Duramax coolant flow diagram?

[Mark Rinker]

Anyone have access to a good pictorial of the Duramax cooling system, showing thermostats, pump, radiator, etc and detailing coolant flow? If so, could you scan and post it - or email it to mark_rinker@hotmail.com?

Thanks in advance...

[More Power]

Coolant travels from the water pump to the engine oil cooler, into the aluminum bellhousing adapter, into both cylinder banks at the back of the engine, then up into the heads, then to the thermostat housing. :)

Jim

[Mark Rinker]

Thanks for the description, JK.

You have mentioned in a past that one of the reasons for two thermostats is redundancy.

Are they 'serial' in their restriction of coolant flow, or 'parallel'?

[killerbee]

parallel, and staggered by 5 degrees. One of them is a bypass stat. When it "opens" it closes off bypass flow.

If you squeeze your top hose, you will hear a rattling sound. This is the vapor purge mechanism "jiggly balls" in the rear stat.

[Mark Rinker]

Interesting. Is there a safegaurd to keep the two from being installed reversed?

My '01 pressurizes the cooling system, but only in cold weather (bypass mode?). Wondering what the effect of removing one or both thermostats would be and continuing to run this high mile engine for another 50K or so, and repowering in the fall before cold weather sets in, creating the coolant loss issue described in other threads.

Would you pull one, or both?

[More Power]

The stats are physically different. Would be hard to install wrong.... :)

Jim

[killerbee]

Interesting. Is there a safegaurd to keep the two from being installed reversed?

My '01 pressurizes the cooling system, but only in cold weather (bypass mode?). Wondering what the effect of removing one or both thermostats would be and continuing to run this high mile engine for another 50K or so, and repowering in the fall before cold weather sets in, creating the coolant loss issue described in other threads.

Would you pull one, or both?

In theory, if you pull one or both, then the lower rad hose would be subject to suction collapse at high rpm.

The front stat cannot be installed in the rear, but I do believe the rear will fit the front housing. If that were to occur (wrong stat in the front) then the bypass would never be closed off, radiator flow would be reduced, and overheat would be the result on a workload session.

But I can't see how running without a stat can be less stressful to a high mileage vehicle.

[Mark Rinker]

Never had any overheat problems, even with the pressurization issues. Just bubbles in the coolant.

Thanks to both of you for your input.

[killerbee]

Mark

I read your other thread. so I see what the context is now. Here is my take.

With gasket issues, the cylinder pressurizes the cooling system. Thermostat type, or lack of, should not have any impact on that. In reality, if you removed them, your truck would never warm up in colder weather, and would take an hour in warm weather. That is bad for the motor also.

That influence of migrating cylinder pressure stands to push out coolant, and the only way to stem that, is to reduce cylinder pressure. So if you have some highly advanced timing, it may help to retard it, but that is a band aid at best.

Solution:

You could go to a coolant with a high BP, like evans, and then drill out the cap, venting it to the atmosphere, that will give the excess gas a place to go, without pushing coolant out. In lieu of evans, you could use 90% EG, that would have little vapor pressure at normal loads and temps. You could probably use it as a daily driver for quite a while this way.

Basically, you are working WITH the problem, allowing it to purge.

[Mark Rinker]

Killerbee - nice article on the LLY overheating issues. I had one that ran hotter than my LB7s, but didn't overheat. Guess I got lucky!

I tried running the cap loose during cold weather pressurization and it puked it out the top of the resevoir instead of the overflow tube. At that time, the focus was on snowplowing and simply keeping the truck running.

I'll drill one cap and see what the results are. Thanks for the idea.

A nearly new '03 DMax engine will be delivered Tuesday. Maybe I can leave it on the shelf for awhile and save money for the labor of the swap. Its a shame to pull a perfectly good, smoke-free, non-oil using LB7 for a $10 gasket.

[killerbee]

This is no remark toward any individual, just a comment on custom tuning. i have been reading about some of the large pulse widths, in combination with some pretty staggering timing advance numbers. In my own tuning, I have had caution buzzing in the back of my head, with the realization that this is a potentially lethal combination for cylinder pressure.

What happens is that this combination my be pseudo-ok for quick launches, and dyno indications, and otherwise non-heatsoak motor conditions. But when the throttle is left open (forgive the gas analogy) for more than a few secs, as in plowing, or towing, that same timing starts really escalating cylinder pressure, due to the ignition advancing effects of load and heat accumulation. Combustion occurs sooner in a nutshell. Peak cp's increase and advance as the load is held constant.

It drives home the importance of tuning with some kind pressure sensing equipment, under real world stress, off-the-dyno type monitoring.

I guess what I am saying is that longevity is traded off much quicker with tunes that do not compensate for dynamically changing heat and load conditions, but especially heat. After working with the EFI gang for a couple of weeks, they finally got these "compensation" tables revived for me personally on all OS's, so folks can start using them (they were inert from the factory). However the "MAP timing" compensation table is still inop, we may have to wait for that one.

[Mark Rinker]

You might take your findings and apply them to the C4500 series. The placement of the engine is entirely different, but I have run across two or three 2005 LLY equipped units with engines replaced already under warranty. One in particular had two turbos replaced before the new warranty engine.

[killerbee]

I have run across two or three 2005 LLY equipped units with engines replaced already under warranty.

what was wrong with them?

[Mark Rinker]

Don't have details from previous owners, just the service history from VIN searches. It would appear both died from prolonged towing while overheated. Turbos, pistons, etc. C4500s are rarely used as daily drivers. Always towing/hauling at higher RPMs due to lower gear ratios.

Personally, I am shopping for LB7s only. Can't take a risk on getting someone else's overheated problem. It seems like there are lots of '05 C4500s for sale, more than any other model year out there...

[carco]

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.............

[killerbee]

off-topic. It is odd that the turbo cooling begins so late. I would guess that it is important that the turbo not be thermally shocked. This was a real concern in turbocharged Cessnas, there were air cooled.

[rob from bc canada]

I do not profess to be knowledgeable in engine technology, but I would expect that running a Diesel at high hp output (towing) with a leaking headgasket would very quickly blow or melt a bigger hole through there, and start warping head or block beyond repair.

Can't imagine it'll get you very far once that starts to happen, and could leave you stranded with little warning, or lead to engine on fire.

If you know which cylinder is low on compression, and you want to squeeze a few more miles out of it, what would it cost to have a small shop install a new gasket just on the one side only?

[redhot]

I am looking for a cooing system diagram as I do not like the way the truck
heats up.2005 year truck

[killerbee]

Your cooling system is not the issue.

Google "thermal feedback duramax lly"

A lot has happened since 2007.

[More Power]

To solve an LLY overheating problem, I recommend owners upgrade the fan, fan-clutch, fan shroud and radiator to that used by the 2006/7 LBZ. All of these OEM items are larger than that used on the LLY.

Jim

[Kennedy]

To solve an LLY overheating problem, I recommend owners upgrade the fan, fan-clutch, fan shroud and radiator to that used by the 2006/7 LBZ. All of these OEM items are larger than that used on the LLY.

Jim

And stay away from "surefire" fixes from relatively obscure sources without a KNOWN track record.

[chris993]

Parts website called GM Parts Giant.com has good diagrams to go with parts lists. I have the 5 volume Helm manual for my 04 and this is a heck of a lot easier way to familiarize yourself with the layout of a system. The manual is apparently for troubleshooting flow charts, torque values, and repair procedures and I have a hard time finding good overviews with diagrams.

http://www.genmotorinfo.com/Picture.aspx?Make=GMC&Model=Sierra&Year=2004&SubModel=2500%20HD%202WD%20-%20New%20Style&SectionID=00&SectionDesc=8-CYLINDER%20ENGINE&PicDesc=2001-2004+CK+ENGINE+ASM-6.6L+V8+DIESEL+COOLING+PUMP+%26+RELATED+PARTS+(LB7 %2f6.6-1)+-+TC00-644&pid=100208TC00-644

Heres the link to the parts list....clicking the Get Info button brings up the diagrams....

http://www.gmpartsgiant.com/Page_Product/PartDetail.aspx?&Make=GMC&Model=Sierra&Year=2004&MakeCode=LG&ModelCode=C&CatalogCode=56C&SubModel=2500 HD 2WD - New Style&mCode=TC25753&eCode=LB7&tCode=M74&RPO=Z88&majorIndexID=00&SupplGroup=80&minorIndexID=TC00-644&SortKey=113

Dont know why the whole URL is not copying as hyperlink, but you need all of the above string ending in 113....

Or just go back to the homepage and click on your vehicle, year, model, etc.