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Crankshaft/bottom end failure symptoms?

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crankshaft or bottom end symptoms
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16K views 20 replies 4 participants last post by  nouggatti  
N
#1 ·
Guys,

I've a noisy engine, and from day one of seeing the car my mechanic has said the variator needs doing as it's that distinctive tap/tap/tap noise, fairly regular and slow, about every 2 seconds when the engine is running.

However it went in for the NCT/MOT here last week and they refused to test it as the engine was too noisy. Now the midsection of the exhaust needed replacing so got that done and the noise reduced somewhat but it's still noisy.

Other than than the noise, I've no loss of power at high speeds, it's fine at 60mph plus, it did cut out twice after starting up, once after I put fuel in, and is just noisy. I've a warning light for the fuel injectors that comes back to the cam position sensor, the tb/variator both do need to be replaced and are due to be replaced in the next week, but I'm just worrying that it's the crankshaft that's going. I've the service history up to the last 10k miles and it indicates regular oil changes and topups.

Any thoughts? It's being checked tomorrow as to the noise but I'm wondering if the lack of loss of power at speed etc is a good sign? Or should I just be patient?

Thanks :)

Edit, I've had a good listen to a few videos from here of bottom end failure vs variator failure and don't think (maybe optimistically) that it's the same as the bottom end, more a dodgy variator.
 
#2 ·
If the bottom end has failed, you'll definitely know about it (see a thread I started called "terminal knocking sound" and the link that Jonalfaspider put in that thread, below).

I bought a replacement car and I'm fairly certain that the variator has gone in that. The symptoms are that I park up when she's warm and then when I come back to her about 5+ minutes later, she makes a noise like a diesel for about 10 seconds and then that noise goes away.

Also, when was the cambelt last changed? You can do the variator at the same time :)

alfa spider noise? - YouTube
 
N
#3 ·
That's one of the threads I checked Starkers, and with mine, it starts out knocking and the noise is noticeable at low revs or when idling at the traffic lights, but far less so at higher revs, and it doesn't seem to have any other symptoms, even today my mechanic said it seems to be running fine.

Cambelt and variator last done 23k miles ago, but five years, hence why it's on the cards.
 
#4 ·
Hmm, if it was the crankshaft, I'd imagine the engine would wobble around more on its mountings, I'd also expect the symptoms to get more pronounced at higher revs.

Can I query your mechanic, is he trusted and independent garage, known to people on here for the correct reasons, or a bloke that you met down the pub who does "a bit of this and that"?
 
N
#5 ·
No he's a pretty good indie, and his son is an alfa enthusiast, first day I drove up they said to me the variator needed doing and spent a good twenty minutes running the engine, that was about 7 weeks and 500 miles ago?

And he's getting a second opinion from a gtv specialist tomorrow as he doesn't think it's the bottom end but wants confirmation before he starts dismantling the engine.

Give you an idea, he checked my airbag light today and as it's caused by the connections under the seats, has decided to solder them together, he's pretty thorough and having had him look after a 156 for three years, I've no reason to doubt him. I didn't ask him to solder the airbag connections, he got the fault code, and decided to do it. His fuel injector light fault I have is exactly what the top indie Alfa mech here got and reset three times. He's also open to questions from a fairly car illiterate person like me, and is fair in his assessment imo. With my 156 the airbag light was the ecu etc so he's someone I trust, he believes in repair rather than replace, and I'm happy with him if that makes sense?

Tonight I went down and asked for the good news first, then we'd a chat about the engine, established we were both on the same page, he doesn't think it's the bottom end, but wants a specialist to check it out first.
 
#8 ·
My knocking engine turned out to be the balance belt tensioner moving. Really sounded bad, get the covers off and have a look.
 
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N
#19 ·
And the winner is..................................

Mitch166!!!

Balance belt tensioner was almost sheared, hanging in by a thread, the last time I drove it a few weeks ago, I wasn't driving it again till it was fixed it sounded and performed so badly, and it was the balancer belt tensioner

Coming home to me Monday :), I'm not a person who needs a car everyday which means my mechanic can take his time and go to specialists in the trade if needed, which is what he did in this case.

Delighted overall :) Can't wait to get her home :)
 
#18 ·
Bedding in period on cylinder bores usually after rebuild or new engine.

Also if you've had any machining done like a head skim for example you'd stick a cheap oil in and flush it through for the first 1k then drain refill with a quality oil and new filter.

These are the only times I'm aware of 1k roughly bedding in/settling periods.
 
#20 ·
:cool:

It's amazing isn't it? Has to be heard to be believed really, a real knocking sound. Anyway, good news mate and not an expensive fix :thumbs:
 
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