M.B. E300 Turbodiesel mystery
Discussion
One morning on startup I noticed an initial lumpiness accompanied by quite a bit of "diesel knock" followed by a puff of blue smoke after start.
Easy diagnosis, a glow plug had gone and this was confirmed by the glow plug light coming back on again for about a minute after start up.
Having had the car from new (nearly 16 years ago) I knew that changing all of the glow plugs was the way to go as unless it turned out to be the one in No. 1 cylinder right at the front, the inlet manifold had to be removed to access all the other five. So I had all 6 glow plugs replaced (apparently 2 were unserviceable) and collected the car later that day (while still warm).
The next morning on start-up, there was still a slight roughness for a second or two accompanmied by some diesel knock and just a very little smoke. However, now the glowplug light remained out after start up suggesting that all glow plugs were working.
I returned to the garage asking whether there were different specifications g/plugs, wondering whether for example they had fitted a "40 watt bulb" where a "60 watt" was required. My thinking was that such a scenario would complete the circuit so preventing the waring light from relighting after start up, yet the actual plugs themselves (or one of them) wouldn't be producing sufficient warmth during the time it was on for the fuel to ingnite efficiently at first.
I was told that if the light remains out after start up then forget about the glowplugs as they must all be OK and think about one of the injectors being a bit clogged/dirty and not giving an even spray at the outset when cold. I was advised to run a bottle of diesel injector cleaner through with half a tank of diesel (I used Shell V- Power for this). But really it's made no difference and as the issue seems proportional to the outside air temperature each morning and the coincidence with the glow plug replacements, I'm back to believeing thaat the problem still lies with the glow plugs. By the way, the battery is fine with good output.
Does anyone have a suggestion or know a good diesel specialist in the Herts/North London area. I've not got a lot of time as I'm due to take the car on a 4 week trip through Europe for work in the coming days.
Easy diagnosis, a glow plug had gone and this was confirmed by the glow plug light coming back on again for about a minute after start up.
Having had the car from new (nearly 16 years ago) I knew that changing all of the glow plugs was the way to go as unless it turned out to be the one in No. 1 cylinder right at the front, the inlet manifold had to be removed to access all the other five. So I had all 6 glow plugs replaced (apparently 2 were unserviceable) and collected the car later that day (while still warm).
The next morning on start-up, there was still a slight roughness for a second or two accompanmied by some diesel knock and just a very little smoke. However, now the glowplug light remained out after start up suggesting that all glow plugs were working.
I returned to the garage asking whether there were different specifications g/plugs, wondering whether for example they had fitted a "40 watt bulb" where a "60 watt" was required. My thinking was that such a scenario would complete the circuit so preventing the waring light from relighting after start up, yet the actual plugs themselves (or one of them) wouldn't be producing sufficient warmth during the time it was on for the fuel to ingnite efficiently at first.
I was told that if the light remains out after start up then forget about the glowplugs as they must all be OK and think about one of the injectors being a bit clogged/dirty and not giving an even spray at the outset when cold. I was advised to run a bottle of diesel injector cleaner through with half a tank of diesel (I used Shell V- Power for this). But really it's made no difference and as the issue seems proportional to the outside air temperature each morning and the coincidence with the glow plug replacements, I'm back to believeing thaat the problem still lies with the glow plugs. By the way, the battery is fine with good output.
Does anyone have a suggestion or know a good diesel specialist in the Herts/North London area. I've not got a lot of time as I'm due to take the car on a 4 week trip through Europe for work in the coming days.
kapiteinlangzaam said:
Sounds like a leaking injector to me, slowly filling the cylinder with diesel o/night - hence the difficult start, blue smoke and temporary rough running.
You need to do a 'leak off test' so measure the flow rates.
Thanks for the suggestion and I'm trying to find a reliable diesel specialist to do that. It's just the timing, the absloute coincidence of an injector going faulty at exactly the same time as the glowplugs being replaced that made me hesitatnt to look beyond the glowplugs.You need to do a 'leak off test' so measure the flow rates.
Thanks to all for your responses.
I've had all 6 injectors "serviced", new nozzels fitted and combution chambers cleaned and tightened. New fuel filter at the same time. Turned out 4 nozzels were leaking/dripping and three were "not delivering properly".
This has cured the diesel knock and any smoke on start up from cold (or after a longish period of inactivity) which is now perfect. But it's introduced a low speed diesel knock instead
The combined wisdom of three garages (one in which I have high confidence) is that after a few hundred miles this will likely just disappear once the new injectors have settled in and any tiny amounts of air that may have entered the system have purged their way out. We shall see!
This new 'knock' is only at low revs and only when the engine is fuelling, not on the over-run or when accelerating above about 1500 RPM.
I have about 900 miles to do in the next few days, mostly motorway so if it hasn't quietened down as predicted then I will be in the south of Spain where the local M.B. Concessionaire for that coast is in my opinion, as good as it gets.
I've had all 6 injectors "serviced", new nozzels fitted and combution chambers cleaned and tightened. New fuel filter at the same time. Turned out 4 nozzels were leaking/dripping and three were "not delivering properly".
This has cured the diesel knock and any smoke on start up from cold (or after a longish period of inactivity) which is now perfect. But it's introduced a low speed diesel knock instead
The combined wisdom of three garages (one in which I have high confidence) is that after a few hundred miles this will likely just disappear once the new injectors have settled in and any tiny amounts of air that may have entered the system have purged their way out. We shall see! This new 'knock' is only at low revs and only when the engine is fuelling, not on the over-run or when accelerating above about 1500 RPM.
I have about 900 miles to do in the next few days, mostly motorway so if it hasn't quietened down as predicted then I will be in the south of Spain where the local M.B. Concessionaire for that coast is in my opinion, as good as it gets.
Assuming it's a 606 engine, these have a couple of typical faults in non-turbocharged form and I'd expect the turbo versions to be the same. The valve seats of the back two cylinders recede and they lose compression at high mileages. Symptoms of this are a very flat-feeling engine & breathing from the oil filler cap when the engine's running. Worn delivery valve seals at the top of the injection pump can cause nailing at low revs and this may be what you're hearing.
Also the serpentine belt damper top mount tends to break up (it has a metalastik bush) and rattle at low revs. This can sound very like nailing. You can diagnose this by (carefully, watching the fan so you don't lose a fingertip) pushing the top of the damper towards the block with the engine running. If it quietens down, the bush is shot. Replace the damper or pull the top bolt, put a thick rubber washer between the damper & block and replace the bolt
Nick Froome
Also the serpentine belt damper top mount tends to break up (it has a metalastik bush) and rattle at low revs. This can sound very like nailing. You can diagnose this by (carefully, watching the fan so you don't lose a fingertip) pushing the top of the damper towards the block with the engine running. If it quietens down, the bush is shot. Replace the damper or pull the top bolt, put a thick rubber washer between the damper & block and replace the bolt
Nick Froome
bolide said:
Assuming it's a 606 engine, these have a couple of typical faults in non-turbocharged form and I'd expect the turbo versions to be the same. The valve seats of the back two cylinders recede and they lose compression at high mileages. Symptoms of this are a very flat-feeling engine & breathing from the oil filler cap when the engine's running. Worn delivery valve seals at the top of the injection pump can cause nailing at low revs and this may be what you're hearing.
Also the serpentine belt damper top mount tends to break up (it has a metalastik bush) and rattle at low revs. This can sound very like nailing. You can diagnose this by (carefully, watching the fan so you don't lose a fingertip) pushing the top of the damper towards the block with the engine running. If it quietens down, the bush is shot. Replace the damper or pull the top bolt, put a thick rubber washer between the damper & block and replace the bolt
Nick Froome
Thanks Nick but none of the valve seat issues you've described. In fact it's quick, pulls like a train and no sign of breathing from the oil filler cap. Also the serpentine belt damper top mount tends to break up (it has a metalastik bush) and rattle at low revs. This can sound very like nailing. You can diagnose this by (carefully, watching the fan so you don't lose a fingertip) pushing the top of the damper towards the block with the engine running. If it quietens down, the bush is shot. Replace the damper or pull the top bolt, put a thick rubber washer between the damper & block and replace the bolt
Nick Froome
Worn delivery valve seals at the top of the injection pump is interesting but one day there was nothing, then the next, after the injectors were removed, had new nozzels fitted and replaced, the full on diesel knock at low speeds. There has to be a connection between that and what was done somewhere.
I've read about the damper on a different forum but dont think that's it. I'll let you know after a few hundred miles
By the way, I've owned the car since brand new in 1998 and have done 226,000 miles in that time. This has been the first time the injectors have been touched.
Nick.
Just a quick conclusion to this.
The "diesel knock" hadn't changed at all by the time I arrived in Malaga some 1,150 miles later. So I took the car to the local MB authorised dealership who immediately identified a problem with the injectors and removed them.
It was apparent that the nozzles fitted in the UK were NOT Bosch but some copy/pattern parts instead. Apparently they look the same but with the precision required, did not match the needs of the rest of the system.
They were replaced with Bosch nozzles and on start up, the engine was restored to it's former (knock free) glory! Running more smoothly than ever and pulling like a train while as quiet as ever in operation.
As soon as I returned to the UK, I presented a copy of the Spanish bill together with a bag containing the mis-matched injector nozzles to 'Diesel Services' who had fitted them. They seemed unsure as to why they had not fitted original Bosch nozzles, speculating that they couldn't obtain them at the time.
But without being pressed, refunded the FULL amount paid in Spain to have the nozzles replaced even though this was slightly more than I had paid Diesel Services. In other words, they refunded more than they had originally been paid, all in under 5 minutes.
I'm well aware of the "naming and shaming" policy on Pistonheads, but rather than seek to shame them, I mention the name of this firm to praise their quick and totally honourable response to something that had gone wrong. It's rare to find any business that will put their hands up and do the decent thing when faced with a complaint weeks later.
Nick.
The "diesel knock" hadn't changed at all by the time I arrived in Malaga some 1,150 miles later. So I took the car to the local MB authorised dealership who immediately identified a problem with the injectors and removed them.
It was apparent that the nozzles fitted in the UK were NOT Bosch but some copy/pattern parts instead. Apparently they look the same but with the precision required, did not match the needs of the rest of the system.
They were replaced with Bosch nozzles and on start up, the engine was restored to it's former (knock free) glory! Running more smoothly than ever and pulling like a train while as quiet as ever in operation.
As soon as I returned to the UK, I presented a copy of the Spanish bill together with a bag containing the mis-matched injector nozzles to 'Diesel Services' who had fitted them. They seemed unsure as to why they had not fitted original Bosch nozzles, speculating that they couldn't obtain them at the time.
But without being pressed, refunded the FULL amount paid in Spain to have the nozzles replaced even though this was slightly more than I had paid Diesel Services. In other words, they refunded more than they had originally been paid, all in under 5 minutes.
I'm well aware of the "naming and shaming" policy on Pistonheads, but rather than seek to shame them, I mention the name of this firm to praise their quick and totally honourable response to something that had gone wrong. It's rare to find any business that will put their hands up and do the decent thing when faced with a complaint weeks later.
Nick.
Gassing Station | General Gassing | Top of Page | What's New | My Stuff