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Car Forum / BMW Cars / May 2004Broken timing chain
Hi Any advice greatly appreciated. The owner of a 1995 BMW 525 TDS has had an unfortunate mishap where the timing chain has broke. The vehicle was stationary at the time. Is it likely there would be less damage to the engine because of this and can the existing engine be repaired if the damage is not too bad or is it best to get a reconditioned engine? The owner would like to keep the car. What are his options, what does he need to know and how difficult is it to get a reliable garage /mechanic to undertake the work? The owner lives in the UK on the east anglian coast but is prepared to go to a 200 mile radius to get the work done properly. What might be a likely cost? Any suggestions or advice please. Yo, dog! > Hi > > Any advice greatly appreciated. The owner of a 1995 BMW 525 TDS has had an > unfortunate mishap where the timing chain has broke. The vehicle was > stationary at the time. But the engine was not or the chain would not have broken. Whether the car was in motion or not is moot. > Is it likely there would be less damage to the > engine because of this and can the existing engine be repaired if the damage > is not too bad or is it best to get a reconditioned engine? Probably less damage because the RPMs were likely lower, so less likelyhood of piston damage and that the damage will be to the head (specifically valves) only. > The owner would > like to keep the car. What are his options, what does he need to know and > how difficult is it to get a reliable garage /mechanic to undertake the > work? Repair scheme would be to pull the head and access the total damage (labor costs only up to here). Rebuilt head is probably all that will be needed. If pistons are damaged he will need to decide if he wants to buy a new (used) engine or repair the one he has. Engine mileage will be the determining factor there. > The owner lives in the UK on the east anglian coast but is prepared to > go to a 200 mile radius to get the work done properly. What might be a > likely cost? Any suggestions or advice please. I'm in the US, have no diesel engine experience, and generally do my own repairs of this kind, so I can't really help you with these questions. -Fred W Cheers Fred............... Have any advice about timing chains in general i.e. maintenance, replacement, how often. I was told once that they do not need replacing, after my friends mishap it sort of kicks that theory into touch . Or is it just bad luck that they can break? > Yo, dog! > > "Hounded Dog" <anon@anon.com> wrote in message > news:c91rop$963$1@newsg2.svr.pol.co.uk... > > Hi > > > > Any advice greatly appreciated. The owner of a 1995 BMW 525 TDS has had an > > unfortunate mishap where the timing chain has broke. The vehicle was > > stationary at the time. > > But the engine was not or the chain would not have broken. Whether the car > was in motion or not is moot. > > > Is it likely there would be less damage to the > > engine because of this and can the existing engine be repaired if the > damage > > is not too bad or is it best to get a reconditioned engine? > > Probably less damage because the RPMs were likely lower, so less likelyhood > of piston damage and that the damage will be to the head (specifically > valves) only. > > The owner would > > like to keep the car. What are his options, what does he need to know and > > how difficult is it to get a reliable garage /mechanic to undertake the > > work? > > Repair scheme would be to pull the head and access the total damage (labor > costs only up to here). Rebuilt head is probably all that will be needed. > If pistons are damaged he will need to decide if he wants to buy a new > (used) engine or repair the one he has. Engine mileage will be the > determining factor there. > > > The owner lives in the UK on the east anglian coast but is prepared to > > go to a 200 mile radius to get the work done properly. What might be a > > likely cost? Any suggestions or advice please. > > I'm in the US, have no diesel engine experience, and generally do my own > repairs of this kind, so I can't really help you with these questions. > > -Fred W > > > Cheers Fred............... > > Have any advice about timing chains in general i.e. maintenance, > replacement, how often. I was told once that they do not need replacing, > after my friends mishap it sort of kicks that theory into touch . Or is it > just bad luck that they can break? I think it was more the latter... Chains don't often break, unless or until they have had other severe treatment. The usual premature wear is due to lack of lubrication from poor maintenance practices such as extremely extended oil changes which cause poor oil flow and also severe engine overheating which can cause warpage of the chain guides. These problems, or possibly extremely high mileage, will result in an excessivley long chain that the tensioner is unable to compensate for. If a loose chain rides up on one of the sprocket teeth (ie skips a tooth), snap goes the chain and then bang goes the piston into the extended valves. So most of the time, you will get fair warning that the chain is loose by listening to the engine at idle. A chain that is beyond the tensioners range of adjustment will make some noise. The insidious part of this problem is, most of us hear our engines everyday (or at least often) and the noise may come on so gradually that you may not detect it as being "different" until it's too late. What can be done on a regular basis, though I have never seen it recommended in *any* maintenance schedule, would be to remove the chain tensioner (which is normally a device screwed into the head from the outside somewhere) and inspect it for how much of its range of adjustment it has used up. When you are nearing the end of the tensioner's travel you know it is time to plan to change the chain, a fun (or expensive) job to be sure... Unfortunately, I do not have any info on the diesel engine's chain tensioners since, alas, we have none in the US. So I cannot tell you how to remove the tensioner in such a way as to tell how much of its range has been used. I suppose you could always just remove the valve cover every now and then to have a peek at the chain(s) but that would only tell if it was already loose and not how much further you have to go. -Fred W Hounded Dog, Sorry to hear about the broken chain. I had mine break at 200,000 km, with little warning (1991 318 iS). Unfortunately, I was at high RPM so timing case, values, and other thins were damaged. Labour was around 25 hours. All is well now, minus the dent in my wallet! General word is that BMW chains last forever, or almost. Definitely want to ensure your timing chain tensioner is replaced/checked regularly, and that you keep the engine oil topped up. Also listen to engine as sometimes worn tensioners can give early warning signs of failure. ,,I'd say that assuming the rest of the car is in relatively good shape, it is worth your while to have the engine fixed. Best of luck. __ James. > Cheers Fred............... > > Have any advice about timing chains in general i.e. maintenance, > replacement, how often. I was told once that they do not need replacing, > after my friends mishap it sort of kicks that theory into touch . Or is it > just bad luck that they can break? > Hi > [quoted text clipped - 4 lines] > is not too bad or is it best to get a reconditioned engine? The owner would > like to keep the car. I heard of one going on a relatively low mileage 325 recently so I guess they're not as relaible as people think. Mayeb something else broke and then caused the chain to snap. If the car was stationary then it'd stop pretty soon after the failure. Had you been cruising at 90mph in gear then yes there could be more damage. I would guess that you might get away with fitting a new (used) head, although it might even be cheaper to fit a whole new (used) engine. |
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