Coolant/Heater related vaccum motor leaking

[UNL1MTD]

 

Pictured above is the coolant related motor that is leaking on my MJ. I'm guessing that it is related to the Heater controls, but I'm not even sure why I'm guessing that. I was working under the truck and noticed coolant leaking onto the starter, it is originating at this spot, specifically where the screws are. I can't say the rate at which it leaks.

 

Anybody know what exactly it is, ways to test/fix it, cost to replace?

 

Thanks,

 

Sean

[tjbliley]

It is a cheap part at the autoparts store. it is a vacuum motor which turns on the heat from the antifreeze. opens the valve. they break if you hit them wrong just moving things around under there. It is an easy fix. Some people have just pulled them but then your heat is on all the time in the core. make the ac work harder I think.

[BLHTAZ]

Yep...it's called a heater control valve and is not a big deal to replace. Just make sure that you bleed all the air out of the system after you are done or you will have overheating troubles that could cost you a lot more money.

[aerocorey]

Is this valve supposed to get vacuum to pull it open or vacuum to pull it closed? Mine isn't getting vacuum and my heat blows cold. I'm gonna tinker with it tomorrow. I can't get the little vacuum hose going to it to make vacuum no matter what position the heater switch is in. If I can't get it working right I'm either going to wire it open or replace that whole section with a "T" fitting.

[Oizarod115]

my truck's heater control valve defaults to hot, so it shouldn't need vacuum to blow hot.

 

turn the truck on, and play with the valve, and have someone tell you if the heater starts kicking warm, if you hold it open/closed (opposite of whatever its doing that doesn't blow hot) it should work.

 

if not then your heater core may be clogged.

[aerocorey]

I'm not as worried about the valve as I am curious why the hose that goes to it never makes vacuum. I'll get the heat blowing hot one way or the other. I like to leave things stock if I can so I'll probably look at the back of the heater panel in the cab when I mess with it tomorrow.

[mfpdm]

I'm not as worried about the valve as I am curious why the hose that goes to it never makes vacuum. I'll get the heat blowing hot one way or the other. I like to leave things stock if I can so I'll probably look at the back of the heater panel in the cab when I mess with it tomorrow.

 

You may want to check your vacuum supply reservoir. It's that football looking thing behind the front bumper on the passenger side. It controls quite a bit of the heater controls that require vacuum.

 

:cheers:

[aerocorey]

I'm not as worried about the valve as I am curious why the hose that goes to it never makes vacuum. I'll get the heat blowing hot one way or the other. I like to leave things stock if I can so I'll probably look at the back of the heater panel in the cab when I mess with it tomorrow.

 

You may want to check your vacuum supply reservoir. It's that football looking thing behind the front bumper on the passenger side. It controls quite a bit of the heater controls that require vacuum.

 

:cheers:

 

That ball is making vacuum, no leaks. The heater doors work fine. Oizarod115 says that valve defaults open, so that means it would require vacuum to be closed. That makes sense since my last MJ had no vacuum to the heater controls but I still had a hot defroster. Seems to me that I've got 2 problems...

 

1. The valve has failed, and it's stuck closed.

2. My heater control panel isn't porting vacuum to the valve when I turn the heat off.

 

If I can free up the valve so it operates smoothly and get the vacuum porting from the heater controls correctly I'll leave it like it is. If not I'll replace the valve with a "T" fitting so it works all the time. There's no A/C in the truck so it won't hurt anything. I'll just go through the vacuum lines behind the heater controls real good to be sure nothing is leaking. Looks to me like that valve's only job is to eventually fail and make my heat stop working.

[HOrnbrod]

I'm not as worried about the valve as I am curious why the hose that goes to it never makes vacuum. I'll get the heat blowing hot one way or the other. I like to leave things stock if I can so I'll probably look at the back of the heater panel in the cab when I mess with it tomorrow.

 

You may want to check your vacuum supply reservoir. It's that football looking thing behind the front bumper on the passenger side. It controls quite a bit of the heater controls that require vacuum.

 

:cheers:

 

That ball is making vacuum, no leaks. The heater doors work fine. Oizarod115 says that valve defaults open, so that means it would require vacuum to be closed. That makes sense since my last MJ had no vacuum to the heater controls but I still had a hot defroster. Seems to me that I've got 2 problems...

 

1. The valve has failed, and it's stuck closed.

2. My heater control panel isn't porting vacuum to the valve when I turn the heat off.

 

If I can free up the valve so it operates smoothly and get the vacuum porting from the heater controls correctly I'll leave it like it is. If not I'll replace the valve with a "T" fitting so it works all the time. There's no A/C in the truck so it won't hurt anything. I'll just go through the vacuum lines behind the heater controls real good to be sure nothing is leaking. Looks to me like that valve's only job is to eventually fail and make my heat stop working.

 

The 1997+ XJs eliminated that water control valve altogether. I did the same, and the heat is better than before. You can get a set of 1997+ XJ molded hoses like I did, or use ordinary heater hose and ditch the valve. And while your heater core is disconnected, flush it out both ways with and hose until it runs clear. And plug up the now unused vacuum line when done. This really works well.