Glow plugs 101 ***Ver. 2.0***

treating harness

treating the harness with contact cleaner was not elaborated on, (unless i missed that part). Does that just involve spraying the cleaner into the harness sockets and hoping for the best?

Hi guys,

I apologise in advance because I *know* I've seen this particular question on here (or something to its effect) but I can't find it now.

*ahem*
Would a CEL for glow plug cylinders 1 & 3 be caused by the wiring harness being wired incorrectly (or, in this case, backwards?) in a PD 2005 Jetta? Engine fired just fine, no other problems, just the CEL.

Would love opinions on this...
Kathy

tortdi said:

treating the harness with contact cleaner was not elaborated on, (unless i missed that part). Does that just involve spraying the cleaner into the harness sockets and hoping for the best?

Click to expand...

Well, the preferred "cleaner" for this around here is a product called "DeOxit D5" from CAIG... it's not easy to find, but it has a way of chemically attacking the corrosion... sometimes more than one "treatment" is needed... It comes in both spray and liquid forms... I bought the tiny bottle of liquid, but I forget why I decided on that...

Basically you turn the harness upside down so that the opening's up in the air, and either spray down into the contact area or use the little brush to get the liquid down there... a Q-Tip with most of the cotton removed will make a good tool to help with the cleaning process... after giving it a few minutes to work, you just replace the harness, clear the code, and see if it comes back... (sometimes it will return immediately, other times after a week... I needed to have this done twice to my harness, and it's been trouble-free for 2 years... of course, now that I've posted this, it will return...)

All the best,

Yuri.

katzw said:

Would a CEL for glow plug cylinders 1 & 3 be caused by the wiring harness being wired incorrectly (or, in this case, backwards?) in a PD 2005 Jetta? Engine fired just fine, no other problems, just the CEL.

Click to expand...

Very unlikely unless you've had the CEL on from the time the car was new... Either the computer is seeing the proper (more-or-less equal) current draw from all 4 glow plugs, or it will throw a code...

On the PD engines (2004-and-newer in North America), the glow plugs are ceramic - and FRAGILE... if you do have dead glow plugs, if you keep running the car with them, they'll "grow" a layer of carbon on the tip, and will be more likely to break off when finally removed... (when the GP's are functioning, they tend to burn off that carbon layer...)

All the best,

Yuri.

ymz said:

Very unlikely unless you've had the CEL on from the time the car was new... Either the computer is seeing the proper (more-or-less equal) current draw from all 4 glow plugs, or it will throw a code...

On the PD engines (2004-and-newer in North America), the glow plugs are ceramic - and FRAGILE... if you do have dead glow plugs, if you keep running the car with them, they'll "grow" a layer of carbon on the tip, and will be more likely to break off when finally removed... (when the GP's are functioning, they tend to burn off that carbon layer...)

All the best,

Yuri.

Click to expand...

Hey Yuri,

I'm sorry, I suppose I should mention, the wiring harness is new from July, and I have had 4 CEL lights of the same type (cylinder 1 & 3) since the wiring harness was replaced. I have had all 4 plugs replaced, and the relay replaced, all through the dealer. The plugs all read from the digimeter perfectly. Still the same light. This wiring backwards is the latest discovery - and we're wondering if this could be the final resolution.

Kathy

If the wiring harness was replaced, they could have made insecure connections for the wires going to GP's # 1 and 3... (or else messed up the wiring completely)...

I hope the dealer was paying for all this work, as it sounds a lot like what we see around here: clueless dealers (and garages) just throwing parts at a problem hoping that one of them "fixes" whatever it was that was faulty...

I'd get away and find a real TDI expert to take care of your car... (but give whoever replaced the harness a chance to go over their "work" and get it right this time...)

All the best,

Yuri.

PS: in Vancouver, we all have a high regard for Tony at Andes Auto Service...

Hi again,

This is all under warranty, and according to Tony (who was very nice on the phone) it should probably stay there to let them deal with for now since it's their mystery. The service manager was a little unsure as to whether this wiring issue would cause the fault, and I perked up and mentioned I thought I had seen it online here, so I was checking in In any case they're keeping it, with work order open so I don't traverse over to the darkside of warranty oblivion and want to make sure the light won't come back. Would just be funny if something like this caused it.. I had no idea my engine would be so anal retentive

ymz said:

If the wiring harness was replaced, they could have made insecure connections for the wires going to GP's # 1 and 3... (or else messed up the wiring completely)...

I hope the dealer was paying for all this work, as it sounds a lot like what we see around here: clueless dealers (and garages) just throwing parts at a problem hoping that one of them "fixes" whatever it was that was faulty...

I'd get away and find a real TDI expert to take care of your car... (but give whoever replaced the harness a chance to go over their "work" and get it right this time...)

All the best,

Yuri.

PS: in Vancouver, we all have a high regard for Tony at Andes Auto Service...

Click to expand...

ymz said:

Very unlikely unless you've had the CEL on from the time the car was new... Either the computer is seeing the proper (more-or-less equal) current draw from all 4 glow plugs, or it will throw a code...

On the PD engines (2004-and-newer in North America), the glow plugs are ceramic - and FRAGILE... if you do have dead glow plugs, if you keep running the car with them, they'll "grow" a layer of carbon on the tip, and will be more likely to break off when finally removed... (when the GP's are functioning, they tend to burn off that carbon layer...)

All the best,

Yuri.

Click to expand...

Seeing as I have a PD with 88K (out of warranty) and I just got a P0672 yesterday I have the following questions.

Would it be better to remove them when hot so as to hopefully have burned off any carbon buildup? Or better to remove when cold so that thermal expansion hasn't narrowed the passage through where they exit?

Should one break...would rotating the crank until the intake valves open and then using compressed air to pressurize the intake/cylinder be enough to dislodge the broken piece? Just trying to get geared up for anything that I may encounter.

thanks

04PDWagon said:

Seeing as I have a PD with 88K (out of warranty) and I just got a P0672 yesterday I have the following questions.

Would it be better to remove them when hot so as to hopefully have burned off any carbon buildup? Or better to remove when cold so that thermal expansion hasn't narrowed the passage through where they exit?

Should one break...would rotating the crank until the intake valves open and then using compressed air to pressurize the intake/cylinder be enough to dislodge the broken piece? Just trying to get geared up for anything that I may encounter.

thanks

Click to expand...

Excellent points all around... I wish I had a solution... let's hope some of the more ingenious and experienced TDI-Techs (you know who you are !!!!) join in this thread and provide help... I think it's a topic that deserves major consideration, given how many people are liable to be affected... (Perhaps its own thread???)

Yuri.

I am new to the thread, and do not have time to read all 30+ pages.

But I would suggest first ALWAYS fix the problem ASAP. Inactive glowplugs seem to get bad carbon build up that never gets "cleaned" off despite the tips being in the combustion chamber. That extra ring of carbon can contribute to them sticking in the head upon removal.

I like to get the car in the shop while at operating temperature, and pull the upper engine cover off and remove the contact bridge, then spray some penetrant at the base of each plug. Usually the heat will help it to wick into the threads a bit. I do this once every 10 minutes or so while the engine is cooling down, then after about 30 minutes I loosen each plug 1/4 turn (90 degrees) and spray again.

Then after sitting another 10 minutes, I slowly turn each plug one turn at a time, spray, turn, spray until they are all loose... but I do NOT pull them out with any kind of socket. And the last few turns are done with a 1/4 drive flexible extension so as to make it virtually impossible to inflict any harsh side-to-side pressure on the tip. Once loose, I use a stick magnet to "suck" them up out of the hole.

As of yet, I have not broken a single one. However I have not had to change that many PD ones YET.

At every oil change on every TDI I service, I spritz WD40 at the base of each glow plug. Always have, and I think it may help inhibit corrosion coming in from outside the head and getting into the threads.

I also instruct everyone to NEVER allow the engine to idle after cold start. Always drive off right away, and try to keep the RPMs over 2500 so the plugs do not stay energized any longer than they have to. TDI afterglow time is ridiculous...like several MINUTES. That is why they never last as long as the old IDI plugs do. The old IDI plugs had an afterglow of about 5 seconds, period. Then they are DONE!

This topic was suggested a long time ago, but has anyone actually tried replacing the ceramic plugs with the older style metal ones? I remember the discussion centering around the voltage difference between the 2, but I never did hear much about it after that.

For a part that has the potential to fail several times over the life of the vehicle, I am ver surprised VW has continued to use such a fragile element for these glow plugs. So much damage can occur for such a simple procedure as changing a $25 part.

Wingnut said:

So much damage can occur for such a simple procedure as changing a $25 part.

Click to expand...

Unless there's a super-secret way to remove them safely that the VW engineers know but for some reason kept to themselves...

I suppose that if anyone figures out some method to control the older-style glow plugs using a source voltage used for the new ones, all the PD folks on this web sit would jump all over it... I have a feeling that the ECU monitors the current draw much more carefully on the PD engines (and probably controls them quite a bit more subtly), and quite likely the older-style GP's can't quite give the ECU fine enough control to deal with the emission requirements... (just my theory...) If someone has some time on their hands, they could try experimenting with using a 2003-style glow plug controller run off the PD ECU's output wires to the GP's...

Yuri.

I checked the plugs yeserday...2 were in the .45 range and 2 were in the .41 range. Seems like the problem is with the wiring. Hopefully I'll get a chance to clean up all of the contacts this weekend to ensure the intermittent fault won't come back.

Hi all

Having just bought a Vagcom unit, I noted I am showing a fault code 'Cylinder 1 Glow Plug Circuit (Q10): Electrical Fault' on my Golf Mk5.

I bought a can of Deoxit D5 and sprayed it into all the contacts on the harness, cleared the code and started the engine, the fault didn't reappear immediately. I then re-checked using Vagcom the day after and the above fault code has come back. But I have never had a 'check engine light' come on in the cluster. Is it supposed to illuminate in this situation? Also, which is cylinder 1 on the mk5(A5) Golf please when you are looking into the engine bay?

I am wondering whether to delve into it more or just leave it, as the car has always started fine every time, and I don't see any carbon deposits on the contacts in the harness area. Any thoughts on the subject would be appreciated.

Thanks.

ukguy said:

I bought a can of Deoxit D5 and sprayed it into all the contacts on the harness, cleared the code and started the engine, the fault didn't reappear immediately. I then re-checked using Vagcom the day after and the above fault code has come back.

Click to expand...

It often takes more than one treatment with DeOxit for it to get rid of sufficient corrosion... (I needed it done twice, and it's been fine for over 2 years since...) As well, some mechanical scrubbing may help as well. (Some people also gently squeeze the outside of the harness at the connection points using pliers... careful not to overdo this and break the whole thing...)

All the best,

Yuri.

I agree with oilhammer. Dont wait on replacement of a fauty plugs or plugs. Never use large tools to remove them. Use small tools and both hands. make certain the tool is traight ALL THE TIME. Use lots of penetrating oil as you go. I helps some if you drive ir really hard for time first, let it cool down nd then try it. NEVER alllow the faulty plugs to remain, as soot builds up to the point that it captures the plug end and this is how breakage can occur.

Thanks very much for the reply mrchill and ymz. So I really do know which cylinder plug (connection) I am dealing with, please can you tell me which is cylinder 1 when looking from the front bumper? Then I will concentrate on that connector. Engine code shows as BKC (1.9 tdi 105bhp) on my mk5 2004 model Golf.

Also, the check engine light hasn't flashed (it's the glow plug light on my car) signifying a problem, should it throw up a warning if one of the glow plugs (or connectors) is actually faulty?

Thanks again guys.

ukguy said:

Thanks very much for the reply mrchill and ymz. So I really do know which cylinder plug (connection) I am dealing with, please can you tell me which is cylinder 1 when looking from the front bumper? Then I will concentrate on that connector. Engine code shows as BKC (1.9 tdi 105bhp) on my mk5 2004 model Golf.

Also, the check engine light hasn't flashed (it's the glow plug light on my car) signifying a problem, should it throw up a warning if one of the glow plugs (or connectors) is actually faulty?

Thanks again guys.

Click to expand...

Normally Cylinder # 1 is the one closest to the front of the engine (where the belts are)... Some of the earlier VW models had the glow plug numbering reversed to the cylinder numbering, although by your model year that should have been synchronized - but who knows... As another of our esteemed Gurus (MOGolf) suggested, to be certain, disconnect one of the glow plug connectors (let's say # 2), run the car 'till there's a CEL, and read the code...

BTW: are you sure you weren't getting a CEL (= MIL = malfunction indicator light or check engine light) ??? A flashing glow plug light is normally related to brake light issues... either a burned out brake light or a bad brake light switch...

All the best,

Yuri.

I see Oilhammer has documented a process to try to avoid breaking the ceramic GPs. The main point: take it slow, easy, carefully.

There are metal ones that can replace the ceramic ones (at least documented), but I haven't found them yet. European part? Hmmm.

If any part needed a customer satisfaction campaign, these ceramic plugs would be above the seat heaters on my list.

UKguy, the "check engine light" for the glow plug fault is a US government mandated feature that you don't have the pleasure of receiving. Canada gets it because they pretty much say if it's good for US it's good for them for the emissions standards and features.

Actually, due to the small CanUS market for VW, they can't justify separate versions of parts (except where mandated by the governments).

ymz said:

Normally Cylinder # 1 is the one closest to the front of the engine (where the belts are)... Some of the earlier VW models had the glow plug numbering reversed to the cylinder numbering, although by your model year that should have been synchronized - but who knows... As another of our esteemed Gurus (MOGolf) suggested, to be certain, disconnect one of the glow plug connectors (let's say # 2), run the car 'till there's a CEL, and read the code...

Click to expand...

I assumed I was kind of leaning to doing the test that way but wasn't totally sure if it would cause any ongoing problems. Am I right in saying the glow plugs serve no purpose when the temperature is above around 2C? Maybe that's the reason I haven't experienced any symptoms, as it only gets down to that in the middle of winter in my part of the UK (Manchester).

ymz said:

BTW: are you sure you weren't getting a CEL (= MIL = malfunction indicator light or check engine light) ??? A flashing glow plug light is normally related to brake light issues... either a burned out brake light or a bad brake light switch...

Click to expand...

Definitely sure I wasn't getting any warning come up in the cluster, first thing I knew about the problem was when I connected the Vagcom. I have just re-read that part of the manual for my car and it states that the glow plug light will flash if there is an Engine fault. It has never flashed...

MOGolf said:

I see Oilhammer has documented a process to try to avoid breaking the ceramic GPs. The main point: take it slow, easy, carefully.

Click to expand...

Can a glow plug be faulty if the glow plug fault code (P0671) goes away and comes back a day or so later, after at least a couple of starts?

Also, when tightening the new plugs, is the correct torque for my mk5 engine 11 ft/lb as stated in the first post? Or has it changed for the more recent engines? Just so I don't mess it up at that stage...

MOGolf said:

UKguy, the "check engine light" for the glow plug fault is a US government mandated feature that you don't have the pleasure of receiving. Canada gets it because they pretty much say if it's good for US it's good for them for the emissions standards and features.

Click to expand...

Ahh I understand now, so major I get the glow plug light flashing on my car only if there is a very major problem detected by the engine controller.

Thanks again for your replies, I am learning so much from this site...I love it!

ukguy said:

Can a glow plug be faulty if the glow plug fault code (P0671) goes away and comes back a day or so later, after at least a couple of starts?

Click to expand...

The detection system appears to be coded so that it keeps track of the number of times (possibly up to 4) that it detects the fault before setting the code.

ukguy said:

Also, when tightening the new plugs, is the correct torque for my mk5 engine 11 ft/lb as stated in the first post? Or has it changed for the more recent engines? Just so I don't mess it up at that stage...

Click to expand...

Still 15 Nm = 11 ft-lbs. The point here is to get them in tight enough so they don't back out or leak compression past the threads. Don't overdo it. They don't hold the entire engine together.

MOGolf said:

The detection system appears to be coded so that it keeps track of the number of times (possibly up to 4) that it detects the fault before setting the code.

Click to expand...

That makes sense, thank you.

MOGolf said:

Still 15 Nm = 11 ft-lbs. The point here is to get them in tight enough so they don't back out or leak compression past the threads. Don't overdo it. They don't hold the entire engine together.

Click to expand...

Understood, then 15Nm it is then. I prefer to use the torque wrench for anything engine related so I don't overtighten and cause massive issues
Thanks for your reply.

Great Job

Great job and many thanks…. I have a glow plug code and this is exactly what I needed to know.
Bensplace
Raleigh, NC

Glow Plug Harness

After some time searching, I have not been able to find any reference regarding the location of the connector for the GP Harness on the NB. Mine is an 02 and I would like to know what-all I have to tear out to get to the hiding place!! Any help would be appreciated.

All worked well.... Thanks

Man your instructions were right on. Mine is a 2002 and the code it gave was for the #2 cylinder when actually it was #3.
All the plugs read a .9 including the new one. (Now I have 3 plugs in the glove box) One thing I noticed in your article was that there was no remediation to use “no-seize”. So I didn’t use any. My glow plug harness was in fine shape. I did order some DEOXIT D5 just because it sounds like something every one should have.
Thanks again.

Glow Plug Harness Hassle

Getting into the last few nice days left up here in the north country so thought I thought I'd better change out the harness before the fear of frost-bitten fingers became a reality. I had just decided to splice in the new harness because I wasn't getting any answers on the location of the connector on the NB. Removed the engine shroud and cut out the old harness as close to the end as I could. With this, I did not have enough working room to make the splices so tried to remove the vacuum tank. Instead, proceeded to drop the allen socket into the far reaches of the engine. Get it with the mechanical fingers--oops--- crawl down and drop the Panzer plate, of course, after getting the ramps and driving up.
That done, canned the idea of trying to splice and went in search of the connector. removed the air breather and what have you and finally got to the "Lair of the Connector" Figured out how to get it apart and came face-to-face with the beast. Disconnected the old plug and, being that it was in the way, I took the side cutters to it. I sure didn't need any extra crap in the way.
Now to just plug the new one in and button the thing up.
***!! The plugs were exactly the same size!!! Better call dieselgeek and tell him about it. That's when he told me that I had probably cut the wrong connector loose and he was right!! Red-faced, I ran back to the garage and did the splicing I needed to do and put it back together.
All-in-all, it was a fun day along with a learning day.
-

Last week I got the glow plug code for the 98 jetta. Followed the great instructions and replaced the harness after checking the plugs (.5 all the way across). The replacement harness was made in Hungary. Had to replace all the fuel lines too as they looked chewed. thanks!

I checked my car using Vagcom and the dreaded fault code P0671 came back. The contacts looked ok, and I have already used Deoxit on them. I then tested each glow plugs resistance using my multimeter. All show exactly 0.09ohms apart from the glow plug nearest to the belts, that shows '1.' on the display (the same as if I left the probes unconnected). So it looks like glow plug 1 definitely needs replacing.

What would you guys suggest, replacing all of them or is just changing the bad one? Also, I am hesitant as I have heard bad stories on this thread about the plugs breaking up as they're being removed. More so on ceramic plugs. I haven't got a clue if mine is ceramic or not. All I know is that it is engine BKC on a Golf mk5 1.9Tdi (2004 model). I took a picture of the bad plug if anyone can tell me if it's one of the newer ceramic ones or not? Thanks!

The fact that there is a coloured "band" on it suggests that this is a metal glow plug, not ceramic.

It is a matter of personal choice (yours) as to whether to replace the bad one or all of them. A search will show this to be a debated topic.