Glowplug replacement - any tips?

[Hibbo]

Hi,
This weekend I will be replacing the glowplugs on my 300D, does anyone have any advice before I crack on? I have heard horror stories about them snapping, but that does seem to be more on newer cars.

I was thinking of soaking them with plenty off penetrating oil and change them when the engine is hot. Sound reasonable? If they do seem a bit tight, am I best to persaude them with a geet big bar, or by hitting a smaller one? Which is least likely to snap them?

Whilst they're out I think I'll do the valve clearances (as I'll be able to turn the engine easily) and replace the rocker cover gasket. Might even steam clean the engine bay too! Actually, I might try and do the injection timing first - expect some questions over the weekend!

 

[Mikesmerc]

Why are you changing them, blown??. Would soak em first, can only help. I think you have to spill time the pump, and you will need a spout pipe thingy to srew on to no1 pump outlet( after removing the nrv).
Mike

 

[Hibbo]

Cheers for the reply Mike,

I've not individually checked them, but they're definately not all working as it struggles to start. The light doesn't come on (but power is applied to them - the only check i've done), but if it starts then dies after a few secs, the light then comes on next time you try.

I've not got the spout thingy that's shown in the haynesie, but I think I have seen gash ways of doing it where you crack no1 injector union and use the primer pump. Will have a good scan round t'internet.

 

[Parrot of Doom]

Get some Loctite Freeze Release spray:

http://cgi.ebay.co.uk/Loctite-FREEZ...ryZ30928QQrdZ1QQssPageNameZWD1VQQcmdZViewItem

Go easy on them. If they snap, you're in trouble. Some people have drilled out the old bits when this has happened, then reamed the threads, turned the engine over for a few seconds to blast any debris out, and then put the new plugs in.

I believe its very important to ream the threads once each plug is out. Its not a job I've done so I can't say.

Worth investigating using an anti-sieze compound as well. Some people even pull them out every year, just to stop them from siezing.

 

[Mikesmerc]

I remember testing the plugs on my old 200D years ago with a live wire from the + pole of the battery and tipping it off the threaded connection for a second(after the live to the plug was disconnected) to see if there is a healthy spark there, this was to confirm if there was a strong circuit through the plug, if a very weak spark or none at all usually meant that the internal resistor coil in the plug had broken down. Warning. These heat up very quickly using this method and you could end up blowing the plug.
These were the days before I knew anything about multi meters and Im not much better now.
Mike

 

[Hibbo]

Thanks for the advice so far,

I will certainly cover the plugs with penetrating oil a few times, and do them with the engine hot. Would blasting them with a blowlamp be of any benefit?

I don't have a reamer, but I may clean the holes out with a solvent soaked rag, but am weary of knocking any crap into the cylinders. Any thoughts?

When I fit the new ones I am thinking of covering the threads with high temperature graphite grease anti-seize compound, is this a good idea? I have heard that it is an idea to overtorque the new ones, as this contradictually (is that a word?) stops the getting seized in. The thinking is that what causes the seizing is carbon and crap getting blown into the threads - grollying them in prevents this. Again any thoughts? (I don't have a torque wrench anyway, so it'll be calibrated white knuckles)


As for the IP timing, I think I am going to use the method where you disconnect the injector pipe from the pump, turn the engine and watch for the fuel welling up. I don't like the drip method as I'm not to keen on removing the element from the IP.

I've also read a good thread on an American site about using the glowplugs as thermocouples and dynamically setting the IP timing to give the highest cylinder temperatures. Very interesting, if I have any joy I will do a good write up on it.

Thanks again to everyone who's replied, and I really would appreciate any other comments.

 

[anyweb]

please document how you do this much like parrot of dooms howtos,

it would help countless others, (take photos !!)

good luck !

cheers
anyweb

 

[Ian B Walker]

Rather than soak in penetrating fluid try Coca Cola. It works wonders. (No this is not a stitch up either )

 

[Parrot of Doom]

I don't have a reamer, but I may clean the holes out with a solvent soaked rag, but am weary of knocking any crap into the cylinders. Any thoughts?

Its only carbon, and possible tiny metal shavings. Its not going to damage anything unless you drop a nut or bolt down there.

I have a mate who has changed thousands of spark plugs, sometimes they break and the porcelain bits fall inside. Hes never had any engine damage, they just spit it all back out.

The best way to stop the plugs siezing up is to remove and re-insert them at regular intervals.

 

[Mikesmerc]

"As for the IP timing, I think I am going to use the method where you disconnect the injector pipe from the pump, turn the engine and watch for the fuel welling up. I don't like the drip method as I'm not to keen on removing the element from the IP."


Removing the union from the pump is very easy, just undo the locking clamp from the union, unscrew the union carefully, remove little spring and plunger from inside the union, replace the union and screw the spout pipe on.
Mike

 

[wireman]

Use copaslip type anti sieze grease on the threads and tighten them to no more than the maximum specified. Any more torque and you will be asking for trouble.

 

[Hibbo]

Right then,
I attacked the glowplugs last weekend. I checked them with a multimeter and sure enough two had failed.
After soaking the plugs three times with a good penetrating oil, once with fat coke and running the engine till it was fully warmed through, I got a socket on the first one, tunrned the ratchet, and - it came out easy!
They all came out easyish, didn't have to force any of them. The inner of one of them had seperated so I couldn't get the nut off to undo the cable, so I just cut the wire and reterminated it. A couple of them where a bit awkward, especially as I didn't have a 12mm spanner, had to use an adjustable on one of them - shocking practice!

I couldn't really get to the holes to clean them out, so I what I did was cover the new plugs' threads in anti sieze grease (loads of it) screw them in finger tight, then remove them and clean them off, apply a smear of anti-sieze (Rocol high temperature stuff) and screw them in properly. No torque wrench, but didn't go mad.

Turned the key, glowplug lamp behaves as normal.


The car then sat till Tuesday morning, started ok but not as good as I would've liked, did a 170 miles round trip, car was faultless.

Came to start the car last (Thurs) night, glowplug lamp behaves normally, engine doesn't start. Not a splutter. Nothing. Turns and turns and turns. I first thought air in the fuel lines, although I've never had that problem before. Cracked the return line banjo union on top of the fuel filter housing and cranked the engine, air free fuel spurted out, no bubbles in the translucent lines either. Took a HP fuel line off the IP, cranked the engine and fuel spouted forth. (I had a horrible feeling that my IP was dead!) Thank folk! I was now at a loss. Even checked that the cam was turning (it was).

After speaking to a mate he said 'Old iDI engine, may not have the best compression any more, needs good preheating, have you checked your glowplugs'. 'Just replaced them' I say, 'Have you checked your glowplugs' he says. 'I've just ****** changed them!' I say. I won't continue but you can see how the conversation went.

I then checked my glowplugs.

All five where fecked!

All five of my new glowplugs where open-circuit after no more than half a dozen starts and 170 miles. I could not believe it.

I dug out the three old plugs that where still working, fitted them and the car then chugged into life as it had been doing before.

The plugs where bought from an ebay seller called "the.portland.group", the transaction was carried out outwith ebay as he was listing them as sets of four and I wanted 5. He didn't actually say if they were branded of not, but gave a Beru part number. Very clever. They where completely unbranded.
I will be sending him a nice email and searching for some reasonably priced Bosch duratherms.

Still can't believe it!

 

[Parrot of Doom]

Get thee off to the nearest Merc dealer, and buy some of theirs.

I have a couple of plugs downstairs if you want to buy them, they're made by Beru and the part number is 0 100 226 235 GN 948

They're for my engine, I don't know if they'll be suitable for yours. Probably not.

 

[Hibbo]

Lovely new Bosch Duraterms

I have just fitted five new Bosch Duraterms, and the engine starts and runs great from stone cold. Only took me half an hour to change them as I'd had the practice (and the right tools this time!)

I got them from these guys http://www.helptoday.co.uk/ have a look on their special offer page.
Five Duraterms for 23-odd-quid (inc vat & delivery) Excellent! Highly recommended - both the plug and the supplier.

Just got to take that rear screen out and do me some welding...

 

[IAN MAC]

When you check the plugs, what readings are you looking for on the meter.
I've got the meter just dont use it for anything but voltage.

Cheers

Ian

 

[Parrot of Doom]

I would imagine a high resistance - measured with the plug disconnected.

 

[Lacy]

When you check the plugs, what readings are you looking for on the meter.
I've got the meter just dont use it for anything but voltage.

Cheers

Ian

Use a meter on low resistance setting (0-200 ohms or similar). Connect one prong to the heater case ( or good earth) and the other prong to the plug terminal. The needle should swing across (or if a digital meter show a very low resistance) if good. If the needle doesn't move or resistance stays at infinity, it's goosed.

 

[Parrot of Doom]

Ah apologies, I thought he meant 'glowplug working'

Whats the wattage of your average glowplug?

 

[Blobcat]

http://www.mavericktechnology.co.uk...cktechnology.co.uk/pico_advanced_glowplug.htm

 

[IAN MAC]

Thanx folks, be doing that later on today.