XJ open/closed cooling system

Couple of thoughts... first I assume you are sure it really did overheat and it isn't just the gage going up?

Second, I've had problems with air lock after changing the coolant. If there is air blocking a hose it's going to overheat. One of those flush and fill kits solved that.

Third, the PO did odd things with the fan, might he have hooked it up backwards? A lot (all?) of those fans will work fine as either pushers or pullers, but if it's hooked up backward it won't cool your radiator.

Forth, with the engine hot and off run your hand over the radiator feeling for hot and cool spots. The whole radiator should be about the same temp, if you find cool spots then you've got a clogged radiator.

Fifth, you might check the dip stick for any signs of foaming in the oil or rust on the dip sick. If you've got a blown head gasket it's gonna overheat no matter what else you do.

Of course you also want to make sure your belt and hoses are in good shape. A lower hose can look fine but collapse at speed and cause the engine to overheat, and of course a slipping belt can cause the water pump to not pump at capacity and could cause overheating.

Good luck!

Jeff DeWitt

Troy wrote:

Bill,

The reason you don't see Renaults on the road, is that this is not Europe.

A fan that always runs, is a fan that is going to burn out soon.

Earle

Yup, it was overheating, steam and fluid and boiling out the bottle cap, with it still on. I notice I can't tighten it either or it will just click over the stoppin point and be loose again.. damn plastic. I'm thinking of replacing the bottle and cap to see if that fixes anything.

coolant wasn't changed before this happened... but I did notice i was a quart low on oil. Maybe I needed that quart to keep cool? I added a quart today and it still overheated.

Fan is wired correctly, although I wonder if and when I get the AC fixed if it'll overheat when its on. The PO said he neighbor wired to fan to run at all times since it was overheating to begin with.

Hmm, noticed that the valve cover was leaking a bit of oil, will check the head gasket also. I'm assuming it even has the original radiator and I heard someone say to replace it after 10 years, well it's been 16 if nobody else has.

I'll check up on the things you mention and give ya'll a follow up.

Troy

I don't think those caps hold pressure, it's just the one on the radiator that does.

While oil does help cool the engine being a quart low isn't going to make it overheat.

I figured as much... the Jeep started overheating so the PO tried a Micky Mouse fix instead of figuring out what was wrong.

They all leak oil, it's annoying but usually nothing more than that. My Jeep ran great for 10 years and 300,000 miles with it's original radiator, and never overheated except when the water pump went bad or when I'd flushed out the cooling system and had a big bubble in it. However when the engine was replaced they found the radiator was pretty rotten, it not only had lots of rust and stuff in it but it had just started leaking at one of the tanks.

The radiators and water pumps aren't that expensive for these beasts. If it was mine I'd first make sure it didn't have a bad head gasket. If that was OK and I was planning on keeping it I'd put in a new water pump, radiator, belts and hoses, and before removing the old parts I'd give the engine a very through flushing out.

I'd also hook the fan back up properly.

Good luck, looking forward to hear what you find.

Jeff DeWitt

Your rad system has been modified, badly it would seem...

The old system has no rad cap for the radiator.

If your rad is plugged up with scale no amount of fans is going to help, it is likely time to flush it out.

Putting power to the secondary fan to make it sort of work implies the primary fan has failed. This would be a normal failure of the fan clutch from age.

To test the fan clutch, you get the engine fully warmed up and watch the fan as someone shuts down the engine. If the fan clutch is working, the blades will stop spinning almost instantly on hot shut down. If they continue spinning, you need to replace the fan clutch.

Changing the cap on the overflow bottle has no effect here, but you could have a bad rad cap. They are a cheap replacement anyway.

If the last owner used the wrong antifreeze mix, it will boil over. I would check that out for too much antifreeze in the mix.

You can also let it warm up with the rad cap off to watch for smoke and/or tiny bubbles. If smoke comes out or if it foams up like a washer with too much soap in it, suspect head gasket.

Mike

This thing must be whacked out real good.... I looked around other posts in the past about this issue, checked out my fan clutch and it would stop spinning almost immediately while cold, but when the engine warmed up it spins quite more than when it was cold... replaced it and everything is running cool! Although, before I was trying to track down a blinker issue; they would come on but not blink. Now the freakin blinkers work too? I think I must have jiggled some wires while wrestling with the fan...

Troy

Oh I have other issues about the xj i'm gonna post in a new thread!

That's great Troy, glad you found your problem. Amazing how much trouble it can be when someone trys to jury rig a "fix" instead of tracking down the real problem and fixes it.

Having jury rigged many "repairs" I know what I'm talking about!

Jeff DeWitt

Troy wrote:

CRAP it overheated last night. I noticed however that after I put in the fan clutch the temp needle never got up to 210 really... kinda past the mark between 100 and 210. But it still overheated. Got up this morning and even though the PO told me he put in a new thermostat I put another one in today. Filled it up and rode around a bit, and it started to get hot but not in the red. I parked it and noticed it was pushing coolant out of the pressure bottle. After letting it sit with the engine off I heard a bubbling come from the heater core hose. It cooled and I drove it again and the temp. stayed slightly above the mark between 100 and 210 again.

Isn't it supposed to be at 210 like in my tj?

Troy

You could have gotten air in the system when you replaced the thermostat. This interferes with the cooling process, and can make a ruckus as it tries to get out. That would explain the bubbling noise and pushing coolant out of the bottle, better than overheating. Sometimes it takes a long time for all the bubbles to work their way out of the system. One of my cars has something like an eleven step process in the Owner's Manual, for filling the cooling system properly.

You shouldn't place much importance in the exact reading of the temperature gauge. If the bubbling eventually stops, and the heater works well in the cold weather, I would call it good.

Earle

Ya it hasn't done it since. Everything seems to be good now.

Troy