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MG TD TF 1500 - CrossThreaded Oil Pressure Gauge

I cross threaded the fitting on the oil pressure gauge in my TF. Some of the threads are totally sheared off. Now, the pipe will not stay attached to the gauge.

> Is there any way to salvage my stupid mistake?

> The brass fitting on the pipe is not deep enough to engage the good threads. Is a longer reach fitting available? If so, could I file off the bad threads, cut the pipe, replace the fitting with a deeper one, then sweat a union to rejoin the pipe?

Thanks,

Lonnie
TF7211

Photos:
Two views of threads on gauge.
One photo of brass fitting.

LM Cook

Ouch. It looks like the end of the fitting is smashed also. May call one of the gauge restoration places and see if they could fix? I think those TF gauges are made of unobtainium unless Will has one... You could measure thread pitch, and go to your local parts store that carries a lot of brass fittings and see if something is close that would thread on. Of course it would have to seal. George
George Butz

I could be totally off base here. But:
The tube end you show. I do not believe its correct.
It shows a cone on the center. It's designed to go into a mating taper.
The gage end shows a boss. There is a fiber washer that slips over the boss and seals against a flat fitting. Perhaps with a counter bore to clear the boss. (It's been some years since I put mine on. )
The flat fitting would leave more threads exposed and fit the boss on the gage.

Is there any chance you have the tube reversed at the junction fitting?

Jim B.
JA Benjamin

Lonnie - the gauge fitting threads can be straightened out with a 1/8 BSP die, but the arrangement of the center of the fitting doesn't look quite right (as I remember from our TD) it should be the same as the arrangement as the early MGB - it has a raised dome shape on the gauge and the end of the line from the engine has a recessed spherical portion in the center and is flat on the outside edge around the spherical portion. A leather washer (or small 'O' ring) makes the seal between the two.

I cannot imagine a brass fitting going onto a steel end of the gauge fitting causing that kind of damage. I think that I would send the gauge and the oil pipe to Nisonger and let them work their magic on the two. Cheers - Dave
DW DuBois


I believe--- Jim B is correct, Here's a photo of the end of the pipe that goes to the gage on a TD--- Not sure about the TF.

Richard Cameron


Lonnie, there's a gage on EBAY right now?

EBAY No. 152222990822
Richard Cameron

My bet is that the tube from the engine compartment is in the wrong way. The end of the tube Lonnie pictured is the correct end to go into the transition piece in the engine compartment and the other end is going to be shaped like what Richard pictured. It still doesn't explain the shape of the piece coming out of the oil gauge. Cheers - Dave
DW DuBois


I just happen to be working on a TD gage on the bench-- Here's a photo of the gage threaded fitting with the raised center section where a leather sealing washer would fit.

Richard Cameron

Lonnie,
Jim B and Lonnie are right. Your pipe appears to be reversed. The union on the bulkhead has a 60° taper cone and the gauge has the flat boss. I would dress the 1/8" BSP threads on the gauge as Dave has suggested and also remove the burrs. It is easy to make up a longer nut but it means having to cut the tube and resoldering. The fittings are available here.
https://www.vintagecarparts.co.uk/categories/vintage-car-parts-taps-pipe-and-fittings-fittings
If the worst comes to the worst I could make a longer nut for you.

Regards
Declan
Declan Burns

The guys are right, pipe backwards. George
George Butz

I LOVE this forum!

Everyone of you was right. The oil pipe is installed backwards. The female end of the union fitting at the engine has a 60-deg cone to fit the pipe end that is currently against my gauge.

I'll clean up the mushroomed tip of the gauge and file the threads. Without the extra space taken by the cone-end, the nut with leather washer may screw deep enough onto the gauge to clear the bad threads and hold securely. Thanks for the photos to guide me.

I knew absolutely nothing about MGs and British cars before I joined this forum. (Still don't know much!) You guys have made my stewardship of TF7211 a joy. I feel that you are looking over my shoulder pointing me in the right direction.

Thanks.

Lonnie
TF7211

LM Cook

For repairing damaged male threads I have a set of these thread files (see photo below). They come in metric and US (and I think even Whitworth/BS) but basically it's just a file that will straighten and repair damaged places in the threads without cutting away too much material - you only cut where you absolutely need to, so more of the strength of the fastener is preserved. They work great for fixing threads where you've cross-threaded or dented the threads on a bolt or shaft. Using a die sometimes takes away more material that you may want, and often on cross-threaded situations it's very hard to get a die started properly in the old lands. You can get these files at Amazon or at most any good tool warehouse.



Kevin McLemore

Yep, they are still available in Whitworth and BSP. See link below. When you get to the website, search for 'thread file'.

http://britishfasteners.com/index.php/catalogsearch/result/?cat=0&q=thread+file

Amazon has sets and individuals of the metric and US files.

https://www.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Daps&field-keywords=thread+file
Kevin McLemore


Lonnie, one more input--- Be sure to check the threads on your copper pipe since the fitting threads may also be damaged internally and need replacing. I see Moss lists the pipe for sale or if you decide you need one, I have a good spare used one. Just drop me an email if you want it.
Richard Cameron

Hi guys -

Here's an update on my cross-threaded oil pressure gauge.

Thanks for showing me that the pipe for my oil pressure gauge was installed wrong. The "ball" end of the pipe only allowed the first couple of threads of the nut to engage the gauge and stripped them. The ball mashed, bent, and mushroomed the extended tip of the gauge.

A club member had an extra TF oil pressure gauge and pipe. He showed me how the two should mate up.

I bought a 12-piece Needle File Set from Harbor Freight for $2.99. I filed the tip of the gauge to the proper diameter to fit into the flat end of the pipe. And I removed or cleaned up the two or three bad threads on the gauge. Easy job with the small files on the soft pot-metal gauge Luckily the threads in the brass nut were OK.
http://www.harborfreight.com/12-piece-needle-file-set-468.html

I installed the leather washer and connected the pipe. With the pipe in the correct direction, the brass nut threaded deeply onto the gauge past the missing threads. No runs. No drips, No errors!

Lonnie
TF7211
LM Cook

Glad to hear your fix worked! Happy motoring.
Kevin McLemore

This thread was discussed between 08/09/2016 and 26/09/2016

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