blown head gasket on a Duramax???

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I would back flush the whole system. Look into the second thermostat. As I remember from what I quickly read that it can cause similar situations. Ill check with my Bro when he returns from vacation he is a duramax guy. I got more experience with the 5.7,6.2, and 6.5l gm 6.9,7.3 ford and my favorite the cummins.
My 250,000 mile 5.3l gas runs perfect with a blown head gasket I can see it leak but it keeps on running. problem started with a bad plastic tank to core seal on the radiator kids overheated it. they filled with wrong antifreeze and whala I get silicone sludge throughout the whole engine blocked heater core.
How many miles you got on it?
Have you put any aftermarket hot rod goodies on it?

I have bought many a vehicle diagnosed incorrectly for a song. Not saying its not a head gasket, but many times its not.

picked up a Cherokee a few years back for 400 put an electric fan in and flushed system and I was in business.

I have a Banks PDA tuner with a Banks intercooler (radiator), Banks ram air and SS exhaust, plus a 6" suspension lift with rear air bags.
Its got only 115k.
 
Look around on this site also http://www.duramaxforum.com they are lot of help there and I read on there daily. I am on there with the same screen name. You may have some air trapped as others have said. When look at the front of the engine valley and locate the thermostats housing there is a bolt on the housing that you take out to let air out and help bleed the system as you refill the coolant. Start with the cheap fixes. Change your thermostats out and the coolant. Flush if you can. If your truck has dexcool in it (the red stuff ). Put that back in mixing red/green gets nasty real quick. The truck should have the red. Change your coolant overflow tank cap. On duramaxes very seldom will you burn coolant or get water in the oil with a blown head gasket. Most times you will get the syptoms you have. Blowing coolant, intermittent heat,and the such. Lb7 engines are notorious for injector,and head gasket failures poor GM design on both. Try taking your truck and giving it a good run, blow some carbon out, come home and park her. Before you leave in the morning see if the upper radiator hose is still hard. IF it is get the check book out or trade her in.
 
That's not too bad for a lb7 engine especially for the injectors, although we would like to see more miles before H/G issues. Refinements were made on the lly injectors and the lbz including a head gasket design change on the lbz engine.
 
Haven't read every reply, so maybe already mentioned, but it could be as simple as a loose or cracked hose leading to the coolant overflow reservoir or faulty radiator cap. The engine will expel coolant into the overflow tank when it warms up. When it cools down, it 'should' pull coolant back into the engine. If the hose to the overflow tank is cracked or loose, the engine will just pull air back in. A couple cycles of this and the engine is low on coolant.

Also the radiator cap is designed to build pressure up to a certain level (ie 10, 12, 15 psi) but it has a second valve which opens under vacuum to allow the engine to siphon coolant back in. If that valve is stuck, full of crud or otherwise inoperable, you get the same condition as above... engine cant pull coolant back in as it cools down and will eventually run low.
 
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That's not too bad for a lb7 engine especially for the injectors, although we would like to see more miles before H/G issues. Refinements were made on the lly injectors and the lbz including a head gasket design change on the lbz engine.

I have a 2004.5 model and it has a LLY engine.
 
Haven't read every reply, so maybe already mentioned, but it could be as simple as a loose or cracked hose leading to the coolant overflow reservoir or faulty radiator cap. The engine will expel coolant into the overflow tank when it warms up. When it cools down, it 'should' pull coolant back into the engine. If the hose to the overflow tank is cracked or loose, the engine will just pull air back in. A couple cycles of this and the engine is low on coolant.

Also the radiator cap is designed to build pressure up to a certain level (ie 10, 12, 15 psi) but it has a second valve which opens under vacuum to allow the engine to siphon coolant back in. If that valve is stuck, full of crud or otherwise inoperable, you get the same condition as above... engine cant pull coolant back in as it cools down and will eventually run low.

But where do the coolant go? If it cools down and doesn't pull it back in then wouldn't it still be in the overflow container?
 
I'm a long time GM guy, 12+ year member of ZR2.com, ZR2USA, founding member of the now defunct NEZR2 off road club, etc.

91 GMC Sonoma - put a new motor in at 155K, sold to a buddy at 180K and he ran it to 230K before it was stolen & wrecked.
01 S-10 ZR2 - 92 K on her, don't drive it much.
03 Blazer ZR2 - 84 K on her, my daily driver, also has a 7'4" Fisher Homesteader (poly blade) plow.
06 Duramax with LBZ, just got her a little over a year ago.

GM had some serious issues with that pink Dex-cool crap in the late 90's and early 2000's. It is ok in a clean, closed system but it HATES air and ANY sort of contamination. A simple leaky radiator cap can result in a lot of air, dust, dirt, pollen, etc getting sucked into the cooling system which will turn into thick brown sludge. The sludge clogs heater cores, small coolant passages, radiators, etc.

Dex-cool also EATS (head and intake manifold) gaskets in those era motors.

Mixing green coolant with the pink Dex-cool is a HUGE no-no. IMO with a diesel, you need to have a professional chemical flush / backflush done. If it was a SBC 5.7 like most folks are familair with, you could drain it, refill with water and a double dose of Prestone flush chemical, run untill hot, drain, do it a 2nd time, then flush and backflush everything with garden hose untill everything runs clear. Considering the complexity of the D-max cooling system (and even the newer generation LS gas motors) I would have a reputable shop do it.

I know a lot of guys who have swapped LS motors into their S-10's or put them into custom 4x4 rock buggies. They can be a royal PITA to get the coolant system vented properly.

I do not have that much experience with the diesel motors, I actually learned a lot reading this thread, but the coolant issues are all over the internet forums. When my Blazer lower intake manifold began leaking, it went straight to the dealer, got a chemical flush, upper & lower intake manifold gaskets replaced and refilled with green "universal" low toxic coolant. I have not had any problems in 2 years now.

When my S-10 was new & under warranty, I had a habit of taking the radiator cap off and checking the coolant level every 5K when I changed the oil. I noticed the brown sludge forming. The dealer informed me to leave the damn radiator cap alone and check the levels via the overflow / recovery bottle. I was letting air into the system unknowingly and causing the sludge formation. They also found the radiator cap to be leaking slightly and replaced it. No further issues, but it needs the intake gaskets replaced now. It developed a small external leak from the left rear head to intake manifold joint, so I have not been driving it untill I have the oppertunity to get it replaced.

For what it's worth, the service manager who did all the warranty work on my S-10, also did the Blazer, and also will do anything the D-max needs. It's funny, she used to drag race in her earlier years. Finding a woman service manager who is a life long gear head is a welcome thing. :cool:
 
But where do the coolant go? If it cools down and doesn't pull it back in then wouldn't it still be in the overflow container?

Ok I'm assuming you are filling the tank to the "cold" full line before starting. (Honestly not trying to be a smarty)Try squezzing the upper radiator hose while filling to help getting the air out like mentioned before. Start the truck with the cap off and moniter the coolent level. If it drops add more accordingly. It may require more once the thermos start to open.
 
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Once you are SURE you don't have any air stuck in your system, watch closely for any air bubbles coming to the tank. Sure sign of HG. Check the level daily and adjust accordingly. Once full if you start blowing coolent out of the tank your screwed.
 
I would also check the EGR cooler and water pump weep hole. EGR delete package or SS replacement maybe an upgrade.

I am not up on the banks tuner but if it does adjust timing for power this will definitely effect your cylinder pressures. If you can tune your tuner back to stock until your problem is corrected fully.

I would definitely do a compression check(dry and wet)

Back in the day we could send out oil samples for evaluation also. Cat dealers had a lab back then. The oil samples where checked for coolant, fuel and metals. It was helpful for evaluation of wear on the high mileage and hours that are common place on commercial vehicles and equipment.

Rudolf would be amazed with what they are doing with his diesels today!

the banks radiator you have looks awesome! the advertising states it has cast tanks but does not state the material. is it cast iron or aluminum?

yes, the duramax is an Isuzu design built to a price point for light to medium duty trucks.
 
But where do the coolant go? If it cools down and doesn't pull it back in then wouldn't it still be in the overflow container?

Generally, it should, though if the engine expels more coolant than the overflow can hold, then it may leak out onto the ground. If you are driving while this happens, the coolant may just drip out on the road as you drive and you won't necessarily notice a puddle. Also, the next time the engine warms up, it expels air which can also slosh some coolant out of the overflow tank. So after a few times, the overflow tank may appear normal.

One thing to do is to observe the overflow tank. It should be at some level when the engine is cold. Mark that level carefully and warm the engine up to full operating temp. The level should rise by some notable amount. Then when the engine cools, it should draw the original level down again. Also with the engine running, if you see any evidence of bubbles forming inside the overflow tank, at the siphon hose, that could mean a head gasket leak allowing combustion gas into the coolant system.
 
"Ok, this may not be your answer but I ran across this and it may help someone.
Cold start, both t-stats closed, coolant pumps to oil filter-flywheel houseing cross over-block-heads-EGR and heater core @ 26GPM. Engines warms to 180* first stage of the primary t-stat allowing some flow to the radiator. At 185* secondary t-stat starts to open flowing more to the radiator. In here @ arond 132* the turbo starts recieveing coolant through a thermo controlled circuit by-pass. At 203* the primary stat is full open. At 212* the seconday stat is full open, all coolant is through radiator and flow is near 80 GPM. Now this is for the LLY engine. bob............." quote from diesel page

So IMHO If you push a cooling system to 212 or boiling point of water make sure your antifreeze is mixed correctly for boiling protection also. because if a system can introduce air, it can also expel vapor to the atmosphere far be it a slower rate than it can bring in air(depending on location of air leak). so it is possible for a component to expand when hot and then contract when cold and hold the residual vapor pressure till morning. this was common on plastic tank and aluminum core radiators.
 
what i have to say is not anything to do with a d max. but we had a similar problem in my wifes sienna with rear heat. took it to three dealers one said nothing wrong same guy a week later replaced the rear heater core. same problem so we go to dealer 2 says the rear controller is no good so he replaced that. week later it's back in the shop now he says the front controller is no good so that good replaced. off to dealer 3 at this time we lost heat in front and back. he said it was low on fluid. then a day later lose the heat in back again. now i'm thinking like a plumber and said to my self this has to be air bound. with no way to burp it i took it to a very steep hill nose up pulled the rad cap rev it a few times i check the rad it's low i fill and rev it low again filled and that was that.

might want to try a very steep hill or a very tall floor jack when you flush and go to refill. hope that works for you. if not might be time for a new truck.
also i haven't read anything here but how is your oil? does it have any milky stuff on the stick?
 
"Ok, this may not be your answer but I ran across this and it may help someone.
Cold start, both t-stats closed, coolant pumps to oil filter-flywheel houseing cross over-block-heads-EGR and heater core @ 26GPM. Engines warms to 180* first stage of the primary t-stat allowing some flow to the radiator. At 185* secondary t-stat starts to open flowing more to the radiator. In here @ arond 132* the turbo starts recieveing coolant through a thermo controlled circuit by-pass. At 203* the primary stat is full open. At 212* the seconday stat is full open, all coolant is through radiator and flow is near 80 GPM. Now this is for the LLY engine. bob............." quote from diesel page

So IMHO If you push a cooling system to 212 or boiling point of water make sure your antifreeze is mixed correctly for boiling protection also. because if a system can introduce air, it can also expel vapor to the atmosphere far be it a slower rate than it can bring in air(depending on location of air leak). so it is possible for a component to expand when hot and then contract when cold and hold the residual vapor pressure till morning. this was common on plastic tank and aluminum core radiators.

Would you mind posting a link? Sounds like a thread I'd like to read :)
 
Sounds like my car when the waterpump went bad. I have a 2003 Impala, and at first it just used some coolant- then up to 1/2 gallon a day- no white smoke- no visible leak. Then, It started the heat going cold- at the same time the temp gauge would go up to 260, all within seconds. Pulled over, boiling over, sprayed coolant out. I waited 5 minutes or so and drove home with no issues. Let the air out, refilled the coolant and started noticing a puddle wherever I parked. It would drip all night, even after it had cooled. Was afraid the head gasket had gone (my car has the 3.4 engine, which is known for head gasket issues), even appeared to have coolant leaking from the side of the engine. Since it was near the water pump, we decided to replace the water pump before spending ~$1000+ on a head gasket. $20 and an hour later no more leak- I haven't added a drop in at least 3 months, and the car hasn't even though about overheating.
 
http://www.thedieselpageforums.com/tdpforum/showthread.php?t=26996&page=2

here is the link for shomodady its on page 2 of the first link I sent.

My experience is with a family owned Jobber truck/car shop so I have seen many different brands of diesels over the years from vw,Peugeot,yanmar,cat,Detroit,cummins, and more than my share of international engines.

I read mainly technical articles trade books and yes service manuals for entertainment. So I am/was the guy that gets called to diagnose the undiagnosable. usually after many hands have touched it. always start with the basics then you evaluate your basic data to come to an educated conclusion.

The only ones who get paid for a misdiagnosis are doctors!

my all time favorite story: I have replaced all the batteries tried three alternators and it still don't charge. I go to the shelf grab the correct serpentine belt and install it correctly(routing). using logic not the diagram on the shroud. remember that many systems depends on your belts with serpentine so any time you lose rotation from slipping you lose performance on one or more items ps/waterpump/brakes/alternator/plow pump etc. all gm I check front components at 60,000 miles in rough service.


lots of info to digest on this thread but for a nerd like me great stuff!
 
The only ones who get paid for a misdiagnosis are doctors!

Unfortunately, the owner pays for parts replacement and mechanic time even if it doesn't fix the problem. It's a rare shop that will eat the cost of failed attempts.
 
So other the last Tuesday and Thursday the heat as been fine,
It still says low coolant on the dash.
I checked hose this morning and it wasn't super hard but more firm like.
I slowly opened the over flow cap (there is NO other cap anywhere on the system) and it had some pressure.
It gurgled and some coolant rose up and bubbled into the container.

I'll check it again tomorrow morning.

I called a radiator shop. Thats all they do is radiators and heater cores. thats it.
I told him what was going on and he said he's not sure if its a head gasket or a thermo stat, but bring it in and he will do some diagnosis.
He charges $130 to flush the system.
 
[quote="NE WOOD BURNER, post: 1611649, member: 25754"

The only ones who get paid for a misdiagnosis are doctors![/quote]

That's why doctors "Practice", the rest of us have to WORK!!!
 
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What about weather forecasters?
 
So other the last Tuesday and Thursday the heat as been fine,
It still says low coolant on the dash.
I checked hose this morning and it wasn't super hard but more firm like.
I slowly opened the over flow cap (there is NO other cap anywhere on the system) and it had some pressure.
It gurgled and some coolant rose up and bubbled into the container.

I'll check it again tomorrow morning.

I called a radiator shop. Thats all they do is radiators and heater cores. thats it.
I told him what was going on and he said he's not sure if its a head gasket or a thermo stat, but bring it in and he will do some diagnosis.
He charges $130 to flush the system.

Dont sound good bud. IF the truck had sat overnight there shouldn't have been any pressure left in the system. The block should have cooled along with the coolant and the expanded coolant "shrunk" back into the block leaving a void in the expansion tank replaced with outside air drawn in through the cap. A cold engine should not release coolant into the expansion tank when the cap is removed. Now a HOT engine will obviously.

In my opinion save the $130 flush and find a reputable diesel shop in your area that is familiar with duramax engines.

When cold you should easily be able to squeeze the upper radiator hose and feel/hear coolant.
 
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