I just recently bought a '00 5.9 4x4 185,000 miles for my daughter from an individual. The water pump and thermostat was replaced prior to me buying the truck. The heater will not heat up and the temp. gauge inside the cab only registers maybe 150. At times, if I "gun" the engine the temp will start to register about 180-200 and the heater will start to work. When it starts to work there is a anti-freeze smell in the cab. Then if I turn off the truck for a while (like go into the store) it goes back to not working until I gun it again. The defroster also seems to not work well either. Any ideas guys? I have flushed the heater core once and am about to do it again since reading other posts.

 

Moved to the 2nd gen section.

 

First you should make sure there is no air bubbles in the system, second, if you smell AF in the truck, odds are the heater core is leaking. Any moisture on the windshield when using defrost? Or puddles on the floor? And third, the PO probably used a POS thermostat from autozone or wherever, and it no good.

 

It sounds like you may have several problems.

1) Wrong thermostat or no thermostat.
2) Leaky heater core or heater hose.
3) Plugged heater core. Might try disconnecting your heater hoses at the engine and then back flush with low pressure water through the hose coming off the water pump and letting the trash drain out the other hose.

 

I flushed the heater core and everything looks good. No trash came out. I flushed both directions for about 10 minutes. I have no leaks on the floor driver or passenger side. Would a bad thermo. cause smells in the cab? and cause the defrost not to work?

 

No. A bad thermostat will either not open and cause the engine to overheat or open too soon and not allow the engine to warm up like it should. Depending on the amibient temperature, running without a thermostat will not allow the engine to reach normal operating temperature.

 

The temp problem sounds like a thermostat that is stuck open and doesn't let stuff heat up. When you romp on the gas, the engine gets hotter and heats up the whole system and that is probably why you get heat.

The defrosters will only work well if you are getting heat to your cab (which is your main issue).

As far as the antifreeze smell. NO, a bad t-stat would not cause a thermostat smell in the cab. Most likely the heater core is leaking, that is a tell tale sign that it is bad.

Usually when a heater core goes bad you start to smell antifreeze, your windows fog up a lot from the inside, and they have a slight film on them. Also, when my heater core went bad I noticed that I would be really congested if I drove my truck and would be fine if I let it sit!

Good Luck.

 

I'm gonna try changing the thermo. I'll let you know

 

GL. I have replaced my thermostat, housing, water pump, hoses, flushed and flushed, and still have very little heat. I gave up.

 

Are you the OP? You have a different username.

If you are the same person, is your engine temp gauge still not coming up to normal operating temp?