So I got a 99 xj and I have no heat.. I have replaced the thermostat and it seems like now that there is no pressure in the cooling system. I've also pressure tested it and it holds pressure fine. It gets pretty warm then cool. Now I live in New England and to not have heat in this season blows! I even went as far as propping the blend door so I can get maximum heat still nothing. Please some point me in the right direction

 

There is no reason to believe that it's the water pump since it hasn't over heated yet and it's been like this for awhile

 

What is "it"?

 

"It" as the heat in the cab

 

Your original post leaves a lot up to the imagination. Let's start from scratch, what has been done as far as cooling system maintenance (other than thermostat) in the past 16 years?

 

I have no idea what has been done in past 16 years.. I just got the jeep in June and it has 137k (don't really think that part matters though) the main issue I'm concerned about is that the cooling system isn't hold pressure

 

That's the easiest thing I've dealt with all day,
No pressure = faulty or missing radiator cap.

 

Funny cause that crossed my mind but I guess I'm just to naive to think that an issue so small can make such a big deal.. I'll try it thanks 👍

 

If the cooling system is full it should be circulating through the heater core, pressure or not. Weak or no heat can be a clogged heater core...but you say it works sometimes? If the coolant is ugly, that might point towards a neglected cooling system that might gunk up a heater core. Do both hoses going into the firewall feel warm? If they are and the blower works, so should the heat...The core can be back-flushed with a garden hose btw. Sometimes that works, sometimes not.

 

I will also give that a try.. I don't really wanna keep throwing money at it so I'll flush out the heater core first.. But again I live in New England so using a garden hose in this weather we've been having lately is going to a lot of fun

 

Fixed ^^

 

Always gotta be that one guy -__-

 

If u don't want to throw money at it, u need to get rid of it NOW. Think about it, it's a 16 year old car and a Jeep at that. If u don't throw money at it, it's days of being a reliable DD r numbered.

 

Not many cars overheat this time of year (wonder why?). A weak water pump means weak flow to/thru the heater core.....at least that's what it says in the FSM.

 

Not many cars overheat this time of year (wonder why)? A weak water pump means weak flow to/thru the heater core.....at least that's what it says in the FSM.