Oil leak found.

Mad4slalom · 7 May 2025

Hi again, well the oil leak that I was thinking was possibly s rear main seal showed itself today . It is the oil pressure gauge line where the thin copper pipe enters the gland nut on the block, it is pushing out there and running down the back of the block and over the outside of the bellhousing. I have not yet tried to see if the nut will tighten up a bit. Any ideas how to reach this? I was wondering if a crows foot wrench might get in there. The kits are now supplied with a plastic line I think, anyone tackled this job ? Looks a bit of a pain, is it hard to get the oil pressure gauge out and re fitted. Any tips or suggestions welcome, TiA

teamzr1 · Thursday at 01:50

There is a fitting that goes over the end of the copper tube
When nut is tightened, causes fitting to compress and prevent tube to pulling backwards and prevent leaking

Roscobbc · Thursday at 10:56

One of the the very early 'issues' I had with my Vette some 20+ years ago was a severed copper oil gauge capillery line. What a mess that created. I simply bought a new replacement 'kit' with varying 'ends' to suit a multitude of vehicles - and yes it was nylon . Can't remember having major issues accessing the engine end of the line - I remember the under-dash part was the usual challenge of lying on your back and trying not to disturb any wires leading dashboard lighting etc......can't recall if I removed the drivers seat.

Mad4slalom · Thursday at 18:10

teamzr1 said:
There is a fitting that goes over the end of the copper tube
When nut is tightened, causes fitting to compress and prevent tube to pulling backwards and prevent leaking

View attachment 30069

Have ordered s new line kit but is plastic not copper. I am wondering if I can shorten the copper line and re use the fitting for now or even plug the exit from the block so I can use it with no gauge until It arrives.

teamzr1 · Thursday at 19:23

You could trim the tube if there is some slack, as long as it fully inserts into the tube connector
Assure if using a tube cutter that you ream the inside of that end to allow full flow
Check to make sure that crimp fitting did properly seat to the tube

Doubt the tube is the problem but the tube connector fittings or just not torqued down the top fitting

Roscobbc · Thursday at 21:06

Arguably the replacement nylon oil line is far more durable and resiliant to 'kinking' than a copper line which will potentially 'age' harden and perhaps become susceptable to 'kinking' if mishandled. Once 'kinked' it will implede oil flow - even worse it can then leak and fracture.

Mad4slalom · Friday at 15:20

teamzr1 said:
You could trim the tube if there is some slack, as long as it fully inserts into the tube connector
Assure if using a tube cutter that you ream the inside of that end to allow full flow
Check to make sure that crimp fitting did properly seat to the tube

Doubt the tube is the problem but the tube connector fittings or just not torqued down the top fitting

I will try and tweak up the top nut just to see if that might be loose. If that does’nt work then I will remove nut and pipe from the fitting . If I was to trim the end of the copper pipe , could I re fit the olive or will that have squeezed tight onto the pipe like a normal plumbing compression fitting? Do you know if the copper pipe and the plastic pipes are the same size and use the same olive ? If I can just fix the leak at the block end to avoid pulling dash /gauge console would be the easiest scenario. Copper feels a bit more solid than plastic but the plastic may be better. Some say they went for a braided stainless line from paragon. I have a 1/8th npt plug coming from real steel just so I can cap it off and isolate the gauge so I can run the motor without spraying oil everywhere. I have a plastic kit on the way but may look for a braided line and then pull the gauge console and do it properly then. Thank you for your help team z and ross And anyone else following.

teamzr1 · Friday at 15:41

Mad4slalom said:
I will try and tweak up the top nut just to see if that might be loose. If that does’nt work then I will remove nut and pipe from the fitting . If I was to trim the end of the copper pipe , could I re fit the olive or will that have squeezed tight onto the pipe like a normal plumbing compression fitting? Do you know if the copper pipe and the plastic pipes are the same size and use the same olive ? If I can just fix the leak at the block end to avoid pulling dash /gauge console would be the easiest scenario. Copper feels a bit more solid than plastic but the plastic may be better. Some say they went for a braided stainless line from paragon. I have a 1/8th npt plug coming from real steel just so I can cap it off and isolate the gauge so I can run the motor without spraying oil everywhere. I have a plastic kit on the way but may look for a braided line and then pull the gauge console and do it properly then. Thank you for your help team z and ross And anyone else following.

The crimp fitting as you see has a certain shape to match the bottom of the lower fitting so when torquing the top nut causes
that fitting to seat to the bottom and also slight crimp it to the tube, so make sure that fitting mates correctly and not the wrong one
Not sure if the same crimp fitting would work for both copper and plastic, you would have to test for that

Maybe using Teflon tape on threads would help ?
Or use like blue thread locker to prevent that top nut getting loose over time

Braided hose being that small could be a bitch because you need like a AN type connector and in cutting the end of the hose can be a bitch with the braid being cut and ends coming loose to fit correctly in a AN fitting ?

In using plastic hose, make sure it has a rating to handle the engine/oil temps

Mad4slalom · Sunday at 17:06

teamzr1 said:
The crimp fitting as you see has a certain shape to match the bottom of the lower fitting so when torquing the top nut causes
that fitting to seat to the bottom and also slight crimp it to the tube, so make sure that fitting mates correctly and not the wrong one
Not sure if the same crimp fitting would work for both copper and plastic, you would have to test for that

Maybe using Teflon tape on threads would help ?
Or use like blue thread locker to prevent that top nut getting loose over time

Braided hose being that small could be a bitch because you need like a AN type connector and in cutting the end of the hose can be a bitch with the braid being cut and ends coming loose to fit correctly in a AN fitting ?

In using plastic hose, make sure it has a rating to handle the engine/oil temps

View attachment 30106

The braided hose kit comes from jeggs with the ends already made up. Removing and re sealing and re fitting the existing block fitting did not make any different . I think the copper pipe union has sealed but I noticed a lot of silicone around the block fitting , some of which I removed. I think I have actually made things worse as winding over with coil disconnected to build pressure has dumped a load more oil out. I have a plastic tube kit . Here and a jegs braided one on the way. After seeing how much oil is pumped out I am now really twitchy about having a pipe of pressurised oil inside the cabin at all , if the gauge end decided to let go then that is going to be a complete mess and at minimum a new set of carpets. Anyone confirm which way around the tapered insert goes in the plastic tube kit as no instructions. Very frustrating

Mad4slalom · Sunday at 17:21

Mad4slalom said:
The braided hose kit comes from jeggs with the ends already made up. Removing and re sealing and re fitting the existing block fitting did not make any different . I think the copper pipe union has sealed but I noticed a lot of silicone around the block fitting , some of which I removed. I think I have actually made things worse as winding over with coil disconnected to build pressure has dumped a load more oil out. I have a plastic tube kit . Here and a jegs braided one on the way. After seeing how much oil is pumped out I am now really twitchy about having a pipe of pressurised oil inside the cabin at all , if the gauge end decided to let go then that is going to be a complete mess and at minimum a new set of carpets. Anyone confirm which way around the tapered insert goes in the plastic tube kit as no instructions. Very frustrating

The block fitting I believe is npt ? Anybody know if that is a taper thread like our bspt I wonder if the original block fitting has damaged threads hence the silicone ?

teamzr1 · Sunday at 18:44

Stock through 1973 C3
Correct reproduction 1968-1973 Corvette oil gauge fitting - 90 degree fitting attaches to the rear of the mechanical oil gauges found in early C3 Corvettes.
Attaches to oil gauge with jam nut and compression fitting from oil line, threads onto opposite side.
(GM Part 6461492)

https://www.ecklerscorvette.com/1968-1973-corvette-oil-pressure-line-gauge-fitting-25-154748-1.html#tab-label-lyonscg_fitment_tab-title

Hose end is tapered

Other kits show -AN4 fittings

Mad4slalom · Sunday at 19:27

teamzr1 said:
Stock through 1973 C3
Correct reproduction 1968-1973 Corvette oil gauge fitting - 90 degree fitting attaches to the rear of the mechanical oil gauges found in early C3 Corvettes.
Attaches to oil gauge with jam nut and compression fitting from oil line, threads onto opposite side.
(GM Part 6461492)

https://www.ecklerscorvette.com/1968-1973-corvette-oil-pressure-line-gauge-fitting-25-154748-1.html#tab-label-lyonscg_fitment_tab-title

Hose end is tapered

View attachment 30138

Other kits show -AN4 fittings

View attachment 30139

Thanks teamz. So my gauge should have this elbow on already ? And the braided end will fit straight on or do I need to buy one?

Mmine is leaking really badly now as The copper pipe fractured when I tried to re fit it. Can I get new olives for the 1/8” copper ?

teamzr1 · Sunday at 20:09

I do not see what year your C3 is and small or big block engine as I see parts are different for oil pressure

teamzr1 · Sunday at 20:13

1972-73 Oil PSI gauge connector is straight

teamzr1 · Sunday at 20:31

More info might help

teamzr1 · Sunday at 20:36

Watch this :

Mad4slalom · Monday at 10:12

teamzr1 said:
More info might help

View attachment 30142

View attachment 30141

Thank you for that teamz. My 72 is a small block , aparently it would have been plastic pipe originally so maybe the previous owner in the usa used copper in the re build as he preferred it. I have a chap hopefully supplying a few correct olives so I can try to remake the block end connection. Here is a pic of the broken off pipe with olive. The other fitting and olive are for the plastic pipe and not compatible.

Oil leak found.

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