In the middle of changing glow plugs on E300DT - PeachParts Mercedes-Benz Forum

cyman73 · #1 04-19-2008, 01:08 AM

Hello all,
I finally removed all the glow plugs without breaking any. Read my last post.

I am in the middle of changing the glow plugs on my E300DT. Thanks to Lightman's thorough instructions, the intake manifold removal was not that bad. Here is my story so far:

Before embarking on this project I read all the forums and tried to educate myself as much as possible. So far I have tried the following based on the many posts I read.

1) I drove the car very very very hard on the highway, using B20 and a full large grey bottle of Power Kleen additive. Initially I would see a large trail of black smoke as I gunned the engine, but in a few days the car wasn't smoking (at least noticeably) anymore. I drove the car hard in order to try to clean any carbon buildup inside the cylinders, since the carbon is responsible for seizing the glow plugs in the head.

2) After I removed the intake manifold, I sprayed Power Blaster on the glow plugs for a couple days. I didn't even put a socket on the glow plugs.

The result so far is that GP #1, 2, and 4 came out very easily. I placed the 12 mm socket on #1 first and applied force to unscrew, it suddenly snapped free. I initially thought I broke it (because that is what I expected to happen), but then realized that it was easily coming out. The same pressure and the same fear struck me with #2. When I got to #3 I knew how much pressure was needed to free up the GP, but it would not budge.

I put #1 and #2 GP back, because I wanted to start the engine and warm it up. I read in other posts, that the GPs would come out easier if the cylinder head was warm.

After mildly warming up the engine. I removed GP #4 in the same way #1 and #2 came out. Applied pressure and suddendly it gave way.

Now to my problem(s).

GP# 5 and 6 slowly began to unscrew. I am going very slow with these two, since they are at least moving. I unscrewed them approximately one turn, then screwed them back in. I have done this a couple times now, but it is not getting any easier. I hope that unscrewing and screwing #5 and 6 will eventually succeed.

I have applied higher and higher pressure (compared to the other GPs) on glow plug #3, but it hasn't moved at all. I really don't want to break any of them.

I read that I might have some luck taking the injectors out and flooding the cylinder with biodiesel in order to loosen the carbon build up.

Does anyone have any advice or suggestions??

turbobenz · #2 04-19-2008, 03:20 AM

if you do flood the cylinder make sure you change your oil afterward, it should just seep past the rings fairly quicky. just curious, has anyone ever tried welding onto a broken off glowplug?

Alastair · #3 04-19-2008, 05:42 AM

Pretty important to change oil after flooding the cylinder with BioDiesel....

It can adversly affect lube-oil and 'polymerise'...

I wouldnt use BioDiesel. I personally would try normal diesel or even a Good long blast of WD-40 down the injector hole, and on a hot/warm engine, but make sure you get it ALL out before you start it!--we dont want to hear of a hydraulic lock and bent rod!...

You don't want to end up like this guy in the UK with his 605!- http://www.vegetableoildiesel.co.uk/forum/viewthread.php?tid=5202&page=2

--About halfway down the page, broken plug, and drilled through the head casting!--

I know the plugs can break in these. What I dont know is why are these more of an issue than other cars...?

Weak plugs or just summit else??

nhdoc · #4 04-19-2008, 06:39 AM

I think you can safely proceed with #5 and #6 the way you are going, just go slowly and try spraying some PB in there as you go working the plug in and out slightly to get it to penetrate...it will carry into it that way.

As for #3 it might just make sense first to try it with a torque wrench and see if you are applying anywhere near what it considered the "safe limit" for them...that torque limit eludes me at the moment but can be found in other posts. I've also posted in the past that I think it is wise to try using an imapct tool on stubborn GPs. There are some low power air or electric tools which would apply the rat-tat-tat impact that I feel would successfully remove them. I bought one recently from harbor freight for $15 which is very compact and has a butterfly control allowing you to easily switch directions. I would bet a beer and a shot that it would remove your #3 in no time.

cyman73 · #5 04-19-2008, 09:14 AM

The thought of a bent rod is making me have second thoughts about trying the cylinder flooding procedure. I am also thinking that maybe the top of the cylinder is not flat which would not allow removal of all the diesel. On top of all these frustrating thoughts, I don't know how hard it is to remove the injectors.

Should I warm the engine every time I try to work on the remaining GPs?

Thank you.

Alastair · #6 04-19-2008, 03:07 PM

Quote:

Originally Posted by cyman73

The thought of a bent rod is making me have second thoughts about trying the cylinder flooding procedure. I am also thinking that maybe the top of the cylinder is not flat which would not allow removal of all the diesel. On top of all these frustrating thoughts, I don't know how hard it is to remove the injectors.

Should I warm the engine every time I try to work on the remaining GPs?

Thank you.

With the injectors out its possible to spin the engine over on the starter, This will remove nearly all the fluid that has been put in there--What doesnt come out the injector hole will exit via the exhaust-valve........

Ally expands more than steel, so it stands to reason the plugs should be easier to remove with a warm engine...

TMAllison · #7 04-19-2008, 05:23 PM

I'd suggest using your torque wrench for removal although I also like the rat-a-tat-tat aspect of an impact wrench if torque is dialed in.

Post 17 in this thread suggests the breaking point is ~85nm. http://www.peachparts.com/shopforum/showthread.php?t=205418&highlight=glow+plug&page=2

cyman73 · #8 04-20-2008, 07:48 AM

Hello everyone,

I further loosened #6 GP and I can turn a couple turns now. I am affraid that I might strip the threads in place (if I haven't already done so) and the GP will just rotate freely, without coming out. Do I have a valid concern?

Thanks.

nhdoc · #9 04-20-2008, 08:04 AM

Quote:

Originally Posted by cyman73

Hello everyone,

I further loosened #6 GP and I can turn a couple turns now. I am affraid that I might strip the threads in place (if I haven't already done so) and the GP will just rotate freely, without coming out. Do I have a valid concern?

Thanks.

If it is coming out as you turn I think you can safely remove it the rest of the way, you are being way more cautious than any mechanic would be. It's not possible for any of us to tell exactly what's going on without being there with you but these don't generally strip their threads, they just break at the point where the GP body attaches to the threaded part. If it is turning with relative ease I think you are home free.

aklim · #10 04-20-2008, 08:28 AM

Quote:

Originally Posted by cyman73

I further loosened #6 GP and I can turn a couple turns now. I am affraid that I might strip the threads in place (if I haven't already done so) and the GP will just rotate freely, without coming out. Do I have a valid concern?

Without being there, I cannot say. However, what I did was to turn it out for about the same number of revolutions as the others and see if the plug moved outwards at all. When it stops moving outwards, I would reverse it and screw it back in. PB-blaster sprays, of course. Then when I turn it out again, I would use vise grips and extract it. It might be that the tip is stuck in the chamber and making removal difficult. I reamed the bores with a gun bore brush and then turned the engine over without the GPs in place to blow out any carbon.

It felt tight when I turned it out but it wouldn't come loose easily so I screwed it back in and I think it cleaned out whatever was holding it in place

cyman73 · #11 04-20-2008, 09:19 AM

I warmed the engine up before doing any more work this morning. I am able to see the threads on #6 so I think it is slowly coming out.

I started turning#5 and it slowly turned a couple times, then all of the sudden the ratchet moved very fast, like the thing snapped. I took the socket off, expecting to find a broken glow plug. But it isn't broken, I was able to screw the glow plug back in a couple turns. I unscrewed it again and then I reached a point where again I felt like I broke it. I looked at it again and it isn't broken. I then tried to unscrew it further and it is again very hard to turn. I stopped for now and I sprayed more PB on the three slow ones.

I tried turning #3 and at least it moved less than one turn.

Things aren't looking very good.

nhdoc · #12 04-20-2008, 09:21 AM

Are the plugs moving in and out as you turn them? If so then you have not broken anything.

cyman73 · #13 04-20-2008, 09:27 AM

I can say that #6 is slowly coming out.

#5 gave me a good scare and I don't know if I should touch it anymore (at least for today).

My ultimate fear is breaking something off, and I will probably either stop trying or try hard enough until something breaks. I wish I knew what I was getting myself into when I bought this benz.

aklim · #14 04-20-2008, 09:30 AM

Quote:

Originally Posted by cyman73

I can say that #6 is slowly coming out.

#5 gave me a good scare and I don't know if I should touch it anymore (at least for today).

My ultimate fear is breaking something off, and I will probably either stop trying or try hard enough until something breaks. I wish I knew what I was getting myself into when I bought this benz.

Wrench on it, I would. Why prolong the agony.

JimSmith · #15 04-20-2008, 11:06 AM

I may be missing some background, but are all the plugs burned out? I am not a believer in removing functioning plugs. I have replaced all of mine in several episodes, but never more than 3 at a time. Last time I had just one burned out. The intake manifold is getting routine now, but still irritates me that everything that goes wrong is under it.

Anyway, I would either get an impact tool or tap the wrench with a hammer to try to knock the plug as you try to turn it. If it is turning it is ok. My first time I found the number 6 plug hand tight, or actually not even snug. I was sure I broke it, even though I hardly put the wrench on it.

Depending on the failure, the plug can become misshapen and be more difficult to get out. Lots of lube and gentle persistence will get you through it. Good luck, Jim