Exterior coolant trickle leak at #3 injector

[JustinM]

So here's this old guy with 50+ yrs shade tree mechanic-in under his belt trying to figure out how this slow leak that has been gradually getting worse over a year now can be coming out around the base of this injector. Seems to me it is too far from the head gasket for that to be leaking. What little I understand about the coolant passageways leads me to think there is no passage in vicinity of the valve cover. At this point I am cleared down to the injector and all that is left to do is lift it out. I am worried that I still won't find a leak point when I do. It's by no means a spurting leak, which leads me to think it is micro. I am hoping some JB weld will seal it off if I can find it.

When this leak began, I would get low coolant message about every 3-400 miles, I didn't even keep track. Now it's around 40 miles. I'm not sure how to tell, but I don't think coolant is leaking into the cylinder.

Truck has 240 k miles and is in good condition, well cared for before and since I have had it. I did egr delete, lift pump, will be changing out the turbo mouthpiece in a day or two. No mods except what's mentioned. Truck mostly sits in driveway, it has pulled a fifth wheel a time or two. All suggestions or advice deeply appreciated.

 

[Nate’s Dmax]

Could possibly be a cracked head. Just a thought.

 

[JustinM]

So, could coolant work its way up through the valve cover without flooding the valve chamber then exit? Can a head crack considering the way this old guy drives? lol

 

[zakkb787]

From the way you talk, I’m guessing it’s an LLY. There’s a few people here that have mentioned something similar to this. Pretty sure that someone posted this same issue recently but no fix yet I think. The head could have cracked in the injector socket. The valve cover is just the top portion. The upper and lower valve covers are sealed by the same gaskets around the injector as they are the outside of the head. The injector does sit down into the head. It could have built enough pressure to blow out the o ring in the injector and seep out. That’s about the only thing I could think of it being. Duramax are fickle creatures. You can run the piss out of one and never have issues. You can baby it and blow a head gasket or break a crank. More than likely nothing to do with how you do or don’t drive it.

 

[Nate’s Dmax]

So, could coolant work its way up through the valve cover without flooding the valve chamber then exit? Can a head crack considering the way this old guy drives? lol

The valve cover is sealed around the injector bore. Zakkb787 explained it good. It was possibly cracked before got the truck even. The LLYs are notorious for getting hot so would be a likely explanation to the crack.

 

[JustinM]

Thanks each of you. You have given me a good mental picture of the design and possible problem. Now I will go lift the injector. Seems like the best possible problem would be the o-ring. Yes it is a 2004.5 lly, wish I could figure out how to list my truck below the message window like all you guys; I have tried.

 

[JoshH]

If it is coming out around the injector, it is a cracked head. There's no other reason coolant would be coming from there. I've never seen it personally, but I've heard of others seeing heads cracked around the injector bore and leaking coolant there.

 

[zakkb787]

James can tell you how to fill out your signature if he chimes in sometime. The o ring won’t be the issue as josh said. They are just there to seal the injector and keep junk out of the injector bore.

 

[JustinM]

You guys sure have been a big help, sticking with me on this. zakkb787, sure sorry to get your report since having pulled the injector as pictured and could find NO o-ring anywhere, looked all over. Does this mean inj were replaced at some point and o-ring left off? JoshH, zakkb787 and Nate, I am left with your analysis that it is a cracked head. Now here's my next question. I have this spare long block with the broken head bolt that I will be replacing both head gaskets, bolts, etc. LB has 208,000 mi, current truck engine 240,000 mi. What would any of you do here; change out the long block after work done or just the head on the installed engine?

One more please, does the carbon on this injector tip indicate need of replacement or can it be cleaned and replaced? No known issues with injectors.

 

[zakkb787]

It’s possible that someone has changed the injectors, also possible that the pressure of the coolant has blown them both off or degraded them possibly. As far as the engine goes 32k miles isn’t enough difference in mileage to change long blocks. Pull the head from your spare block, have it pressure checked, valves and seats checked and replaced as needed, and have it decked. Then install with a new grade c LML head gasket. The only new parts you will absolutely need are the gasket, new head bolts, and an injector install kit that includes new copper washers and O rings.

This being said, you have an opportunity here to prevent future failures if you don’t mind the extra work. Knowing one head is cracked and having a whole new set, I would heavily consider doing both heads since you’re already going to be halfway there. The difference in cost won’t be terribly much and it’s peace of mind that another issue won’t show up soon especially with those miles and being an LLY. I would also HIGHLY recommend changing your water pump while there. It will be more accessible having half the engine torn down. As far as the injectors go, I don’t think there’s any issues with the buildup. A few of mine had the same buildup in them. I very very carefully cleaned them with brake cleaner before reinstalling. This may be frowned on by some but it worked for me.

 

[JustinM]

zakkb787
Deeply appreciate this good advice. If new o-rings were installed on this inj, hopefully stopping the leak at least temporarily, is there some method to determine that the head is indeed cracked, without having to open things up to find out? Compression check?

 

[zakkb787]

I wouldn’t just install the o rings and run it for a while unless it’s absolutely necessary. You run the risk of the head cracking more and also injector bodies will rust when exposed to water too long. You could try a bore scope, but the crack may be too small to find without the pressure of the cooling system. You may could try to pressurize the cooling system and see if you can find the leak that way but you’ll have to be careful with that. I doubt a compression check will tell you anything

 

[JustinM]

Thanks to each of you who have tried to convince me that the head is cracked. After having slept on it, I think I have finally come to terms with it. Searched for a shop in my E Tenn area that I feel good about and think I have found one in Cleveland. I hate to think where my head, the one I wear a hat on, would be without all the help I have received here. Most definitely will follow up here when all is done for the record.