OK, heres the full story.
Cam belt changed by incompetent mechanic who admitted
he got it wrong the first time but eventually
put it on correctly. I check oil level and set off on
holiday. Car does about 600 miles and breaks down. Recovery man
checks oil level at side of road after car standing for about 1 hour.
No sign of oil on dipstick. VW dealer looks at engine and discovers
damaged camshaft and hydraulic tappet(s) on one cylinder plus
'internal damage to engine' plus 'engine run low on oil'.
Result, new engine required. I'm hoping to have a look at the old
engine this weekend. The car is 4.5 years old
regards
Chris
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hmm mechanic got it wrong: if incorrectly timed engine valves could have hit piston and both damaged. Then timing corrected .
You go on holiday and drive fast?
Internal damage results in hole in piston, oil disappears through exhaust and then you run out of oil..
That sounds like a possible scenario.. When the car stopped had it been making noises, or did you notice a lack of power or any other symptons or did it go bang? The latter is usually unlikely .. my experience is you usually get a warning..
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I drive very steadly rarely going over 70 mph and very rarely over 3000 rpm. Car is fully loaded with kids and camping gear. No warning whatsoever other than a slight 'ticking' noise. No noticable lack of power. Car only ran for few seconds (30)after noise indicated that something was very wrong.
Chris
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If the oil went through a hole in the piston you would have seen the smoke from France.
Did you see any smoke ?
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Hi Chris (Cabsmanuk),
my sympathies to you as I would be gutted if this happened to me in this situation. However, my sympathies don't answer any of your questions...
I am not familiar with your engine, but in general terms, I cannot yet connect the faulty installation and subsequent rectification of the timing belt with the failure and symptoms you describe.
What seems to be highly probable is that the breakdown (camshaft failure) was caused by running low on oil. The next question is (as you say): what caused the engine to run low on oil? And also was this connected to the timing belt work?
There are 3 main ways oil can escape the system:
a] Leakage; from gaskets, oil seals, porous metal/ casting problems, rusty/ damaged sump etc.
b] Via the exhaust, due to burning; most commonly because of worn valve oil seals, worn/ broken piston rings or turbo seals;
c] Entry into the water system; normally because of (head) gasket failure.
Firstly, I assume the "incompetent mechanic" and the VW dealer you mention are two separate outfits. (!) Can the VW dealer confirm the timing belt was indeed installed correctly as per "incompetent mechanic"s claim?
2] Carry out examination of the engine to determine cause of oil loss. This should be reasonably obvious as significant oil loss occurred in only 600 miles. (I still would like to know the exact volume of loss).
3] Ticking noise: worn or oil-starved hydraulic tappets make a ticking sound (this can be clearly heard on old petrol engines e.g. my Rover V8). You might not, however, be able to hear them so clearly on diesel engines due to inherently higher engine noise. On a modern diesel, I would imagine that, by the time you hear a strange noise whilst driving on the motorway, major damage has already occurred.
(I would imagine that) you would notice if there was a hole in your piston when driving, loss of power, noise, smoke etc. It is a 4-cyl diesel, relatively low in power and propelling a large, loaded car, which would tend to make any power loss more noticeable.
Not really much progress here but it may help you ask the right questions when you have a look at your old engine this weekend.
Keep us posted on what you find out.
CMark
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I've just come back from 'inspecting' the old engine. I took my camera
expecting to photograph the damage. What do I find? The engine is virtually intact,
the cylinder head has not even been removed. The only damage visible is
one of the hydraulic tappets has broken into a few pieces. The valve stem can still be seen.
I asked how they know there is 'internal damage' answer is 'because
a compression test shows it'. I ask them if they would
remove the head so that I can take a photo of the 'internal damage' which they
have agreed to do. I will return on Friday with my camera.
I suppose the question I now have to ask them (VW) is why does a broken hydraulic
tappet require a new engine?
I suppose they could (would) say that bits of the broken tappet will have dropped
into the engine and this will result in internal dammage.
I'll post the results on Friday.
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Sniff, sniff, sniff....
I smell a rat And a BIG one at that!!
OK, oil starvation has maybe caused the tappet to fail, BUT if your 'mechanic' turned the engine over with the cambelt in the wrong position there could have been a valve/piston clashing moment, which could have fractured the tappet, later causing it to fail. If the valve has not dropped, then it is unlikley to have done enough damage to wreck the engine, and even if the piston has been damaged beyond repair, it is unlikely to be cheaper to replace the engine (but then again, at main dealer prices....) than the piston.
Low oil normally causes the big ends to go first as they float on oil and are under a lot of strain. A tappet, I wouldn't have thought so.
This still leaves you the question of where did the oil go? If you'd leaked say 2 litres in 600 miles it would be everywhere. If it's gone out of the exhaust, then you should be able to tell as the exhaust will be wet and oily (rather than dry and sooty as it should be).
I'll be intrigued to see what they find inside the engine, although I wouldn't put it past them to 'make' some damage when they get the head off and find it's alright inside. Maybe you should have insisted on being there when they took it off.....
Richard
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Finally got to inspect the engine on Saturday.
It's clear from the amount of oil in the camshaft bearings and
oilways etc. that failure was not due to oil starvation.
Camshaft bearings are as new.
One hydraulic tappet has totaly disintegrated with bits of metal
everywhere.
Other tappets show a certain amount of 'hammering' on the face
where the cam contacts it.
One valve head has snapped and lodged itself sideways into the valve seat.
The other valve in the cylinder
is bent. The piston in that cylinder is a bit chewed up but not holed.
Other valves in other cylinders I can't say 'cos they're all closed
with the camshaft off.
Man at VW dealers says damage is consistent with mechanical failure
following (initial) incorrect fitting of cambelt. Unfortunately this is
only his personal oppinion and VW won't put it in writing.
After a bit of arm twisting and calls to VW head office they have agreed
to release the engine into my safe keeping with a deposit of £500. I hope
to go and pick it up this Saturday
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Hi Cabsmanuk,
good feedback. Forgive me for this long post, stating what might be obvious, re-covering previous ground and thinking out loud but what you?ve got is:
[1] one broken valve,
[2] one disintegrated tappet (is this the one that belonged with the broken valve?),
[3] one bent valve in same cylinder,
[4] subsequent damage to piston and cam, AND
[5] loss of a large quantity of oil (perhaps 1.5 litres or more?) in only 600 miles.
[1] The breakdown was not caused by camshaft failure but valve breakage. This was broken by contact at some point with the piston. So what caused it to be hit by the piston? Either [a] timing belt error or [b] valve seized in guide ? lubrication problem.
I would have thought that if the initial incorrect timing belt fitment was the cause of the bent-then-broken valve then surely the other pistons would also have tell-tale indentations in the soft aluminium from contact with their valves, something to look carefully for.
Question ? did the VW garage check the timing belt was correct before they took the head off?
The other possible cause for a dropped valve is due to the valve sticking open in its guide due to lubrication failure and then being whacked by the piston as it comes up to the top of its stroke (top dead centre - TDC). Close examination of all the valve stems and guides should reveal any lubrication failure. They should look all very smooth, shiny and highly polished; if there are signs of scuffing or bluing due to excessive heat this would point to lubrication issues.
The valve failure mechanism due to above is much the same as with timing belt failure or catastrophic incorrect belt fitting. The valves run at an angle to the piston (in many engines) and so when contact is made the valve stem is bent just under the head. When the spring closes the valve it then doesn?t sit squarely on its seat and will tend to be bent back again and so forth until failure. Diesel engines are much more prone to breaking valves in this way due to their higher compression ratios resulting in much smaller gaps between the piston top and the cylinder head at TDC.
Valve guide lubrication works differently, on a much more microscopic level, than engine bearing lubrication where high volume and pressure are important. So even though the cam bearings are OK the valve guides might not be (though unlikely, IMO).
Land Rover had a huge problem with sticking valves on their pre-Tdi Defender diesel engines in the late 80's, but I cannot recall any incidences of valve heads breaking off, probably due to valves running more in line with the piston and thus getting more squarely smacked by it. I drove a 110 with an intermittently sticking valve for more than a thousand miles on one of my expeditions in the Egyptian desert. We couldn't rectify it ourselves. IIRC Land Rover solved the problem by changing the metallurgy of the valve stem to improve its lubrication properties.
Sticking valves make a loud ticking noise, one tick (per valve) per engine revolution. Although with a well-insulated engine bay (definitely not a Defender), the windows up and the kids in the back singing away to their favourite CD you might have thought this was a "slight ticking noise".
[2] If the tappet broke up first (for whatever reason) the valve would surely have remained shut. If the valve seized shut the tappet would be under huge strain and could break up. Has any one seen a tappet break up after a timing belt failure?
[3] the valve guide should be checked carefully for signs of lubrication failure.
[5] The key question here still is: did the oil loss cause the failure or was the oil lost as a result of damage caused by a bent valve possibly caused by the initial belt fitment? Secondly, what caused such a quantity of oil to be lost in 600 miles? If the initial piston ? valve contact cracked the valve guide could that allow sufficient oil to be lost in 600 miles? The engine block should also be examined for lubrication failure ? piston rings etc. We still need to know how much oil was left in the sump and how much went missing.
Can any mechanics familiar with this engine comment?
Chris, why did you have to put a 500 quid deposit for them to release your own engine, and why did you have to twist some arms to get them to agree to this??? Very strange...
Also, as a final thought, try an internet search to determine whether this failure is occurred previously.
Hope that helps,
CMark
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I finally got my engine back from the VW dealers after paying a returnable deposit of nearly £600. It's a VW recon engine and I suppose they will recon mine and sell it on again! All ancillaries have been stripped off and all that is left is the block and head. I'm not sure yet how much oil is left in the sump but there is no sign anywhere of oil starvation. My visual assessment of the damage is:
Engine:
other than the cylinder where the main damage occurred there is no sign of
any damage to pistons at all. The valves are flat headed and arranged
vertically.
Head:
Hydraulic tappets
Number 1 inlet no damage
Number 1 exhaust domed, fractured and marked
Number 2 inlet no damage
Number 2 exhaust domed, fractured and marked
Number 3 exhaust domed, fractured and marked
Number 3 inlet disintegrated
Number 4 exhaust domed, fractured and marked
Number 4 inlet no damage
The damaged tappets are domed by about 2 to 3 mm, the fractures
look like 'star fractures' radiating from the centre of the tappet.
The witness marks are made by the cam lobe and look to have been
made by a single 'strike' away from the centre. The centre of the
tappet shows damage that looks to have been made by repeated 'hammering' of the cam lobe on the tappet.
All the tappets still fit nicely in their bores, not seized, loose
or scored. Even now there is plenty of oil in the tappets
and oilways.
Undamaged tappets have perfectly flat mirror finished faces with no
signs of scoring, fracture or wear.
Camshaft
The camshaft is intact and shows damage only on the lobes relating
to the damaged tappets. The camshaft bearings are in perfect condition
with plenty of oil in the oilways.
Valves
On 3 cylinders there is no sign of any damage to the valves.
On the other cylinder, the head has sheared off the inlet valve and
lodged itself sideways into the valve seat. The exhaust valve whilst intact has a bent head. I suspect this happened when the inlet valve head was flying round inside the cylinder. The stem of the inlet valve is still in it's guide and not seized.
A few things puzzle me.
1 How can the tappets be domed? I would have expected them to be dented if anything.
2 Why not all the tappets?
3 Why no witness marks on the pistons, even in the (virtually non-existant) surface carbon on the piston crowns
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Hi cabsmanuk,
curiouser, and curiouser...
All the exhaust tappets are domed?
Time for a second opinion and/ or to get in touch with an engineering consultant, methinks.
Can nobody else here in the Back Room shed any light on this???
CMark
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Finally got round to checking the oil. There is no shortage of oil in the engine at all. The reading on the dipstick is exactly midway between the high and low mark. I'm having the engine inspected by an independant engineer. I'll post the findings when I have them.
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Hi cabsmanuk,
"There is no shortage of oil in the engine at all. The reading on the dipstick is exactly midway between the high and low mark"
WHAT??? This surely doesn't add up with what has been reported previously by 2 independant mechanics. (The recovery man found "no oil on dipstick at all" and the VW dealer said it had "been run low on oil".)
What is going on here???
IF your engine has not been tampered with (and anyway, why would anyone ADD oil to your knackered engine whilst at the VW dealer) then this whole engine-run-low-on-oil-it-is-therefore-the-owner's-fault thing is a TOTAL RED HERRING.
I await your next installment [1] with baited breath,
CMark
[1] read: posting
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has it got the correct dipstick ?
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The only way you could do this sort of damage to a hydraulic tappet (that I can think of) would be a loss of oil pressure causing the inner part of the tappet to be hammered against the outer by the rotating camshaft. The fact that you have most of the tappets in this state, would suggest to me a sudden loss of top end oil pressure at high speed. I have seen hydraulic tappets destroyed internally by such a failure (although they looked OK from the outside - they were almost new, but I soon found out the truth when I transferred them to the replacement engine). Either an internal oilway blockage or a failed oil pump? Keep dismantling and you might find the answer.
Richard Hall
bangernomics.tripod.com
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