July 31

2007 Audi S8 52L V10 Carbon Deposits



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Mark: Hi, it's Mark Bossert. I'm here with Mr. Bernie Pawlik. Pawlik Automotive in Vancouver. Vancouver's best auto service experience. We're talking cars. How you doing Bernie? 

Bernie: Doing well. 

Mark: So today's victim is a very interesting, very unique vehicle a 2007 Audi S8 with a V10. It had some carbon issues. What was going on with this vehicle?

Bernie: Yeah, so this vehicle came to our shop actually for a number of issues. And actually this particular item we're going to talk about in this podcast wasn't one of them, but it was something we discovered while we were doing another service. So one of the issues we found with the vehicle was an oil leak coming from the oil filter housing gaskets.

To replace those gaskets or seals, we had to remove the intake manifold. And when we did, we found some severe carbon deposits on the intake valves, which you know, while we were there required some service.

Mark: So, carbon deposits. What causes this? 

Bernie: Well, there's a number of reasons of course, just the process of combusting fossil fuels, you know, there's a lot of carbon, the deposits will develop in certain areas of the engine and the combustion chambers on the pistons and so on. So this vehicle uses a direct fuel injection system. So what happens is it directly injects the gasoline right into the cylinder. 

There's several ways to inject fuel. There used to be a throttle body injector, which is kind of like a carburetor that sat at the top of the intake manifold. Then a much better system, which is used on most vehicles for many years is called port fuel injection, where the fuel injectors are in the intake manifold, right on the port above the intake, just right at the edge of the cylinder head and inject the fuel just before. The valve would suck it in. 

But what works better is actually direct injection. It can get lower emissions, better fuel economy, more horsepower by injecting the fuel directly into the engine, like a diesel engine. So that's the direct injection system. The downside of it is carbon deposits form in the intake valves and there's nothing to wash them away.

The reason the carbon deposits get there is through the crankcase breather system. The crankcase breather system will circulate. It'll take the gases that escape past the pistons, and it'll recirculate it back in the engine, burn it up, because otherwise... Letting that stuff go out in the atmosphere is horrific.

It's among the worst pollutants you can create. Not CO2, but like of all NOx. You know, in the olden days, cars used to have a thing called a road draft tube and those pollutants would come out. That's one of the best things they've ever done on cars to reduce emissions is to put a closed crankcase ventilation system in.

However, with this type of engine with the direct fuel injection, the intake valves are prone to getting carbon deposits on them. And over time, the deposits can get so severe it'll affect your engine performance. In this engine although it didn't come in for that issue was right at the verge of that kind of thing occurring based on the deposits. And we'll look at pictures in the second, you can kind of see what it is. 

Mark: So I'm going to assume that burnt on carbon is going to be like charcoal briquettes kind of fused onto the back of the valve and the stem. How do you get rid of those? 

Bernie: So there's a couple ways. What we did with this particular vehicle, we have a walnut blasting machine. It actually blasts walnut shells. So it's like a sandblaster. But of course, as you can imagine, putting sand anywhere near an engine, something as precise as an engine is a very bad thing.

So walnut shells are a good alternative. They're hard, but they're soft at the same time. And, of course, they burn up. So, if piece of walnut show where to get in the combustion chamber, instead of just grinding the side of the cylinder, it'll just burn up in the combustion process.

So we have a walnut shell blasting machine and is basically a sandblasting gun with a shop vac kind of attached and the procedure is basically we close the valves on each port that we're cleaning. And then we blast it with the walnut shells, suck everything out and then move on to the next.

So that's kind of how it works. There's also some picking involved because, you know, sometimes you need to get in a pick and move it out of the way and some chemicals to clean things sometimes helps as well. But this is what we're doing at this particular service. Now, there are preventative measures that you can do.

We'll talk about that later and I'll get into pictures right now. So there's our beautiful Audi V10 engine. You can see 4 of the spark plugs, 4 of the coils on each side. The 5th one is hidden. But a lot of these, I mean, a V8, V6, V10, they all kind of look similar on an Audi. They're just more cylinders.

2007 Audi S8 52L V10 Carbon Deposits

So there's the top view of the engine. A couple of things featured here. As I said, these I'm moving my mouse pointer around, the ignition coils in each bank, these bright red things. And the other red items is the wiring to the ignition coils. This item here, you see 1 on both sides. This is the high pressure fuel pump. So, this provides a high pressure fuel to the fuel injectors. And throttle valve on this side here. Probably 1 on the other side as well, facing the other direction and the air intake pipes here. So there's a couple of things. Oil filler cap there. 

So, let's go a little further into our pictures. So this is a before picture. Now, I apologize. The quality is not fantastic. This is taken with my Borescope camera, which is a fairly low, very small. It looks great on our screen, but it's a pretty small picture capture. So, move my mouse pointer around. That is the intake valve.

2007 Audi S8 52L V10 Carbon Deposits

Mark: Sort of somewhere in there. 

Bernie: Yeah, somewhere in there. As you said, it looks like a charcoal briquette. I mean, this just looks like the inside of a barbecue. That's been, you know, it hasn't been cleaned for about 10 years. This is the valve stem. I mean, just remember these things because you're going to be amazed when you see that, even though it's low resolution, you'll be amazed at the picture that you see when it's done. Got one more view of the crusty valve.

2007 Audi S8 52L V10 Carbon Deposits

There's another view of the valve from a slightly different angle. But again, you can see an awful lot of deposit. You can sort of see an opening here.

I mean, I'll just get into the picture of the, of the clean valve because that really shows a lot.

2007 Audi S8 52L V10 Carbon Deposits

So, that's after. Hard to imagine what was there. There's a tiny little bit of carbon left over here that we didn't quite remove, but you can see the valve. There's the valve stem where the valve rides and you know, nice and clean. A lot of, room for the air to flow through, nothing to get in the way of, yeah, nothing to get in the way the airflow to the engine.

And this is a very close up shot, as you can see. Let's see, do we have another view here? Maybe this one. 

2007 Audi S8 52L V10 Carbon Deposits

Not quite as good of a picture, but nonetheless, kind of gives you an idea. 

So just have to do this again. Before. After. Big, big, big, big, big, big change. 

Mark: Clearly going to make a pretty drastic difference in the performance of the vehicle in terms of power, probably smoothness, even fuel economy.

Bernie: Oh, absolutely. Yeah. Huge, huge difference. 

Mark: And these kind of deposits, they affect all engines? 

Bernie: Any internal combustion engine can have these problems, but anything with direct fuel injection system. So these are, you know, lots of vehicles use different names.

I can't remember what the VW is it? TSI or something. TSI, stratified injection. I think they, they call it Mazda call it Skyactiv. They all have their names, but I think pretty well, every vehicle that's been built in the last 10 years, almost every one of them has direct injection.

Cause it just works way better than port injection. So, you can check with us or check with your local shop, but you know, it's important to deal with these valve issues. And so there are ways that you can prevent it, which I know is one of the questions that you were going to ask me.

Mark: So, how do you prevent? 

Bernie: Yeah. So there's several things. First of all, change your oil regularly. And that is, depending on the maintenance schedule. Probably more often than the manufacturer suggests. I'm going to hammer on BMW, but they're often 24,000 kilometre oil change intervals. Ridiculously way too long. You should change it at probably 12,000, half as much. And the reason why is that over time is as that oil gets older, it's full of the chemicals and combustion, the oil combustion byproducts. Thanks, Mark. That's the word I was looking for. It just gets full of that. And so as the crankcase breather gases go through the intake system, it's just got more contaminants and more things that can stick onto the valves.

So that's one thing that you can do yourself a big favour, change your oil at a decent interval. The other thing is use top tier gas. So how do you know? Top tier is basically an additive package is put into fuels. It's sort of, I guess a request from vehicle manufacturers to gasoline companies put this stuff in the fuel and it'll prevent the deposits from forming.

So it won't stop it entirely, but it keeps it down. And so top tier fuels, you'll find it at any branded gas station, like Chevron or Esso or Exxon, depending on where you live. And even cheaper places like Costco that sell fuel, theirs are usually top tier. There's directories you can look at online. A lot of times there'll be a sticker on the gas pump that says, this is a top tier fuel. It doesn't matter if you use regular premium or mid grade. Top tier fuel all has the same additive package. So the only reason you want to use premium is not for better additives. You only wanted for octane boosting capability. 

Third thing, maintenance every 30,000 kilometres. Take it to your shop, take it to us if you're in Vancouver. We can do a, we call it GDI gasoline direct injection cleaning where we spray chemicals directly into the intake system right onto the valves. As close to the valves as we can. Takes a little while. The chemical soaks in and burns off those deposits. So, if you do it on a regular basis, it won't look like this Audi looked. 

So, those are some things. There are definitely things you can do to prevent this issue from happening. And it happens on, you know, like I said, any vehicle with GDI, gasoline direct injection, which is most vehicles built in the last 10 years or older. I mean, this is an 07, this vehicle. So it's approaching 20 years. 

Mark: So how did the Audi run after the service? 

Bernie: Well, it ran really well. Now, as I said, there was a few other things we fixed and we didn't really notice an issue with this particular thing. But one thing you will notice, by the way, if you do start having these deposits building up is, you could notice the car doesn't have quite the power it used to have, but it's sort of a surefire sign is the check engine light will come on.

And usually it'll be misfires on startups and certain performance issues. And that's often a sign. It's very common on VW and Audi products to start having those codes and it being from carbon deposit issues.

Mark: So this has a V10, why would they use a V10?

Bernie: More power, smoothness. Yeah. I mean, it's not a very large engine. It's only a 5.2 litre. I mean, there's a lot of V8s that are much larger. But of course, you know, the more cylinders you have, the more smooth power you have and more torque.

Mark: And how are these Audi S8s for reliability? How's the mileage on this? It's quite old. Like you said. 

Bernie: Yeah. I can't remember what the mileage is on this car. I don't have it in front of me. It's a good car, but it is a top of the line, four door sports sedan with the biggest engine that Audi offers you know, fancy electronic suspension system. It's got all the bells and whistles you could ask for. It's a nice car. It's decent for reliability for sure, but it's going to cost you a lot more money to fix than your average car. 

I mean, I was thinking about, you know, while doing the walnut shell blasting after doing four cylinders, I'm going, okay, there's six more to go. And, you know, if this is a 4 cylinder engine, we'd be done by now. So this is the kind of thing that, you know you're changing spark plugs. There's 10 of them, not six or four or eight. It all adds to the cost of, you know, the more cylinders, the larger the engine, and the fancier stuff, the more to go wrong.

 I think the best thing to do is just know you're driving a fantastic car. You can buy these cars used for a fraction of the price of a new one, just budget a fair bit of money for maintenance and repairs. And you'll be good. 

Mark: If you're looking for service for your Audi in Vancouver, the guys to see are Pawlik Automotive. You can reach them on their website. You can book there at pawlikautomotive.com or you can call them (604) 327-7112. Pawlik Automotive, Vancouver, BC, Canada. And of course, thank you so much for watching and listening. We really appreciate it. Thanks Bernie. 

Bernie: Thank you, Mark. Thanks for watching.

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Bernie Pawlik

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