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Discussion Starter · #1 · (Edited)
If some dont remember, my 98 Sierra has had a re-ocurring problem at idle. The truck would take a long time to crank over and once started the trucks idle was realy bad. After several discussions regarding the issue on the old site, I decieded to change the manifold gasket.

Well here is a picture of the valley pan. Does everything look ok? What is all that built up black gue running from the front passanger coolant port, to the rear of the motor. I think it is burnt antifreeze. Has anyone else seen this type of leak before?
 

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Discussion Starter · #3 ·
And I have one more question. Should my valves have this much build up on them. There is 1/4"+ of carbon build up around them.
 

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When I tore my engine down last summer, I found that my valves had the same amount of crap built up on them. I took and chipped it off, soaked them and polished them up, nice and shiny. then did the seals while I had them out. I noticed a little better High RPM breathing (like when merging, or racing I suppose) .

My guess as for the black sludge, would be oil, if you take notice of how the rocker arms and tops of the valve stems are sorta stained, the oil can also turn darker brown, when it sits, like in a valley pan. That's just my guess, but I won't say for sure, Chriss will tho!

BTW: What kind of oil were you running in that engine?
 

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Do you use 87 octane gas, regular unleaded? If yes to this question, I think that pretty much explains some or all of the carbon build up. Mike :cool:
 

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Discussion Starter · #6 ·
I have used Mobil 1 Synthetic since new.

Chuck B.
 

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After reassembly,I'd get abottle of GM top engine cleaner and run it through the intake,that should help to clean up the valves.
 

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Discussion Starter · #9 ·
Mike, yes I use 87 octane. So its time to switch, hah!

Chuck B.
 
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