Its getting cold here in NW and I just purchased a 98 cherokee. I introduced my self in the introduction center. I was told buy the owner that there were no mechanical issues with the Jeep, however I get 30 minutes into my journey home and realize I still don't have any heat. Last night I tried to flush the coolant, it was late and Walmart was out of the additive. Anyways flushed according to instructions and some nasty stuff did come out. Still no heat.

I decided to dig further into it and removed the heater core hoses at the engine and tried to flush water through the normal way, no luck. I tried back flushing it and a lot of rust came out and water eventually started to flow albeit there was still significant back pressure on my house but I would say it filled up a 3 gallon bucket in 3 minutes or so. So I tried flushing through the proper way again and it seemed to be flowing about the same as it was backwards (which one would think it would).

Next I removed the upper and lower radiator hoses to see if the radiator was plugged. Water was flowing from the top out the bottom without any significant restriction.

Hooked everything back up thinking I was going to get heat and I did not. I'm thinking I might have a water pump issue. My top heater hose gets nice and hot by the engine but the return is ice cold. The upper radiator hose did not get all that hot even when the engine was fully warm and the bottom seemed relatively cool. If I would squeeze the bottom trying to relieve air or what not I would feel some heat come into the top radiator hose.

Now the strange thing is if I had WP failure I would thing the jeep would over heat. Am I incorrect in that statement? I drove the jeep on the express way and got stuck in a traffic jam and the temp gauge never exceeded the 210 tick mark.

Also this bugger seems to be making a clicking noise, what is it and is that normal?

 

If the water pump is good and the heater core is clear, both heater hoses at the firewall should get really hot. If both heater hoses get hot, the problem could be the flapper doors in the heater box under the dash. Lumpy crud anywhere coolant flows is a sign of owner neglect.....going too long without proper maintenance. Time for some bumper-2-bumper TLC. The clicking noise is the evap/emissions thingy....normal.

 

Well both heater hoses are not getting hot. This is true even after I flushed and back flushed the heater core and was able to get some flow. Will the jeep over heat if the water pump is not working or marginally working? What's the best way to test the water pump. I pull the cap and don't see any circulation. However its not over heating so IDK

Any other suggestions?

 

This time of year, the XJ probably will not overheat with a weak water pump however, the water pump is just one link in the XJ cooling system chain and u know what they say about a chain with a weak link(s). A weak water pump can effect heater performance. I'm not aware of a water pump test....it's a $40 part, I'd suggest replacing it. Here's a pic of a water pump that didn't leak, didn't make noise and didn't pump either. LOL The way the XJ radiator is set is set up, u can't see coolant circulation. Money spent on replacing the variuos links in the cooling system chain will be money well spent. The cooling system is NOT one of the areas where "if it ain't broke, don't fix it" applies. U can bet that something in the cooling system will fail at the most inopportune time when regular maintenance is not performed.

 

One thing I've noticed is that my heater works better when I am driving, with higher RPMs say 1500-2000. When I'm idling, after a minute or two, the heater is noticeably cooler. Could this be a sign that my water pump is not performing at its finest and should be replaced?

Sorry to threadjack, it seemed related though.

 

Well I plan and doing a water pump and a thermostat as soon as possible. We will see if that fixes it. I've heard that NAPA thermostats are better, something about them opening farther, is this true? I'm also going to devise a way to circulate some cleaning solution through the heater core only. I have a product at work that is used for cleaning old boiler systems and I think it will work good in the heater core. I've also thought about letting some CLR sit in there (Heater core only) for a while. Has anyone tired this?

 

WARNING! If u go to the CLR web site, they specifically say "do not use in a automotive cooling system" but don't take my word for it, take theirs. Not sure about NAPA t-stats being any better, opening any more than any other brand t-stat.....does NAPA make anything?....or do they just put their NAPA label on a part manufactured by someone else. Stant does make t-stats, Google them.

Heater performance dropping a lower speeds can basically be attributed to coolant flow being reduced due to a weak water pump or partially clogged heater core or both. '96 down XJs have a heater control valve that cause poor coolant flow, thus poor heater performance.

 

I imagined so with the CLR, however if I just circulated it through the heater core and flushed it good before connected it to the system I would think it should be ok.

Is there a similar control valve on my '98 that could be causing issues?

 

Think about, the heater core is made of thin copper/brass or maybe aluminum construction. Chances are, since lumpy crud has already accumulated in the heater core, some metal erosion has already taken place (thin metal has gotten thinner). About the only area that CLR wouldn't "eat" is the thick cast iron engine block/head. Again, the CLR site says don't use it in an automotive application. I would recommend u don't guess and "think it should be ok"......take heed as to what the CLR site says and don't use it.

The heater core is a major PITA to replace (dash removal)....the last thing u want to do is take a chance of expediting a heater core leak by introducing a caustic material into the heater core that may eat away at a thin spot.

Antifreeze/coolant is fairly cheap....I'd recommend removing both heater hoses (from the stat cover and water pump) and continue to flush both ways (garden hose) every 3-4 days for the several weeks in hopes of passages in the heater core gradually opening up.

Only '96 and down have a heater control valve.

 

Good point, maybe there is something better suited for this. I did see some other people around the web doing this, but since it is such a PITA to remove maybe I better play it safe

 

If one hose is hot and one is cool, then there is little to no circulation going through the core.

Without a water control valve for the heater, further research will be necessary to see how '97 and later control the flow.

 

It is my understanding that later model XJ's do not have a water control valve

 

Yes, that's what I said. But something is controlling the water somehow, somewhere. Since the Jeep does not overheat, I think that's where you should start looking.

 

I'm pretty sure that you just have a plugged up heater core. You had the proper procedure before, you just need to keep doing it. Continue to backflush, then reverse direction, then repeat. Just keep doing that until you dont get anymore pieces out. Then run your engine for a while. Keep in mind - You may have pieces of trash in your cooling system that will plug up your heater core again as soon as you run the engine. Try to drain the system as fully as possible. Remove the bottom radiator hose and flush water through the radiator as well as the engine block. Reassemble everything and try again.
All the radiator flush chemicals in the world won't work if they can't actually flow through the cooling system...

 

'97 and up XJ's don't regulate the amount of water flow through the heater core. They always have full flow. They regulate teperature by controlling the amount of hot/cool air that is mixed in the HVAC plenum...

The most likely way water flow through the heater core can be restricted is by having a clogged heater core.