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6.2L Diesel 1982-93 6.2L Diesel - Member access forum for any questions or information exchange related to the 6.2L engine.

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  #1  
Old 01-06-2012, 10:22 AM
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TrenchFoot TrenchFoot is offline
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Location: Snoqualmie, WA
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Default Broken Glow Plug

While tearing down my project 6.2 I ran into some bad news with my glow plugs. Two had been sheared off by the PO when he pulled the engine, which I had planned to pull with an easy-out.

But more concerning was that one of them had also a missing tip. There was nothing left to fish out of the chamber, the whole tip is MIA. I am trying to avoid pulling the heads since the block has only 100k miles.

Most of the older posts I've found focused on fishing out what you can. But it isn't clear just how detrimental it is to the cylinder to have a GP tip banging around in there. I'm sure the textbook, leave-nothing-to-chance answer, is to pull the heads and look for damage to the cylinder wall.

Is there anyone out there that's willing to say this happens all the time? Broken tips tend to find their way out the exhaust valve? Life is too short to lose any sleep over this little matter?

Any help is appreciated.

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1978 Jeep Wagoneer with a 401 gasser. 1993 6.2L J-code 599 and a Banks Sidewinder being prepped for a swap.
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Old 01-06-2012, 01:48 PM
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I'm by no means an expert here, but from what I gather, there isn't much clearance between the piston and head, so a loose glow plug tip could cause some havoc.

Also, if you have the engine out already, it may not be a huge project to take the heads off. You will may save yourself some aggravation actually, as once its in your jeep, it may be more difficult
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  #3  
Old 01-06-2012, 02:47 PM
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Default And now, the head gaskets...

Yeah, that's what I figured. I chatted about it with my Dad, a retired diesel mechanic/machinist and he thought the same. I also forgot about the potential damage to the exhaust valve that a wedged tip could create.

Oh well, just gotta add another couple hundred bucks and another couple evenings to the project.

Sounds like FelPro gaskets are the preferred route. Is there a preferred head bolt I should be looking for?
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1978 Jeep Wagoneer with a 401 gasser. 1993 6.2L J-code 599 and a Banks Sidewinder being prepped for a swap.
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Old 01-06-2012, 03:55 PM
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Some years ago I spoke to a military mechanic who told me too many tips are left in the engine - to find there own way out. Most lost tips do find their way out without causing too much damage. Some break/bend pistons, and some damage valves. All of them produce some cratering on the piston crowns.

I'd pull the head(s) to allow doing a better job removing the broken plugs anyway. It's much harder to do in the truck...

Jim
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Old 01-06-2012, 04:10 PM
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I hate to be the harbinger of bad news, BUTTTTTTTTTTTTTTT, If you can't find the broken tip, you need to yank the head/s and make sure its not in the cylinder.

There is approximately .045" clearance between the piston and the head with the piston at TDC.
There is simply not enough room for that broken part to stay.

The damage that these can do can range from serious carnage to at minimum a severely dented piston.

If the broken piece happens to get caught in a valve and hold it open, the piston will hit the valve as it comes to TDC, the result, game over, engine destroyed.

I would very quickly spend the few dollars $$$$ involved for a set of gaskets and Bolts before I would chance having a broken plug tip left behind.

At 100K the gaskets can be close to used up, depending on the manufacture date of the engine.

The early ones were not nearly as good as the Felpro gaskets sold today.

Use the late style 6.5 gaskets with the reinforcing on the end cylinders.

The other option is if you can get a hold of a little small fiber optic viewer that will fit into the cylinder past an open valve and be able to look the cylinder over well to be sure nothing is in there.

Good luck

Missy
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Old 01-06-2012, 06:22 PM
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Default Pulling Heads...

At TDC there's only 0.045" of clearance? Yikes. Here's to hoping I'll get off with just buying new gaskets/bolts.

Thanks for reminding me about the 6.5 Fel-Pro gaskets on 6.2s. I'd read Jim's article in the 6.2 Volume II book a while back, but had forgotten about the guidance. Since my block is a 599 and won't have the extra water passage of the early blocks, a pair of Fel-Pro Q9701PT gaskets are in my future.

Thanks again for the help.
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