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[GreenMachine]

Hey my buddy in Vancouver, his gf is a jeeper/keeper, and he's tryin to figure out why her heater won't blow hot, I suggested maybe Air in the coolant system, he swears her thermostat is good, and it's not even that cold there....

I have never worked on an older Cherokee, let alone played with heater cores, lift kits are more fun, but I'm trying to help a buddy out,

I asked if the rad hoses were squishy or firm, he said kinda half way, I suggested taking the cap off and getting the air out of the system, it's worked on friends Hondas, And their heaters have blown hotter than the day they rolled off the lot, after a coolant top up.

He said it could be a vacuum line issue? But I have never heard of vacuum lines working with a heater core? Like I said I also don't play with heaters,  I'm going to send him the link to this thread,

Any ideas would be appreciated.
Thanks guys!

[TL-Iguana]

the thermostat could be good, but it could also have been installed upside down. Theres still probably air in it, it sounds like it needs to be burped. The rad cap may not be the highest point in the system. You can burp it there but if its lower than a hose the air is in that hose up high..

[cLAY]

Some of the older XJs had a coolant valve on the heater line that controls the flow into the core. Also on many vehicles there is a blend door that mixes hot and cold air together to get the temp you want. Both are controlled by vacuum(some vehicles use cables or electric motors). So yes his issue could be vacuum related. Does cruise work? Does his 4wd lights work? Does the airflow switch from where its set at to dash when flooring the unit up a hill? These all indicate a vacuum supply problem. Main cause is the plastic tank mounted in the front right corner of the front bumper. Its a vacuum reservoir, it often cracks and tehn you don't get any vacuum to the other systems.

[GreenMachine]

Some of the older XJs had a coolant valve on the heater line that controls the flow into the core. Also on many vehicles there is a blend door that mixes hot and cold air together to get the temp you want. Both are controlled by vacuum(some vehicles use cables or electric motors). So yes his issue could be vacuum related. Does cruise work? Does his 4wd lights work? Does the airflow switch from where its set at to dash when flooring the unit up a hill? These all indicate a vacuum supply problem. Main cause is the plastic tank mounted in the front right corner of the front bumper. Its a vacuum reservoir, it often cracks and tehn you don't get any vacuum to the other systems.

Hey, they said the 4wd lights, and cruise is out, so definitely the issue, any other tips? Something they could do themselves? Or is it easier to take in?

[cLAY]

Start with the plastic bottle in the front right corner of the bumper. See if the bottle is cracked/broken. Can sometimes be repaired with JB weld if money is tight.  Make sure lines didn't pop off. If that's all ok see if vacuum is getting to the bottle. If not the. Trace line back to where its broken or disconnected. If its getting vacuum then trace the lines coming out and see if they are broken disconnected.

[GreenMachine]

thanks for the help!

[cLAY]

FYI  we don't delete tech threads. Chances are if you had this problem someone else will as well and by using the search function they may find this thread and be helped out as well. 

Title is something descripitive so the the search engine can easily pick it up.