MOvermyer

My 99 Sport has no heat. The air is blowing out but not hot. I have disconnected the heater hoses from the engine and flushed them and the heater core out with water. It flows great through both directions. What would the next step be? Thanks

Scott_Sport99

are the hoses hot?
If so the flap that directs the hot and cold air may have broken.

Kuro89

check for vacuum leaks, the heater valve is vac operated, or it could be the valve itself is bad.

DFlintstone

Yea those valves......I think you can see (or feel with your finger) the lever move when you switch from hot to cold. Also you can CAREFULLY remove the vacuum line and see if it changes, sucking/not sucking. Those things are made like those toy cars where you push on the bumper and it flies into pieces!

The hoses into the firewall are the ones that count. Don't apply full house pressure. Putting 50 Lbs into something made to handle less than 20 is not good.

MOvermyer

Haha, the crash test dummies toys? those things were awesome! Thanks for the tips. I will check the valve and the heater hoses. I'll let you know what I find.

djb383

'97 up don't have a heater control valve in the heater hoses.

yamanube

I didn't want to make a new thread just to have somebody tell me to search but I have been browsing for a while and cannot find a solution or even get pointed in the right direction. My '01 has no heat, I will likely try to flush the heater core this weekend but what exactly switches the system from hot to cold? AC works fine, blower works fine it just doesn't seem to do anything when I turn the temperature control dial.

Red82

Hows your thermostat? I replaced mine and had heat!

DFlintstone

Lots of cars, including my older jeeps have a valve in the heater hose that turns the heat on or off. DJB informs us yours doesn't. (thank-you DJB) I would guess it's not on the engine so that would leave under the dash. (a Celica valve will drip on the gas pedal).

I would think you would want to find the valve before trying to flush it......That's all I got.

(and yea Red, I need to check/change mine)

djb383

No heater control/coolant flow valve anywhere on '97 up.....coolant flows to/thru the heater core the moment the motor starts on '97 up. The heater door (allows air to flow thru the core) could be remaining closed and not allowing heated air to pass from the heater core box and on to the vents.

yamanube

I have a gut feeling this is my issue. My coolant is good, my temp never fluctuates abnormally. Is there a common malfunction that causes this or do I just have to start poking around?

djb383

It's 11 years old and a Jeep. Probably everything between both bumpers needs to be poked/looked at some time or another......

yamanube

Okay....what controls the door that controls air flow over the heater core? Vacuum or electric servo?

djb383

I think it's all vacuum and cable operated.