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It's dead, Jim?


phantom_iv

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I was hoping my first post to this forum would be under better circumstances, but hey, that is life sometimes!

 

So I have a BMC 1.8, which until recently was working fine. On its last outing it threw a drive belt from the alternator, but otherwise seemed to be going ok.

 

So fast forward a month, replacement belt installed, turn it over... spins but no sign of ignition. Checked there is voltage across the glowplugs, checked there is fuel to one of the injectors, all good. Having read another thread on this forum I though it would be good to check if there is any smoke from the exhaust while turning over.... none. But there is smoke coming out of the air intake! Having removed the (somewhat gummed up) air filter, still definitely smoke from the air intake when it turns over.

 

This suggests to me that something has gone badly wrong leading to the outlet valves not closing, and hence being well beyond my mechanical capabilities. Currently trying to find an engineer who isn't too busy to come out and take a look, but I'm preparing for a big bill!

 

Should I be hopeful that there are some relatively easy fixes to these symptoms, or should I be looking towards the new engine end of the spectrum?

Edited by phantom_iv
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I was hoping my first post to this forum would be under better circumstances, but hey, that is life sometimes!

 

So I have a BMC 1.8, which until recently was working fine. On its last outing it threw a drive belt from the alternator, but otherwise seemed to be going ok.

 

So fast forward a month, replacement belt installed, turn it over... spins but no sign of ignition. Checked there is voltage across the glowplugs, checked there is fuel to one of the injectors, all good. Having read another thread on this forum I though it would be good to check if there is any smoke from the exhaust while turning over.... none. But there is smoke coming out of the air intake! Having removed the (somewhat gummed up) air filter, still definitely smoke from the air intake when it turns over.

 

This suggests to me that something has gone badly wrong leading to the outlet valves not closing, and hence being well beyond my mechanical capabilities. Currently trying to find an engineer who isn't too busy to come out and take a look, but I'm preparing for a big bill!

 

Should I be hopeful that there are some relatively easy fixes to these symptoms, or should I be looking towards the new engine end of the spectrum?

 

The engine cooling circulation pump is driven by the belt that came off the alternator, so if you continued running the engine for more than a few minutes after the belt came off then it would have overheated.

 

The reluctance to start and run now may possibly be due to this, but if the engine didn't seize at the end of it's last run then you may be lucky and any damage may be limited to the head gasket. If there is any more serious damage than that it won't be anything that isn't repairable, and although it could get fairly expensive, it will be a lot less than a new engine.

 

Depending on where you are, I may be able to call in and take a look at it towards the end of this week.

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Hi, welcome to the forum. When the alternator belt broke did you continue to motor along or did you stop immediately? I'm assuming it's keel cooled so the alternator belt will also drive the water pump. If you have run it for any length of time with the missing belt you may have a head gasket failure due to over heating. Turn the engine over with a spanner on the bottom pulley to see how much compression you have.

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Hi, welcome to the forum. When the alternator belt broke did you continue to motor along or did you stop immediately? I'm assuming it's keel cooled so the alternator belt will also drive the water pump. If you have run it for any length of time with the missing belt you may have a head gasket failure due to over heating. Turn the engine over with a spanner on the bottom pulley to see how much compression you have.

 

The engine's own centrifugal water pump will be driven by the same belt as the alternator irrespective of whether the engine is keel/skin tank cooled or heat exchanger cooled.

Edited by Tony Dunkley
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I don't have it in front of me right now, but the engine has two alternators in an arrangement not entirely dissimilar to http://www.calcuttboats.com/wpimages/wp6a6b69de_06.png- as far as I can tell this belt only drove the one alternator (the nearer one in that picture, at least the belt isn't long enough to go round anything else), the second belt remained intact. Am I right in thinking that the water pump is driven by the large pulley immediately above the crankshaft? If so then this was still turning.

 

Thanks for your offer to come and take a look, Tony, I'm down on the Thames near Staines so might be a bit far for you?

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When the alternator belt broke did you continue to motor along or did you stop immediately?

 

It was running for a while unfortunately, didn't put two and two together immediately, only found the belt had gone later. I am wondering wether it was just a bad day and the two problems were unrelated, unless of course I've missed something in the belt arrangement (limited visibility so always possible)

Edited by phantom_iv
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I don't have it in front of me right now, but the engine has two alternators in an arrangement not entirely dissimilar to http://www.calcuttboats.com/wpimages/wp6a6b69de_06.png- as far as I can tell this belt only drove the one alternator (the nearer one in that picture, at least the belt isn't long enough to go round anything else), the second belt remained intact. Am I right in thinking that the water pump is driven by the large pulley immediately above the crankshaft? If so then this was still turning.

 

Thanks for your offer to come and take a look, Tony, I'm down on the Thames near Staines so might be a bit far for you?

 

Yes that is the engine circulating pump pulley so that's good news in that it immediately eliminates the possibility of any overheating damage.

To diagnose the problem there are various checks and procedures that you can do yourself whilst being talked through what you're doing over the phone.

I'm busy just now, getting some grass cutting done before it gets dark, but if you would like to call me later on 07486 541302 we can probably get a bit closer to tracking down what's gone wrong.

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Did the engine boil, if not then as you suggest the water pump belt was still intact.

 

Being a 1.8 I'm assuming that the pump drive is independent of camshaft drive, forgive me if I'm wrong.

 

Two things:

 

1) Lift the oil filler cap off. When cranking can you see valves moving?

 

2) If they are moving, I would crack open all the injectors to make sure you properly prime the HP side. Just opening one can give the impression all is well where air is still present.

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Yeah, it's quite common to have smoke from the air intake after a failed start. The engine gets near TDC and then turns backwards for half a revolution blowing exhaust back through the inlet valves, so not something to worry about (unless yer air filter is on fire!)

Edited by mross
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Yeah, it's quite common to have smoke from the air intake after a failed start. The engine gets near TDC and then turns backwards for half a revolution blowing exhaust back through the inlet valves, so not something to worry about (unless yer air filter is on fire!)

 

Even while it is cranking?

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Someone came over to look at it today - I wasn't there to see for myself but two broken valves and a camshaft apparently... hoping that is all that is required to fix it.

 

Oddly it was working fine last time it was run - the only think I can think of is that the timing chain slipped when trying to start it, leading to an unscheduled piston/valve interaction.

 

Thanks everyone for your help and suggestions!

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Don't bank on it. I would expect pistons and maybe conrods as well. That is if the diagnosis is correct.

 

I find the idea of a broken camsahft hard to reconcile with BMC engines unless it was a faulty casting from new. I also find the idea of the timing chain jumping a bit hard to accept. I have seen a 1.5 (admittedly different to a 1.8) with so much wear on the timing gear the chain had worn away the cover.

Edited by Tony Brooks
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Don't bank on it. I would expect pistons and maybe conrods as well. That is if the diagnosis is correct.

 

I find the idea of a broken camsahft hard to reconcile with BMC engines unless it was a faulty casting from new. I also find the idea of the timing chain jumping a bit hard to accept. I have seen a 1.5 (admittedly different to a 1.8) with so much wear on the timing gear the chain had worn away the cover.

 

The 1.8's are nothing like as tolerant of worn chains and tensioners as the 1.5's. The timing chain is more than twice the length of the 1.5, and only engages with about one third of the teeth round the bottom of the crankshaft sprocket before passing over a fairly crappy spring loaded mechanical tensioner on it's way to the pump sprocket.

 

I've known a few that have jumped a tooth and bent valves and pushrods, and occasionally cracked or broken a rocker or two, but as you say, a broken camshaft would be something of a first.

 

I did alert the owner of this one to the possibility of the timing chain having jumped a tooth last night on the phone, and for the benefit of any other owners of 1.8's with more than 2500 hours on the clock, I would recommend renewing both timing chain and tensioner as a maintenance precaution against breakdown and engine damage.

 

It's really quite hard to understand why, having made a distinct improvement on the 1.5 by going to a 5 x bearing crank on the 1.8, the makers then spoiled the engine with such a badly designed and engineered mess in the timing case.

Edited by Tony Dunkley
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Someone came over to look at it today - I wasn't there to see for myself but two broken valves and a camshaft apparently... hoping that is all that is required to fix it.

 

Oddly it was working fine last time it was run - the only think I can think of is that the timing chain slipped when trying to start it, leading to an unscheduled piston/valve interaction.

 

Thanks everyone for your help and suggestions!

 

I've not seen a broken valve. The ones I have seen where pistons have hit valves have been bent and a big dent in the pistons. On a push-rodded-vave diesel engine where the valves are vertical I have only seen bent push rods and broken rockers.

 

While a belt, and not chain, the only time I have suffered a failure is when trying to start the engine.

 

I just hope you are lucky and the damaged localised to camshaft and valve-gear.

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So do I but it would be wise to ensure the OP sees the allegedly broken parts.

 

 

Very shrewd suggestion as the board appears to consider 'two broken valves and a broken cam' pretty unlikely.

 

Many technicians are entirely honest but some will go to extraordinary lengths to stand by and cover up their own misdiagnoses.

This is the case in my own industry at least. Sadly.

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yes, it turns out that this was a miscommunication over a dodgy phone line. Very much as everyone expected, the headline items are bent pushrods and broken rockers, caused by failure of the timing chain tensioner. All in all could have been a lot worse, hopefully will be back in service soon!

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