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MG MGA - Oil gauge flexi pipe failure

I let my son and his girlfriend use my car for the weekend, first time ever which was a bit scary. They returned it after several hundred miles driving in one piece but I noticed a trail of oil. We restarted it and oil was spewing out of the flex hose to the oil gauge. Very very luckily it had only lost about 1.5li of oil but at the rate I found it the sump would have been empty within a few more minutes.

The pipe was new 6 years ago so that was very annoying. I have refitted the original pipe which was on it for 30 years and its back in action but I was surprised to notice that the flex part of the pipe can rotate against the nut when its tight.

Anyone else had a failure of new flexi pipes?

John
John Francis

There are a couple different designs of end fittings. One looks like full diameter hose all the way to the flare nut, and no swivel (as original I think). This seems to be very robust.

The other has a very small diameter short pipe between the flare nut and hose crimp fitting atone end, including a swivel joint. Some years ago I broke one of these during installation on a big Healey, resulting in some delay and cursing. I don't think there is any benefit for the swivel in this application so recommend avoiding those if possible.

The one currently on my MGA came from Moss Motors in 1986. It is the stout solid end type with Teflon inner lining (lifetime guarantee), still in service after 30 years and 350,000 miles (and ditto for the Teflon lined fuel hoses at the carburetors).
Barney Gaylord

My daughter just read this and said " I bet you have one in your car Justin!"

She is correct, I keep a spare oil pressure gauge hose tucked away on the boot floor at the back alongside the rear valence. ( with spare brake and clutch hoses)

She calls me Justin as a shortened version of " just- in-case"!😀

Cheers
Colyn
Colyn Firth

Yeah, I carry a spare too, but I bet it gets used for someone else's car before I need it.
Barney Gaylord

And the spare is useless if you loose all the oil before you notice it!
I wonder how quickly will you ruin an engine if you loose all pressure when driving? Probably depends on the load at the time I expect.

Barney I think I have an original pipe back on. It has a yellow band on it, which I think is the Petroflex mark. There is no swivel joint but it still rotates. Doesn't seem to leak at first glance though. The new one came from Brown & Gammons and I'm not sure I can tell if it had a teflon liner. Maybe I was just unlucky.
John Francis

If oil is all gone when idling with no load, it may run a few minutes with no problem.

If oil is all gone when cruising casually at half throttle and a few thousand rpm, it will likely be half a minute before you hear it rattle.

If oil is all gone when running full throttle near red line on the tach, it will likely be five seconds before you hear it rattle. BTDT, more than once, but not because of hose failure, it was the oil pump cavitating at 7000 rpm.

If you get off throttle and shut it down immediately when it stats to rattle, you may get away with replacing the crankshaft bearings and nothing else. If you ignore the rattle for more than ten seconds the bearings will be down to steel and you need a new crankshaft or regrind.

Original oil pressure signal hose was Smiths Super-Flex hose with a spiral wire wrap. See bottom of page here: http://mgaguru.com/mgtech/fuel/fu109.htm

If you still have the hose that failed, take a picture of it, then cut it open and see if you can get a picture of the inner lining. My bet says it was not Teflon lined.

Barney Gaylord

This happened to me in my MGB three years ago. I stopped to get a coffee and a half mile later I smelled oil burning. Momentarily I assumed it was coming from the car in front of me..... until I noticed zero oil pressure. Friends and neighbors were out in abundance as I was flatbedded home.

I was fortunate, no apparent engine damage. The hose under the stainless steel mesh had ruptured without warning. It was recommended to me to get a hose professionally made in a local shop but I haven't been able to find one to to it. Apparently the fitting is metric which seems to be the reason they don't want to touch it.
Brian Denis

Most other MGA owners think I am an idiot for carrying so many spares around all the time and I hope I didnt come across as being a bit pompous for reminding everyone about this. (being a "Pompous idiot" is not really me!:)

John, for my longer trips I always carry a litre of oil around with me to top up the oil level as necessary.

Maybe Barney can tell us if the engine would survive for a time with just a litre of oil in the sump?

Colyn
Colyn Firth

Yes it will run okay with just one liter in the sump, if you take it easy and don't suck air and don't overheat the oil. You might be surprised how many MGs may be running around with about 2-quarts in the sump.
Barney Gaylord

Like Barney I had a new one fail on installation- the swivel joint collapsed as I nipped up the nut onto the gland on the block. I called Moss UK and was immediately refunded. Can't remember where the replacement came from, but it's a stainless braided one with swivels both ends - I generally don't like braided hoses because the outside always looks good but hides the condition of the rubber hose perfectly.
dominic clancy

Barney and Dominic, still around, after all these years!

This the first year in 18 years that I haven't taken the car out. Too much stuff going on.

Glad to see that I recognize two names.

Cheers,

Art

p.s. Barney, I still have that rebuilt gearbox that you put together and that I bought 18 years ago, UNISTALLED resting under my workbench I guess the one I refurbished wasn't all that bad.
Arthur DiLello

Picture of failed pipe. It has no teflon liner just a rubber tube.I'm also wondering how tight the braid is around the rubber. If there was a big difference in diameter that would have allowed the rubber to overstretch.
The problem is I can't tell if the new pipe has the same weakness.

In terms of early warning if this pipe fails the oil doesn't drop onto anything hot so there is no tell tale smell. I once had a tappet cover come loose and oil dripped onto the exhaust and burnt so gave me a nice early warning. That was forty years ago and I find it hard to think how I tightened it up on dark cold wet rainy evening around Coventry bypass. I think I was going to see my girlfriend in London so maybe that was the reason I managed it.
I checked my tappet covers last night and it was a pig to get a spanner onto the bolt heads especially the front one.
John


John Francis

Failed pipe at the bottom, original pipe in the middle and new pipe from Brown and Gammons at the top. They are all different lengths and have different hex sizes! Just received a Moss one which is a bit shorter than the original.


John Francis

The overlong pipe will cause early failure as it imposes greater buckle/twist at each end, which a shorter pipe wouldn't.

Regards
Colin
Colin Manley

Mine failed last year. Just a small leak so I guess I am lucky I noticed it before it got worse. From reading this thread, it seems checking it on a regular basis would make good sense.
Graham
Graham V

As I reported in an earlier thread I lost all my oil through a failure of the swaged fitting on the feed to the oil cooler. Fortunately I noticed the 0 psi and stopped (I think!) in time to prevent damage. However, once bitten I installed a simple system to autodetect loss of oil:

Buy the old style pressure switch which was common on 60 and 70's cars. Fit a three way adaptor at the end of the flexible feed to to the pressure gauge and mount the switch.

In the electrical circuit fit a buzzer rather than the useless (small sized) warning light. Left like that the buzzer will sound as soon as the ignition is turned on but on ebay you can buy for about £6 a "power on delay" relay which only puts power onto the switch after a settable delay (30 secs is ideal). That way, the buzzer won't sound immediately after the ignition is turned on but once the timer runs down for the first time the switch will be primed to sound the buzzer immediately after oil pressure failure occurs.
Graeme Williams

This thread was discussed between 07/08/2016 and 15/08/2016

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