Jump to content

V6 Glow Plugs


CRC

Recommended Posts

Ok, so I've got at least a couple of glow plugs not working on the old girl now ..... sub zero starts result in an easy start, but a dump of blue smoke out of the exhaust and a lumpy sounding engine for about 10 seconds, and after that everything is fine. Warm and hot starts are fine, and even when the temperature is a few degrees above zero there's no sign of any smoke.

I know how to check them with a multi meter, I'm aware that they should be changed on a hot engine with a good supply of Plus-Gas on the threads, but I'm also very aware that they can break off and leave bits in there, resulting in either an expensive head removal or, in worst case, a head replacement. The number of specialist tools for sale on EBay confirms that it seems to happen quite a lot, so I'm more than a little wary.

I'm not sure I want to do it myself and I'm a little reluctant to ask my mechanic mate to help, because nobody breaks these things on purpose, but if they do, then there's potentially a big, expensive problem, which someone has to pay for.

If I take it to a garage, I'm not sure what their view is .... if they break one, do I get the bill for the ongoing aftermath or do they cover it?

Or do I just put up with the puff of smoke?

Link to comment
Share on other sites

Look on the Beru website and you should find the maximum torque which can be applied to a glowplug body. Use a LH torque wrench to remove the plugs on a warm engine, after thorough soaking in a proper releasing agent such as Plus Gas - not WD40.

If the plug(s) will not shift at the maximum applicable torque, seriously consider leaving them alone. Breaking a plug body in the head is not a good idea. Ensure that you apply pure torque to the plug using the correct deep socket. Any bending force will make breakage more likely.

rotodiesel.

Edited by rotodiesel
Link to comment
Share on other sites

Occasional 1-cyl or even 2-cyl misfire at startup is not unusual on the 2.5, mine did it from time to time even during 1st winter from new, though it was at -12deg C and stone cold car.

I found cold starts improved a lot after I advanced basic injection timing to top of Skoda spec (which I did to cure occassional 2s+ crank-up followed by puff of fuel mist from the exhaust), this winter my 2006/116k miles Superb started on 5cyls only once, and that was in the UK at -2degC, I have been to Europe incl the Alps since and no cold start problems whatsoever.

Check the plugs first with ohmmeter (which you wanted to do anyway), see how duff they are. If there is still 1/3rd to 1/2 original current left (less than 2x to 3x resistance of a new plug), perhaps double-cycling ignition is a better idea than replacing the glow plugs or doing anything else at this point in winter.

If some plugs are blown, I'd replace them before next winter, if they are still heating at least a bit, I'd also check basic timing and advance it towards ~0.6ATDC. It's a lot cheaper, faster, and safer adjustment as long as you have access to VCDS, a flat screwdriver (to open belt cover), torque wrench, ~6mm? hex socket and about 15min of time on a warmed up engine. Fiddly adjustment but very simple, loosen 3 bolts on injection pump wheel and nudge it 1/2 tooth (that's the fiddly bit, small adjustment like this is already a degree), restart engine, recheck timing, repeat until timing is 0.6-1.0 deg ATDC (VCDS "engine" - "basic settings" tab). Hope this helps.

Link to comment
Share on other sites

Thanks for the advice. I did check that the injection timing was within spec the other day with a Vagcom device .... can't recall the exact numbers, but is was within the range.

Regarding the torque wrench, I have a nice 3/8 drive torsion bar type of torque wrench with a dial on top which is very useful when working on my old BMW bike, as most of the aluminium threads on those are very prone to stripping. The Beru site states that the maximum tightening torque for a 10 mm glow plug (which I think these are) is 15 NM, which is about 50% of the scale on my torque wrench, so tightening them correctly won't be an issue.

However, I couldn't find a "loosening" maximum torque. I guess it might be the same as the tightening torque, but I wonder if it's a bit like fitting a canister type oil filter - hand tight is fine when fitting it, but a lot more torque is needed to get it undone again?

What actually causes the problem .... is it that the plug breaks under excess torque (leaving you with nothing to grip), or that the threads strip as the plug is wound out?

Thanks again.

Link to comment
Share on other sites

Thanks for the advice. I did check that the injection timing was within spec the other day with a Vagcom device .... can't recall the exact numbers, but is was within the range.

Just to clarify, It has to be at top of range, the range Skoda quotes 0.8 - 2.8 deg ATDC, anything 1.5deg+ is way too large for this engine. Good luck faultlessly starting it above 2deg ATDC, even with top quality fuel, new glow plugs and warm weather. 2.5TDI injection timing needs to be set to 0.8-1.2deg ATDC for good cold startups.

Edited by dieselV6
Link to comment
Share on other sites

Just to add to this, my 2.5 occasionally starts like it's got blown glow plugs, though they were all changed (plus 1 cylinder head!) 3 years ago.

Then I also noticed it would run high idle (1200 rpm) on some cold starts.

I would also occasionally get a cold start message on the display something about checking service manual for coolant...

VCDS says I have a faulty coolant temperature sensor, which I will be replacing shortly.

Just mentioning this in case you might have the same problem.

My glow plugs broke off 3 years ago, they did not strip the threads. The garage recommended a new cylinder head after trying all sorts of things to extract the old ones out - including a couple of days in an engineering workshop.

Be very careful with these - they are very slender and take not much torque at all. Keeep soaking in Plus Gas or Break Free for days, and only try removing when the engine is super hot - Aluminium has a higher coefficient of thermal expansion than steel so you have the best chance of getting the plugs out. My local garage used a seat cutter to make sure that the new ones seat nicely on the conical sealing face - apparently the old ones were leaking a bit, so carbon was building up in the glow plug chamber.

Make sure you apply some anti-seize compound on the new ones too. Keep us posted and good luck!!

Link to comment
Share on other sites

Thanks for that. The thought of feeling one "go" is not something that I hope to experience.

I replaced my coolant sensor a while ago as I was getting a fault and the temperature gauge on the dash developed a mind of it's own.

The only symptoms I get at the moment are the ten seconds or so of lumpiness after starting and the cloud of blue smoke that initially fires out of the exhaust..... apart from that the car is fine ... smooth, pulls well, good mpg etc.

Think I'll leave it till the Spring, when I probably won't notice it for another nine months :)

Link to comment
Share on other sites

I also get lumpy idle now for a few seconds as the coolant sensor is sending the wrong temperature to the ECU, but the readout on the dash is OK.

This weekend when VCDS was plugged in with the engine stone cold it was showing coolant at -9 deg C and a minute later jumped to +3 deg C... that would set injection timing on cold start in the wrong region, hence that;s how I interpret the cold start lumpiness. But in your case it is probably the glow plugs....

Link to comment
Share on other sites

I checked the coolant temperature using a Scandi reader today and it was showing 4.5C prior to starting. The outside air temperature had risen to about 7.5 at that time, but there's a fair bit of thermal inertia in that big old lump I reckon. Car started fine with no smoke today ..... as it seems to do when the temperature is above freezing.

Link to comment
Share on other sites

I've just checked my pump timing too. It's on the extreme retarded point. Probably explains, at least to some extent, lumpy cold starts. So weekend job is to adjust it I guess! Never done it before. So pretty excited at the prospect of tinkering!

Edited by oh_superb
Link to comment
Share on other sites

When you say extreme, hopefully you mean +2deg - 3deg ATDC, if it is 6deg+, the belt jumped a tooth or stretched.

Worth checking timing belt tensioner setting, it is right under the injection pump belt, the marks should align.

Just make sure the engine is fully warmed up, above 85degC, and that the timing is measured using "basic settings" and not "measuring blocks", when using measuring blocks timing is retarded on purpose to reduce nox and make engine sound nicer.

Undo timing belt cover, only half needs be removed, but best to undo the lot as it is easier to take out.

Loosen the 3 bolts that mount the shorter timing belt wheel to IP drive, and rotate the pump wheel slightly, we are talking 1mm on the outside of the wheel at a time. Retighten bolts, run engine, recheck timing. Make sure to tighten bolts to correct torque afterwards.

I set mine to 0.6deg ATDC, but anything 0.6-1.2 is fine.

Other than that, be prepared to adjust 2-4 times, as I think 1 timing belt tooth worth of distance is ~4 degrees worth of adjustment.

Edited by dieselV6
Link to comment
Share on other sites

I did the check using basic settings, group 004, then timing checker. Pump timing was floating around the red line and the message read something like pump timing late. It even cut out a couple of times, though not sure exactly how I managed that. Injection sounded very advanced revs went up a bit then quietened down revs dropped started shaking and dead. I don't know if this is because its quite retarded so this disturbs some of the things it has to do. I think I might have been flicking through some if the measuring blocks when this happened but the timing check was definitely in basic settings and glow plug light was flashing. I have not actually checked the degrees of retard but I will do this before hitting the engine with the spanner. Is this something you check in basic settings block 004 too? Thanks for the advice on checking the belt timing but hopefully it will not be that extreme. The kit used was genuine Skoda and has only done 35000 miles, but you never know.

Link to comment
Share on other sites

Without starting timing checker, just look at the numbers in basic settings group 004. Second or third field lists timing in degrees with ATDC /BTDC mentioned there, at least in genuine VCDS. It is "actual timing" if there are 2 blocks listed (requested vs actual).

Make sure engine coolant temp is above 85deg C, one of adjacent groups (001-003 in Measuring Blocks?) shows it.

You can see the tensioner when you undo belt cover for adjustment, it has 2 pointy marks that need to be aligned, no extra effort needed other than looking at them.

Link to comment
Share on other sites

I adjusted the timing today, was approx 4deg ATDC, now at 0.7 ATDC (fluctuating at 0.6-0.8). Do you have the torque for the 3x bolts on the right hand sprocket? The engine now sounds crisper at idle.

Link to comment
Share on other sites

Just a point to those planning to do this: 1 deg crank angle corresponds to 0.6mm on the outer dia of the inj pump wheel. A temporary mark on masking tape stuck on wheel and a mark on timing cover lined up initially and used as reference for each adjustment in my case worked well but there are alternative approaches. If you do it this way make sure you remove the tape before restarting the engine. In my case I needed 4 deg of advance which was approximately 2.5 mm, but the fine adjustments were a bit trickier, the final one requiring 0.25mm, which was the thickness of the pen mark itself on the tape! Good fun though, thoroughly enjoyed it. Tensioner marks were good.

Edited by oh_superb
Link to comment
Share on other sites

I am glad you had it sorted, sorry do not remember the torque, but ?25Nm? or similar rings a bell. Hopefully cold starts improve.

Re fine adjustments, yes, as I said it's a fiddly job, though easy enough.

Link to comment
Share on other sites

I've found a guide that specifies 22Nm so I'll do a check in not too distant future.

Not only are the cold starts miles better, but the fuel consumption on the commute to work has reduced by an unbelievable 15-20% according to the onboard computer. On the 8 mile journey to work used to do 32-33 mpg, now 38-39. Back home (100m drop in altitude) was 37-38 now 41-42mpg. At the 1st mile point in the morning used to show 19-20mpg journey average, now 24-25. The only thing that's changed is that previous tank was Shell now on Asda fuel but doubt that would have made it any better as I have previously run it on all sorts of brands throughout the winter and the mpg numbers were quite consistent. Just before I set the injection timing to 0.6atdc I went on a slow motorway run (90 mile round trip) due to heavy traffic but in 5th gear most if the time (tiptronic) and averaged an unbelievable 54mpg, and that was running 4 degrees more retarded. It might get even better now, though not sure if the IP will correct back to reference timing when cruising or whether the timing will now be truly more advanced than before. But considering my post-adjustment mpg improvements it seems that it does run more advanced. I hope my summertime engine starts improve now too. It did require long cranking when left in the sun all day as glowplugs were inactive and timing was too late to fire easily just on compression with no extra heat in the combustion chamber. All I can add to this now is that those folk who have the v6 lump and access to vcds to check their timing and advance to 0.6 deg ATDC as the engine loves it. It's easy enough to do.

Edited by oh_superb
Link to comment
Share on other sites

Hmmm ... might have another look at my timing settings.

Figure they must be about right as my mpg is so good. I regularly do a 25 mile trip on good A roads to a hilltop town (though the speed can vary due to lorries, tractors etc) and I always get 44-46 going there and about 52 coming back (we're quite a bit lower.) If I'm really in economy mode, coast down hills (it's a manual) and use the very lightest of pedals, the best I've ever seen is around 60 coming back home, but that's normally in the summer and takes abit of achieving in the winter.

Just for the hell of it, I bought some Millers Ecomax additive "snake oil" the other day and added it at the rate of 1 ml per litre, and I'm not seeing any improvement in mpg, but the engine really seems to like it on cold starts, seems to run smoother than normal (especially early on when cold) and the power seems crisper off turbo and less of a "step" as the turbo comes in.

Maybe it's just the placebo effect coming in here, but I can see why people talk well of the stuff ......

Having never owned a diesel engine before, it seems strange to talk about timing AFTER TDC. Presumably you squirt the fuel in just slightly after TDC where the compressed air temperature has just achieved maximum and the piston has just about started it's downward stroke?

Link to comment
Share on other sites

Basic timing is timing setting when engine is idling, at minimum amount of fuel injected. Think of it as a zero/reference position for injection pump. For larger fuel amounts and/or larger rpm, the pump advances the timing by means of an electrical solenoid, so that the fuel burns at optimum point in the stroke. But it can only advance the timing so much, so if basic timing is delayed too much, there will be a small impact on mpg. At the same time, on startup basic timing is used, less delayed timing allows for the fuel to warm up more and hopefully start burning in the cylinders while still close to TDC.

Note moving the timing past 0deg towards BTDC dramatically raises peak cylinder pressure and temperature and is not recommended, especially on startup, on a cold engine. Plus the engine will sound like a tractor. 0.6-1.2deg ATDC is just fine.

Edited by dieselV6
Link to comment
Share on other sites

  • 3 years later...

When setting the injection pump timing should the fuel pump sprocket be held stationary whilst adjusting the position of the sprocket mounted on the on the camshaft? Can the camshaft-mounted sprocket be moved by hand or are other methods needed? Not had to adjust timing this way before so some advice would be much appreciated. Thanks in advance.

Link to comment
Share on other sites

Pump sprocket should not be locked, it will move slightly during adjustment. Moving camshaf sprocket by hand is quite tough but possible, a lever that can work on sprocket spokes is much easier to use for this.

Edited by dieselV6
Link to comment
Share on other sites

Thanks dieselV6, I had read a guide to doing this (I think it was in the vcds forum on briskoda) which seemed to recommend using something to hold the pump in place whilst moving the pulley on the camshaft but I couldn't work out how that would change the timing... Thanks for making it clear, looks like a job for Sunday.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Community Partner

×
×
  • Create New...

Important Information

Welcome to BRISKODA. Please note the following important links Terms of Use. We have a comprehensive Privacy Policy. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.