Question about GMC Sierra 1500

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Late 1999 4.8 Liter V8 GMC Sierra Seem to be losing small amount of coolant. No visible leaks, no power loss, engine is smooth and runs excellent. No water in oil, no oil in water, no overheat (runs around 190 degrees according to in dash gauge ). Heater will not get hot, barely warm. Replaced blend door actuator, no difference.

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Posted on Dec 31, 2010

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I have a coolant leak

The first thing you need to check is for visible leaks, once you turn your vehicle on, there have to be some kind of leaks, pay attention since if the leak drop on top of the manifold, it will evaporate and you won't notice it.
Another thing to look for is excessive heat, with the vehicle on, put yourself in front of the vehicle, if you feel an excessive amount of heat, then probably the head gasket needs replacing, and it evaporate the coolant.
So as you can see, if there are no visible leaks, it is probably a problem from the inside of the engine.

Sep 22, 2015 | 1999 GMC Yukon

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I have a 1999 gmc sonoma 2.2 liter truck I have coolant leaking around and out of transmission ..any help would be appreciated

if the coolant is coming out from in between the transmission & the engine it usually means that one of the freeze plugs on the back of the engine is rusted out. keeping the right amount of coolant in the cooling system keeps them in good condition longer. when mine went out I had them replaced with brass plugs, they will last longer.

Nov 14, 2014 | Cars & Trucks

2 Answers


5w30 in cold months 10w30 in warm to hot months. High milage if its over 75,000 miles.

Apr 20, 2014 | GMC Cars & Trucks

1 Answer

Recently started idling ruff with loss of power

You will need to figure out if it is fuel or ignition related.
If you have not done a tune-up by replacing plugs and other parts within the past couple of years, start there. Including the fuel filter.
Is the check engine light on ?

Jun 29, 2012 | 1997 GMC Sierra

1 Answer

Engine runs smooth and the head gasket has been replaced,I already know I need a new radiator..There is a small amount of white smoke at start up,and my oil is milky looking>

milky sump oil is coolant in the sump
could be head gasket
could be the aluminium housing behind the water pump has corroded and leaking water into the sump
that will account for you thinking that you need anew radiator

May 08, 2017 | 1999 Chevrolet Suburban

1 Answer

Losing coolant in my 2000 gmc sierra

These motors are famous for the intake manifolds leaking coolant.Have a pressure test put on the coolant system and look for a leak around the intake manifold corners.Check all four corners i've fixed many of these.

Nov 11, 2011 | 2000 GMC Sierra

1 Answer

Thermostat location on 1999 4.8 L v8 GMC Sierra

Hello Admin
The location of the thermostat is on the right front side of the engine about half way down on the end of the radiator hose.
It is visible on the diagram below just above the AC compressor. The bolts that retain it are also shown.

Dec 30, 2010 | 1999 GMC Sierra

1 Answer

Idle problem when brakes applied

Sounds like you have a vacume leak on your brake booster ....with engine running have someone press the brake while you listen on the driver side by the master cylinder the large vacume line going to the booster behind the master cylinder is most likely the vacume leak...and if so you can get what you need at your local parts store ...

Nov 20, 2009 | 2004 GMC Sierra 1500 Crew Cab

1 Answer

Where is the oil level sensor located? oil guage wiggles between 40 & 60 at idle and stays on 60 on the road.

That's not oil level you see on the gauge -- that is oil pressure in pounds per square inch (PSI). It is normal for the pressure to fluctuate when the engine RPM goes down. If it stays on 60 PSI on the road, you are very lucky -- that is excellent oil pressure!

May 28, 2009 | 1999 GMC Sierra

1 Answer

Coolant leak 2003 sierra 2500 crew cab, gas engine. Great truck!

Check the oil, and make sure it is not turning a milky brown color. If it is, then you probably have a leaking head gasket/cracked head/cracked engine block. I normally wouldn't recommend this, but put some stop leak in it since the leak is not severe. Hopefully it will take care of it.
Good Luck

Mar 26, 2009 | 2003 GMC Sierra

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