my heat sucks!

with winter right around the corner i'd rather try to fix this before its too cold. just wanted to bounce these ideas of people who might know. so my '98 xj 4.0 has a very small leak in my radiator and my heat is more like warm air. it gets cold up here so i could use some advice. would putting in a new radiator fix my heat problem? or could there be something blocking my heater core or something else related to that area? i plan on fixing the radiator either way but i would rather know before i change it out and i still have the same problem.

also, any good JY radiator swaps or am i limited to direct fit xj stuff???

I'm going to think out loud a bit. With a leak in the radiator, you're likely never able to build up the proper amount of pressure in the cooling system. However, even without the pressure buildup, I think you would still have coolant flow going to the heater core, unless it is plugged. I'm going to be investigating a similar situation with my cousins '01 XJ. He has a cracked radiator endtank that spews out steam when the vehicle gets up to operating temperature.

He also has not had heat in the vehicle for about a year now - even before the radiator endtank was cracked. This was evident when I removed his heater core lines as they were bone dry and had what looked to be pieces of rust in the lines. I tried to backwash the heater core with a coolant flush kit that uses a garden hose to induce a backflow into the cooling system. Lots of brown, mucky water came out of the top of the radiator when I directed water through the heater core, but still no heat...

I have the heater core lines completely removed right now to clean them out while I have the whole engine torn down (replacing the head...he blew the head gasket too) and I plan to blow the heater core out somehow - either with compressed air or water, but I can let you know how that turns out. Crossing my fingers that I don't create a leak in the heater core because then the dash needs to come out...

It's not likely that a new radiator will improve your heat. Does the engine even get hot enough? (Thermostat?) If it does, do the heater hoses get good and hot?

I have a 98 XJ Limited and when I bought it last December I had a fairly decent radiator leak. Even with the radiator leaking the heat still blew HOT in the cabin so I'm thinking you have heater core issues. When I replaced the radiator, I noticed no change in the heat, although it was already hot. I usually have to turn the dial down to about halfway during my commute because I start sweating.

If the engine runs, and there is a thermostat (195 degree stock), and coolant flows through the heater core, you should have heat.

Question: is there even a thermostat installed?

TerraWombat said:

With a leak in the radiator, you're likely never able to build up the proper amount of pressure in the cooling system.

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'98 XJ has an open coolant system, pressure doesn't build up. Pressure in the radiator directs excess coolant to the over flow bottle. This bottle has an open end on it.

With a leaking radiator, you will still have heat.

My DD '99 is having the same problem. The heater core is probably clogged, I've been too busy to get to it. Flushing it out wouldn't be a bad idea. Check the two lines that go into the heater core in the engine compartment. If they are getting nice and hot, then your blend door is probably flapping. If one hose is hot and the other isn't, then you have a clogged heater core.

Begster said:

'98 XJ has an open coolant system, pressure doesn't build up.

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Untrue.

The "16lbs" written on your radiator cap is the pressure the cooling system runs at. Open means the overflow system is open to atmospheric pressures, not the entire cooling system. (Conversely a closed system has no unpressurized parts of the system. At operating temperature even the overflow system is pressurized.)

Start by fixing your radiator. While you are doing that flush your heater core (disconnect the heater hoses and run a garden hose to each of them flushing both directions). You might also check to see if your heater control valve is cracked.

One other thing to look at is the heating controls themselves. There should be, some cables and/or vacuum lines (depending on year) that control both a heater vent valve and a heater core coolant control valve. Again I'm not sure of the exact setup of your year. I fixed my buddies 97 TJ by reconecting a cable that had come loose and left his heat on constantly for 3 years.

moore994 said:

One other thing to look at is the heating controls themselves. There should be, some cables and/or vacuum lines (depending on year) that control both a heater vent valve and a heater core coolant control valve. Again I'm not sure of the exact setup of your year. I fixed my buddies 97 TJ by reconecting a cable that had come loose and left his heat on constantly for 3 years.

Click to expand...

Not 100 percent, but pretty sure his 98 would not have the coolant control valve, and he should have coolant flow through the heater core full-time.

Just had the heater and evap cores replaced in mine, from what the guy at the radiator shop said, the heater was plugged solid!

GSequoia said:

Start by fixing your radiator. While you are doing that flush your heater core (disconnect the heater hoses and run a garden hose to each of them flushing both directions). You might also check to see if your heater control valve is cracked.

Click to expand...

I'll be doing this tomorrow after I install the cylinder head on the Jeep...I'll let you know how it works out.

from everything i have came across all points to needing to flush your heater core. and i also understand this is a common xj prob. im goin to be flushin mine this weekend myself i have low heat

On the Jeeps with heater valve, in particular

-Run the heater every week or two for 5-10 minutes YEAR AROUND! Same for the air conditioner-YEAR AROUND.

Keeps all the seals lubed and 'flushes' some fresh additives around.

Heep Good Medicine! (all vehicles)

Orange

thanks for all the replies. there is definately a thermostat in there. i will check the hose temp.'s leading to the heater core when i get to work today. and if thats not the problem ill be pulling my dash apart tonight.