Heat, no heat... Gauge up, down!

[trinogt]

Since I have owned this '98 B2500, the heat has never been good. Sometimes it will blow warm, sometimes cold, no matter how long it's been running. Most of the time the temp gauge shows cold, like it was just started. Once in a while, it will go up to the normal range, but not for long. The heat situation stays the same when that happens.
I just put on a new thermostat (doggone vertically mounted crap!). I put in new coolant/water mix at 50/50. Nothing changed.
New seals in the compressor line connections fixed the a/c, nice and cold. But the heat! What's up?

 

[beaujt]

did ya get the right thermostat? how about the guage itself?

 

[Bryan22]

sounds like you've got some air trapped in the system.

 

[trinogt]

The thermostat doesn't look quite the same as the last, but it fits... It doesn't work any better/worse than the last one. I ran the truck with the cap off the rad until I saw the coolant moving. I watched it burp once, then I waited a while longer to make sure the air was out before installing the cap. The thermostat is the right part number. I double checked it when I got home off the net. Anyone have trouble with a stat not quite right?

 

[COLDRANGER]

Try these

purge the heater core by running a garden hose to one end and leaving the other open. Flush it both ways. I can bet this will help if not solve the problem. The other possibility is a bad stat, somthing like one in 8 are bad from the factory. test them by suspending them in a pot of water and they should open before the boil. Or you can use a candy thermometer to check for accurate opening.

 

[trinogt]

Yeah, the flushing would be easy since someone installed a garden hose fitting from a cheap flush kit on one of the heater hoses. Will certainly have to try that one!
Will be nice to have some lengths of hose on hand so I can direct the flush water to the ground...

 

[ReD-rAnGeR]

i have a 98 ranger and i have had this problem before, and it has comeback. the temp gauge on mine runs normal range but i can see it move when thermostat opens so there must be air, ahhh, now were talkin. i pulled the front end on ramps and flushed and back flused heater core and then let it run with cap off, fill it up until normal level in radiator and that worked.gotta do it agian after i flush system.