ok i got an 89 4.0 xj, i was just capping off my leaky heater core earlier and was looking at what at first looked like a filter in the heater hose right before going into the heater core. when i looked at it again noticed theres a little lever on the bottom of it and a small plastic line coming off the end going through the passenger side firewall. can anyone tell me what that is? i dont have a picture at the moment but i might be able to post one tomorrow.
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what is this part?
- Thread starter mtndew
- Start date
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Not a filter, it is your coolant control valve (or as the barbarians refer to it as the heater control valve). It is vacuum actuated from the dash.
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Exactly.
- Location
- Rainy side of Washington
Sure, block the vac line and replace the valve with two pieces of 1/2" (trade size not real size) copper tubing.
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Things that need a properly operating vacuum system:
Cruise control
D30 CAD axle for 4x4
Vents for defrost/dash/floor
Brake booster
Idle
4x4 light in the instrument panel
Coolant control valve (heater control valve)
There is a "ball" or "capsule" vacuum reservoir behind the front bumper. The vacuum line running to it passes behind or under the battery and loves to break in that area.
When you don't have a good working vacuum system you won't have 4x4 because the vacuum motor on the D30 CAD (NP231 equipped only) won't engage or hold engaged the disconnect collar. When you don't have vacuum reserve every time a load is put on the engine your vents will default to the defrost position. Without enough vacuum your cruise will either not engage at all or will drop out anytime the engine is under load.
Fix the vacuum system.
Eliminating the coolant control valve is a common mod. The coolant control valve was eliminated on later model XJs anyway, but they did have a different heater air box system. Pros of elimination--constant coolant flow reduces the chance of the heater core clogging. Cons of elimination--some say your a/c won't work as well, some say they feel heat in the cabin all the time, others say no problems at all.
Cruise control
D30 CAD axle for 4x4
Vents for defrost/dash/floor
Brake booster
Idle
4x4 light in the instrument panel
Coolant control valve (heater control valve)
There is a "ball" or "capsule" vacuum reservoir behind the front bumper. The vacuum line running to it passes behind or under the battery and loves to break in that area.
When you don't have a good working vacuum system you won't have 4x4 because the vacuum motor on the D30 CAD (NP231 equipped only) won't engage or hold engaged the disconnect collar. When you don't have vacuum reserve every time a load is put on the engine your vents will default to the defrost position. Without enough vacuum your cruise will either not engage at all or will drop out anytime the engine is under load.
Fix the vacuum system.
Eliminating the coolant control valve is a common mod. The coolant control valve was eliminated on later model XJs anyway, but they did have a different heater air box system. Pros of elimination--constant coolant flow reduces the chance of the heater core clogging. Cons of elimination--some say your a/c won't work as well, some say they feel heat in the cabin all the time, others say no problems at all.
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Nope, just checked today. Mine is a 2.1 Diesel so i guess the vacuum system is kinda different. No AC either... which kinda sucks.
Don't know if my D30/NP231 absolutely needs vacuum to operate, i'll have to look into that.
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
What year?
- Location
- San Jose, CA
:scared:
'94. Seriously :laugh3: They kept making them through '94 for europe, it was replaced in '95 by the crappy 2.5 VM diesel..
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Ok, I will try and rummage around in the FSM 93 and 94 parts catalog tomorrow and see what I can find on the diesel rigs.
- Location
- Rainy side of Washington
I can't tell you whether vacuum is needed via the parts catalog with any certainty, but I can tell you how to find out... check the passenger side axle tube on the front axle. If there is a cast steel (iron?) housing hanging off the back below the passenger side upper control arm mount (which should be part of the same cast housing) and some vacuum lines running to it, you need vacuum for the front axle. Otherwise, you don't!
If you don't have vacuum lines going to the front axle housing, you shouldn't need it for the transfer case either, as the transfer case just has a vacuum switch on it to engage the front axle when needed (and IIRC does not have the vacuum switch if the front axle is a "non disconnect" type one.) Your part time 4wd light may not function without vacuum (I forget how it's set up on the vac actuated cases) but seriously, who needs a light on the dash to tell them they just pulled the 4wd lever?
If you don't have vacuum lines going to the front axle housing, you shouldn't need it for the transfer case either, as the transfer case just has a vacuum switch on it to engage the front axle when needed (and IIRC does not have the vacuum switch if the front axle is a "non disconnect" type one.) Your part time 4wd light may not function without vacuum (I forget how it's set up on the vac actuated cases) but seriously, who needs a light on the dash to tell them they just pulled the 4wd lever?
