03-14-2008, 12:52 AM
Join Date: Mar 2008
RE: No heat and over heating... NEED HELP!!!
no heat = no water in heater core or restricted flow
over heat = no water in radiator or restricted flow or bad fans or no fan operation
stuck themostat = good heat at heater core but over heat...thats not the problem
bad fans = over heat at idle but may be fine cruising depending on ambient temp but still will have heat inside
keep in mind of course, if coolant is boiling or vaporzed heater core will not transfer heat because water pump is not pushing anything.
if your're in freeze country, make sure coolant/water ratio is correct.
other things to check...lower radiator hose collaps...if the radiator is restricted, the lower hose can sometimes suck closed....that why they usually have an inner spring. This could cause occasional overheating.
So..make sure coolant is full. start engine from cold and turn heater on low..leave rad cap loose..check to see how long before heat (2-3 minutes). Then keep hand on upper rad hose to feel for themostat opening or watch coolant flow and watch for air bubbles in coolant (maybe 5 minutes) tighten cap and Let idle till fans kick in (10-15 minutes) then hold at about 2500-3000 rpm and watch lower hose for movement or collaps. Also check back for heat after fans kick in and feel upper hose for boiling.
flip on AC also to check for fan operation (some models)
If overheats fast while at idle with no bubbles, you may have defective thermostat
If overheats fast with a lot of bubbles even when cold, you have bad head gasket, craked head or block.
If overheats slowly at idle and fans never kick in...do AC check to see if fan works then...if so you have bad fan temp switch (not relay)
If fans never kick in, do a hard wire to battery positive ti test fan itself
If fans kick in and still no over heat, do high rpm test for lower hose collaps.
If lower hose holds in place, start all over but leave cap off and bring up to normal temp, look in rad and rev engine and watch for coolant level drop...a little is ok but if 4-5 rows of core expose, you may have restricted rad