Talk me out of Headgaskets

kdelorme17

New member
Nov 23, 2022
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Recap of whats happening in as much detail as I can tell

Truck Runs well, idles well, pulls well and otherwise seems well. I get a low coolant light and the reservoir is low. I top it up and it'll push it out the overflow within an hour or less to a certain point (probably half reservoir) and stay there never going lower. I don't notice a puddle under the truck when parked for long periods of time. Only notice it dripping out of the overflow from the tank right Infront of the passanger door if I park somewhere after its hot. I live where its cold now, on start up it'll fire up fine but will have about 2-3 seconds of a white cloud out the exhaust (smells more like unburnt fuel than coolant but i've never put my face in it). I can take the coolant cap off when its cooled down and most of the coolant will return, its not like its burning it and its gone forever, some has gone because of the overflow thing but the coolant will gargle and come back for the most part. coolant is clean. oil is clean. just flushed the coolant properly. Truck is Deleted from the previous owner so I don't have details on that (Don't know if there's a way that it can be done incorrectly and pressurize the cooling system somehow).

Ive seen a LOT of the videos posted will show carbon coolant tanks that look black or milky oil but both are perfect, not even a hint of carbon in the coolant fluid and Just finished an oil change and it was also perfect. Is there something other then head gaskets to check at this point. Everyone rushes to get to there but seeing if theres anything else someone has in mind..

Thanks
 

Dozerboy

Well-known member
Jun 23, 2009
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Could be EGR, Bullet reservoir cap, Or possibly I've been told sometimes the thermostat causes. 75% it's head gaskets. My head gaskets were blown for at least 2 years while I drove my truck trying g to talk myself out of it just like you. I even went on a 3,000 mile camping trip pulling my 12,000 pound RV a few months before I pulled the heads off. It never missed a beat other than burping half the coolant out the reservoir.
 
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2004LB7

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Dec 15, 2010
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I've read stories of people just loosening the cap on the reservoir when they want to continue to drive it before replacing the head gasket. some did that for years and thousands of miles. they keep driving as long as it ran good
 

660catman

Member
May 18, 2021
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I had same issue back in January. Lost coolant because the pressure pushed it out. Had rad cap removed while truck running and the engine side reservoir bubbled constantly pushing coolant out the top. With system sealed the upper rad hose was rock hard the next morning. It was the head gaskets.


2013 Sierra SLE 2500HD Crew Cab
 

Dozerboy

Well-known member
Jun 23, 2009
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I've read stories of people just loosening the cap on the reservoir when they want to continue to drive it before replacing the head gasket. some did that for years and thousands of miles. they keep driving as long as it ran good

Those people must not tow or hotrod. I tried that and boiled the coolant and shot it everywhere pretty fast. Even tried just making a tiny hole in the valve of the cap to just slowly vent extra pressure. Just ended up with a junk cap.
 

2004LB7

Well-known member
Dec 15, 2010
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Those people must not tow or hotrod. I tried that and boiled the coolant and shot it everywhere pretty fast. Even tried just making a tiny hole in the valve of the cap to just slowly vent extra pressure. Just ended up with a junk cap.
climate may have been a factor. and maybe coolant concentration. can't see it working too well towing in the heat without pressure on the coolant. but unloaded my LB7 ran cool enough to not need the fan most of the time. probably needed thermostats
 

496 BB

Head Thread De-Railer
Feb 20, 2009
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Going thru same thing right now except it was like urs for a lil while then all shit hit the fan and cant even drive it now more than 1 mile. If that upper hose is hard over night and pressure still in reservoir Id say hg's. Trust me I tried to talk myself out of it for months too. 130k on mine
 
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JoshH

Daggum farm truck
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Feb 14, 2007
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I drove my truck for probably 5 years with bad head gaksets. I would get a low coolant light 2 or 3 times a year and add coolant. The truck never got hot and never mixed oil and coolant (I've actually never seen a duramax mix oil and coolant because of bad head gaskets). Except for fact it held pressure on the cooling system even when cold, you would not have known it had a bad head gasket. What you're describing sounds like bad head gaskets to me.
 
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036.6turbo

Active member
Jan 17, 2014
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My LML is doing the same thing. Continually get the low coolant warning. My never loses coolant, just pushes it to the other side of the tank. I loosen the cap, it flows back, message goes away for awhile. But it always comes back.

Truck never overheats, never pushes coolant out, never mixes oil and coolant, even when hauling heavy.

I can't bring myself to pull the heads, when it never actually loses any coolant.
 

Dozerboy

Well-known member
Jun 23, 2009
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The truck never got hot and never mixed oil and coolant (I've actually never seen a duramax mix oil and coolant because of bad head gaskets).

I always send my oil off to the lab for Analysis. They never detected any coolant in my oil. After driving for years with a blown HG too.


They always look for any trace amounts of coolant and oil to avoid costly downtime when you have your oil analyzed.
 
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Dallas S

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Jun 17, 2009
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I drove my truck for probably 5 years with bad head gaksets. I would get a low coolant light 2 or 3 times a year and add coolant. The truck never got hot and never mixed oil and coolant (I've actually never seen a duramax mix oil and coolant because of bad head gaskets). Except for fact it held pressure on the cooling system even when cold, you would not have known it had a bad head gasket. What you're describing sounds like bad head gaskets to me.
We have many sh*t gold gaskets mix coolant and oil. They will hydro lock too. I always said Dmax hg won’t mix until the last couple years. Early two designs we have never seen mix.

We also have never had a egr cooler cause pressurized cooling systems..