MTSkull

It was 17° this morning and my heater only blows warm air. Definitely not hot. Temperature gauge is showing around 200°. Do I have a bad thermostat or something else?

djb383

200F coolant temp should be plenty for a good heater. U probably have weak coolant flow thru the heater core (core most likely plugged with crud or possibly a weak water pump) and/or a heater box blend door that is not opening/functioning correctly. I'd suggest start easy 1st and disconnect both heater hoses at the motor and try sticking a garden hose in one of the heater hoses and give it a good flushing. There should be a good stream of clear water coming out of the other heater hose after a few seconds of flushing with the garden hose. Hook it all back up, fill with proper coolant mix and go from there.

MTSkull

Where is the heater box blend door locataed at? TIA

djb383

Heater box is under the dash, toward passenger side. Both heater hoses (under the hood) should be really hot if coolant circulation is good thru the heater core.

Crispy

First thing is to check your coolant level. Add if needed. Then check if the hoses to and from the heater core are hot. If only one is hot then undo them near the front of the engine and run a garden hose thru. Not with a spray nozzle either. If that fails you may have a blend door issue.

Jim_K

Mine has always been this way. When I flush it, it comes out clear. Not sure if both hoses are hot. I will have to check that out. I'm sure its not getting flow. I have even tried a full coolant flush with running the peak cleaner threw the system for X about of hours. It got better but still not hot. My bet would be the heater core being clogged for you and myself.

djb383

May be clear coming out but is it a good solid stream coming out? Are u sure u have a t-stat in place?

Jim_K

good solid stream and everything. Have no checked out the t-stat. My temp gauge works fine.

tjwalker

Flushing the heater core is not a bad idea.

What is the history of "routine" cooling system maintenance? IE: fresh coolant changes every 30k or so?

Poorly maintained cooling systems almost always result in a clogged heater core.

djb383

.......then carefully feel both heater hoses under the hood, both should be really hot to touch. Where does the needle point?

MTSkull

I will check the heater core hoses tomorrow. I can watch the temp gauge cycle through going from just over 210 to just below it. So I am asuming the thermostat is working fine. I don't remember the gauge cycling as much this summer.

Zoider

I'm not even getting warm air. Flushed the heater core, very little gunk came out, both hoses are hot. The coolant is topped off and looks very clean. I've only had it for a few hundred miles so I don't know the maintenance history. The heater control valve appears to be working and if I manually override it still no heat.

Top radiator hose is very hot, bottom is just warm, you can hold it for 10-15 seconds so I'm thinking it's a flow problem of some kind? Any suggestions?

<can't find the freezing emoticon>

99 Purple XJ

For flushing the heater do what i did it worked flawlessly take both heater hoses off the engine side and fill one side of the hose with water and the hose you put water into put an air nozzle in their and blast it out do that as many times needed to get all of the gunk out and do both hoses it worked very well for me and cleared my heater core to new watch this video

MTSkull

I just checked both my heater core hoses are hot. Should I try to flush the core?

tjwalker

I have successfully used the technique in the youtube video before for a stubbornly clogged heater core. Use CLR, but don't leave it in there too long. 30 minutes is enough.