cold heat

[jares99]

Firtst thing i live in ohio and right now it is cold. I noticed the other day that when my truck is warmed up, while driving down the road the heat blows hot. but when I stop my engine temp gauge drops and the the air turns cold coming out of the vents front and back.

It wasn't always like this just started doing this a week ago (really annoying at traffic lights)

Anyways does anyone have any ideas on this if the heater core was bad wouldn't it always blow colder. And the front and back vents are on seperate cores(i think not totally sure) It is a 98 EB 4X4.

 

[monsta]

How's your coolant level?

 

[EXMAN]

I live in Cincinnati, Oh and also have a 98 EB 4x4 and when it gets real cold outside my heat fluctuates. Step on the gas and it gets cool. Fluid levels are fine. I was thinking of replacing the thermostate.

 

[jares99]

coolant levels are fine

 

[rwinch]

What does the temp gauge do? The 98 EB has the tow package, which means it has "super cooling", and remote oil and tranny cooler. If it is real cold out, it could cool things too much (ever see semi's with the radiators mostly blocked off in winter).

My 98 EB does not do this, but I notice that it does not get as hot (gas milage is also worse in cold weather).

Another thought...could the water pump be going bad????

 

[jares99]

the temp gauge will drop down to cold when I stop
and the water pump isnt leaking at all that I can see and the coolant level is still good.

 

[rwinch]

From my experience, it sounds like your thermostat is shot. They usually fail open, and since the guage drops, it is consistant with what you are experiencing: cooling without any regulation.

As usual, the thermostat lives under the upper radiator hose attachment where is enters the engine block. My service manual states that this is the likely cause. Be sure to get the thermostat and the sealing o-ring that goes with it.

If you are mechanically inclined, this should be a 1/2 hour job. If not, maybe 35 minutes.

You may want to pick up a Hanynes or Chilton manual while you are out shopping for parts.

Good Luck