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  #1  
Old 07-05-2013, 06:36 PM
Skid Row Joe's Avatar
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Is Helicoiling glow plug cavities a valid fix?

Just had two glow plug cavities helicoiled on a '99 W210 turbodiesel. Glow plugs were stuck because of carbon build-up, and were summarily drilled-out......

Is this an acceptable, permanent, long-term, viable fix or repair? The car seems to be running perfectly in the 50 miles or so, being driven daily since the helicoiling installs.

Will it ever compromise the seal of the cavity to the atmosphere, i.e. loss of compression, or shoot the glow plug out / malfunction?

I'm skeptical as to the feasibility aspect of anything approaching long-term (years/10s of thousands of miles) on a helicoil in the glow plug cavity.

Any actual, experience in this arena greatly appreciated!
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  #2  
Old 07-05-2013, 07:08 PM
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I'll break it down:

1. Helicoils typically work well. The only drawback in a glow plug application is that you have to snap off the insertion tab after the coil is installed in order to allow the GP to go through.

2. The GP seals at the shoulder not the threads so the only concern is the coil being robust enough to hold the GP in place tightly.

3. When I drilled my one bad GP out, I used a "Timesert" which is like a helicoil but it's a solid cylinder that, in my opinion, is a more solid solution.

Hope that helps, ask away if you have any more specific questions.
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  #3  
Old 07-05-2013, 07:19 PM
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Quote:
Originally Posted by KarTek View Post
I'll break it down:

1. Helicoils typically work well. The only drawback in a glow plug application is that you have to snap off the insertion tab after the coil is installed in order to allow the GP to go through.

2. The GP seals at the shoulder not the threads so the only concern is the coil being robust enough to hold the GP in place tightly.

3. When I drilled my one bad GP out, I used a "Timesert" which is like a helicoil but it's a solid cylinder that, in my opinion, is a more solid solution.

Hope that helps, ask away if you have any more specific questions.
Yes. Can the helicoil be replaced by a "Timesert?"

What is the cost for a new head on the '99 E300? If you know?
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Old 07-05-2013, 07:53 PM
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The Timesert has a special drill and tap to prep the hole for installation. It may be possible to re-machine the threaded helicoil hole to accept the Timesert but I wouldn't bank on it.

Here's a picture of the Timesert I installed when I repaired my #6 GP hole.



As far as a price, I have no clue. I would just check ebay. Heck, I've seen some guys buying whole OM606 engines for $300.
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  #5  
Old 07-05-2013, 08:11 PM
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Quote:
Originally Posted by KarTek View Post
Heck, I've seen some guys buying whole OM606 engines for $300.
That was me
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  #6  
Old 07-05-2013, 08:36 PM
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Because as previously stated the Glow Plugs sea on the tapered shoulder right where the Element comes out of the Plug if you nicked the threads a little while drilling there may be enough threads to use it the way it is since the Torque is not much.

The disadvantage of any drilling is that if it gets off center the Glow Plug May not seal on the Shoulder correctly and Carbon may build up between the Glow Plug Body and the Glow Plug Hole.
Because of the above reason which ever thread restoration Kit has the best Pilot Drill might be a good choice.

A Helicoil in Aluminum has no strength issues and I believe it removes the least parent Metal and if you have the correct set breaking off the bottom Tab should not be an issue.

If for some reason you believe your Glow Plug might not seal at the shoulder you can slide a thin Copper Crush Washer over the Tip of the Glow Plug that has an ID and OD to match. If you heat that Washer red hot and cool it will become soft.

Fuel Injection Shops should have some washers that would work as they get more then they need in the Fuel Injection Pump Gasket Kits and ACE Hardware may have them.
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Old 07-05-2013, 11:51 PM
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Quote:
Originally Posted by Skid Row Joe View Post
Just had two glow plug cavities helicoiled on a '99 W210 turbodiesel. Glow plugs were stuck because of carbon build-up, and were summarily drilled-out......

Is this an acceptable, permanent, long-term, viable fix or repair? The car seems to be running perfectly in the 50 miles or so, being driven daily since the helicoiling installs.

Will it ever compromise the seal of the cavity to the atmosphere, i.e. loss of compression, or shoot the glow plug out / malfunction?

I'm skeptical as to the feasibility aspect of anything approaching long-term (years/10s of thousands of miles) on a helicoil in the glow plug cavity.

Any actual, experience in this arena greatly appreciated!
We have used helicoils in far more stressful applications than GP's.
As they are not going to be removed any time soon ~ hopefully only every few years, you should not get too concerned.
Nate's use of a Timesert is an alternate & in some situations is a better choice.
I would have used a helicoil. You now have a hard metal thread for the GP to screw into & minimal loss of head metal.
If when the new GP fails you find the helicoil unscrews with the GP you may wish to weigh your options.
There are many applications where alloy has steel thread inserts as the alloy thread is not durable enough. You could look on your situation as an upgrade.
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  #8  
Old 07-06-2013, 01:03 PM
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Quote:
Originally Posted by Skid Row Joe View Post
Just had two glow plug cavities helicoiled on a '99 W210 turbodiesel. Glow plugs were stuck because of carbon build-up, and were summarily drilled-out......

Is this an acceptable, permanent, long-term, viable fix or repair? The car seems to be running perfectly in the 50 miles or so, being driven daily since the helicoiling installs.

Will it ever compromise the seal of the cavity to the atmosphere, i.e. loss of compression, or shoot the glow plug out / malfunction?

I'm skeptical as to the feasibility aspect of anything approaching long-term (years/10s of thousands of miles) on a helicoil in the glow plug cavity.

Any actual, experience in this arena greatly appreciated!
I think there is only 2 ways the Original Glow Plug cavity could have gotten Carbon; they were loose; or, they did not seal in the sealing area for some unknown reason.
If the Glow Plug holes/cavity was machined properly and the Glow Plug was not loose I think the Carbon build up inside of the Glow Plug cavity would likely be due to some localized warping of the Aluminum Cylinder Head.
So Helicoils or not if the Head warps and mess with the sealing area of the Glow Plug it could cause a leak.
I think the Helicoils are Stainless steel so I don't believe there is going to be rust between it and the Glow Plugs unless the Glow Plug itself rusted. A Neverseeze type compound on the Glow Plug threads should prevent that Rust.

In your particular case I would likely have coated the whole of the Glow Plug body between the where the Tip/Element comes out of the Plug and the top of the Threads. That way if they for some reason Carbon again filled the cavity they would not get easily trapped.
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  #9  
Old 07-07-2013, 06:31 PM
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With ya'll's input and experience, I have something to reflect on and learn from here, and possibly discuss with my indy. Much appreciated, thank you'all!
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  #10  
Old 07-07-2013, 06:46 PM
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Ins Co was unable to find any reman cyl heads when mine was ruined.

A new head from MB was approx. $3k. Stocked in Atlanta as I recall.

Difficult expense to justify on a 14y/o vehicle.
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