BMC 1.5L Glow Plugs

[jacksonp_uk]

Hi

 

Anyone know a way to remove the tip of a glow plug that has sheared off when unscrewing the glow plug please? BMC 1.5L Diesel engine.

 

thanx

 

Paul Jackson

Edited March 4, 2007 by jacksonp_uk

[Keeping Up]

I know this is a common problem.

 

If there's any thread left you may be able to use a stud extractor, but it's more common for them to shear just below the thread.

 

The usual answer is that you have to take the head off, but I've been told by a well-respected boatyard engineer that if you're brave enough you can sometimes blow them out just by starting the engine (and stand well clear !!!!!!!)

 

I take NO responsibility for the consequences.

[David Schweizer]

Hi

 

Anyone know a way to remove the tip of a glow plug that has sheared off when unscrewing the glow plug please? BMC 1.5L Diesel engine.

 

thanx

 

Paul Jackson

This is a common experience with the BMC 1.5 I did exactly the same thing to the engine in my boat. I was told by one engineer that it is possible to drill the tip out. Apparently it is actually a narrow tube made of very thin material inside which is a ceramic core carrying a fine filament, and offers little resistamnce to a sharp drill. Once drilled out you crank the engine and hopefoully blow the bits out. Needless to say I did not try it, and sucessfully managed to continue starting the engine for the next eight years on only three glow plugs. The engine was completely re-built last year and the broken tip was removed, however since the re-build I have noticed little improvement in starting the engine from cold. Moral - Leave the old tip in with the broken plug screwed into the head to seal it and don't worry about it unless starting becomes a real problem.

 

As a matter of interest the best way to remove the glowplugs from a BMC 1.5, and avoid breaking the tip, is to unscrew it about 1/12th of a turn and re-tighten , then unscrew 1/6th of a turn and re-tighten. Continue this appraoch at 1/12th intervals until the plug feels free, this process breaks up the carbon deposit which virtually glues the plug tip into the head.. Once out the hole should be reamed out with a 11/64 long shank drill, these are quite difficult to find and most people settle for 4mm long shank drill which is available from places like Screwfix.

Edited March 5, 2007 by David Schweizer

[jacksonp_uk]

This is a common experience with the BMC 1.5 I did exactly the same thing to the engine in my boat. I was told by one engineer that it is possible to drill the tip out. Apparently it is actually a narrow tube made of very thin material inside which is a ceramic core carrying a fine filament, and offers little resistamnce to a sharp drill. Once drilled out you crank the engine and hopefoully blow the bits out. Needless to say I did not try it, and sucessfully managed to continue starting the engine for the next eight years on only three glow plugs. The engine was completely re-built last year and the broken tip was removed, however since the re-build I have noticed little improvement in starting the engine from cold. Moral - Leave the old tip in with the broken plug screwed into the head to seal it and don't worry about it unless starting becomes a real problem.

 

As a matter of interest the best way to remove the glowplugs from a BMC 1.5, and avoid breaking the tip, is to unscrew it about 1/12th of a turn and re-tighten , then unscrew 1/6th of a turn and re-tighten. Continue this appraoch at 1/12th intervals until the plug feels free, this process breaks up the carbon deposit which virtually glues the plug tip into the head.. Once out the hole should be reamed out with a 11/64 long shank drill, these are quite difficult to find and most people settle for 4mm long shank drill which is available from places like Screwfix.

 

Thanks David for your useful and detailed advice.

 

Paul J

[Bitwobbly]

In a couple of weeks I will be changing all four heater plugs.

I don't quite understand, or I've missed something very obvious, if the plugs come out ok then there's no need for the drill?

Is the drilling to remove the tip if it snaps off?

 

Dave

[Serendipity]

In a couple of weeks I will be changing all four heater plugs.

I don't quite understand, or I've missed something very obvious, if the plugs come out ok then there's no need for the drill?

Is the drilling to remove the tip if it snaps off?

 

Dave

 

Hi Dave,

 

The drill is to ream out the carbon that will have accumulated in the space inbetween the glow plug 'needle', and the chamber it is in.

[John Orentas]

Hi Dave,

 

The drill is to ream out the carbon that will have accumulated in the space inbetween the glow plug 'needle', and the chamber it is in.

 

 

 

It is a complete waste of money changing fully functioning glow plugs, if they are taking a current they are OK, they don't even degrade with age.

[Bitwobbly]

Thanks for that John, much appreciated advice.

Two heaters have failed, may as well change all four.

Mind you engine not fitted with a thermostat either so doing that at the same time. ho hum happy days.

 

Dave

[Serendipity]

Thanks for that John, much appreciated advice.

Two heaters have failed, may as well change all four.

Mind you engine not fitted with a thermostat either so doing that at the same time. ho hum happy days.

 

Dave

 

I reamed out the carbon two months ago and improved starting enormously, but it's back to difficult starting again. Because i've suspected for a while that there has been either a stuck open stat, or none at all, only yesterday I actually got round to checking it out. Found there was no thermostat, replaced it and now running at 85c instead of 50, so should hopefully keep things a little cleaner. I just hope the stat wasn't removed originally because of overheating problems.

[jacksonp_uk]

Hi

 

Have now got the engine with the sheared plug installed and running. Started very easily with only 3 plugs working...phew. Will have a go at removal when I get time in future.

 

cheers

 

Paul Jackson

[Speedwell]

This is a common experience with the BMC 1.5 ....

Thanks David - Very useful information. I've taken a copy to add to my workshop manual in case I have trouble in the future.

Arthur

[Bones]

Do glow plugs ever leak diesel?

 

ah ha! I have answered my own question. They do... that means the seal must need replacing? Is it easy... and what do I need to know before I take them apart?

Edited May 22, 2008 by Bones

[alan_fincher]

Do glow plugs ever leak diesel?

 

ah ha! I have answered my own question. They do... that means the seal must need replacing? Is it easy... and what do I need to know before I take them apart?

See your other thread, but the answer is no.

 

They have to form a seal that can withstand the enormous compression of a running engine, (cylinder contents compressed down to well under a twentieth of their original volume), and if they are a close enough fit for that, no diesel will get past them.

 

Anyway what diesel is in the cylinders is a fine "mist" from the injectors, there is not lots of it in liquid form looking for a way to try and escape!

 

If people are worried whether their glow plugs are working or not, you can disconnect the wire(s) linking them all together, and try just one at a time through an ammeter. All should, of course, draw a similar current.

 

Must admit I've never checked all ours work, because it starts every time, (famous last words! )

[RobinJ]

It is a complete waste of money changing fully functioning glow plugs, if they are taking a current they are OK, they don't even degrade with age.

However, if you periodically remove and clean both the heater plug and the hole, then they will last longer and not shear off when they do fail!

All these problems are caused by build up of carbon deposits in the combustion chamber and arround the heater plug leading to hot spots on the heater plug and them sticking in the hole!

[LEO]

Hi,

 

I had this problem, found it easiest to remove the cylinder head and replace all 4 glow plugs. It's pretty easy to remove a BMC 1.5 cylinder head.

 

You need a special spanner to tighten / re-tighten the 4 cylinder head nuts under the rocker shaft and it's worth getting the head skimmed before re-fitting it. You will also need a new gasket set.

 

I have a redundant 'head nut' spanner PM me for details, it's about £20.

 

Hope that helps.

 

Albi

[dr pepper]

You can also 'make' one of these crows foot spanners by welding an 11/16 ring end spanner to a scrap socket, most garages will do this for the price of a pint.

[JohnP]

Hi,

 

I had this problem, found it easiest to remove the cylinder head and replace all 4 glow plugs. It's pretty easy to remove a BMC 1.5 cylinder head.

 

You need a special spanner to tighten / re-tighten the 4 cylinder head nuts under the rocker shaft and it's worth getting the head skimmed before re-fitting it. You will also need a new gasket set.

 

I have a redundant 'head nut' spanner PM me for details, it's about £20.

 

Hope that helps.

 

Albi

 

Hi Do you still have the special 11/16" crows foot head spanner? Is it an original or one that has been made up ? I am interested in buying it but depends on price!

Regards

JohnP

[OptedOut]

You need a special spanner to tighten / re-tighten the 4 cylinder head nuts under the rocker shaft

 

I seem to remember it's easier to unbolt the rocker assembly and work with a normal torque wrench/socket etc, or am I thinking of another engine?

[LEO]

I seem to remember it's easier to unbolt the rocker assembly and work with a normal torque wrench/socket etc, or am I thinking of another engine?

Hi,

 

I have since changed engines, I seem to remember the re-assembly process was much easier with the special spanner, which were originally supplied as special tools by BMC. I was contacted by a boat owner in Spain who had a BMC ( and read CWDF) who bought my spanner for Eu30. So it's happily tightening 'nuts' in Spain.

 

Gardners, (which now demand my attention) need a similar special spanner for tightening several head nuts under the rocker shaft.

 

There was another thread on this subject that suggested several ways to tighten the head down without a special spanner but indicated there was good chance of distorting the rocker shaft if the proposed method was carried out by anyone without 'above average' fitting skills.

 

Hope that helps..

 

Leo.

[OptedOut]

I used the shaft off method as I only had a socket set plus some odd tools.

I was a Fitter/Turner in another life.