Glow Plug Life

[RussellAisbitt]

I have a 2004 CLK 270 CDI with 32,000 miles. It has a Brabus D4 Conversion which may affect glow plug life, but I can't really see that it should.

About 4 Weeks ago I had the glow plug warning light come on. I booked it into County Mercedes Cheltenham and they replaced Glow Plug No.4. I was a little annoyed to find that glow plugs are considered a wear item and are not covered by the warranty.

When I picked the car up the glow plug warning light came on again (I hadn't even left the dealership). As it was closing time, they couldn't take a look straight away and I had to book it in again for the following week.

I have no complaints against County Mercedes Cheltenham, I think they were as surprised as I was that another should fail so quickly after they had just replaced one. In the end, they collected my car, changed the glow plug (This time it was Glow plug No.3.) and delivered my car back again in less than 4 hours, and they didn't charge for it's replacement.

I have only ever owned one other diesel before a little Peugeot 306 whose engine didn't require any new glow plugs in the 4 years and 50,000 miles I owned it.

Does anyone have any idea how long these MB glow plugs are supposed to last?

 

[Satch]

Is it an EU3 or EU4 engine?

Looks like plug life on EU4 engines is going to tend to be shorter. For example the newer Bosch plugs have a control unit that can run them on for up to 15 minutes (at a reduced power) after a cold start up to help reduce emisssions.

But EU3 or EU4, they are considered a wear item

 

[RussellAisbitt]

Is it an EU3 or EU4 engine?

Don't know for sure. But I would imagine it is EU3.

 

[Parrot of Doom]

My 1998 1.9 Audi A4 did 138000 miles over 6 years, never once had a glow plug changed.

 

[Doodle]

Just replaced all 5 on the C250 at 36k.

The car is nearly 9 years old, however, and spent the first 8 years of it's life being owned by the proverbial old lady (my grandmother), doing short runs around town and being laid up for 4 months while on holiday; something that does nothing for the plug life.

 

[DrNick]

Had two sets on my E300 over 2 years (50K). I would suggest that you replace them in sets. Once one goes, the others are probably not far behind, and on the E300 anyway, you have to take the inlet manifold off to get to them, so makes sense to do them all at once.

Never changed a plug on my 405TD (4 years and 100k) or my Brava 100TD (3yrs and 75K)

 

[Dieselman]

I have a 2004 CLK 270 CDI with 32,000 miles. It has a Brabus D4 Conversion which may affect glow plug life, but I can't really see that it should.?

More fuel raises the cylinder temperatures. Everything in there will have a shorter life.
You may also find that the injector squirts either on or very close to the glow plug for starting. The additional fuel will overheat the plug quickly.

About 4 Weeks ago I had the glow plug warning light come on. I booked it into County Mercedes Cheltenham and they replaced Glow Plug No.4. I was a little annoyed to find that glow plugs are considered a wear item and are not covered by the warranty.

Spark plugs are considered a wear item, why not glow plugs?

 

[RussellAisbitt]

More fuel raises the cylinder temperatures. Everything in there will have a shorter life.
You may also find that the injector squirts either on or very close to the glow plug for starting. The additional fuel will overheat the plug quickly.

I understand where your coming from. But the Brabus conversion will only generate extra heat when I use the extra power, usually when overtaking. So that probably amounts to no more than 10 minutes worth at 3-5 second bursts over the course of an entire year.

Spark plugs are considered a wear item, why not glow plugs?

Ultimately everything wears out, gearboxes, power steering pumps, water pumps etc. But as Glow plugs can last for several years and in excess of 100,000 miles in other cars, it could be argued that they are burning out prematurely in Mercedes. If a water pump packed up within 30K miles and 2 years you would expect it to be replaced under warranty wouldn't you?

 

[Satch]

Modern glow plugs are very different in form and function to those commonly found a couple of years ago. At best the older ones would get to 800/850C and the high temp ones to about 1000C.

http://www.boschautoparts.co.uk/pcGlow13.asp?c=2&d=1

"The sheathed-element glow plugs reach a maximum glow temperature of 1300 ºC, about 250 degrees higher than metal sheathed-element glow plugs, and can hold a temperature of 1150 ºC"

Just for reference, the melting point of cast iron is 1260C. They also live with the business end in a high temperature high pressure environment. None of that is going to give a very long life.

 

[RussellAisbitt]

That's an enlightening article you posted. As you posted earlier, it appears modern glow plugs can run for up to 15 minutes after the engine has started to help the engine run when cold. I'm not surprised they burn out.

 

[Dieselman]

I understand where your coming from. But the Brabus conversion will only generate extra heat when I use the extra power, usually when overtaking. So that probably amounts to no more than 10 minutes worth at 3-5 second bursts over the course of an entire year.

It doesn't work like that. The fuel is injected under a higher pressure so more fuel enters the cylinder most of the time. This will increase the temperature, that's how the engine delivers more torque.

 

[RussellAisbitt]

The Brabus conversion is only a chip and filter change. The turbo is the same, the capacity is the same, the bore, stroke, compression are all the same as standard. The only difference is that it is capable of a little higher boost, and squirts more fuel in when using that higher boost.

Cruising along at say 50mph my converted car needs no more power or torque than a non-modified car. Don't forget the gearing is the same so the rpm will also be the same.

At a given rpm if an engine is developing more torque, then it is also developing more power and if the power required is more than is needed to maintain a steady speed the car will accelerate.

 

[Dieselman]

At a given rpm if an engine is developing more torque, then it is also developing more power and if the power required is more than is needed to maintain a steady speed the car will accelerate.

Obviously, but everytime you accellerate there will be more fuel than normal injected.
A chip only alters one aspect of the tune of the engine. That is to inject more fuel. This in turn creates additional heat. If there was more/cooler air forced into the engine then the heat level would be reduced again.

If you don't think I have a valid point ask Mercedes if they will honour your warranty with a chip conversion. Their answert will be an emphatic NO for the reasons covered.

If you want a graphic demonstration fit an EGT gauge.

 

[RussellAisbitt]

Your prepared to accept that at a steady speed a converted car will require no more torque and power than a non converted car and presumably accept that it therefore doesn't require any more fuel.

Can you also accept that for a given rate of acceleration, both cars will require the same amount of torque and power and therefore will require the same amount of fuel.

I appreciate if I plant my foot so far down that it generates more torque and power than the standard car can deliver, then a modified car will burn more fuel and consequently generate more heat. But using the same power settings as the standard car, I see no reason for the modified car to burn any more fuel. If it did then almost by definition it would be producing more torque and power.

I started this thread to ask a question about glowplug life and I do appreciate everyones input. Judging by the various responses it seems that MB's glow plugs do have a relatively short life. In addition, I was talking to a friend this evening who is on his second BMW diesel (3 Litre). Neither has had a glow plug change, and the second car has now done over 130,000 miles.

 

[Dieselman]

Your prepared to accept that at a steady speed a converted car will require no more torque and power than a non converted car and presumably accept that it therefore doesn't require any more fuel.

Can you also accept that for a given rate of acceleration, both cars will require the same amount of torque and power and therefore will require the same amount of fuel.

I appreciate if I plant my foot so far down that it generates more torque and power than the standard car can deliver, then a modified car will burn more fuel and consequently generate more heat. But using the same power settings as the standard car, I see no reason for the modified car to burn any more fuel. If it did then almost by definition it would be producing more torque and power.

Sorry I don't seem to be able to make myself clear.

Everytime you call for accelleration the injectors will input more fuel. You will feel this as quicker accelleration or the same rate of accelleration in a higher gear and faster throttle response. This is because there is more fuel injected. The extra fuel will increase the cylinder temperature and the engine will produce more torque.

This torque will happen right through the rev range so there will be more torque at lower revs.
Forgive me if I'm wrong but this is why you purchased the tuning chip isn't it?

Now lets take the senario of more torque at lower revs. Not necessarily more torque than the engine could generate at peak torque previously, just more torque than there used to be at the same revs.

To generate the torque the engine requires more fuel. This generates more heat Ok so far?
As a result of the torque being generated at lower revs the amount of injested air is lower. The engine injests a set amount per stroke multiplied by the revs.
Thus due to a higher fuel input and increased torque output the combustion process will be hotter.

I appreciate that if you NEVER accellerate any quicker than you used to without the chip the fuelling will be the same, but that isn't the case, the engine will accellerate more quickly even in neutural.

Please fit an EGT gauge and report your findings W/WO the chip.

 

[RussellAisbitt]

I appreciate that if you NEVER accellerate any quicker than you used to without the chip the fuelling will be the same

Finally, some common sense.

but that isn't the case

No, I'm wrong, you've lost the plot again.

Why you can't accept that someone who chooses to modify their car does't go around with there foot to the floor all the time beggars belief. I drive very conservatively, average 43 mpg and 99.999% of the time do not use the extra power.

Please fit an EGT gauge and report your findings W/WO the chip.

Now your just being silly.

I suggest we just agree to differ in our opinions.

 

[jeremytaylor]

For what it's worth, I'm with Dieselman on this.

I had my C270 re-mapped by Superships, but it smoked more and in the end, co-incidentally or not the EGR valve failed (which is when you see how much smoke these engines can really produce! ).

I've re-mapped other engines no trouble, but not this one.

And yes, glow plugs are service items.
And yes, I would always replace them as a set.