Spark plugs and fuel filter stuck.

[LisaC]

Hiya all,

I took my CLK 320 (Y reg) to our indi who is usually fab and can do almost everything. I say almost because he was unable to change 5 of our 7 spark plugs (why on earth does one car need 12 spark plugs in the first place?!?). Basically, the previous owner only had the basic services done and changing the spark plugs and fuel filter are apparently not included in the services and if they were, they have never been changed which means the previous owner has been royally ripped off. Yes, I have told them to stop using their old garage!

My indi said the spark plugs were stuck so badly he didn't dare welly them out for fear of damaging the threads or the head (yes, I did listen, not that I know what the threads or head are). Also, the fuel filter is corroded into place and he had to leave that as well. Now, me being a complete novice (though I did manage to mend my roof handle with his help) am wondering if I really need to change all 12 plugs or will the car bumble along quite happily on 7? If not, does anyone have any idea how I can get these little bleeders loose?
As for the fuel filter, I'm assuming that anything corroded in place is not a good sign. Any idea how to get it out?

Thanks in advance!

 

[grumpyoldgit]

12 spark plugs???
I may be wrong and I'm sure someone who knows better will be along to put me right, but unless you have a CLK GTR 6.9litre V12, I would have thought that you only have 6 spark plugs, assuming that it's a V6 with one spark plug per cylinder.

 

[Howard]

12 spark plugs???
I may be wrong and I'm sure someone who knows better will be along to put me right, but unless you have a CLK GTR 6.9litre V12, I would have thought that you only have 6 spark plugs, assuming that it's a V6 with one spark plug per cylinder.

You are wrong indeed

A 320 has 12 plugs .....

My 430 has 16 of them !

 

[Danny DeVito]

You are wrong indeed

A 320 has 12 plugs .....

My 430 has 16 of them !

Jaysus

 

[sinewave]

Welly the Feckers out, it's gota be done!

 

[grumpyoldgit]

Lifted from another forum

Lycoming, who has been making aluminum heads for around 80 years, says to remove a stuck spark plug:
1) Warm engine.
2) Use an inverted funnel - small side around the spark plug - aim a co2 fire extinguisher at the plug. The inverted funnel keeps the co2 off the head itself.
3) Let fly the co2!
4) Unscrew plug.

 

[Ian Donkin]

...why on earth does one car need 12 spark plugs in the first place?!?!

Manufacturers twin plug engines (that's two per cylinder) to allow them to run a higher compression without the risk of detonation (or pinking) you might experience in an otherwise identical single plug setup.

Twin plugged engines don't need as much timing advance to burn the fuel completely as the flame front has less distance to travel and a more even cylinder temperature can be maintained.

Alfa have had a twin spark engine for years and Porsche introduced it in the late 80's for their road going cars in the 964 version of the 911. It's a tuning technique that's been around in racing circles since Noah was a lad.

 

[Auto-mobile]

Hiya all,

I took my CLK 320 (Y reg) to our indi who is usually fab and can do almost everything. I say almost because he was unable to change 5 of our 7 spark plugs (why on earth does one car need 12 spark plugs in the first place?!?). Basically, the previous owner only had the basic services done and changing the spark plugs and fuel filter are apparently not included in the services and if they were, they have never been changed which means the previous owner has been royally ripped off. Yes, I have told them to stop using their old garage!

My indi said the spark plugs were stuck so badly he didn't dare welly them out for fear of damaging the threads or the head (yes, I did listen, not that I know what the threads or head are). Also, the fuel filter is corroded into place and he had to leave that as well. Now, me being a complete novice (though I did manage to mend my roof handle with his help) am wondering if I really need to change all 12 plugs or will the car bumble along quite happily on 7? If not, does anyone have any idea how I can get these little bleeders loose?
As for the fuel filter, I'm assuming that anything corroded in place is not a good sign. Any idea how to get it out?

Thanks in advance!

Needs to grow a pair, I don't see what the problem is, plugs may be mega tight I for one have never damaged the thread even removing the tightest of spark plugs on the 112/113 engines, As for the fuel filter anything that gets damaged (bracket/pipes) can be replaced relatively cheaply.

 

[markjay]

Needs to grow a pair, I don't see what the problem is, plugs may be mega tight I for one have never damaged the thread even removing the tightest of spark plugs on the 112/113 engines, As for the fuel filter anything that gets damaged (bracket/pipes) can be replaced relatively cheaply.

You can avoid replacing stubborn plugs, but if you insist too much then the other risk is that the ceramic bit of the plug breaks off during the removal attempt, which then makes removal of the plug mandatory even at the price of damaging the thread, and leaving the old plug is no longer and option.

 

[grober]

Did he try it with the engine really really hot? Otherwise you're in for the long haul. Lots of anti seize compound such as plus gas or loctite "freeze and release" applied over quite a few days- maybe the careful application of a specialist impact air tool also. When a professional mechanic comes across a problem like this he has to balance "risk against reward" and there is also the "time spent/invoiced on the job " factor also. This may cause him wisely to "bottle it" . You may have to take it somewhere else where time may not the primary factor or they specialise in this or similar types of problem- broken seized injectors/glow plugs in cylinder heads for example where their greater experience will give them more confidence to take on the job Or discuss and agree the consequences and costs to you of any further action by your specialist should the worst happen--- unlikely though!

 

[Ian Donkin]

You can avoid replacing stubborn plugs, but if you insist too much then the other risk is that the ceramic bit of the plug breaks off during the removal attempt, which then makes removal of the plug mandatory even at the price of damaging the thread, and leaving the old plug is no longer and option.

I'm not sure relying on one working plug per cylinder is sound advice for the long term good of an engine designed to burn fuel efficiently around the presence of two working plugs.

 

[sinewave]

I like the Fire Extinguisher idea.

Makes sense of the Laws of Physics!

 

[Danny DeVito]

Bull by the horns..... Take advice if needed then go at it like a something or other. You can't give up never as a serious engine dude. You tell the customer 'this might cost' or 'this might not work' but go at it anyway, pass it on if needed but you gotta sort it, what ever it takes

 

[markjay]

I'm not sure relying on one working plug per cylinder is sound advice for the long term good of an engine designed to burn fuel efficiently around the presence of two working plugs.

It was a general point relating to spark plug replacement. Obviously any plug that does not work needs replacing.

There's however a debate whether plugs should be replaced at 4 years at all (other than to prevent them from seizing in future).

On my other cars, Toyota and Renault, the plugs are only replaced based on mileage, not time, and as both cars are low-mileage and will never reach the 60k specified by the manufacturers, their plugs would never be replaced - which was confirmed by the respective dealers.

Said that, I am personally in favour if replacing the plugs, and Olly changed them on my Renault, but on the Toyota it's an engine-out job so I gave up on it - it's a 1998 car which we had from new, 40k miles on the clock, and still gooing strong with the original factory fitted plugs.

 

[MarkJunedd]

Lycoming, who has been making aluminum heads for around 80 years, says to remove a stuck spark plug:
1) Warm engine.
2) Use an inverted funnel - small side around the spark plug - aim a co2 fire extinguisher at the plug. The inverted funnel keeps the co2 off the head itself.
3) Let fly the co2!
4) Unscrew plug.

Although i'm not doubting the above method, it does sound very plausible, i think it would be very difficult to do on a M112 as access to the plugs is a bit tight anyway especailly the rear ones. When i changed mine they were all a bit tight but all came out eventually.

 

[LisaC]

Thanks all!

For some reason I didn't get any notifications that there had been a reply
I'll tell my indi to grow a pair, from a very safe distance.

Yeah grumpy, my car has 12 spark plugs and Howard....16!!!! OMG!!!

Markjay, the spark plugs are all still working, they just needed replacing according to the mileage and the service advice, as the car has now done just over 100K. Apparently, they recommend changing when the car has done 80K.

I don't know if he tried to get them out with the engine hot, I'll give that a go so thanks for that bit of info grober. He left us the new plugs so I have them to hand. You're quite right, he did weigh up the cost factor as ruining the head would have cost us shed loads of money. Though I do realise it's not good for the engine to have non functioning parts, Ian.

What's an M112? And what's an inverted funnel?!? Are we talking funnel, as in something used in the kitchen for bottling up, turned upside down? As I said, novice. Sorry! I like the fire extinguisher idea as well, sinewave

I'll take the car to a dealer to get the filter changed as I'm assuming they'll have the filter parts in stock. Or am I assuming too much!?!

Thanks again for all your good advice.

 

[grober]

An M112 engine is the "series" of Mercedes petrol engine you have in your car. Mercedes-Benz M112 engine - Wikipedia, the free encyclopedia ----- and the "inverted funnel" is just what you surmised correctly. Idea being to direct the freezing liquid /vapour on to the plug itself rather than any surrounding parts of the engine which you want to keep warm to exploit the contraction of the plug to break the locked threads. Modern freeze release sprays use the same principle but in a more controlled fashion than the "fire extinguisher" method.
the major problem on these engines is always getting access to the part in question.

ps make sure the replacement plugs are the long life platinum or iridium tipped plugs that have that long change interval. There are cheaper ones but they need more frequent changes and as you know --- this is probably not a good thing! post the exact plug type = manufacturer and number/letters on here and someone will check for you

 

[Stratman]

If you don't fancy the fire extinguisher, try some plumber's freezer spray instead.

As before, get the engine hot then freeze the plug with the spray. You should get a directable pipe with the spray as well so the funnel shouldn't be needed.

You can also get freezer spray from Maplins.

 

[LisaC]

Thanks for your patience, grober! I just read the article, very interesting. I can't find the spares, he-who-should-be-disobeyed has tidied them up. Apparently, they are somewhere safe... I'll check the type before we try to change, so thanks for that.
Thanks Stratman, I'll give that a go when we find the spares!