1987jeepxj

i just bought a 1987 jeep xj with the 4.0 and the heater blows but it just blows cold no matter how hat the truck is!! does any one have an idea of what this could be it would help me alot!!

matejcekautoworks

bad heater core..... maybe burp the system, bad linkage

JackGTX440

I've had three XJ's every one of them has done that, and my brother's '98 TJ too. The cooling system/heater core's seem to get corroded and plugged after time. I use one of the cooling system flush guns to blow it all out. It blows water along with a 20 psi push from the air compressor. You would be amazed what comes out! Mine is starting to need it done as we speak.

prerunner1982

I have a similar problem, but I believe it is related to the valve that allows the coolant to go through the heater core. When it is hot outside the valve opens normally, and if I leave it on heat it will work when it gets cold. But if I dont switch it while it is still hot outside it wont change once its cold.

So you might check the valve. If it isnt opening to allow water into the heater core, the heater core wont have hot water to pull the heat from.

whowey

Start with the valve.. It is vacuum controlled so make sure that you do not have either a broken line to it or numerous other vacuum leaks.

Then use a Chevy tool(big hammer) and tap on the ends of the valve. It will often corrode inside and not move anymore preventing the hot water from getting into the heater core.

If that doesn't do the trick, try back flushing the heater core. Remove the hoses from the heater core tubes and attach a garden hose to the outlet. Run water through it for a few minutes and watch to see the flow of water. Also look for junk coming out of there.

Rainycity

How does a guy flush the cooleant in these dang older cherokee`s? (1989)
I have to add fluid through the overflow bottle due to no radiator cap to speak of, or at least not one I can see. Kind of a different system than I`m used to.

BuckB91XJ

The XJ heater control valve is a beautiful "NOT" invention. I bet yours is bad, if you flush your cooling system and that doesn't fix your problem, my money would be on the heater control valve. I hope this helps.

finneys98xj

if it has a petcock that why orunhook the bottom hose. it is a closed system rad. I hate them.

finneys98xj

you can convert to a open system