# 6.0L heating up? Rad flush req'd??



## ontario026 (Dec 22, 2008)

Ok, my truck is 2000 silverado 2500 with the 6.0L, the last couple days while heading down the highway the temperature gauge has climbed to probably 3/4, getting fairly close to the red zone, but not quite there... both times I noticed it, the needle stayed there for 30sec or so then dropped back to normal..... a few other times in the past when it has been cold the heater occasionally has not blown as hot as it should for a period of time, then normally will work itself out.... I got the truck with about 90K miles on it, and it now has about 144K miles on it, I have never touched the cooling system, with the exception of topping off the resevoir with coolant (used mercury marine coolant which is dexcool...) To the best of my knowledge no one has ever added green coolant... 

any thoughts on this? I would assume either the dexcool has broken down or coagulated and possibly disrupting the flow of coolant temporarily, or else the thermostat is getting sticky and sticking closed?

Does anyone know the procedure that gm dealers would use for a cooling system flush? do they normally do just a dump and refill? or do they pull the thermostat and reinstall the housing and flush w/hose etc?? 

My gut feeling is that I should flush the cooling system and might as well swap the thermostat while I'm in there... anyone experience anything similar?

Matthew


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## Newdude (Dec 4, 2006)

It could be possible that you have an intake or head gasket leaking. If I recall, one way to test that is with a voltmeter. Place both leads in the coolant, and if there is a positive charge, that would lead to metal content in the coolant.


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## B&B (Nov 4, 2006)

ontario026;970212 said:


> Ok, my truck is 2000 silverado 2500 with the 6.0L, the last couple days while heading down the highway the temperature gauge has climbed to probably 3/4, getting fairly close to the red zone, but not quite there... both times I noticed it, the needle stayed there for 30sec or so then dropped back to normal..... a few other times in the past when it has been cold the heater occasionally has not blown as hot as it should for a period of time, then normally will work itself out.... I got the truck with about 90K miles on it, and it now has about 144K miles on it, I have never touched the cooling system, with the exception of topping off the resevoir with coolant (used mercury marine coolant which is dexcool...) To the best of my knowledge no one has ever added green coolant...
> 
> any thoughts on this? I would assume either the dexcool has broken down or coagulated and possibly disrupting the flow of coolant temporarily, or else the thermostat is getting sticky and sticking closed?
> 
> ...


If it isn't just low on coolant then it sounds more like it just needs some overdue service and the T-stat has suffered from it. If it hasn't been done in many many miles the Dexcool is very likely long overdue for service and a through flush (includes back flushing the heater core), a fresh T-stat and some new coolant will likely fix it right up.


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## B&B (Nov 4, 2006)

Newdude;970216 said:


> It could be possible that you have an intake or head gasket leaking. If I recall, one way to test that is with a voltmeter. Place both leads in the coolant, and if there is a positive charge, that would lead to metal content in the coolant.


There's no water in the intake on the LS engines and being a 2000 6.0 will have iron as opposed to aluminum cylinder heads so a head gasket issue would generally be very unlikely, as they're not known for them anyway...unless the cooling system is neglected of course. 

Using the scientific method  of checking the coolant with a DVOM doesn't tell you that metal from a possible deteriorating gasket has made its way into the cooling system, so it won't tell you if a gasket is failing, and most gaskets have little metal on them anyway these days. It's done to check the amount of electrolysis going on in the coolant. Anything over about .01V and the coolant is getting close to needing serviced. Old timers swear by it but I've never found it to be all that accurate. A PH test for the coolants condition and a hydrocarbon test checking for combustion gases in it (if you suspect a blown head gasket for example) is far more accurate. Not that the DVOM test won't tell you anything, as it does tell you a little; it's just not all that accurate with todays coolant compositions.


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## ontario026 (Dec 22, 2008)

well it was about -14C out this morning and the temp gauge heated up to normal, with no intermittent 'spiking' but she wasn't blowing heat like it should... it was warm at best when driving and at stop lights it would blow cold air.. So I dropped the old girl off at the GM dealer and they are going to flush the cooling system PLUS the heater core (not normally part of the cooling system flush) and throw a new thermostat in there for good measure too....

I'll post results later... 

Matthew


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## Newdude (Dec 4, 2006)

B&B;970425 said:


> There's no water in the intake on the LS engines and being a 2000 6.0 will have iron as opposed to aluminum cylinder heads so a head gasket issue would generally be very unlikely, as they're not known for them anyway...unless the cooling system is neglected of course.
> 
> Using the scientific method  of checking the coolant with a DVOM doesn't tell you that metal from a possible deteriorating gasket has made its way into the cooling system, so it won't tell you if a gasket is failing, and most gaskets have little metal on them anyway these days. It's done to check the amount of electrolysis going on in the coolant. Anything over about .01V and the coolant is getting close to needing serviced. Old timers swear by it but I've never found it to be all that accurate. A PH test for the coolants condition and a hydrocarbon test checking for combustion gases in it (if you suspect a blown head gasket for example) is far more accurate. Not that the DVOM test won't tell you anything, as it does tell you a little; it's just not all that accurate with todays coolant compositions.


Hehe...thanks for the correction lol...I think I had a brain fart when I posted that earlier...a huge one...


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## ontario026 (Dec 22, 2008)

well I picked it back up from the dealer, about $320 later, fresh coolant, flushed system and heater core, plus swapped thermostat... I have only driven across town so far, but it seemed to be blowing more heat that I have ever had it make... i'll have to see after a few highway trips if the temp gauge stays rock steady like it always used to.....

Matthew

P.S. the service guy claimed lots of junk came out when the flushed the cooling system, didn't get a chance to talk to the tech.......


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