air bubbles back through coolant resevoir constantly pushing coolant into the reservoir & not allowing it back into cooling system thus causing "low coolant" light to come on.this happened after an overheating episode when i noticed my temp go up to about 210 briefly. i immediately replaced thermostat & radiator which was leaking a little. the bubbling reservoir started after these repairs.
why is air bubbling back through coolant resevoir on 1991 GMC Suburban 2500
by dwallyt in Waynesboro, VA on December 11, 2010
ANSWER by Superbob on December 11, 2010
I'm suspicious you have a blown head gasket or two. A mechanic could check for combustion products in the coolant fumes to detect carbon moxide (CO). If there's CO ion the coolant, you have a head gasket problem. I'd check that first. Here's a directory list for you: http://repairpal.com/directory?address=22980&car_brand_names=GMC