Hi there, my timing belt failed on my 2001 1753cc Endura diesel engine Focus TDDi, car had done 140,000 miles and the replacement belt lasted less than 45,000 miles before half the teeth stripped with the inevitable result, but enough of that, should have followed HJ's advice about changing it every 35k!
Anyway, I am in the process of removing the cylinder head which needs replacing (camshaft in 3 pieces etc etc) but the question is, how do I check the pistons/conrods. I have been told I need to check that piston extension and check they are all the same (using a dial test indicator) but what measurements are acceptable or unacceptable and is there anything else to check? I was going to buy an exchange cylinder head provided the bottom end is OK but am unsure what is acceptable or not acceptable!
Thanks for your help...
Edited by Dynamic Dave on 24/09/2009 at 01:39
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You could just check they are all the same (as you have been advised), if they are, then it's likely none are bent...because it's far less likely they all bent exactly the same amount.
Also check for free play (up and down at TDC), put a finger on top and rock the crank back and forth, you will soon feel any knocking, unusual marks on bores, cracks in pistons, marks on the top (apart from what the manufacturer put there...that sort of thing.
If cylinder head is not cracked or damaged, might be best to replace the parts in the head that are.
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Thanks davecuk for the advice. Another question, if the pistons and conrods are all OK and I measure their protrusion with a dial test indicator, if they are all the same should they be within a few thou or is a 0.1mm, of 0.5 mm?? You see what I mean, I need to gauge what is good and what is bad!
thanks again
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Hi,
It's highly unlikely that the bottom end has suffered. Usually with cambelt failures its the top end that gets wrecked - as you've found out. Furthermore, you can check the tops of the pistons to see how hard they've hit the valves. If they are only lightly marked then most likley the kinetic force has been transferred upwards. You say you need a new head because the camshafts broken - however it may only need a new camshaft and a set of valves which would be cheaper.
Keep us informed of your progress.
Robin the Technician
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Ian as the other poster has said, there may not be problems. With your dial gauge, unless it's a really good one, you may not be able to accurately measure differences down to a few though (in fact it's quite likely you won't.
If the feel test is OK, and it looks OK, no extra marks, no funny sounds, cracks etc..It's easier to stick a fixed (preferably) or exchange head back on and see how she runs. If there's no problems, smoking excess vibration etc.. then your going to be OK.
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Thanks for the info guys. Because the camshaft is in three pieces, three of the camshaft bearing caps as are broken as are two of the shims I was guessing that the at least a few of the valves and guides may be bad so I thought it would be better just to get an exchange head! Will have the head of this weekend to assess the pistons so am hoping they are OK.
The other motivation to fix the car is that the wife says that if the car is beyond economic repair she wouls like a facelift Audi A3 5 door with leather......
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I use a flat bar with a hole in the middle which allows me you use the depth measuring pin on my digital vernier. If you have fairly heavy impacts with the valves then ensure the piston can move back and forth and side to side to ensure the piston has not been compressed and trapped the top ring. Do this with the piston 1cm below TDC. I suspect it will all be well. Regards Peter
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At 140k, I'd be tempted to drop the sump and replace the big ends, main bearings and piston rings at the same time. This will also give you a chance to check for damaged ring grooves.
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Isn't this one of these 'stressed' engine blocks, where removing main end caps can distort the block?
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It could be an integral part of the chassis but if the car is supported on the chassis then I can't see a problem.
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No it's nothing to do with the chassis, something to do with the way it's assembled. IIRC you can't obtain big and main end shells.
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Hello again guys, an update. The head is off and the pistons have some fairdly light dinks in the top of them, they wiggle slightly side to side so the rings seem OK and turning the crank seems fine.
The only anomaly I have is that if I measure the piston protrusion for each piston using a DTI, pistons 1 and 4 protrude 0.8mm at the top of their stroke, and pistons 2 and 3 protrude 0.4mm. Is this normal or is it indicative of a problem? As I said, everything else seems fine...
thanks again
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I wouldn't worry about it - it sounds like something to do with the piston grades. Plus measuring the piston protrusion on the limited falt surface area on an engine block would to say the least be difficult. From what you say the pistons are only slightly marked so i would leave well alone on the bottom end. You say in turns over on the crank easily which indicates the rods or cranks not bent. I think its worth putiing a head on it - I'm sure it'll be ok.
Robin the Technician
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I have heard of numerous instances of belt failures on the old Endura DE engine (which is basically this engine with a different fuel system and camshaft drive design), and in every case, the engine has fired straight up and run fine with a new head, and the bottom end left well alone.
Surprised the belt should fail so soon though. My old company ran dozens of these for three years and between 80 and 100k and not one broke a belt. My own one had 99k on the clock when it went back. It was due its first belt change in a thousand miles. On these engines, the timing belt only drives the camshaft (off the fuel pump sprocket). It is very short, and very lightly stressed, in contrast to the old DE which was a swine for snapping belts prematurely.
Edited by DP on 28/09/2009 at 00:35
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UPDATE - just thought I would update you all after your good advice....
In the end I bought a reconditioned exchange cylinder head from a helpful company in Telford (called Head First if I am allowed to mention them). Changed the water pump as well as it was on the original that had done 140K - just as well as there was about 0.5mm of play in the bearing so it was on the way out!
I bought a Ford belt and tensioner and noted that the belt looked a lot meatier than the non-Ford one that had stripped its teeth.
Also worth noting the EGR was very gungy and with the inlet manifold I scooped out several spoonfulls of tarry gunge from each port. After cleaning the EGR with carb cleaner and the inlet manifold with Jizer it was all a lot cleaner!
Anyway with it all back together it is driving sweet as a nut with little smoke and all seems fine.... phew!!
Thanks again!
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