Engine Failure - Thoughts?

[mogdobz]

Well my engine packed up today! It was fine this morning. Started without complaint later in the day but after I pulled away it quickly developed a knocking noise - this rapidly deepened and power dropped away. Within fifteen seconds and about the same number of feet traveled I knew it wasn't getting anywhere. I pulled over and parked. The engine was running very unsteadily at any choke setting - a bit like it was running too lean. The visceral juddering grumble and knocking suggest something fatally mechanical, but I'm no expert. Any thoughts on what it could be?

[mowogg]

Possible head gasket. Can you check the compression? If you don't have a guage can you see how easy it is to turn over on the handle?

[oliver90owner]

Are you sure it’s not gearbox (or even clutch) related? Maybe your whining gearbox has finally said “enough is enough”?

If a head gasket, every second stroke on the starting handle likely has no compression - the most often head gasket failure is between numbers two and three. If the gasket is proven to have failed, the cylinder head may need skimming.

[myoldjalopy]

I would expect more of a clattering noise were it the head gasket. An actual knocking could well be a broken crankshaft - its happened to me in the past - engine developed a knocking noise which increasingly got worse and it soon became obvious I was not going to be able to drive home.

[mogdobz]

Thanks for your thoughts, all. Tremendously helpful.

I doubt it's transmission related. The gearbox is a bit crotchety but I don't think it would reach into the motor and strangle itself - more likely a dying gearbox would do some big buzzing clanking grinding noises? Unless anyone knows any stories to the contrary!

I'll look around for mayonnaise in the radiator and lack of compression first. Then if it doesn't seem to be the head gasket I will investigate the innards.

I hear that draining and straining oil can be useful for identifying bits of metal indicative of catastrophic failure - can anyone say if this is or isn't a good idea? Particularly since I can't warm the oil up?

[mogdobz]

I would expect more of a clattering noise were it the head gasket. An actual knocking could well be a broken crankshaft - its happened to me in the past - engine developed a knocking noise which increasingly got worse and it soon became obvious I was not going to be able to drive home.

It did seem fizzy whizzy clattery, but I only forced it twenty yards down the road to park before taking it out of its misery and calling the AA. My main priority was turning the thing off

What sort of symptoms does a broken crankshaft generally produce?

[myoldjalopy]

From my own experience, a broken crankshaft was a loud knocking that progressively got louder, together with a loss of power. Your 'fizzy wizzy clattery' might well be head gasket - its hard to tell at a distance simply from a description of the noise. But a failed head gasket will not always result in mayonnaise in the cooling system, if the breach is between two cylinders. I had a head gasket failure between cylinders 1 and 2 once and the result was a clattering noise, rather than a knock, but no mayonnaise. So a compression test is a better way to go, initially.

[mogdobz]

From my own experience, a broken crankshaft was a loud knocking that progressively got louder, together with a loss of power. Your 'fizzy wizzy clattery' might well be head gasket - its hard to tell at a distance simply from a description of the noise. But a failed head gasket will not always result in mayonnaise in the cooling system, if the breach is between two cylinders. I had a head gasket failure between cylinders 1 and 2 once and the result was a clattering noise, rather than a knock, but no mayonnaise. So a compression test is a better way to go, initially.

Thanks very much for your advice. I checked today and there's no compression on the second stroke. No mayo in the radiator, though.

I suppose head gasket is now the leading theory!

[myoldjalopy]

Yes, it won't take long to remove the head and take a look.

[mogdobz]

Updating just in case anyone finds this thread in the future and finds conclusions helpful...

So far the issue has evaded diagnosis. The oil is perfectly clean, there's no mayo anywhere, and it sounds to fresh ears more like a catastrophically bad timing issue than anything. Nonplussed I therefore am taking it to the professionals.

I'll update when the work is done so anyone else with simular issues might know where to look.

[rocco]

It is absolutely helpful and interesting for me to read these kind of threads. I hope you get the issue resolved soon.

[myoldjalopy]

Agreed and hope it is fixed soon. But why would it be timing if the car was 'fine' in the morning? I can't see why the timing would slip on a drive, unless the pinch bolt was terribly loose. Be interesting to find the answer to this.
The clean oil and lack of mayo does not rule out a head gasket failure if it blew between two cylinders.

[ManyMinors]

The best thing would be to purchase an inexpensive compression tester and record the 4 compressions. As others have already said, a gasket failure between 2 cylinders gives exactly the symptoms mentioned but no coolant loss or oil in the water. A simple job to fix

[myoldjalopy]

Plus the OP has said in an earlier post "there's no compression on the second stroke". Were it me I would at least be taking the head off to take a geek....

[Classiccars]

We replaced a blow head gasket with the payan type as advised much stronger and used on ralley minis

[svenedin]

We replaced a blow head gasket with the payan type as advised much stronger and used on ralley minis

Payen head gaskets are no longer available for the small bores but Minispares sell their own version. It is very robust and well made.

https://www.minispares.com/product/Clas ... o%20search

[mogdobz]

Thanks all. I do have a fair notion it being the head gasket, but I'm not about to take its head off myself - simple job it may be but, on reflection, I've decided to let the garage have a go. It's the sort of job I'd like to do with someone around who's done it themselves before. Knowing me I'd put it back on upside down back to front and make an engine that generates petrol and absorbs CO².

Also - I recollect it did sound a little bit fizzy on the morning before its health issue. Not terribly so, of course, else I'd have stopped, but I did think it seemed a bit breathy. More gasket vibes, there. On the other hand, no gases escaping and it didn't sound fizzy when I restarted it the other day: just very very unhappy, as if it was only running awkwardly off-balance on odd cylinders, trying to leap off its mountings.

[myoldjalopy]

Thanks all. I do have a fair notion it being the head gasket, but I'm not about to take its head off myself - simple job it may be but, on reflection, I've decided to let the garage have a go. It's the sort of job I'd like to do with someone around who's done it themselves before. Knowing me I'd put it back on upside down back to front and make an engine that generates petrol and absorbs CO².

Also - I recollect it did sound a little bit fizzy on the morning before its health issue. Not terribly so, of course, else I'd have stopped, but I did think it seemed a bit breathy. More gasket vibes, there. On the other hand, no gases escaping and it didn't sound fizzy when I restarted it the other day: just very very unhappy, as if it was only running awkwardly off-balance on odd cylinders, trying to leap off its mountings.

Sounding 'fizzy' in the morning may have been the gasket starting to break up between two cylinders, which then became worse leading to the 'running awkwardly off-balance'. If you don't feel confident about removing the head then, yes, let the garage take a look (one that knows about these vintage cars! There have been some alarming stories on here about certain 'mechanics' who haven't a clue!).
Good luck and, as stated before, it will be interesting to hear of the outcome of this.

[mogdobz]

It was the head gasket, a straightforward failure between the first two rings. Took me a while but it's all sorted now. I did let the mechanics do it, seeing as we know a few good old boys familiar with the A Series. At this point I'm quite optimistic that nothing else should be wrong, but I will keep an ear out for any other weird noises.

Mystery solved! Thanks for all your help and advice, all.

[myoldjalopy]

Good, glad its fixed. The more we learned, the more it sounded like head gasket failure. That's exactly where my gasket failed - between cylinders 1 and 2. And that's why no symptoms of oil and water mixing.
Happy motoring!