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While driving on the motorway my '64 Super Minx experienced what certainly seemed like an engine failure. Since getting it home on a trailer I must admit I'm not experienced enough to guess just from symptoms what might be to blame, or if that's even possible to guess, but would be interested in some thoughts! I will be doing a leak down test shortly.

Symptoms from the breakdown

  • Sudden loss of power at ~80mph.
  • Change in engine tone (mechanically slightly louder, but not rattly).
  • Smoke escaping from engine (and into the interior).
  • Thick white smoke coming from oil cap when removed (like shisha smoke!)
  • Engine oil at same level as beginning of journey, no major leaks, no change in colour or consistency.

Before the breakdown

  • Engine would consistently burn oil at a rate of ~1ml per mile.
  • Exhaust fumes were relatively clear when warm, though white when engine cold.
  • Engine oil and filter replaced regularly, kept topped-up to max.
  • When I first got the car one of the cylinders wasn't firing. After injecting a bit of oil into it it seemed to seal and there was enough compression to ignite again, though there was an increased tapping noise for about 100 miles that eventually subsided. That was about 5k miles ago.

After the breakdown

  • Engine starts and runs with no noticeable noise difference (though this is at much lower revs of course).
  • The sound from the exhaust seems louder, though still consistent (firing on all cylinders by the sounds of it).
  • Coolant level doesn't appear to be depleted.
  • Engine oil level still the same, still the same consistency.
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  • Was smoke coming from the exhaust or just into the cabin? Does the smoke smell sweet like antifreeze or musky like oil?
    – JPhi1618
    Nov 7, 2017 at 20:20
  • @JPhi1618 I didn't check the exhaust in time - first instinct was fire so was at the front with an extinguisher. I think the smoke inside was closer to antifreeze, though there wasn't really enough to be sure. Regretting not giving it a good sniff when I took the oil cap off...
    – tjbp
    Nov 7, 2017 at 20:25
  • Great detail on the question. White exhaust when it's cold outside can just be water vapor. Water is a byproduct of the combustion. The white smoke normally points to a head gasket issue, and you may only see it when the engine gets hot. I'll let others with more experience write some answers.
    – JPhi1618
    Nov 7, 2017 at 20:32
  • I'd gladly chime in with my extensive Hillman experience... If I had any... I would pull all the spark plugs and look for consistency in color, and then perform both a cold and hot compression test.
    – SteveRacer
    Nov 8, 2017 at 3:56
  • @SteveRacer spark plugs all looking surprisingly healthy, and cold and hot compression test results virtually identical to 6 months ago (about 60-70 psi on each, not great but workable).
    – tjbp
    Nov 14, 2017 at 13:35

1 Answer 1

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The white smoke from the oil filler is steam, the hot oil causes any water in the oil pan to boil and escape as steam as soon as possible.

Water can enter your oil pan in two ways.
-Condensed moisture from the air that gets inside the oil pan
-Some gasket or seal leaking coolant

The former isn't harmful and it's not possible to stop it.
If you don't drive the car often, and you experience cold weather, it's normal to get some water in the oil pan. It causes the infamous 'mayo' or 'yoghurt' on your dipstick and oil cap.If you drive the car for a while, all the water will get boiled out of your engine soon enough.

The latter is harmful though, as you probaby guessed already. You should see a drop in coolant level though if lots of steam are violently escaping. If you don't, it's probably just moisture from the air. If it smells kind of sweet, it's probably coolant.

It's very well possible that these things may be unrelated to your breakdown.

If it always ran fine, my bet would be on fuel starvation.

This can have several causes:
-vapour lock
-blocked fuel lines and filters by dirt and rustpowder.
-dirty floating chamber
-stuck needle or something

If some chunk of dirt in your fuel system suddenly decides to come loose, it can be enough to starve the engine. But you may be able to start it again, only to discover that it still runs terrible as soon as the loose chunk of dirt has settled elsewhere.

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  • Didn't know about the water vapour - interesting. As it happens there's no obvious mayo, but there must have been water in there. I've now run compression and leak down tests and there isn't a difference to pre-breakdown results. My suspicion is that the water pump bearing is on its way out and affecting general cooling efficiency, and the loss of power was the main jet getting blocked (this has happened before thanks to the previous owner painting the inside of the fuel tank). Pending me finding a better explanation in the coming weeks, yours is probably the closest thing to a right answer!
    – tjbp
    Nov 13, 2017 at 15:34
  • @tjbp But then you should see elevated temps and feel play on the pump. If you don't, I wouldn't replace the pump yet. And the fuel filter should have blocked any loose coating from entering the carb. Are you sure it's the tanks coating? By the way, if the tank has been coated badly so that chunks of coating come loose, i'd consider replacing the tank, or installing a bigger filter that can handle chunks of coating without restricting fuel flow too much.
    – Bart
    Nov 13, 2017 at 16:04
  • I'm not entirely convinced of the reliability of my temperature gauge, since on a hot day after several hours running it suggest the engine is a little under workable temps (there's no way my rusty old rad is that efficient). There is a little play on the pump - should have mentioned. As for the tank's coating, the filter does catch bigger flakes, but I think tiny deposits get through and build up in the jet over time. Planning to replace the fuel line in its entirety this week so will probably get a new tank too.
    – tjbp
    Nov 14, 2017 at 13:39
  • @tjbp I'd go for a bigger fuel filter to be sure that it doesn't choke the fuel line, even when it gets filled with gunk from the tank. If it can't take out particles that build up in the jet, i'd find it not a very good filter tbh. By the way, if you have a normal pressure cap on your radiator, and it doesn't pass steam when the engine is hot, the engine can't be that hot. If the cap is rated at 1 bar or 14.5psi, the temperature of the water can only reach 120C or 250F before your radiator starts to spew steam. Still, if the waterpump seems to be on its end, it indeed should be replaced.
    – Bart
    Nov 14, 2017 at 20:32

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