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73-87 Chevy _ GMC Trucks => Suburbans => Topic started by: mk_tacticalranch on June 11, 2015, 11:11:27 am

Title: '86 K20 running hot, burning rich, blowing smoke at start up and dying
Post by: mk_tacticalranch on June 11, 2015, 11:11:27 am

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

Title: Re: '86 K20 running hot, burning rich, blowing smoke at start up and dying
Post by: LTZ C20 on June 11, 2015, 11:46:30 am

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.

Title: Re: '86 K20 running hot, burning rich, blowing smoke at start up and dying
Post by: mk_tacticalranch on June 11, 2015, 01:05:55 pm

Thanks what I was afraid of! Thank you!

Title: Re: '86 K20 running hot, burning rich, blowing smoke at start up and dying
Post by: LTZ C20 on June 11, 2015, 01:42:14 pm

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

Title: Re: '86 K20 running hot, burning rich, UPDATE
Post by: mk_tacticalranch 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

Title: Re: '86 K20 running hot, burning rich, blowing smoke at start up and dying
Post by: FlatBlack77 on July 02, 2015, 03:20:05 pm

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

Title: Re: '86 K20 running hot, burning rich, UPDATE
Post by: bd on July 02, 2015, 03:34:07 pm

Quote from: mk_tacticalranch on July 02, 2015, 02:07:35 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.

Title: Re: '86 K20 running hot, burning rich, blowing smoke at start up and dying
Post by: Harleygirl on July 02, 2015, 06:44:48 pm

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...