Author Topic: '86 K20 running hot, burning rich, blowing smoke at start up and dying  (Read 3513 times)

Offline mk_tacticalranch

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I need some help trying to figure out what is going on with my rig.  I have a 1986 K20 Silverado Suburban. 3/4 ton, 4x4, 5.7L gas 350 no A/C.  Recently it started blowing white smoke upon start up and immediately dissipates.  Its been running hot, normal running temp is 210, now it stays around 235.  On really hot days it will die while driving slow (in parking lots and driving down our driveway).  There is no coolant leaking, oil isnt milky.  Its running rich also.
I'm not sure where to start...

Thanks

Offline LTZ C20

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Sounds like it's burning coolant and at low speeds the coolant is gumming up the spark plugs so it's making it die because it can't burn the fuel and air. The cause of this is usually a blown head gasket or a cracked cylinder head.
LTZ Cheyenne C20

Offline mk_tacticalranch

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Thanks what I was afraid of! Thank you!

Offline LTZ C20

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Your welcome. It's common if the engine has ever severely over heated.
LTZ Cheyenne C20

Offline mk_tacticalranch

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Re: '86 K20 running hot, burning rich, UPDATE
« Reply #4 on: July 02, 2015, 02:07:35 PM »
My burb hasn't been dying or blowing smoke anymore.  I changed the thermostat and water pump.  I am still running hot so now im going to replace the head gasket.  BEFORE i dig in, any special tools i need?  Any parts I should replace while im in there?

Thank You

Offline FlatBlack77

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you will need a torque wrench for sure if you dont already have one.

"When you are a hammer, everything looks like a nail"
'77 C/10 - 350/350 mild street motor

Online bd

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Re: '86 K20 running hot, burning rich, UPDATE
« Reply #6 on: July 02, 2015, 03:34:07 PM »
...I am still running hot so now im going to replace the head gasket....

Run a compression check or cylinder leak down test first to determine whether a cylinder is actually leaking and which one it is.  Make sure a teardown is warranted and isolate the problem to a specific cylinder or cylinders.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Harleygirl

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We had a 79 Blazer that ran hot as well. We ran a compression test and everything looked ok. It turned out the distributer as dirty inside so the weights that advance the timing weren't working smoothly.
We cleaned the and lubricated the centrifugal weights and the truck runs great.
It's worth a try before doing something more major...