The Stovebolt Site Forums The Shop Area General Truck Talk Oil pressure - capillary tube

re-using the original gauges and motor on my 50 GMC. Bought a new oil pressure line / capillary tube, from LMC that included the tube and two fittings like the stock ones. the problem I have is that the fittings slide off the ends of the tube. the original line had been compressed some how so that a ring or lip was formed about a 1/4" from the end of the tube. this lip/ring or ridge (whatever the proper term is) would retain the fitting and seal it when the fitting was screwed into the gauge on one end and a hose from the engine on the other.

Called LMC and they said that they had never had a customer bring this up before and they would check it out and get back to me...so far no response. Thought maybe I could go to NAPA and pick up a different fitting that would be a compression on the tube end but have come up with nothing.

Anyone have any ideas how I can make my tube/fittings seal tight or could recomend a different setup/fittings?

Thanks

Alex

There should be compression rings that slip over the tube. Tightening the fittings will compress it.

you need to tighten the nuts to compress the ferruls. no different than any normal compression fitting

They aren't compression fittings though. You can tighten the fittings all you want but you can still pull the tube right out with out that "ridge" around the tube being present.

Alex

I wouldn't say mine had a ridge but tightening the nut sealed the fitting. It is a different type of fitting than a compression fitting.

The ferrels are the "ridge". It's a little brass ring that gets squeezed between the nut and the fitting,
Scott

Sorry for piggybacking on this thread but I have a question that relates to this. I am working on a air gauge on my GMC and after removing the nut on the back of the gauge, I can't get the tube out. It is a plastic line and I can see the brass ring or ferrul but it won't budge. Is it just tight, more WD40? or am I missing something.
Bill

The original oil line fittings had a nut that compressed itself into the copper line- - - - -no compression sleeve. It was a one-time use item. I recycled the one on the 216 I just put on a run stand in the school shop by filing off the extended part of the oil line flush with the nut, and running a 3/16" drill bit through the original nut. Then I installed it onto a new piece of copper tubing and tightened it into its original fitting on the engine. Sometimes it's possible to re-use the nut that way, but usually a new nut must be used if you can find one. It was once a stock item in the Dorman fitting assortment at every LGS. I haven't seen a new one like that in at least 20 years.
Jerry

Jerry,

I posted a part number for that nut, which I think was used on 216, 235, and early 261 engines; however, I removed that post because I think that GMC used a different fitting than was used on Chevrolet engines.

Maybe someone will clarify this. If the GMC and Chevrolet fittings are the same, the nut is readily available from NAPA and others (I'll post the Weather-Eaton part number).

Tim

Is this the type of fitting?

These are what was on my 248. Our local store keeps them on the shelf with the assortment of other fittings. They are a goofy compression fitting. They slide onto the tubing and you push the tubing into the recieving fitting and tighten the nut. This very slightly crimps the end of the tube so the tube wont slide out, but its not the greatest of seals. They can be loosened and tightened again, but after several times they dont make a very tight seal.

Jeff

This is what is on the 216/235/261. Eaton 6100x2 (NAPA carries this part)


Tube Connection / Fitting, 0.125 in (3.2 mm)
3 Images

Part: WH 6100X2
Product Line: Weatherhead
Material : Brass
Tube O.D. : 0.125 in (3.2 mm)
Description : Nut
Dimension C : 0.375 in (9.5 mm)
Dimension D : 0.130 in (3.3 mm)
Dimension L : 0.500 in (12.7 mm)

Those are the fittings Jeff. I went ahead and used a little bit of silicone around the tips of those fittings and tightened them down. The next day I fired her up and discovered the fitting were now dry but that 4" rubber hose (that is the bridge between 3/16" and the 1/8" tubing) is now leaking...good oil pressure + good connections + 60 year old rubber hose = puddle. Stopped by the store and picked up a 3/16" compression to 1/8" pipe + 1/8" pipe coupler + 1/8" pipe to 1/8" compression...that take care of it.

Alex