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BMC 2.52 litre Glow Plugs


Guest JohnT

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Hi

having recently serviced the engine on 'Lady' which is a BMC Tempest Commander 2.52, I had arrived armed with a 4.3mm drill bit to clean the glow plug holes(as per the manual).

Having removed the plugs carefully, out a half turn in a quarter turn, etc until fully screwed out. I did have a couple of tightish ones that had carbon on the heater elements, at the end of the threads I had to use an open ended spanner (under the shank where the hexagon is)to use as a lever to apply pressure while I worked the remaining length out. I of course in the process dropped one into the bilge! When I had them all out I noted the type Lucas HDS 265.

When I tried the drill bit it rattled around in the hole! (no comments please) so I measured the heater element with a vernier caliper and was surprised to see they were 4.8mm ah, it must be the later engine with the bigger heater element which although mentioned on the ASAP parts site I have not found reference in any of the manuals I have sighted.

I would guess that a 4.9- 5.0mm drill would do the job in this case but of course i did not have that size with me!

A search of the tool box did supply a good quality cross head screwdiver (not chrome plated) of 5mm, it made an ideal reaming tool to clean out the holes with some grease in the slots to catch the carbon (withdraw and clean, re-apply grease regularly). Worked a treat.

For reference the engine was fitted new in the boat in 1980, so I would guess the engine is 1979/80 prodution model. The plugs to my knowledge had not been removed and cleaned for at least two years (200hours).

I did get a quote from a mobile service engineer to carry out a full service, they quoted £140 and I supplied the parts other than the oil (allready had them) I enquired what this included and was told - engine and gearbox oil change, oil and fuel filter change, and a general check over. It did not include doing the glow plugs or the tappets nor checking or changing the impeller!! nice work if you can get it! How many peolple think these things have been done at service?

Anyway I hope the above helps you and encourages you to service your plugs or get someone else to do them.

The more carboned up they get, especially around the hole into the combustion chamber the less effecient they are and the harder to start your engine becomes.

cheers

JohnT

:Stinky

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Hi John

We had a lot of starting problems last year on our BMC1.5. Sometimes I would have to heat and crank 4 or 5 times, occasionaly meaning I had to jump the starter battery from the domestics.

Darren at DRL Marine lent me his reaming tool (drill bit brazed to a brass rod). I had never done this before, so I proceeded with caution taking the plugs out. They all came out fine with a bit of squeaking. I tested them all, and all worked ok too. Reamed the holes, popped the plugs back in and hey-presto, instant starting.

She sat idle from end of November until a couple of weeks ago, when I heated her for 30 seconds and she started after about 3-4 seconds of cranking on all cylinders. Not bad for a 30 year old engine and I saved myself a good lump of cash by the sound of it too! :wave

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Been wanting to do this for months now (on our BMC1500).

Currently, I have been frightened off by warnings of an apparent (reported) danger of the tip of the glow plugs breaking off and falling into the cylinders when disturbed after years of neglect.

My dilemma is that I have no idea when they were last removed (and we have owned Ella for 8 years now).

I won't be touching them until I stand ready to take the cylinder head off if the worst happens.

Am I being too cautious?

Steve

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Been wanting to do this for months now (on our BMC1500).

Currently, I have been frightened off by warnings of an apparent (reported) danger of the tip of the glow plugs breaking off and falling into the cylinders when disturbed after years of neglect.

My dilemma is that I have no idea when they were last removed (and we have owned Ella for 8 years now).

I won't be touching them until I stand ready to take the cylinder head off if the worst happens.

Am I being too cautious?

Steve

Hi Steve

I can understand your consternation, a few precautions should help ease the way though. A few sprays of the threads with pro gas or at least wd40 preferably a few days before you plan to remove. Run the engine to get it warm not hot! (expands everything a bit giving more clearance) and remember half a turn out then quarter of a turn in, and if things start getting really tight take it to the professionals.

Good Luck

JohnT

:Stinky

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Thanks John,

I think that I'll regularly apply a tiny bit of Plus Gas throughout the season where the glow plug bodies meet the cylinder head and wait until the end of the season to try and remove them.

(nothing like hedging your bets) :)

cheers,

Steve

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Hi Steve

I had no idea when our plugs were last out either. I decided just to go for it as starting was becoming a real issue, and it really wasn't a problem. A couple of them sqeaked a bit, but I just took my time and eased them out. One of them still had to be encouraged after the threads were clear of the head due to the carbon build up. The only problem I had was having to loosen one of the fuel feed pipes as it was right in the way.

I have heard that if the tip of a plug does break, the easiest way to remove it is to crank the engine and hopefully the broken part will get blown out of it's hole. I can't say I'm too keen on trying that though! :o

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Hi Mark,

It does work but not every time. I have used the method with success and have also removed the head to send away.

bearing in mind we do ours every year I think there is an element of luck involved but the chances of breakage are very slim.

When you check the heaters make sure they glow at the end and not in the middle, also dont burn your fingers ;)

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Hi all,

Thanks for the advice.

I don't know what these glow plugs look like when withdrawn (a picture would be appreciated if you have one).

I imagine that the danger time is when the plug is clear of the thread but still supported within carbon build up around the element (so I'll be extra careful to keep it square until it's fully out of the head).

All the best,

Steve

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Hi Steve

Heres a little picc of a typical plug

post-264-136713493527_thumb.jpg.

The long sticky-out bit is a metal tube with a ceramic core which glows red hot during heating. If this is encrusted with carbon, the air inside the combustion chamber can't heat up and therefore starting becomes a problem.

The unscrew-retighten method described by JohnT helps reduce the risk of breakage by loosening the carbon deposits, but any breakage normally occurs just below the threads.

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Hi

the photos below show the plug mainly used in BMC 1500 1800 2.5 although some use one with a thicker heater element(see my original post) note how narrow it is at the heater element and hence how easy it could be to snap it off.

The other photo might help to undersatnd how they work.

cheersbar

JohnT

:Stinky

post-148-136713494226_thumb.jpg1193x280[ekm][1].jpg]

post-148-136713494238_thumb.jpg.jpg]

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  • 2 years later...

Hi i have a question on the glowplugs i have the old champion ch50 in my old girl can anyone tell me the equivalant or are the bmc 1.5 same for the bmc commander 2.52 1970's/1980

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Not as daft as it appears! I suspect I need some form of remote fitting using hose.

Trevor

http://www.normanboats.co.uk

You may well find they have a throat adaptor in the range Trevor, so maybe no need to go down that route. If you do have to fit a remote one the finding the trunking to match the throat should be a simple matter.

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  • 8 years later...

I have found this thread very useful in searching for replacement plugs. I found the old (now obsolete) Champion AG50 fitted To my BMC 2.52. Latterly called CH50, I found the spec for these as follows:

overall length:100.5mm

thread size: M10x1.0mm

heater length: 31.7mm

heater diameter: 4.9mm

hex size:16mm

terminal:M4x0.7

voltage: 11.5v

The conclusions I could make from this were that the 4.37mm drill bit recommended by the manual to ream out the carbon in the heater tube would be too small, as mentioned above, and when I tested this on one plug tube I found I was removing only carbon (no metal) when using a 5.5mm drill bit. 
On searching for a suitable replacement, sure enough the Delphi HDS265 has the same spec as the CH50, but also appears to be obsolete. I have ordered some from a Delphi shop online and will check them against the AG50s when they arrive. Also in anticipation of the ongoing need I have identified a current type which appears to be broadly similar to the CH50, the CH185  or the NGK Y-503J. They has a slightly shorter heater (but not a short at the CH32) and a smaller hex size, but  otherwise could well be an ongoing possibility. I have also ordered some, after they arrive I intend to check and compare. If they are suitable I will test the NGKs on the engine.  Has anyone else found current suitable alternatives?

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And an update on my last:

The online shop I used to order the HDS265 plugs cancelled the order and refunded it because the HDS265 is obsolete and they cannot source them any more. So its either CH32/HDS227/Bosch 0250200035/NGK Y-302 (which are also obsolete, not quite the right size - and the price is rising) or finding a suitable alternative.

IMG_0537.jpeg

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Thank you I hoped that would be the case, I will feel more confident when I try the newer alternative I have identified, as the thread is the same spec M10x1.00 and the heater is longer than the CH32 and shorter than the AG50.

The glow plugs are in a swirl chamber (see the cross section below), the possible replacement is used in older European cars like Peugeots and Fiat and the Citroen AX and Saxo.  The only catch is that the distance between the shoulder (at the top of the heater) and the start of the threads on the AG50 is 19mm and on the NGK Y-503J it is 23mm, this means that 4 threads fewer will be holding the glow plug in place (probably leaving about 6 or 7 threads holding it instead of 10).  I have calculated assuming a peak cylinder pressure of 1000PSI and heater tube diameter of 5.5mm (sorry to mix units) that the maximum force pushing the glow plug out is just 17kg, again assuming the head is cast steel and not aluminium, I believe that 6 threads holding the plug in will be enough to withstand the force.

On another note, I have found that the dimensions of the KLG GS103L plug (which was recommended in the manual alongside the Champion AG50) is similar to the Champion CH32/CH39, so my conclusions are as follows:

1. There is no availability of Champion AG50 replacements.

For reference Champion AG50 cross comparisons are:

Champion CH50 - obsolete

Delphi HDS265 - obsolete

Durite 0-130-50 - obsolete

2. The other recommended glow plug in the engine manual is KLG GS103L. This plug has a shorter thinner heater and cross compares as follows:

Champion CH32 - Obsolete

Champion AG39 - Obsolete

Beru GV112

Bosch 0 250 200 035

Delphi HDS227 - Obsolete

NGK Y-302 - obsolete

E200PE

The down side with these appears to be the fragility of the heater (being only approx 3.5mm diameter - compared with the AG50 of 4.9mm), but they are more available and appear to have been fitted to the Morris Marina and Leyland 154 tractor.

 

I am going to try the NGK Y-503J once they arrive, mainly because I would prefer to have the bigger diameter heater to reduce the risk of the heater breaking during extraction in the future, and having a slightly longer heater it might also improve starting performance (my hope is to reduce smoke emissions which occur for a short while immediately after starting from cold).

These NGK Y-503J cross refer as follows:

Beru GN912

Bosch 0 250 202 020

Champion CH168

Champion CH185

Lucas HDS350

 

I have gleaned all this information from various online sources (except for the details about the AG50 plugs fitted to my engine which are first hand information). I hope this is helpful to others, but if not I should be able to refer back to it in years to come in case I forget it all :-)

 

 

1481512705_Screenshot2019-12-09at12_36_41.png.b2406fbf3d8b48a66671d71defbb7624.png

Screenshot 2019-12-09 at 12.36.41.png

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