Noisy Clattery Diesel

[chrislloydie]

My diesel is very noisy and clattery for first 15 seconds then it idles nice and quietly. Only happens on first start of the day. Seems to be worse in the cold weather. Also get a bit of light smoke for few seconds.

 

Any suggestions as.to the cause?

[chrislloydie]

Its an 02 tdi 115 auto (pd) with 142k miles.

[chromedome]

Check the aux belt tensioner. If you look down at the belt you will see a white pulley/tensioner. If it's jumping about it needs changing.

 

When mine failed, early starts with the screen heaters on made it sound like a tractor. Tensioner changed and now sounds ok and tensioner not jumping about.

[viperclive]

Turn the radio up lol! That's what my other half would do.

[xavier]

takes a few seconds for oil to get circulated round the oilways and provide the necessary lubrication. I'm with clive on this one, though maybe check your oil level if you haven't already and if it's been a while since changes get one done?

[seatkid]

My diesel is very noisy and clattery for first 15 seconds then it idles nice and quietly. Only happens on first start of the day. Seems to be worse in the cold weather. Also get a bit of light smoke for few seconds.

 

Any suggestions as.to the cause?

 

One or more of your glowplugs are probably broken or not working.

[acecard]

One or more of your glowplugs are probably broken or not working.

Mine is often clattery on winter mornings. Contemplated changing glowplugs but the warning light goes out after a few seconds although taking longer in the cold - seems normal for a diesel engine, didn't think any plugs could actually be broken.

Could this happen even though the light goes out?

[seatkid]

Mine is often clattery on winter mornings. Contemplated changing glowplugs but the warning light goes out after a few seconds although taking longer in the cold - seems normal for a diesel engine, didn't think any plugs could actually be broken.

Could this happen even though the light goes out?

 

Yes

 

The light indicates you should wait before attempting to start the engine. The timing of this is controlled by the ECU and temperature sensors. The colder the engine and ambient is, the longer the light will stay on. During the time the light is on, power is applied to the 4 glowplugs, which heat to the point of glowing white hot inside the cylinder, the point is to heat the air locally and help the diesel fuel ignite properly without delay.

 

If a glowplug is faulty, (it usually goes open cicuit like a broken bulb) then that cylinder will not heat and until the engine has run for several seconds, the fuel will struggle to ignit correctly or ignite late resulting in banging/clattering/smoke etc etc.

 

The light does not indicate the glowplugs are actually working.

 

Pull the busbar off the glowplugs and test the glowplugs for continuity to the engine block with a multimeter. They should measure around 0.3 - 0.8 ohm when cold. Replace one that show high resistance or open circuit.

[acecard]

The light does not indicate the glowplugs are actually working.

Thanks seatkid - you live and learn.

Always thought that the light going off indicated that all glowplugs had successfully reached operating temp.

[chrispb123456]

The light going out is the indication that you can start the engine but doesn't mean the plugs have switched off, when the engine is cold the plugs remain active up to about a minute this is to avoid smoke excess engine noise and keep emissions as low as possible.

 

[acecard]

The light going out is the indication that you can start the engine but doesn't mean the plugs have switched off, when the engine is cold the plugs remain active up to about a minute this is to avoid smoke excess engine noise and keep emissions as low as possible.

So it would be advisable maybe to wait 30 seconds in very cold weather after swtiching on as a matter of course (assuming glowplugs are working anyway)?

[seatkid]

So it would be advisable maybe to wait 30 seconds in very cold weather after swtiching on as a matter of course (assuming glowplugs are working anyway)?

No

 

I personally feel it is a myth that the plugs stay on for a long time after the light goes out. I doubt it, its a couple of seconds maybe.

 

Its worth pointing out that the temperature sensor used to calculate glow plug time is not the same one that drives the temp gauge. A faulty temperature sensor can give too short glow plug time which affects cold starting also.

 

2 of my glowplugs failed at about 60k giving a lumpy start, now I have 125k on the clock I think maybe 1 or 2 of the other original plugs have gone as I have a lumpy start for 2 or 3 seconds again if the car is left outside on a really cold night (below zero).

[acecard]

Must admit that the expense of glowplugs deters me somewhat from changing them. I have done about 50k now so would assume they could be on the way out.

Is there much harm done by the lumpy/clattery starts?

 

But look on the bright side - with a couple of faulty spark plugs, you're dead :D - just loved to see those bright blue sparks flashing all over the engine compartment on a wet winters night - my trusty old mini you know

Edited March 13, 2013 by acecard

[seatkid]

Must admit that the expense of glowplugs deters me somewhat from changing them. I have done about 50k now so would assume they could be on the way out.

 

Expense? NGK glow plugs cost me about £7 each IIRC. Admittedly my Mk1, the glow plugs are very easy to change, IIRC MK2 glowplugs are under the rocker cover which is a bit of a nuisance... You only need change the faulty ones.....they either work or they dont

 

Dont buy cheap glowplugs (e.g. fleabay (a lot of fakes) or noname brands - they dont last long at all) stick to OEM e.g. NGK/Bosch/Beru etc from reputable suppliers (try GSF/EuroCarparts/VWspares.co.uk)

 

 

Is there much harm done by the lumpy/clattery starts?

 

Not really, just that really cold starts (e.g. -5 deg C or below) might be difficult without all the glow plugs working.

Edited March 13, 2013 by seatkid

[SilverBeast]

No

 Its worth pointing out that the temperature sensor used to calculate glow plug time is not the same one that drives the temp gauge. A faulty temperature sensor can give too short glow plug time which affects cold starting also.

 

Are you sure about this? When I replaced my faulty 2 wire temperature gauge/engine management sensor the glow plug light that always stayed on for 7-10 seconds reduced to a couple of seconds (even in the current colder weather -2C in my garage)

[seatkid]

Are you sure about this? When I replaced my faulty 2 wire temperature gauge/engine management sensor the glow plug light that always stayed on for 7-10 seconds reduced to a couple of seconds (even in the current colder weather -2C in my garage)

 

Just checked the TIS wiring diagrams.

 

Mk1 Diesels (Tdi) have a dual temp sensor - one element drives the temp guage the other feed to the ECU for engine control inc glowplugs.

 

Mk2 diesels (PD) have a single sensor to the ECU only - the temp guage is probably driven from the ECU.

 

Its also worth noting there are other temp sensors - e.g. on the MK1 there is a fuel temp sensor built into the fuel distributor pump and and air charge sensor - in the TMAP sensor and/or MAF sensor?

 

So my comment about the glow plugs relate to the MK1 Tdi.

[chrispb123456]

Just for info while having VCDS out today checked the time the glow plugs remained active from a cold start, 1 minute 10 seconds with an air temperature of 2.5 deg c

 

MK2 1.9 TDI 115ps

[chrislloydie]

Finally got round to checking my flow plugs and found three of the door to be knackered. Changed all four fairly easily, couple of scary moments when trying to undo the old ones. Lol

Will see how it starts from cold over the next few days. Hopefully a bit less smoke and diesel smell.

[chrislloydie]

Glow plugs not flow plugs.

[chrislloydie]

New glow plugs havent cured the problem unfortunately.

 

Car is also very noisy on acceleration but lovely and quiet when cruising. Also seems a little down on power.

 

Im wondering if the timing is out?

[chrislloydie]

The noise I get on acceleration is hard to describe. Its a kind of low growling noise but if you listen carefully if sounds like a knocking. Like something is bouncing around when you put your foot down. Only happens under load. Does the aux belt tensioner make this kind of noise? If its the aux belt tensioner would it be noisy all the time as mine only does it under load.