Sounds like you have a good plan...ive had the light on and off since ive had the truck and just of recent a blown headgasket finally showed its ugly head. Just watch your coolant levels and engine temp for any bad signs of getting hot and you will be fine til you figure it out:drink

 

Dexcool no longer eat seals. You can check your upper radiator hose after it has been parked all night and see if it is firm. If so likely head gasket beings you have a LBZ I dont think it is head gaskets. More likely to be the water pump take a look at lower radiator hose see if you can tell if coolant has been running down it.

 

^^ What he said. I had to add just a little once or twice, and over several months, before I noticed my water pump weeping, ever-so-slightly.

And, a big 10-4 on that *()&*&^(^ Dexcool!! I love your devil's coolant name.

 

Just a few things to check.
Check the upper radiator hose when the engines cold like over night before you start the engine. If its collapsed then you might have a bad coolant cap, that might be the reason.
My dealer about 4 yrs ago claimed this is normal BS, I contacted a STANT engineer he said he has told GM numerious times this is not normal, it's a bad coolant cap.
One other reason I was having this happen after replacing the coolant cap about every 1 1/2 yrs was, my truck came with those "Seal Tabs" in the coolant reservoir which turned the coolant from a pretty red/pink color to a brown sludge color. At first I thought I had a blown head gasket, it turned out to he because of the seal tabs dissolved.
After replacing my third coolant cap I figured out it was the thick brown sludge on top of the coolant tank that was causing the upper hose to collapse and the rad cap not releasing the pressure when the engine was cold.
I've solved the problem by slowly getting the brown slime out from the tank.

 

Thanks for all the help guys. I just filled up the coolant. I did notice a bit of the brown sludge color. I will monitor the level every day for the next week and also check the upper hose tomorrow morning before work.:thumb

 

I used those blue shop towels, rolled it up and stuffed down thru the cap opening, holding on to it on one end.
The coolant level will drop doing this, so you will have to add more coolant each time you get done.
I did this numerous times and for several days to remove as much of this crud with the engine hot. Of course GM does not really use these tabs anymore, but if you have your radiator flushed at a shop they will put more tabs in. Tell them NO, of course they will play that warranty scare or possible coolant leaks scheme on you.

I had mine flushed the summer of 2010 and they insisted on putting in those tabs and I let them, but I did not know any better at the time.

 

4. sensor in the tank is bad

 

Mine randomly comes on and off whenever it feels like it but it's never low. Go figure.

 

Dont know if somebody has already said it or not but check and see if its the water pump leaking. It may be bad thats whats wrong with mine.

 

My randomly comes on to I think it on how I park. But I have never seen high temps. Nor have I ever been low on coolant.

Sent from my PC36100 using AutoGuide.com App

 

If its an lbz I'd put money on tranny lines, mine are leaking now.


Sent from my Autoguide iPhone app while doobin a smokie

 

Soooooo while I was putting my exhaust on I found this... possible coolant system leak? I started it, drove it 3 min, then shut it off an this is what happened. Any ideas?

:help

 

Soooooo while I was putting my exhaust on I found this... possible coolant system leak? I started it, drove it 3 min, then shut it off an this is what happened. Any ideas?

:help

Several dealers claim this is normal, "NOT".
I had a similar problem 4 yrs ago and got this normal BS from my dealer.
I called "Stant" and talked to the main engineer he said this was not normal, replace the cap.
The deal refused to install a new $10 radiator cap under warranty, so I bought a new one at the GM parts, that solved the problem, at that time.

One other thing to look for is does your coolant reservor have a tan/brown color??
If so then it has the "Cooling System Seal Tabs" in it, mine did.
This also causes a problem, the cap can not release the pressure overtime if there is a large amount of this slime floating on top of the coolant.

I figured this out after replacing the cap about once a year for 3 years.
I used several of the blue shop paper towels rolled up stuffing down inside the reservoir getting out as much as I could over several days.

Doing some searching I found out that GM has actually quit putting these tabs in.
Some parts departments and shops are still trying to sell and install them.

I still had the original cap that I thought was defective and put it back on, no more problems with the top hose sucking in.
It was the seal tabs causing the problem, for me anyway.

 

Try taking your rad cap off and soaking it in soapy water for a bit and cleaning it. They are supposed to let air back into the system and can't if they are dirty, and will cause that sucked radiator hose. That solves it most times. The other option is just buy a new rad cap and put it on. Try that before anything else.

 

I turned the truck off yesterday and noticed a hissing sound from the front passenger side. I did not have time to pinpoint it. I will try later today.

 

Also, I posted this thread about a month ago, http://www.duramaxforum.com/forum/0...rum/06-07-5-lbz-lly-duramax-powertrain/128071-coolant-leak-issues-resolved.html about trying to find a leak on my LBZ. might be something to check into as I was having some of the same issues as you are.

 

Hissing was from your a/c normal. If hose is sucked shut put a new cap on it.

 

2015 Duramax Coolant Leak w/900 miles

Howdy, I'm new here and unfortunately my first post has to do with a leak on my new 2015. I drove the truck from KC to north of Dallas on its maiden voyage with no issues. Next day I get the "low coolant" warning. Top it off and see no sign of a leak. It sits over the weekend, I hop in it and get the same warning. This time I top it off, drive and return home. Within an hour I have 2 puddles in front and behind the pass front tire. Overflow? Leak in a line? Couldn't find where it's coming from, and all of the hoses seem to fit tight. Thanks for any guidance!

 

Two things you can do, ONE, take it back to the dealer I'm sure it's under warranty.
TWO, crawl under the truck with a flash light and look up in the area where you found leaks on the ground.

 

D.R.C.
1) the dealership service dept was closed on Saturday 2) if you read my post, you'll read that I did look for the source of the leak, and was unable to find it. I was hoping there was common problem already discovered by some of the other 2015 owners. A quick fix or a word of advice to get me through the weekend.

 

I'm sorry but I don't think anyone would be able to come up with any answers unless they looked at your truck.
Did you check the coolant tank overflow, and the coolant tank in general.
If there's a leak it's coming from somewhere and someone should be able to track it down.
The EGR cooler outlet hose is also in that gereral area going back up towards the heater, it's a long 5/8 " heater hose that has several 90's in it.

 

JP dirtymax

A couple days ago I got stuck in some sand in my 2500hd 4x4 LB7 trying to get by the water to unload my fishing gear. In four high, I ran the RPMs up to about 2700 and truck started moving. It was maybe a minute and a half when the big truck started to grab and was moving out of this loose sand when a radiator quick connect broke going to the heater core. I immediately shut the truck off. The following day got the new connection, complete with the hose disconnect tools and changed it out. We filled it back up with water and cranked it. The first think I notice was that it cranked differently then usual. With the cap still off the tank trying to make sure there was no air in the system I then noticed the water was surging out of the water tank with a rhythm matching the engine cycles. We decided to drive it home. A crazy whistling sound on and off all the way home and an antifreeze smell in the cab. The temp surging from 200-230 to hold way. I figured out the whistle was water being forced thru the over flow. I got home a let it sit all night. The following morning I checked the driver hose. It was soft. It's not smoking but a small bit of seam comes out of the water tank. This morning i noticed a large puddle of oil under the oil pan. I think I have a cracked head. What do yall think. 238,000 miles and before this ran great other than variance in temp. Any advise is welcome guys. Thanks.

 

My issue ended up being a crack in the coolant reservoir just below the sensor.