QOTW #95 – Avoiding common V12 engine problems

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Welcome to Bamford Rose and another question of the week. Before we get into this week’s question of the week, if you haven’t already done so it really helps us if you can subscribe to our channel. Click us like and let us know your comments on this week’s question of the week. So, this question asks about all of the things that could cause a V12 engine to fail. And if you’re new to the Aston range of V12S, how can you check that any one of those doesn’t happen to you? How do you check that it’s not a problem that’s occur in our car that you’re thinking about buying? And I guess in ownership, how you can preventative maintenance avoid these problems happening to you?

So, this question specifically asks about misfiring and this will be from a plug coil or maybe a little bit too much oil pull over. And the misfire causes unburnt fuel to rest on the face of the catalyst. The fuel explodes on, the catalyst the catalyst breaks up and as we know from previous videos that we’ve done the engine ingests the Debris and then goes on to fail the engine. The AMDs system has got a fantastic misfire monitor which can be used real time to uncover which cylinders are misfiring and then steer someone into taking the correct action to repair the problem. As far as misfire is concerned, I always say that if you’ve had a service inspection done and at that point of service. You’re sure that there is no misfire whatsoever, everything is in good service.

Plugs are good, coils are good, there’s no oil pullover from the breeder circuit, then you’ve got to be mightily unlucky in that following year to encounter a misfire which then goes on and fails the catalyst. Still today, of all the catalyst faders that we see, absolutely none of them have been existing customers of Bamford Rose. This is because obviously our service checks for any cause of misfire and a car will not go out the door after a service with a misfire or if it has got a misfire the customer is not alerted to the fact. So, this question asks how do you check for it at home if you haven’t got all of the equipment.

Before I answer, don’t feel too frustrated at home that you can’t do all of the checks that the dealers can do. Because they’ve got all of the equipment. As you’ll see here, it’s a good example of all the gear and no idea. This data log was from a DBS that came here for a post purchase inspection and we picked up the DBS had some misfire. The independent reseller that sold the new owner that car would obviously not take our word that it had some misfire. So, the new owner took it to a franchise dealer just to get the misfire statement rubber stamped. This screenshot is what the franchise dealer took of the real-time misfire monitor and concluded that there was no misfire present.

I had a telephone conversation with the new owner and said, Well there definitely is a misfire present, you know you need to get this sorted out. It’s quite dangerous to run with misfire and not get it sorted. So, he did take it back to the independent reseller who put it on their test equipment. And this is a picture of the snapshot of the misfire which they took. Here is a one-minute video of a condition which we held the engine at, where as you can see from the misfire counting up on a couple of individual cylinders there this is pretty serious misfire. This is because you can’t just plug a computer in at idle and interrogate fault codes and expect the computer to tell you exactly what’s wrong. You have to go fishing for the problem.

So, in these two instances here a franchise dealer and an independent garage they’re both missing that a car is severely misfiring. As you can see from the two columns of misfire counting up on my video here. So, it’s a case of hunting out misfires in various conditions when you run the engine. Firstly, I’d start the car from cold and just allow it to tick over and allow it to get fully warm. Maybe you do this once a month. It’s part of your Sunday cleaning regime or something on the car. But just start the car up, allow it to get warm, allow it to tick over and you’re listening to the exhaust note through that transition from cold start to fully warm. And you’ll be checking that there are any uneven sort of pulses in the exhaust note. Maybe you can hear (Ba, ba). You should hear a perfectly smooth exhaust note. Any stuttering like that is indicative of a misfire.

The next would be to hold the engine at about 1,500, 2,000 RPM part throttle. Hold it there for about 30 seconds, again you try to feel any shuddering in the chassis on a door frame in the seat frame and hear any popping out of the exhaust. And then simulate a 70 mile an hour motorway cruise. Maybe take it up to about 2500, 3000 RPM path roll. And again, do exactly the same thing to check for any vibration in the chassis or exhaust popping sounds. Then from cold start to fully warm at idle simulating a little bit of engine speed and load, you’ve checked the engine across the important ranges and across all of those. You can determine whether there’s a misfire, that should be a normal part of a misfire check and it’s what we did on this particular car. Because whether we were driving it on a test drive or into the workshop from the car park, we sort of detected that this DBS was a little bit lumpy. We suspected that there was a misfire.

It took quite a bit of detective work. It didn’t really appear at idle and didn’t really appear at your 70 mile an hour sort of motorway cruise condition. It was this engine speed in between as you can see from my video about 1800 rpm a little bit of throttle. But I don’t believe that if you perform that test at home that I just mentioned earlier and you listen for any erratic exhaust pulses or you try and feel any vibrations in the chassis. I’m pretty certain that you would be able to detect misfires that way as well as our equipment would do here in the real-time misfire monitor. It’s just the real-time misfire monitor on my laptop that is actually giving some data to the misfire. The frequency that occurs and how many misfires in a certain amount of revolutions, it’s recording. Whereas just physically trying to detect that yourself doesn’t give any data to the severity of the misfire. But as these two dealers did here, just plugging in and expecting the computer to tell you something is definitely the wrong approach.

So, back to this question, once you’re sure there is no misfire then your catalyst should be perfectly okay for the service interval. Next biggest problems for the V12 are caused by low engine oil level. So, this is very simple to check, but you’ll be surprised at the amount of people that don’t check their oil level because they think it is an electronic dipstick like their daily driver. They expect the car to tell them that the oil level is low and unfortunately, the Aston is not electronic oil level sensing. Every thousand miles or every three tanks of fuel, just check the oil level from cold on level ground. Allow it to go down to halfway between min and maximum and then put a straight liter in.

And this problem will overcome the failure of the begin bearing on cylinder 6 and cylinders 12, because they’re the last in the oil circuit feed. So, that’s the second sort of big killer of V12 engines that you can check for. The next is the dreaded DB9 tick which really does only happen on earlier engines, the engines which don’t have the cut-out oil channel in the small bearing. And that certainly doesn’t happen to the 470 BHP DB9 S and onwards the 510 DBS and V12 V. This is only the early level DB9 450 BHP. So, the easiest thing to do here at point of purchase is as I say in other videos, run the engine to develop the tick if it’s going to tick. And the easiest thing to do here is run the engine when it’s fully warm, about 3,500 RPM for a good 4 minutes. And then drop it back down to idle and just listen on the underside of the car.

Put your head behind the driver’s side wheel and see if you can hear a quite pronounced ticking sound. If you’re unlucky enough to have that wear in the small M bearing occur in your ownership and not spotted at a pre-purchase inspection. Unfortunately, it’s an engine strip and renew of the small M bearings and then that problem has gone away. Final bit of advice would be on the electrical side, get the tracker disconnected if you’re not using it. Avoid allowing water to ingress into these cars especially if you get a bit of water in the passenger footwell body module starts to get upset. A couple of other areas in the boot in the car so or ingress is a real bad thing. And if you get the car serviced regularly or at least regular enough according to the mileage that you accrue, then that decent level of inspection should alert you to any problems.

Which turn into something bigger, you know preventative maintenance on these cars is often better than actually fixing the problem when it occurs. Ownership of one of these cars if you’re new to Aston, especially DB9 you know it’s approaching 15 16-year-old can be a bit daunting. But if you’re aware of these care points, everything has been checked if you are of the mindset of doing preventative maintenance before it turns into a problem. Then the ownership experience can be much less of a headache and much less expensive repairs to deal with. These cars are beautiful and there is nothing on the road, which comes even close. So, they’re definitely worth the little bit of jeopardy, definitely worth checking out that you get a good car.

And the whole point of channels like this is just to get the known issues out there. So, new owners especially if they’re purchasing the car that’s harboring a problem, don’t get caught out. Hope you found that little chat about the V12 and some of its potential problems of use. And we’ll see you on the next question of the week.

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