Hi,
I've had starting problems when the weather has been cold, so I thought it best to change the Glow Plugs. The problem is that I've changed all 3 except the one nearest the clutch. It will not come out of the hole. It unscrews until most of the thread is showing, but will not come out even if I pull on it with pliers. I've screwed it back in for now.
Silly question, any ideas why it will not completely come out of the hole and what can I do?
Thanks
Paul
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Im surprised you can get it out so you can see threads but nothing then happens. In one sense this is OK as at least it is not really stuck in. The key is not to do damage to the threads or head.
I would ondo it until the threads show and then soak it in Plusgas. Be patient. Don't rush it. Soak it every 2 hours over a day, and then try again.
Did you put copper grease on the new plug threads?
Edited by MW on 27/03/2008 at 16:39
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Thanks MW.
It is odd I can see the thread, but cannot pull it out. I will try plusgas: is that better than WD40?
No I didn't use copper grease on the new plugs I put in. Should I take them out and grease them?
Paul
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I will try plusgas: is that better than WD40?
Loads better. The former is a true penetrating fluid, the latter just pretends to be.
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>>any ideas why it will not completely come out
The tip will either have expanded up if the plug has overheated, or will just be covered in carbon. Keep trying to get it out as per MW's suggestion.
Don't even dream of starting the car with the glow plug threads out - the plug will fire out like a bullet! Very dangerous!
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Thanks Number_Cruncher.
I had wondered if it has expanded, but had not thought of carbon. The state of the three I took out was: 1 - little carbon, 2 - more carbon than 1, 3 - carbon and oil. All three were thinner at the middle.
Paul
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Go for Plusgas, it really is good especially if have patience. Been using it for 35 years starting with a 1962 A40 that had rusted nuts added to it as a free extra.
The problem is you are nearly there, and can almost see the end. There is a great temptation to 'have a go' and whip it out with force. After the end has snapped off you will want to rewind the video, but it is too late. It could well be carbon in which case a little bit might snap off and it then comes out. Or you loose metal. The body of these plugs is quite soft and can easily snap off. The Mercedes sites have pages devoted to cases where a few pounds of torque on them and they snap off.
I reckon if you soaked almost any nut for a week in Plusgas it would come off. The problem is most just spray some on and wait two minutes and then have a go. Try every two hours or so for a day.
You must grease these threads with copper grease, or next time you need to take one out, the same problem will arise.
Let us know if it works.
Good luck.
Edited by MW on 28/03/2008 at 10:04
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Vinegar is better than Plusgas for carbon. It loosens it (and rust as well). Takes 2-3 days tho.
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Thanks MW,
I will try the Plusgas. I have to use the car over the next few days, but next week can leave it for a few days so can give the plug a good soak. I'm very aware of not wanting to break anything off as the cost of getting the head off will be hundreds of pounds. I'm also aware that if the plug will not come out, it must do so soon as it may indicate there is a real problem with it and it may fall apart so damaging the engine. I will get the copper grease and use of the three new ones.
I will let you know what happens.
Paul
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Why bother to change it? Most diesels will start readily with only 3 Glowplugs altho it maybe lumpy to star with. Some PSAs never have the 4th Glow plug changed as access is difficult, and remain as good starters .
If you are having starting problems with 3 good GP I would start looking for other reasons, air leaks etc.
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How did you get on?
I'd concur with pmh, leave it as-is........will save you a whole lot of grief.
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I still haven't had any luck with it. The plug just turns and will not come out, so I assume the tip is well swollen. With three new plugs the car starts ok in warm weather, but needs a good crank over in frosty weather: it used to start with just a touch of the ignition key.
Paul
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If it still struggles to fire up in cold weather with only three operational glowplugs, next thing I'd check is the valve clearances. I bet they'll be tight....
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The car was serviced 2000 miles ago, so I assume/hope the valve clearances were checked. However, I will check with garage.
Paul
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Valve clearance checks in-service as notorious for being left out/forgotten..........
I'll bet my bottom dollar they weren't checked!
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I'll ask tomorrow. Shame that these things can be forgotten, when they are paid to be done!
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