Glow Plug Replacement 2.5Tdi - Not As Bad As I Thought

[dieselV6]

After a few harder than usual engine starts over the last month, I found out a couple of days ago that 3 out of 6 glow plugs are blown.

Original glow plugs were Beru, NGK are of good quality but slightly different build, thin tip vs thick ended Beru. NGKs warm up faster but cool down faster too.

 

Yesterday I replaced all 6 with NGK ones that I got at GSF (by the way, they have 33% off with NOVE33 code). So far they work OK, but 3 cold starts only and no frost so early days yet.

 

Bearing in mind the horror stories about engine head replacements due to stripped glow plug threads, I soaked them with penetrant fluid overnight. It also helped to use reversible torque wrench, on which I could see the torque while undoing each plug. Breaking torque for the glow plugs  is quoted at 35Nm, and I must say this is very close to what had to be applied to remove them. Overall, 2 plugs just came out easily, 2 put up a little fight, and for remaining 2 I had to screw them in/out several times by half turn around mid-way while adding penetrant fluid before they came out.

 

For anyone doing this job on a V6 TDI, the plug nearest to the air intake takes a universal joint to come out, and the plug closest to turbocharger requires undoing air filter hose at turbocharger side. Deep 10mm socket and a long extension are required for the rest.

It also helps to use a short PVC hose to remove/insert plugs, and to fashion a wire tool to unhook the glow plug caps, doing it by hand is tricky. 

 

In my case, new plugs also did not thread in easily as the head is quite tired after 8 years/130k miles, but with a bit of anti-seize and some wiggling it is possible to screw them all the way in. Tightening torque is usually quoted at 15Nm-20Nm, NGK quotes 20Nm and I tend to agree with 20Nm on an old engine head. After initial torqueing, undo the plug 1/2 turn then torque again and see if it ended up in the same position, if not then the thread still has some way to go. Whatever you do, do not cross-thread the glow plugs when putting them in.

 

Hope these comments help the next person doing this job, it is quite easy apart from the risk of damaging the threads.

 

[Gaz]

Nice to know it's not necessarily a do it if you dare job.  

 

I still think i'll leave mine all the time it starts - I know my luck   

 

Gaz

[CRC]

Mine was taking a little longer to start in the colder mornings .... still started OK, but the number of revolutions seemed to be increasing and there were a couple of times when I feared that the battery power was starting to go before the engine fired, so I figured I'd change the original Varta battery out with another Varta as the original has done sterling service for almost nine years.

 

The link below shows the one I ordered .... bit more Ah capacity and Cold Cranking Amps, a decent price and the dimensions are identical to the original, apart from being slightly less tall. It turned up the next morning and seemed fully charged, though I gave it 24 hours on the trickle charger to fully take it to the max.

 

Also took the opportunity to replace the broken window scutttle while I was doing it ( £21 from main dealer) and found it much easier to re-fit without breaking by undoing the single Torx bolts and removing  the bracket at each end as Roto once advised. Would think that it's very difficult to break the scuttle when these brackets are out as you don't have to "lever" it into place. Removing the battery is MUCH easier without the scuttle in place and with a helping hand from my son, it's very easy to lift out, though I would hate to have to try it on my own  as the small of your back is going to take a fair bit of torque.

 

So far, so good. Starter cranks faster and doesn't fade away and the engine is much quicker to fire up, though no real frosts to test it with at the moment.

 

The  thought of stripping a glow plug thread scares me in a big way  .... congrats for taking the plunge.

 

http://www.tayna.co.uk/Type-110-Varta-Silver-Dynamic-F18-585-200-080-P7709.html

[rotodiesel]

Cranking speed is critical with diesel engines. Below a minimum critical cranking speed, the rate of rise of air temperature in the cylinder as it is compressed is insufficient. This means that heat lost to the cold engine block and head will be faster above a certain equilibrium point than the heat gain from compression. If the equilibrium point is below the ignition temperature - it won't fire. 

 

I would recommend anyone with a diesel car to replace the battery if the cranking speed is noticeably below normal. If you don't, you will soon be stuck on a cold morning. 

 

I also had 9 years' excellent service from the OE Varta battery. Naturally, I replaced it with another of the same make. The battery size for the 1.9 is entirely adequate (hence the life), so I fitted the same size. Access is a complete pig - Wolfsburg numpty department at its finest.

 

rotodiesel.

[CRC]

Seems like I'm going to have to bite the bullet and at least test mine, as I had to have two attempts to get mine to start yesterday (it had been freezing overnight)

The new battery has plenty of poke, and it started fine on the second attempt, but who knows how many of the glow plugs are actually still working.

 

Could you give a little more information on the wire tool you used to unhook the glow plug caps please?

 

Thanks

[dieselV6]

Coat hanger wire and pliers are all that is required, in fact in this case it was an old coat hanger that I mangled to the required shape. Hooked part goes under the bend in the glow plug cap. A little bit of spiral shape above the hook helps grip the cap when pulling it off. I'm sure the shape as well as appearance could be improved, but for the <1 minute it took to make it, I think it works perfectly. Handle needs to be curved a bit in order to access the glow plug cap closest to turbocharger without removing turbocharger intake pipe (though you do need to remove the pipe if you are replacing this glow plug). Photos below.

 

 

Note if you decide not to replace glow plugs afterwards, make sure to push all caps in fully, they should click. 

 

HTH

Edited 26 November, 2014 by dieselV6

[CRC]

That's brilliant thankyou .... just spent half an hour looking round the garage and wondering how to do it.

 

Off to find a coat hanger !!!

[CRC]

Took a while to find one of those old coat hangers, but managed it in the end.

 

It worked well on the first four I tried, but as the resistances measured to ground were infinite, infinite, 438 ohms and 1241 ohms, I figured I'd just assume they were all shot and have ordered six NGKs from GSF as they have a 25% discount code at the moment.

 

Have squirted Plusgas down into the wells and have a long, decent quality 10 mm 3/8 drive socket that fits over them fine. Also have a decent small 3/8 drive torque wrench that goes up to 35 Nm. Will wait for them to arrive, pick a "non-raining day", cross fingers, pray for guidance and, very carefully,  give it a go ..... gulp.

 

Surprised it starts as well as it does at the moment ......

 

 

Thanks again.

[dieselV6]

I guess 8 years is a long time for glow plugs, to be honest I think I will make them a consumable item from now on and replace every 4-5 years together with transmission oil. They probably will be easier to undo after 4 years as well...

 

You also need 3/8" universal joint for the glow plug closest to the intake, I tried other ways but universal joint was the only one that worked out. Best to do this one last.

 

One other thing you might want to find somewhere is the old style "analogue" torque wrench, they're cheap and show torque value as it is applied, very good in avoiding broken glow plugs (or threads). I got mine on one of my trips abroad, from Biltema in Sweden about 5 years ago, and it laid unused until this glow plug job.  I'm sure they must be selling them here as well, and cheaper than regular "click" ones.

 

The "click" torque wrenches usually only click when tightening the bolts, while undoing the bolts you can apply any torque you like (and break off the glow plug). On dial style torque wrench, you see the actual torque applied while undoing the glow plugs, the 35Nm is the manufacturer's limit for which the glow plugs are guaranteed not to break when unscrewing them. I went to 40Nm on a couple of glow plugs, but would not dare go further. For tightening the glow plugs, use the "click", or ratchet style torque wrench. Photo of the dial style wrench below.

 

 

HTH

Edited 26 November, 2014 by dieselV6

[CRC]

My 3/8 drive torque wrench is similar to that but much shorter and has an anlogue dial with a kneedle that goes round the dial to a max of 35 Nm.

 

I bought it at a boot sale for peanuts a few years ago and it's been invaluable when working on my old BMW K75, especially on the allen bolts that proliferate on the thing and have softer threads than the engine threads. I tried using a 1/2 drive torque wrench on it once, but I think they're hopelessly inaccurate at low torque settings and led to a couple of stripped threads.

 

Because this torque wrench is so short ( about 8" long ) the max 35 nm is about all you can sensibly pull with it, so it kind of limits itself, if you see what I mean.

 

Have also ordered a Laser 10 mm glow plug removal tool from fleabay for £8.46 which is a 3/8 universal joint with a 10mm hex deep socket attached to it. Possibly overkill, but I figure that having the right tools to do this job properly wiil pay dividends in the end as the cost of getting it wrong could be huge.

 

When you took your old ones out, were they the ceramic or steel type?

 

Thanks

[dieselV6]

Glow plugs on 2.5TDI are metal on all variants AFAIK. I think ceramic ones were only used on PD engines (and perhaps on the CR ones).  

 

The only difference between Beru and NGK is that NGKs are thinner tipped and warm up faster and to higher temp as a result.  

NGK quality is good, same company made good spark plugs back in my petrol days, but thinner tip might mean that they will burn out faster. Then again they should start the car better because of higher tip temperature. We'll see.

 

Good luck with the job, let us know how it went. 

[CRC]

All done ... it was a nice dry, warmish Saturday morning so I thought I'd give it a go and it was much easier than I expected.

 

On Wednesay I ordered the new glow plugs and the removal tool, tested a few and found them knackered and squirted a decent amount of Plusgas down into each hole. Drove the car a few times after that and the smell from the Plusgas was noticeable in the engine bay but not in the car. As each glow plug lives in a "well", the Plusgas all stays where its supposed to be for the best effect.

 

The photo shows the tools I used.

 

A syringe with Plusgas and a bit of 6mm silicone air line to get it to where it does most good.

 

The 3/8 Laser Tool, 3/8 extension bar and the 3/8 analogue torque wrench. The Laser tool has a nice 6 point socket so no real chance of rounding them off.

 

A 1/4 drive 10 mm deep socket with UJ and long extension bar with T handle. Possibly would have done the job but the socket is a multi point socket and I would have had to get a 1/4 to 3/8 adaptor to get onto the torque wrench.

 

Decent quality long nose pliers .... found that I could get onto the plug caps OK with these and you get a bit more wiggle and purchase.

 

Piece of 6mm silicon tube - the perfect size to push onto the plugs and pull them out or put them back in.

 

Method as follows:

 

1. Take car on 5 mile run to warm it up.

2. Remove cover and unclip a few cable ties for better access.

3. Resolve that if torque wrench needs more than 30 nm, then I'm leaving it in there and putting some Plusgas and waiting.

4. Remove 3 caps on side and Plusgas all those three plugs.

5. Start on the easiest access one first with the Laser tool and torque wrench . Starts to turn at 20 nm .... success.

6. Once thread has started to turn, use 1/4 drive T bar and 10 mm socket as it gives a much better "fingertip feel". I can feel the thread catching on small bits of grit, so only undo slightly them reverse action promote some Plusgas movement. Treat it as if you're cutting a perfect thread with a tap ..... in a bit then clear, in a bit more ...etc etc.

7. Take your time. If it feels a little rough, go slower, use some moe Plusgas etc.

8. When it comes out, remove with silicon tube, use sparse Copaslip on the new thread of the new one and start the thread using the silicon tube. Remarkable easy to start the thread with this method.

9. When tube looses grip, use 1/4 drive socket to carry on tightening ( screwing back up on occasion)  and pinch tight to finger tip pressure on the T bar.

10. Tighten to 18 nm with the 3/8 torque wrench and Laser tool.

11. Repeat 5 times, having loosened and pushed out of the way the air inlet hose on that last one.

12. Celebrate with a cup of coffee.

 

I tested the six that came out and 4 were "open circuit", 2 had resistance og hundreds of ohms, and all the new ones had resistances of 1.5 ohms.

 

Bring on those frosty mornings !!!!

[CRC]

For some reason the picture didn't attach to the previous post, so trying again.

[CRC]

and again

[dieselV6]

Glad to know it went OK. One other thing I did was to re-torque the new glow plugs after an hour long drive, 3 of them moved a tiny bit further, but to be honest they were not loose.

[oh_superb]

Excellent and useful reference for that day when I need to them all AGAIN!

Last time it turned out expensive, probably because I left it to someone else to do.

[Gaz]

I still think i'll leave mine all the time it starts - I know my luck   

 

Gaz

 

And my luck arrived at about -2c this morning 

 

My other car is in bits because the back window seized open.  Was on my way to Lydd Car Breakers this morning, but she really didn't want to start.  Took four or five attempts before she caught.

 

I think I'll book it in as I can only work outside on the drive, and it's too bloody cold at the moment.  Was -2c when I got to the scrappy and that wasn't funny.

 

I suppose it'll make sense to just be done with it and replace all six, particularly if I'm going to use the NGK ones - not that I actually know what's in there at the moment anyway.  

 

Gaz

[oh_superb]

Just be aware that someone else might rush it.. happened to me... I am definitely doing this myself next time.  It's been 5 years they have not been touched, so perhaps soon I shall tackle it.

The other thing is, perhaps your battery is weak, and the cranking speed is slow?  I noticed a big improvement in fire-ups with the new Bosch S4 battery.

[Gaz]

New battery when I bought it in Feb 2012.  I'm sure it wouldn't have been the battery I'd put on it, but it seems okay.  It spins over, fires, then doesn't catch.  I know what you mean about people rushing, and it does seem pretty straightforward.  Maybe I'll go over to GSF tomorrow, once I've put Rex back together.

 

If only the bloody howling wind and rain will stop!

 

Gaz

[CRC]

There's a BIG difference when starting on cold, frosty mornings now.

 

I would say the engine now fires on all six after about three revolutions of the engine on the starter (maybe 1-2 seconds?), and it now very rapidly settles to an even firing.

Before the plugs were done, it would take three or four times longer and would belch out a bit of smoke as the cylinders chimed in and settled. Seems to drive sweeter in that first quarter mile as well, but that might just be me.

 

Definitely worth doing ..... or at least finding out with a multimeter how many are actually working in there.

[oh_superb]

Mine is now belching smoke again and shaking for 5-7 seconds like misfiring on 1-2 cylinders.

Can someone recommend a good way to test individual glow plugs? In my experience the resistance test is unreliable. It's been 5 years since all 6 were changed for genuine Skoda MD supplied ones.

Edited 12 December, 2014 by oh_superb

[dieselV6]

Resistance test is reliable so long as you test for open circuit and not bother with exact resistance value - and if you get smoke and shakes, chances are some glow plugs are blown. I use top of injection pump as ground for ohmmeter when testing, the other lead goes to plug under test.

 

But after 5 years, glow plugs definitely light up much slower than when new, plenty of videos on youtube. Still, I'd only bother replacing all if 2 or more were blown on a V6.

[oh_superb]

I'll get under the hood tomorrow.... do some basic tests and see how many and which ones are suspect, then apply PlusGas and see if it/they budge.

If they undo OK, then off to GSF /ECP and spend some cash.

I remember the garage telling me they applied some sort of aluminium based grease on the G/P threads before fitting them, and they also re-cut/cleaned the gas sealing face in the head to ensure no carbon/ and good sealing.  I do not have such a tool, but I hope that the GPs will come out easy and will give me no headache.

[oh_superb]

Despite the horrible tooth ache, I decided to venture outside in the cold... 

Checking the glow plug resistance was easier than the impending root canal treatment! 

OK, checked 5 out 6 and all were under 1 ohm.

Only one more to check, under the compressor pipe (cyl 3?) as this was a bit inaccessible and it was getting dark.

If this one checks out ok too, then I'm baffled... I'll need to check the looms for continuity I guess.

[oh_superb]

Well, now checked the final glow plug too, and that one is ok too, so all are reading under 1 ohm.

I have also checked for continuity between all the glow plug positive terminals and terminal number 1, and again all read continuity.

I wiggled the cables around a bit to ensure that there isn't a dodgy electrical connection at this point and all seems OK.

yes, some cables you can see the bare copper as at some point they were installed through some unfriendly angles that put a lot of strain on the cable, but the continuity is still there.

One of them was very close to a grounding point on the head.  I suppose if it was genuinely grounding it would have blown the fuse.

I have, however, swapped two cable around so that the potentially dodgy one is now not going through an adverse twist/bend, but instead goes straight to the next cylinder.

 

So once again I'm at a loss as to why the machine sort of misfires on cold starts, but I'll see if anything improves, though I very much doubt it will.  I have no reason to suspect low compression on a cylinder, after all the engine has been maintained well with regular oil changes, and I also checked the injection pump timing a few months ago.  The only other thing to check would be coolant temperature sensor reading, this has previously had me over on this car.

 

The other potential problem are the ageing glow plugs, they work, but not quite the same as when they were new.  I could also try double glow plugging before cranking over.

Edited 14 December, 2014 by oh_superb