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4.3 Problems

T

TruckDude94

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Location
Colorado
Hey there yall,

So I have a problem with my truck here. Its the 1997 GMC 4.3 c1500. So I went to start it up to leave school today and it blew a huge cloud of white/grey smoke. After seeing this, I immediatly shut off the motor. For good measure I checked the oil to make sure nothing was out of whack, no milky color nor was it low. Started it up again with no smoke that I could see. The engine in this is a remanufactured motor put in 5 months ago. It has less than 10,000 miles on it. This only happened once before that I recall, and it was a quick puff and nothing more, so I didnt think much of it. I should also mention that after I got to work after school, I shut the motor off and waited a few mins. Started her up again and sure enough a puff of whitish grey smoke. What could this be? I hope they did not screw up something when they installed the motor :mad2: Thanks yall :hihi:
 
I should also note that this does not happen while driving at all, just occasionally at startup. Saw the big cloud of smoke and it spooked me out, so figured I probably need to find out what it is.
 
Warranty?
Get it checked out by the re-builder now. You have oil from a bad valve guide or a head gasket leak. Is the cloud fading away like water vapor or hanging around like oil?

These engines are famous for bad valve guide seals and a puff of white smoke on startup after sitting all night. This may be your past smoke issue with the 2 min restart smoke being a popped head gasket.
 
Does it smoke a bit when you are decellerating from highway speed? That's an indication of bad valve guide seals and would help explain the startup smoke.
If that's the case than a good set of umbrella seals will take care of it. In any case, if it's still under the rebuilder warranty then that's where to start.
 
just tried it on the highway, didnt smoke at all, accelerating or decelerating. Got home from that and no more smoke yet (knocks on wood). Wondering if it might have just been something that got in one of the cylinders. Runs fine btw
 
The smoke that fades away is water vapor then from coolant getting into the combustion chambers esp. when pressurized after shutdown and restart. She will run fine till the coolant locks up a piston by hydrolock or scoring from oil contamination on that hole. Not something I would play with. Get it in for warranty ASAP.
 
Another very good possibility is if whoever put the engine in did not take the time to squarely seat the intake in place and properly torque the intake. If the intake is just thrown on it will crack teh intake gaskets and allow coolant to run from the coolant passages into an intake runner. The VICTOR REINZ gaskets have been updated to help prevent the plastic gaskets from cracking by putting steel inserts in them at the bolt holes so that if teh intake is overtorqued it won't completely crush the gaskets. FEL PRO is still making the old style ones that break OFTEN. CARQUEST carries VICTOR REINZ which is the OEM gasket maker for GM.
 
There are also Fel-Pro gaskets that are aluminum-framed instead of the failure-prone plastic, which eliminates all problems forever.

The PN I'm coming up with is: MS 98002 T
 
brought it by the shop, they said it was bad valve seals. Since the engine is still under warranty it wont cost anything :D
 
@btfarm Stupid question I know, but what is the functional difference between the regular seals and umbrella seals?
 
This shows an umbrella type seal. Your stock seal is a square cross-section o-ring that is inside the valve guide. I usually run both when I assemble cylinder heads.

valve seal.gif

These next 2 are for non machined valve guide bosses and machined (with the metal bands) which I prefer.

valve seal1.jpg valveseal2.jpg

BTW, It's NOT a stupid question. I'm more than happy to clarify.
 
Is it hard to start when it does this? Like excessive crank times?

I know the spider injection system in these have the FPR on the outside that can leak fuel when sitting overnight. If this is your issue, I suggest replacing all of it with a new upgraded Multec II injection system for improved fueling and added smoothness.
 
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