Hello. I have an 01 LB7 Duramax. I have lately noticed variance in my truck's cooling system reservoir level. It was down a bit so I loosened off the cap. At a certain point of loosness the pressure in the syem was vented, returning the coolant level to a close to normal level yet spitting some coolant out of the overflow. I thought this odd especially when the engine was cold. Tried a new cap, nothing changed. When it is running it runs flawlessly and if the cap is off, you can see that it is bubbling in the reservoir. There is a slight loss of coolant but it's like it is only as much as what goes out the overflow when I remove the cap to vent the system. The temp guage has never gotten real hot and in the winter it does not get anywhere near normal operating temp in warm weather on the gauge. I have added more power to the engine in the last year with no noticeable adverse effects. I have seen other posts on other sites that suggest a head gasket or possibly a leaking injector cup seal. Does anyone have any idea what this might be and have a suggestion as to how to pinpoint the problem? Where could this gas be coming from? Both of those scenarios make sense but are there any other possibilities?
Thanks

 

I wouldn't think it was an injector cup unless you recently had injectors done. that doesn't mean it's not that, but i would think it was your head gasket first.

 

try washing the rad cap in hot soapy water, if that doesnt help, try a new cap ($12 at a dealer) and then if thats not it then its probably Headgaskets especially if the upper rad hose is still hard after sitting over night

 

Have you done a combustion gas detection on the coolant?

 

this may or may not work... the best way to know 100% sure that its gaskets is to have each cylinder pressure checked, i would start with Cylinder 2 on the front drivers side, that is the most prone to blowing out, then cylinder 7 on the back passengers side, it is also prone to blowing

 

If its got a blown hg and its leaking combustion pressure into the cooling system it will show every time there bud. Maybe we should go more in detail and explain to bring each cylinder to the top, get the correct adapters and buy a leak down gauge and pressure test each one to determine if there is a combustion leak. Then pressure test for coolant leaks?

Always start with the easiest tests first
My lb7 lost cylinder 1 first

 

Mine didn't show on a exhaust gas test.... this is why I say this... but it might..

 

There is a hose connected to the top radiator hose outlet which leads back to the turbo. I am assuming that it carries coolant to cool the turbine side. Is it possible that I have some boost leaking past something in the turbo charger and getting into the cooling system there? Any ideas on this theory?

 

anything is possible.... but get an exhaust gas in coolant test done(you need diesel specific fluid) and then if it shows nothing get the cylinders pressure tested... My guess is your headgaskets... I was in denial too..

 

Diesel specific? Lol every bottle i have ever seen say for gas and diesel engines on the side of it?
I have a Volvo in the shop that ill take a video example of how to use the kit.