Heater Problem - A true mystery

[onerareviper]

OK. Can't seem to figure this one out.

Have a 1998 GTS. The heat only blows warm/hot when it is cold outside AND the operating temps. are low. After driving a few miles, no more hot air only cold is blowing from the vents. What is going on? I checked the cable on top of the water valve, and it is connected and seems to be working properly (at least from the outside). Any ideas?

Thanks.

 

[LETHAL GTS]

Maybe a vacuum issue. You notice it always while driving or mainly after a hard sprint? I know these cars A/C will stop blowing cold air when under hard acceleration. I don't know if the heat works the same way. The A/C issue is vacuum related if memory serves.

 

[Jeff Torrey]

Your radiator needs more coolant, its running low. On cold starts there is enough in the system to blow in the beginning, but once you get it up to temp. The system ***** air and no more heat.

 

[onerareviper]

Thanks Jeff. I'll take a look at the tank behind the front facia. I did burp the system about 2 months ago, though?

 

[SNKEBIT]

the heat only works to the right of the dial, the a/c works on the left side of the dial. You cannot get heat to come out the vents in the dash.

 

[onerareviper]

SNKEBIT,

I here ya, but I can't get heat from the defrosters or bottom vents. Still need to check the antifreeze level and possibly burp again. Just haven't had any time the past day. It's just so strange... Below 50 degrees when I turn the car on in the morning (cold start) I get heat for about 5 minutes, then switches to cool air only (without me touching any controls). This leads me to believe the above post (from Jeff) about the antifreeze level is probably correct. I'm thinking when the thermostat opens, I don't have enough antifreeze to support the heat. BUT, if it's above 50 degrees, no heat period. Even on cold starts. You would think the thermostat would be closed in this case, at least for a few minutes. I'll report back after checking the antifreeze, etc...