners.com/threads/index.html

 

[TR3driver]

Nope, not Whitworth, nor BA. It's a screwball metric size. Sorry I don't have the info handy, but I measured very carefully and it doesn't match any of the BA or BS or SAE threads. I've got the size at home, will try to post later when I get home.

 

[TR3driver]

Nope, not Whitworth, nor BA. It's a screwball metric size.

Oops, sorry, my bad. I was thinking of the tach & speedo studs, which are M5x0.75. The oil gauge is 3BA. Different on later cars I'm sure, but I checked several of them from TR3/A and they were all 3BA.

Only source I could find was British Tools & Fasteners, who have a steel hex nut in 3BA.
https://www.britishfasteners.com/index.php/products/ba-nut-3ba-steel-3680

Or there are some ebay sellers in the UK that have them in brass
https://www.ebay.com/itm/Land-Rover...arts_Vehicles_CarParts_SM&hash=item566743661d

 

[karls59tr]

Thanks for the info Randall. Most appreciated.

 

[dklawson]

It's worth picking up a few of the smaller BA taps and dies if you are going to work much on SU pumps and/or Smiths/Jaeger gauges. You can make your own gauge nuts by re-tapping slightly smaller thumb nuts from the hardware store when you have the right tap. I got mine from BritishFasteners (Randall's link above).

 

[martx-5]

It's worth picking up a few of the smaller BA taps and dies if you are going to work much on SU pumps and/or Smiths/Jaeger gauges. You can make your own gauge nuts by re-tapping slightly smaller thumb nuts from the hardware store when you have the right tap. I got mine from BritishFasteners (Randall's link above).

On the TR3 there are quite a few BA threads besides the ones mentioned above. Be very watchful of any thread smaller the 1/4". It's likely to be a BA thread.