Glow plugs

Philip Chidlow · Post by **Philip Chidlow** » Sat Oct 22, 2011 12:15 pm

Recommendations for the 19 n/a diesel? Are BERU or Champion OK? And if the former, any item code? If neither, what's best? Bosch? NGK?

KevR · Post by **KevR** » Sat Oct 22, 2011 1:24 pm

NGK from www.beal.org.uk for £4.30 each + vat. Cheaper than cheapies from Ebay I think. Although I've had no problem with no-name ebay cheapies in the past, may as well have something decent at that price.
Also, I only ever change the ones that have actually failed rather than changing all of them at once. It's a waste otherwise.

Post by **Defender110** » Sat Oct 22, 2011 8:23 pm

KevR wrote: Also, I only ever change the ones that have actually failed rather than changing all of them at once. It's a waste otherwise.

I'm the opposite, I figure if one has gone then the others can't be far behind so prefer to replace all four for years more reliability.

Post by **mat_fenwick** » Sat Oct 22, 2011 8:27 pm

A little hint to making the job easier next time is to cut a little slot in the eyelets on the connecting cable - then it means you don't have to undo the nuts/washers all the way and risk dropping them...

KevR · Post by **KevR** » Sun Oct 23, 2011 10:09 am

Defender110 wrote:
KevR wrote: Also, I only ever change the ones that have actually failed rather than changing all of them at once. It's a waste otherwise.
I'm the opposite, I figure if one has gone then the others can't be far behind so prefer to replace all four for years more reliability.

Hmmn, that's like changing all the bulbs in your house because one's gone pop...

The last (single) one I changed was 20,000 miles ago and the rest are still going strong, so I'd have wasted at least 60,000 component miles if I'd changed them all at the same time!

Post by **Defender110** » Sun Oct 23, 2011 11:07 am

KevR wrote:Hmmn, that's like changing all the bulbs in your house because one's gone pop...

Do you mean you don't

I used to agree with your way of thinking and have done the same but I've also had 3 fail in quick succession (several weeks / months apart) and prefer to have the feeling my car is rarely in need of repair rather than it is in the garage every few weeks. I used to be the same with exhausts only replacing the piece with a hole but soon realised all the other sections wouldn't be far behind and it is often much easier to replace the entire exhaust than just put in one piece. So I now prefer that once I get a warning signal I use prevention rather than cure.

philhod · Post by **philhod** » Mon Oct 24, 2011 10:25 pm

I also only change them when they fail. I only use Bosch and in 25 years of diesel ownership Have only replaced 3.

If you have a bigish ammeter you can check how many amps the unit is pulling. If I remember correctly it should be pulling 32 amps, 8 per plug. IE if it's only pulling 24, one is down etc.

Post by **Defender110** » Mon Oct 24, 2011 10:57 pm

You can just measure the resistance on each plug with multimeter to see if ones failed.

KevR · Post by **KevR** » Tue Oct 25, 2011 10:03 am

Defender110 wrote:You can just measure the resistance on each plug with multimeter to see if ones failed.

Or check with a bulb - one wire to battery +, one wire to top of glow plug, If the bulb lights up, it's probably ok, if it doesn't, it's definitely knackered.

Oh, and don't forget, before measuring by whatever method, disconnect the bus-bar from all the glow plugs or you'll get a false reading (not that I would ever forget to do that. No. Not at all. Ahem.)

Dollywobbler · Post by **Dollywobbler** » Tue Oct 25, 2011 10:49 am

I must check the ones on my Mk1. With one burst, she won't start at all. With two bursts, she'll just about start but will then cut out. Give her three bursts and she'll smokily fire up. Mind you, she's not getting much use lately which doesn't help.

Post by **Defender110** » Tue Oct 25, 2011 11:52 am

philhod wrote:I also only change them when they fail. I only use Bosch and in 25 years of diesel ownership Have only replaced 3.

I'm very happy for those who have got away with this but the job of the heater plug is not just starting it is to preheat the bores to get them up to operating temperature quicker, this not only aids starting but minimises engine wear in the bores and help ensure even tick over. As with most service items they do have a limited service life and should be changed in sets. I have been a proffesional diesl fitter since 1977 and have many times come across customers who only change the plugs when their engine finally won't start one winters morning often then finding 1,2,3 or even all 4 heater plugs not working which have all failed at different times causing uneven engine wear. When you change just one this is inevitably going to be working better than the remaining 3 again causing uneven engine wear. Glow plugs don't just instantly fail they often dim down before finally failing. Comparing glow plug replacement to light bulbs in your house is pure tosh as every room in your house uses the bulbs at different times for differnt periods and hence are all have differing life spans. Heater plugs are all fitted in the factory at the same time and all do exactly the same job at the same time for the same periods. Replacing servicable items before they fail is in my book good preventative maintenance and I personally will continue to do so for piece of mind and to ensure even engine wear whilst maintaining even tickover when cold and will continue to recommend this practice as is the norm.

Way2go · Post by **Way2go** » Tue Oct 25, 2011 2:16 pm

This sounds a nice theory, but in practice the glowplug is unlikely to transfer much (if any) heat to the bores considering the mass of metal/water it would need to heat and the short time of it's operation. Especially when compared to the fast gradient heating effect of the exploding mixture. Its heat surely is just intended for the initial compressed mixture volume?

Post by **Defender110** » Tue Oct 25, 2011 2:37 pm

Not at all that is it's exact job with timers used on many to keep them on after the engine has started until the chamber is warmed up.

http://en.wikipedia.org/wiki/Glowplug

philhod · Post by **philhod** » Wed Oct 26, 2011 11:53 pm

Well I've been a mechanical maintenance engineer since 1960 Whilst I agree the glow plug or any pre heat medium does a little more than just get it to light up, It has absolute minimum effect on engine wear.
This wether it be on a BX, the 16 cylinder Submarine engines I've worked on
(the bigger ones have compressed air start) This turns the motor till it's hot enough to add fuel, with no ill effects as to wear.
Other large diesels such as power generation stand by units have 2 plugs per cylinder, but again have only changed the odd one when failed, with no adverse problems.
Just for info once an engine has started, if all systems are functioning correctly, all cylinders will be up to temperature within 25 seconds.

Dollywobbler · Post by **Dollywobbler** » Sun Dec 18, 2011 3:49 pm

New glow plugs are finally on order. Getting very tricky to start now - should have acted earlier!

However, I did wonder what sort of voltage I should expect to see at the glow plugs themselves. The car's been sitting since Monday and I was getting 10.5v at the plugs, compared to 12.4 across the battery.