Glow Plugs

Damaged glow plugs have been known to swell and require removal of the heads to replace them ($$$) or even break off into the cylinder (boom, or $$$)

It is dependent on the vehicle, of course, but Ford OEM glow plugs are under $10 each.

Labor would be there if you don't do it yourself, but I wouldn't let it go.

Now if was your glow plug control module or something electrical and you decided not to bother fixing it, that would be different than a possible physical failure that it sounds like you may have.

It's up to you, I'm pointing out the risks that could be associated with ignoring it. Risks are not guarantees, either ;)

As DiskDoctr pointed out other things can happen but they are unlikely. But I would get them replaced because it will make for harder starting in cold weather which puts a further strain on your starter and batteries.

They aren't difficult to do on the LBZ but if you aren't the do it yourself type have the dealer do them. If you don't get them replaced make sure to plug in the block heater for a few hours when the temperature drops to 32 or below to make starting faster; it will still start with bad glow plugs and no heater in even colder temperature but it will be an ugly start.

Note if you use the block heater it should be on for a few hours, don't just plug it in for 1 or 2 hours especially if the temperature is at or just above freezing. The LBZ compares temperature readings from several sensors and plugging in the block heater for a short time when the temperature is NOT well below 32 may trigger a CEL as I found out right after I bought mine new in December 2005. The sensors do a cross check and use of the block heater for a short time will fool the system into thinking one of the sensors isn't reading correctly. The CEL can be reset by a reader or it will reset itself after a few normal starts; the only operational change I found when it was on for this issue was the transmission wouldn't shift into 6th (second overdrive ratio).

I have the same engine as you. I had one burn out around the first of the year. I just got around to replacing it last month. I just burn out another one the other day. If I have time I will replace it this weekend. I would replace it when it gets cold though because "I" don't like fuel knock or rattle.

There is no danger to let it go as you said other than hard starting when very cold.

Change them all and be done with it....some risk in leaving a bad glow plug.

You are lucky it's just glow plugs. You don't even want to know what replacing injectors costs...and you have to do them all as a set.

Sorry but a burnt out glow plug does not swell like has been reported by a few on here. It doesn't do anything but not heat the cylinder and aid in cold weather starting.

Why glow plugs swell.

I have an 07 Classic LBZ, lost #7 glow plug last year. Kinda shrugged my shoulders, I have 7 more, it'll start in the cold Alberta winters. And it did, no problem.

I do hate looking at the check engine light though. Took it to the dealer this past spring and they told me he same thing, replace all 8 for the small extra time and cost. Suppose I could do it myself but I'm tending to not turn my own wrenches any more.

Plugged my code reader in a month ago when it went into limp mode under a heavy haul, found that I now have #3 glow plug out as well. Now I'm down to 6. Still starts just fine, but winter is coming soon here. Suppose I should change them.

(Limp mode issue was not related to the glow plugs, it was a fuel pressure problem)

But in answer to your question, voice of experience here, I never noticed a difference with one bad plug. Will I with 2? Unknown. Maybe....

Might not get around to changing them. Work has been really bad and my income is way down from a few tears ago. We will see how it starts at minus 25.

I have a 2006 LBZ with 177,000 on it and have had numerous glow plugs replaced over the past 10 years (I bought it new). Earlier this summer after a 2,000 mile trip towing my 5'er I had another one fail as well as 1 injector. The dealer was told to only replace the one glow plug and obviously the injector, but somewhere the word didn't get to the technician and he replaced all 8 glow plugs. Since it was clearly written on the work order I got all 8 glow plugs replaced for a reduced cost on them plus zero labor. The cost of the injector was another story $$$$$.

Turtle n Peeps wrote:
Sorry but a burnt out glow plug does not swell like has been reported by a few on here. It doesn't do anything but not heat the cylinder and aid in cold weather starting.

Why glow plugs swell.

I find it amusing that dealers suggest replacing all the plugs when GM DOES not. I had a CEL light come on while towing and in Montana. Dealer said it was glow plug. I responded that it was emission related and I could continue until I got home. He agreed and cleared the code bit it came back on in a thousand miles or so.
Got back home, checked the owners manual and under the emission warranty it was still covered but a $100.00 deductible. Dealer wanted several hundred dollars for 1 plug. I called GM and they also said it was not covered. Finally convinced him that it was. Paid the $100.. A second plug failed later and I then found a TSB giving instructions on replacing ALL after doing a OHM check but I don't remember what the trigger point for doing so. Dealer had issues with that. Paid my $100. deductible and had it replaced. Later had a $100 check from the dealer stating the second plug was replaced as a "good will" gesture.
After my third failure I bought an OEM glow plug for about $20. and replaced myself. Takes a small deep well socket and small combination wrench of which size I do not remember. Disconnected the wires and carefully tried to remove. Turned surprising easy. Put a little never seize on the threads and put the new one in. 30,000 to 40,000 miles later I traded for a new truck and never had another issue.
If I were you I would carefully see if the plug will turn and if so do myself. If it does not break loose then I would have the dealer do it. If you decide to replace them all I would change the ones I could and have the dealer do the rest.
Changing them all will not be cheap. Dealer will probably mark them up to $60-$70 or so and labor would be at least $100. per hour. IIRC, dealer tried to bill me for over $200 for one. Replacing all may run closer to $1000.

Turtle n Peeps wrote:
Sorry but a burnt out glow plug does not swell like has been reported by a few on here.

Let me clarify: Damaged glow plugs can swell or break off and it does happen more often with non-OEM in the Ford Powerstroke.

I did not intend to imply that glow plugs that are DISCONNECTED swell while disconnected (from being in the cylinder or some other reason?), though I didn't specifically state that part.

Notice I didn't use the term "burnt out," rather disconnected. There are a number of reasons a glow plug may stop working in a particular cylinder. Glow plug physical damage, electrical harness, connectors, etc.

That being said, I'm not an expert on Duramax, either.

At a MINIMUM, if pulling the cover to replace ONE glow plug, I would ABSOLUTELY replace all the ones on that side. Is it necessary to pay (DIY time or service labor) to remove the other valve cover to replace them...it depends. I probably would, since I usually DIY. If it wasn't too much in service labor, I'd have it done, too.

Why?

Well...on the Powerstroke, the glow plugs and injectors use the same Under Valve Cover Harness (UVCH), which use the same wiring harness connectors. It is wise to replace the UVCH at the first sign of trouble, including glow plugs (easy and cheap). Usually around $200 for all glow plugs and both UVCH. No brainer.

The Duramax may be different ;)

DiskDoctr wrote:

Turtle n Peeps wrote:
Sorry but a burnt out glow plug does not swell like has been reported by a few on here.

That being said, I'm not an expert on Duramax, either.

At a MINIMUM, if pulling the cover to replace ONE glow plug, I would ABSOLUTELY replace all the ones on that side. Is it necessary to pay (DIY time or service labor) to remove the other valve cover to replace them...it depends. I probably would, since I usually DIY. If it wasn't too much in service labor, I'd have it done, too.

LOL, I can tell. ;) There is no glow plugs under valve covers for the LBZ (the engine the OP and I have) They are out in the open just like a sparkplug is on a gasoline engine. Instead of a sparkplug boot it has a small wire and a nut to hold the wire on. Then it's just a matter of unscrewing the thing just like a sparkplug. (Pretty easy job unless you keep on dropping the nut. :o )

The OP asked if a burnt out, non operating or whatever you want to call it glow plug would hurt the engine if left in place. The bottom line is; NO.