Question about 1998 GMC Sierra
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Posted on Jan 02, 2017
SOURCE: leaking antifreeze
A quick check you can do to help your troubleshooting is to remove the radiator cap then start the vehicle. (Ensure radiator filled so you can see fluid level). Watch the fluid inside the radiator. Initially after you start the vehicle you will get some small air bubbles but they should go away in less then a minute. If after a couple minutes you have bubbles continually coming up or it starts bubbling out of radiator then you can bet on the Head gasket. If you do not get the bubbles it dosen't rule out either one but if they are there as described then you can look at the head gasket.
Posted on Aug 16, 2008
This is not a problem for an amateur
If it is a gasket I would clean the engine and then drive it a few miles to get it hot then with a flash light try to see exactly where it is leaking it could be a pin hole in one of your hoses or your radiator
Posted on Mar 13, 2009
it could but- check passenger side front where heater core line go into manifold right behind alternator the hose line is connected by a press clip into an alloy fitting this fitting gets eaten away by anti freeze and hose angle pulls back on fitting the part is $18 at dealer and is screwed into manifold use caution if ur r going to replace at very edge of aluminum manifold---and check ur water pump bolts the 2 longer ones should have a lock sealant on them they bolt in thru a water jacket
Posted on Oct 24, 2009
I see a lot of lower intake gasket leaks on these but usually you get an external leak or you'll find coolant mixed with the oil, not a misfire. Upper plenum is dry on the 3.1 and just bolts onto the top of the lower intake. We usually apply pressure to the cooling system overnight with the spark plug removed from the misfiring cylinder. If there is coolant in the cylinder come morning then you only have to figure out where it is coming from. If the plenum is removed during the test you might be able to see where the coolant is or isn't coming from with a borescope by looking down the intake runner.
Posted on Jun 02, 2010
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