Timing chain went out through the cover... could have the engine survived?

[Nestor Espinoza]

Hello,

 

A few days ago posted here a question about an engine with a strange behaviour, and apparently I found the cause, a tad too late.

 

I had the engine idling and it suddenly stopped, at once. No bangs or scary noises, just a short thump and it fell silent. I looked inside the engine bay, nothing suspicious, no smoke, I thought I would crank it. At the first crank nothing happened, but at the second attempt it turned freeely, so much so that the crankshaft now keeps on turning after stopping the starter.

 

I had a good look and found that the timing chain broke and was pushed against the bottom of the cover, that's why the engine stopped so suddenly.

 

I am hoping that because the engine was just idling and it stopped at once there is no major damage, is that wishful thinking? Tomorrow morning I'll remove the timing cover and the rocker cover to see if I can get any valve action by turning the camshaft by hand. If the valves work I reckon the engine would be good to go after installing a new timing chain and sprocket set. Is there anything else I should check?

 

What I find strange is that the crankshaft spins so freely, as if all the valves were open. Any pointers for the inspection would be appreciated.

 

Thanks,

 

Nestor

 

[Bod]

Prepare yourself for bad news.

Broken timing chains or belts, are very often expensive.

Others will say just what to look for.

 

Bod

[bizzard]

Some bent valves I should think.

[RLWP]

Wishful thinking.

 

Start by taking the rocker cover off and see if you have any broken rockers

 

Richard

[wullie]

Would help with engine type, i have found with this type of fault usually means head removal to replace bent valves, can in worst case broken cam shaft/rockers, i have also had fit new belt/chain engine starts runs ok, you may be lucky as only on tickover, but it depends on engine type age good luck take it one step at time and remember to ensure you have timing set to proper marking when fitting chain.

[rogeriko]

Unfortunately its impossible for all the valves to be closed at the same time so one of them will have hit a piston, thats the thump you heard when it stopped. If you are lucky just a broken rocker or two. But probably a bent valve as well. I just changed the cambelt on my VW golf last week,now that was a tricky job there's only one inch clearance at the end of the engine!

[Arthur Brown]

Hopefully most of the bits will be recognisably large, and the main castings are intact.

[magnetman]

What engine is it?

[RLWP]

BMC 1500: http://www.canalworld.net/forums/index.php?showtopic=72319#entry1459142

 

We are in the BMC section too

 

Richard

[magnetman]

Oh

its a BMC. Just noticed the forum its in

 

Thanks RLWP

Edited December 13, 2014 by magnetman

[boathunter]

A friend of mine used to run a small back street garage. When I say run... We called in "Fiasco Motors".

He had a similar job in - cam belt broke, valves bent.

He had head skimmed and tested and valves sorted, reassembled, but forgot to lock the cam timing and...

He then replaced the few bent valves and...

Did it again.

How we laughed.

Take your time.

[Albion]

Hello,

 

A few days ago posted here a question about an engine with a strange behaviour, and apparently I found the cause, a tad too late.

 

I had the engine idling and it suddenly stopped, at once. No bangs or scary noises, just a short thump and it fell silent. I looked inside the engine bay, nothing suspicious, no smoke, I thought I would crank it. At the first crank nothing happened, but at the second attempt it turned freeely, so much so that the crankshaft now keeps on turning after stopping the starter.

 

I had a good look and found that the timing chain broke and was pushed against the bottom of the cover, that's why the engine stopped so suddenly.

 

I am hoping that because the engine was just idling and it stopped at once there is no major damage, is that wishful thinking? Tomorrow morning I'll remove the timing cover and the rocker cover to see if I can get any valve action by turning the camshaft by hand. If the valves work I reckon the engine would be good to go after installing a new timing chain and sprocket set. Is there anything else I should check?

 

What I find strange is that the crankshaft spins so freely, as if all the valves were open. Any pointers for the inspection would be appreciated.

 

Thanks,

 

Nestor

 

I'm afraid that you've answered your own question with the statement highlighted in red. The first attempt, it couldn't turn over on the starter. On the second attempt it now spins freely and runs on after the starter has disengaged. This means that there is no compression to bring it to a halt and so you must have bent valves IMO.

Roger

[RLWP]

Bet it's worse than that! It would be very neat if the offending valves were neatly bent to sit in the 1 millimetre (approx) clearance when the piston is at TDC. My money is either on spectacularly bent valve stems or broken rockers. If pushed - I'd go for rockers

 

Richard

[David Mack]

It isn't always bad news. Some years ago my wife had the timing belt fail on her Rover 214 in the fast lane of the M6. After coasting across 2 lanes to the hard shoulder she was picked up by the AA and towed off the motorway. We got the car back to our local garage, where they didn't have to do anything more than replace the timing belt. No bent valves or anything!

[rogeriko]

On a diesel engine the pistons come all the way up tight against the cylinder head, there is no room for a slightly open valve.

[RLWP]

It isn't always bad news. Some years ago my wife had the timing belt fail on her Rover 214 in the fast lane of the M6. After coasting across 2 lanes to the hard shoulder she was picked up by the AA and towed off the motorway. We got the car back to our local garage, where they didn't have to do anything more than replace the timing belt. No bent valves or anything!

 

Petrol engine

 

Richard

[John V]

only seen it once, the bolts holding the cam shaft bearing caps stripped. The head was a write off.....I suspect this one might be.....as it happened at very low revs the bottom end/conrods/pistons might be ok even if the piston heads have a few minor digs in the surface

 

edit to add.....the engine I saw the cause was the cam chain tensioner having come to bits and it all trying to go round the pinions as well as the chain

Edited December 14, 2014 by John V

[RLWP]

Really, I'd want to check the rods as I bet some are bent

 

Richard

[John V]

Really, I'd want to check the rods as I bet some are bent

 

Richard

 

It's sometimes surprising what little damage there can be if it was only at tickover.....all hinges on where and what was the first thing to snap....as you say it would pay to inspect everything, which lets be honest doesn't involve much more work !!!

[RLWP]

Equally, I stripped an apparently perfectly running SR3 with two very bent rods

 

Richard

[Alan de Enfield]

I had a similar with a ride on mower with a Perkins 103 engine - the engine just died, no huffing, puffing or banging, just like turning the key off.

 

Thought - strange, started it, it went about 5 yards and BANG.

 

Repair man who took it away said I had dropped a valve, which had then gone out of the side of the engine - huge crack.

 

If I hadn't of started it again he said I may have got away with it, but, as it was, it was a right-off.

[Albion]

Bet it's worse than that! It would be very neat if the offending valves were neatly bent to sit in the 1 millimetre (approx) clearance when the piston is at TDC. My money is either on spectacularly bent valve stems or broken rockers. If pushed - I'd go for rockers

 

Richard

I'm not ruling out other significant damage Richard but, the primary cause of no compression is bent valves. If the damage were restricted to bent stems/broken rockers only but the valves still seated then you would have compression and the engine wouldn't continue to rotate under flywheel inertia after the starter disengages. Or big holes in the pistons of course.

Roger

Edited December 14, 2014 by Albion

[John V]

first off an apology. I answered this thread without looking to see which section it was in (the problem with new content) as a result I hadn't realised it was in BMC.....Doh!!!. The engine I saw it happen to was an 1800 Ford diesel (OHC)....sorry all !!!

[RLWP]

I'm not ruling out other significant damage Richard but, the primary cause of no compression is bent valves. If the damage were restricted to bent stems/broken rockers only but the valves still seated then you would have compression and the engine wouldn't continue to rotate under flywheel inertia after the starter disengages. Or big holes in the pistons of course.

Roger

 

Let's wait and see what the OP reports

 

Richard

[Tony Brooks]

I agree with Richard that we should wait and see. I also agree that with vertical valves the pushrods and rockers could well have been subject to damage. Even if some valves are bent those items should be checked.

 

What I am less clear about is how a broken timing chain would cause a loss of compression on all four cylinders. I would have thought that the likelihood would be that only two cylinders would suffer damage and I am sure even one cylinder's worth of diesel compression would stop the engine spinning after no more than 1.5 turns.

 

Once the head is off, even if the pistons look as if they will be OK, I would advise that an accurate micrometer or vernier depth gauge be used to measure and compare the piston head height relative to the block face. It may have bent one or more connecting rods.