Overheating won't stop

Hey fellas, I have an 89 XJ, 4.0 with 204k and the closed cooling system. I've recently put in a new water pump, flushed/filled the radiator, tried to burp the system by parking downhill, and put in a new 195* thermostat.

Despite all this, I can drive my jeep around in the 90* weather for about an hour, and then my temperature starts to creep up to the red until I let it cool off for about 10 minutes, giving me another 10 minutes of drive time before I have to stop again.

I thought that the new thermostat was an improvement, you can watch the temp gauge go to around 210, then drop to 180 over and over, until it doesn't drop anymore (after about 15 miles) and the temp stays at about 205 for a bit, until it just starts to rise up to infinity.

I'm thinking of going ahead and converting to the open system via an overflow bottle , filler neck, and new heater valve, like on Madxj.com, but I'm worried that it's not going to make a difference.

My radiator is about 80k old, and it's been flushed a few times recently, so I really really don't want to buy a new one, and am hoping that that's not the problem.

So what I'm asking you fellas is, what do you think the problem is? Neither I nor my dad have really seen anything like this so we're stumped. Fan clutch is a maybe, but how can I tell if it's working or not?

My 89 was a terrible until I switched over to the open system. I tried to get the closed system to work but the pressure bottles and caps I had were junk. Not to say the closed system can't work well, I just couldn't get it to my rig cool.

I did the Moroso filler neck cheap conversion and I never had another problem after. Jeep changed it to the open system for a reason. The closed system is just too problematic. Of course, this is all my opinion.

I converted my 90 to the open system using a GDI 3-row radiator a few years back. I'm not terribly impressed. It works almost as good as stock when it was fresh. The only thing that helps out is that you need to replace the switch for the electric fan with an aftermarket one which is adjustable and I have the electric fan come on earlier than it did stock.

I replaced the radiator on my 88 MJ with a two-row from performance radiator, leaving the closed system in place. It works better than the open system conversion.

Try burping the system by filling through the upper radiator hose. That may be the main advantage to the filler neck conversion.

Fred

Thats probably becuase you used a GDI, but as others have said the closed system works just as well as the open system when functioning properly. Lol, better in your case.

Two things to look at:

1) Make sure the electric fan works. I had a heating problem and nearly ready to buy a new electric fan, open the hood to look at it to yank it out and discover I had failed to reconnect the electrical connector.

Do a test by turning on your AC and notice when the compressor clutch engages, the electric fan should run also. If it not then you may have a fan relay problem. If the electric fan comes on then you need to look at the next suggestion.

2) You did not mention the age of your mechanical fan clutch. I have adopted a 5 year service life for a fan clutch. You should install a new one, the "test" gives the wrong results more often than not.

I changed my fan clutch after over heating, I found it was the OEM clutch because the AMC part number was stincled on it. With the new one installed I much more air moving. I places my hand near the ac compressor and pulled it back quick because the breeze scared me and had not been there before.


If these fix the problem then call it done, if you notice your XJ running at 210 or over then change the thermostat and the "pressure cap" on the bottle. You can only get it at the dealer, never see it in a parts store.

My XJ has been through 3 or 4 pressure caps/bottles, all of which were bought at the dealer. The current one is fine, i'm pretty sure, as there's a really noticable *HISS* when I open it up while the engine is hot. My electric fan also definitely works, I can hear it while sitting at a stoplight, and when I almost overheat, I keep the ignition on/engine off, to keep the rad fan going.

When your jeep was overheating, martin, did the new fan clutch fix the overheating? I'm probably going to go pick one up tomorrow during lunch at work.

This overheating problem really pisses me off though. It runs fine for about a half hour, or a trip to Cary (30 mins away at about 50 mph with a few stop signs), with the temperature a little below 210, then it just starts heating up more and more. It's a real pain in the ass.

So are you overheating in traffic or while driving down the road? If you are overheating in traffic but it cools off when driving down the road, its definitly your fan clutch. Your fan clutch only really comes into play at speeds under 20 mph, over that there is enough airflow so it isnt really necessary. The way you mentioned the temperature fluctuating like that in your original post makes me wonder if you got all of the air out of the system. Like you probably already know, its very difficult to get it all out.

When I overheated my XJ was on a night when it was 20 degrees out. I actually heard a squeeling, pulled over, turned off the engine and open the hood. The 115K fan belt had broken. I then start it up and it no longer turning the water pump or any other power accessory.

I try to drive home the 1/2 mile and get stuck at a red light on a Sunday night, it began to boil over so I make a right on red and parked it in a shopping center parking lot. Walked home and came back in a couple of hours, drove it home and the temp never warmed up.

I then changed the hoses, coolant and figured I was fixed. It still ran hot, more than 210 on the gauge, so I replaced the fan clutch. It still ran the same. I then went to a radiator shop that been in business since WW2, told them the problem. They told me to change my thermostat, they said one over heat to 225F can perminately damage a thermostat. I go get a dealer thermostat, fixed the problem, also changed the 'radiator cap" and considered it "fixed" since the temp was at the same place on the gauge as it had been before the fan belt broke.

So my overheating was not like yours, mine was collatoral damage due to a borken fan belt.

PS: Here is a website which tells you how to burp air out of the engine, you have to remove the temp sensor from the head, works very well. http://www.olypen.com/craigh/cooling.htm

RyleyF said:

My XJ has been through 3 or 4 pressure caps/bottles, all of which were bought at the dealer. The current one is fine, i'm pretty sure, as there's a really noticable *HISS* when I open it up while the engine is hot. My electric fan also definitely works, I can hear it while sitting at a stoplight, and when I almost overheat, I keep the ignition on/engine off, to keep the rad fan going.

When your jeep was overheating, martin, did the new fan clutch fix the overheating? I'm probably going to go pick one up tomorrow during lunch at work.

This overheating problem really pisses me off though. It runs fine for about a half hour, or a trip to Cary (30 mins away at about 50 mph with a few stop signs), with the temperature a little below 210, then it just starts heating up more and more. It's a real pain in the ass.

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I have a feeling the current manufactor of the bottles and caps the dealers are using is subpar. I had two on my old 89 and both failed. Nothing is more frustrating than buying over priced parts that don't work.

I put on a new fan clutch, but I don't have very much gas at the moment so I didn't see if that fixed it. How much does a radiator rodding cost? I think i'm in for a new one.