Snapped/sheared Glow plug 3.0TDi BMK engine

bentwenty

Registered User
Morning all.
With all the cold weather recently, my A6 decided it was time to dust off the old glow plugs and give them a blast of current.
Unfortunately one of them wasn't quite up to and and brought the light on. I scanned the codes and found cylinder five to be the issue.

So I started poking about, I wish I hadn't! First thing I noticed was the electrical connector which had been bodged up with electrical tape :(
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No problem, Audi will sell me one with a length of wire for £19.95 which I'll solder on later.

I then ordered a glow plug on ebay for £3, they sent a pack of four for the same price! When they arrived, I got a nice deep 10mm socket on the old one and started trying to get it out.
But even the small 8" ratchet I was using was enough to shear the head off the glow plug!
It has snapped between the hex and the threaded section
d036e34917abc46586e37e7cdad7598d.jpg

The body and thread are still seated fine, and the engine has been running perfectly for a few days now. But the hex just spins.
Unfortunately access is very limited, whatever I decided to do, I will have to remove the intake and disassemble the fuel rail.
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I am now deciding between two options:
1) buy this kit for £40 and do it myself
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That would involve snapping off the hex with the proved tool, then using the step drill to drill out the thread and at the same time drill a tapping drill hole for the provided tool. Then use the provided tap to tap the body of the plug. Then screw in the extraction tool and pull the remains of the plug out and clean up the threads in the head with the provided tap.
I think I can probably do it, but if I screw up, it's a new head!
2) have a local engine machining specialist (Maynards engines, Stroud) do it for me. I'm certain they will do a good job, but they charge £60/hour, and it could well take a few hours. I am going to try and pop over one evening this week and have them look over it and discuss it with me.

I would be very interested to hear and thoughts you may have or any experience you have and with this!
Ben
 

NHN

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Get a pro to do this, new head etc will be immensely expensive, for the sake of a few hours, peace of mind is worth allot more.
 

bentwenty

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Get a pro to do this, new head etc will be immensely expensive, for the sake of a few hours, peace of mind is worth allot more.
I think your right on that. I'm going over there either this evening or tomorrow and see what they can do. I may offer to strip down the fuel system and intake for them so they only have to do the head work.
 

B5NUT

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Your final option is to leave it alone, the car will start fine with 5 glow plugs working. I would also not recommend doing the job yourself if swarf or other metal bits get into the cylinder from the drilled out glow plug then it's goodbye engine. To do the job properly it will need the head removing.

I replaced my glow plugs last year but one of them is well and truly stuck, and would not budge so it has been left, it's still working and does not chuck up any codes but it does need replacing. I'm planning on doing the chains this year on my engine so when I rip the engine out I will take the head off and send to the machine shop to remove the plug.
 

bentwenty

Registered User
Your final option is to leave it alone, the car will start fine with 5 glow plugs working. I would also not recommend doing the job yourself if swarf or other metal bits get into the cylinder from the drilled out glow plug then it's goodbye engine. To do the job properly it will need the head removing.

I replaced my glow plugs last year but one of them is well and truly stuck, and would not budge so it has been left, it's still working and does not chuck up any codes but it does need replacing. I'm planning on doing the chains this year on my engine so when I rip the engine out I will take the head off and send to the machine shop to remove the plug.
It is very tempting. I've not had any problems starting it at all. It is throwing a code and the annoying flashing light. But that could be solved by putting a new glow plug in the connector, screwing the glow plug into a grounded cast aluminium project box. It's a big bodge, and I'm not sure I would be happy with it, but it would work...
Alternatively, is it possible to make the ECU ignore any codes for cylinder 5 glow plugs? I have VCDS. That would also be a bodge, but a neater bodge! lol
 

bentwenty

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is the flashing light all the time, or just at startup?
All the time, code clears but then comes back with flashing light every cold start.
 

B5NUT

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I guess it's due to the connector being open circuit, it normally just sticks an error code on the engine. There are no VCDS ticks that I know off to disable the light and the the alloy box sound like a very bad bodge. looks like your going to have to go down the expensive route, as I don't know of any blanks/resistors etc that would fix this, as there are is a lot of current going down that wire.. It's interesting that someone has repaired that cable I wonder the the plug has been changed before & it's been cross threaded when put back in!
 

bentwenty

Registered User
I guess it's due to the connector being open circuit, it normally just sticks an error code on the engine. There are no VCDS ticks that I know off to disable the light and the the alloy box sound like a very bad bodge. looks like your going to have to go down the expensive route, as I don't know of any blanks/resistors etc that would fix this, as there are is a lot of current going down that wire.. It's interesting that someone has repaired that cable I wonder the the plug has been changed before & it's been cross threaded when put back in!
Yes or at least very high resistance. I will measure it later.
Yes I think there has been some kind of bodge in the past, that electrical tape is a dead giveaway!
I think this car is a bit too nice to deserve that kind of bodge, but on the other hand I don't want to spent £100-200 on some thing which is not causing a problem.
Yes I would expect some thing in the order of 5A, at 4.4V that's 22W, so an aluminium clad resistor that is capable of sinking that kind of current is going to be as big as a glow plug.
 

Arrkon

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Usually, glow plugs (metal ones) are around 5 ohm, Ceramics are under 1 ohm. so based off 13.5 max voltage (will obviously dip under cranking), you're likely looking about 35W for metalic plugs and over 180 for ceramic...
 

desertstorm

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You could disable the fault code but that would have to be done in the engine map. You could leave it but it's liable that it would fail an MOT as there is a warning light on the dash.
To get around that just a case of connecting a glow plug up temporarily for the MOT .
Did you make sure the engine was upto temperature before trying to remove the plugs, This is the best thing to do.Less likely to snap them and best to use a 1/4 inch ratchet.
If you are considering trying to remove and replace it I would take it to a professional garage who you trust rather than having a go yourself.
ATM the engine starts and runs fine and it will with just 5 plugs, TBH I am surprised it is complaining that 1 is out as on my B8 3.0 TDI you can have 2 duff plugs with no lights.
 

bentwenty

Registered User
You could disable the fault code but that would have to be done in the engine map. You could leave it but it's liable that it would fail an MOT as there is a warning light on the dash.
To get around that just a case of connecting a glow plug up temporarily for the MOT .
Did you make sure the engine was upto temperature before trying to remove the plugs, This is the best thing to do.Less likely to snap them and best to use a 1/4 inch ratchet.
If you are considering trying to remove and replace it I would take it to a professional garage who you trust rather than having a go yourself.
ATM the engine starts and runs fine and it will with just 5 plugs, TBH I am surprised it is complaining that 1 is out as on my B8 3.0 TDI you can have 2 duff plugs with no lights.

I have now measured each plug, the other three I could measure easily where 0.5 Ohms, the rated current according to GSF is 25A, so assuming 12.5V that seems very reasonable. But cylinder 5 glow plug was 0.0-0.1 Ohms (my handheld fluke doesn't offer any more decimal places), so it seems it's failed short! I was surprised by that as I would expect the failure mode to be open!
Also for reference, I believe the code it throws is something like cylinder 5 glow plug electrical fault in circuit.
When I removed it, I had just got back from my 45 minute commute home, so it was well up to temp, and I was using my smallest 1/4" drive ratchet.
I also went to my trusted engine machining specialist, he estimated 1-2h labour for the actual removal of the glow plug. He is happy to do it with the head on, as all the machining will be done to the thread of the glow plug, and the body will be plugging the hole preventing any swarf from entering the cylinder.
He was happy for me to strip down the fuel rail and intake in the carpark as it saves me paying for a couple of hours labour and they will need them removed to gain access to it.
As its not causing any major problems, I'm aiming to do it the second week of February as they have good availability then.
 

bentwenty

Registered User
I've had some new developments:
Before having the machining done, I wanted to be certain it was the plug causing the problems. So I made this
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it's a glow plug in a bit of pipe with a ground connection.
It seemingly hasn't solved the problem! And now it's throwing the same code for cylinder 6 as well which I haven't touched!
0342f6d853156ff7da14cf3db0bdc44d.jpg

I don't understand what the code means! Can anyone shed any light? If it was wiring gone open, I would expect the code to say open circuit!
 

desertstorm

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If you are measuring the resistance of the Glow plug in cylinder 5 after you have twisted the top off I am not surprised it is reading as a short circuit.
You are correct the normal failure mode is open circuit.I believe these glow plugs are rated at 4.4V and not 12V as you are assuming. They certainly are in the newer cars. Thus you can't test them off a 12v battery as they will quickly blow.
The glow plug controller turns the current on and off very rapidly to the glow plug with a varying duty cycle to allow the glow plug to heat up quickly and then run without blowing.
The glow plugs you have sound very cheap at £3 each what make are they ? . Beru, NGK or Bosch are the only ones I would think of using. OE plugs are Beru and would be the ones I would refit.
The new plug you have has a red seal on it so is a metal plug. Are the plugs in your car metal or ceramic . Ceramic plugs have a white seal.
They should not be mixed. The controller is designed for one or the other.
The fault code you are seeing looks like it's saying the glow plug is open circuit. How thick is the conductor in that wire and how long is it. With the current supplied to the plugs it's resistance may be more than the plugs internal resistance.
I would have used a battery jumper cable clamped onto the body and connected to a good earth.

https://www.ngk.de/en/products-technologies/glow-plugs/glow-plug-technologies/ceramic-glow-plugs/

https://www.ngk.de/en/products-technologies/glow-plugs/glow-plug-technologies/metal-rod-glow-plugs/

Looks like the glow plug in cylinder 6 has failed. They tend to fail at similar times. This is a good thread regarding this engine. I have attached the document off Elsa Win for this engine.

http://www.vwaudiforum.co.uk/forum/showthread.php/134034-Which-Glow-Plugs-for-3-0TDI-(BMK)
 

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bentwenty

Registered User
If you are measuring the resistance of the Glow plug in cylinder 5 after you have twisted the top off I am not surprised it is reading as a short circuit.
You are correct the normal failure mode is open circuit.I believe these glow plugs are rated at 4.4V and not 12V as you are assuming. They certainly are in the newer cars. Thus you can't test them off a 12v battery as they will quickly blow.
The glow plug controller turns the current on and off very rapidly to the glow plug with a varying duty cycle to allow the glow plug to heat up quickly and then run without blowing.
The glow plugs you have sound very cheap at £3 each what make are they ? . Beru, NGK or Bosch are the only ones I would think of using. OE plugs are Beru and would be the ones I would refit.
The new plug you have has a red seal on it so is a metal plug. Are the plugs in your car metal or ceramic . Ceramic plugs have a white seal.
They should not be mixed. The controller is designed for one or the other.
The fault code you are seeing looks like it's saying the glow plug is open circuit. How thick is the conductor in that wire and how long is it. With the current supplied to the plugs it's resistance may be more than the plugs internal resistance.
I would have used a battery jumper cable clamped onto the body and connected to a good earth.

https://www.ngk.de/en/products-technologies/glow-plugs/glow-plug-technologies/ceramic-glow-plugs/

https://www.ngk.de/en/products-technologies/glow-plugs/glow-plug-technologies/metal-rod-glow-plugs/

Looks like the glow plug in cylinder 6 has failed. They tend to fail at similar times. This is a good thread regarding this engine. I have attached the document off Elsa Win for this engine.

http://www.vwaudiforum.co.uk/forum/showthread.php/134034-Which-Glow-Plugs-for-3-0TDI-(BMK)
Thanks for the reply, thats some very good info!
Thanking about it, I suppose it is very possible that the electrode is shorting to the body now its snapped.
I found that they are all indeed rated at 4.4V and 25A, but they are individually connected (as the controller is able to tell exactly which plug has a fault), and I couldn't imagine Audi making a system that would drop 12v down to 4.4, the heat losses would be incredible! But it all makes sense if they are PWM'd like you said! I forgot how sophisticated even a 10 year old Audi is!
I haven't tried testing them out the car as I haven't managed to get any out!
Yes these are indeed cheap and nasty! they are SVAC. I am now thinking I'll buy a whole set of OEM ones and do them all when I have the machining ones. I'm going to start soaking them in plus gas now so hopefully I can get them out ok! I'll use these ones for testing to be sure its the plug first.
As I still have my suspicions about the, I will remake the setup with thicker wire and a better earth terminal, then try it again for cylinders 5 and 6. The wire I had used was about 0.5mm^2, it looked roughly the same size as the wire for the connector, but as you say, we are talking a few Ohms max, so it wouldn't take much to throw the code! I now have 2.5mm^2 and much better terminals.
Thanks for the info on the fault code, I wasn't sure how to interpret it, could have been upper limit for current, or resistance to me!
Those threads look to be worth a read, will look later!
Thanks for the Elsa PDF, I do have a copy of Elsa, but I need to re-install it, will do that tonight!
 

bentwenty

Registered User
To add: having read through the PDF, it is entirely possible that my engine has ceramic plugs, and so the metal one I fitted blew the first time it was used. Will check later.
 

desertstorm

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I would throw away those plugs you have bought and get some decent make items. Metal glow plugs are the old style type plug and are used for a short period only maybe upto 10 seconds and the way they are heated and run by the glow plug controller is different to ceramic plugs.
These can be run for several minutes after the engine has started to provide extra heat in the cylinder and assist in smooth running and reduced emissions / faster warm up.
 

bentwenty

Registered User
Yes I plan to buy a full set of OEM ones now. The plug that I had wired in has failed open. But as far as I can tell, my engine has metal plugs, at least for cylinder 4 which I could get a photo of.
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I have just done the test again for cylinders 5 and 6, the code disappears with my extra plug, confirming that they have both failed.
As I have some doubt as to wether my engine has metal or ceramic plugs, is there another way of checking? Perhaps the coding?
I find it odd that the plug I fitted went open within one day! I know they are cheap, but that almost seems like it's not the correct plug!
 

desertstorm

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bentwenty

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It seems the plugs you have in your car are metal type GE115 is the Beru part number.
If you have removed one already then you should be able to see what the part number of that was.
http://www.ebay.co.uk/itm/Various-V...410188?hash=item4623355bcc:g:VvQAAOSw7I5TvUtz
car parts 4 less is the on line trading part of ECP. The parts tend to be cheaper .

Karl.
That looks like the ones, I'll start dousing mine in plus gas and hopefully I can get one out to check the part number. once I'm sure I'll order a full set. I assume from the photo that I will need to swap the connectors over from my old ones?
Ben
 

bentwenty

Registered User
Thats a generic picture on the Ebay advert I linked to. The GE115 should be the same plug as you have in the car.
http://www.cs-parts.de/index.php?a=337
The Audi supplied parts have an Audi part number and Audi rings logo on them, but they are BERU supplied plugs.
Ah I see, I hadn't cottoned on to the stock picture. Will get them ordered once I've had one out! Thanks again.
Ben
 
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