another hunting trip ruined

thanks to the XJ. '90 with 4.0, 200k on the clock. about 10 minutes away from home started to overheat in 20 degree weather on the highway. sick of this happening, and i just got a school refund check so i'm looking to get a whole bunch of stuff fixed this week. couple questions though.

been having the cooling problem for a while now, was stranded out at the lake with no parts stores around so the jeeps been running open cycle (no thermostat) for like a week after the last one jammed up on me. could this in anyway be detrimental to the engine other than my heater?

valve cover has a small leak as well, it's getting fixed. your thoughts on making your own vs precut cork ones?

also alternators. any way to test which is bad (alternator/voltage regulator) on the car without removing it for a bench test? voltmeter on battery reads 12.6 volts with car off, and 12.4 with car running. as far as alternators, any noticible difference in reman vs 100% new? the parts store shows two listed as OEM, a 60-something and a 100amp. what was the actual OEM put in them rated at?

anymore ideas/advice for me?

thanks for the input,
hunter

As far as the thermostat not being there, I know in a lot of vehicles if its not there to stop the coolant flow your temp will never go down cause it just keeps cycling through the block getting hotter and hotter.
As far as tha gasket goes, high temp RTV should work but I would go with an actual feltpro gasket.

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Cherokee's eat Taco's

I've never seen a vehicle get too hot with no thermostat installed, usually they just stay at like 150 to 160 degrees and never warm up so your gas mileage goes way down.

The actual felpro gasket works well, just make sure you scrape both surfaces clean, optionally apply gasket sealer shellac to it, it can help. Removing the serpentine belt makes getting at the lower bolt much easier.

Try putting a new thermostat in. Make sure your aux. Fan turns on when its supposed to and that your clutched fan is working properly.



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Cherokee's eat Taco's

I've seen cars over heat with no t stat, make sure you have NO leaks. Even if the cooling system doesnt get low on coolant right away a small leak wont let it get to system pressure when it warms up and that will cause it to boil and over heat. Sometimes it will even register as running cooler then normal if its boiling over and has air in it. Also if you havent replaced that plastic fill bottle, I'd replace it. I got a sweet aluminum one with a regular 16 pound cap on it for 125 bucks from macs radiator. Also, if you have air trapped in the system I like to bleed it out by removing the temp sensor on the back of the head, fill til coolant runs out and reinstall the sensor. Also, I had a bad gauge and it always read hotter then it was. I had lots of issues but I now own a bran new 87 XJ, lol.

Might want to check your water pump. Sounds like it isn't circulating. There should be a small hole on pump which is supposed to drip coolant when it has gone bad. If it isn't dripping it still could be bad. That's my guess (Have had 3 dif xjs overheat and 2 of them were water pumps crapping out).

As far as the altinator the differant amps are for differant xj options. One with power leather seats and power windows and locks would require a stronger amp alt. My 90 renix had power nothing and only ac so it called for a 60 amp. Since I knew I wanted to run other stuff down the road (lights, winch) I bought the 100 amp one. Getting a stronger one then you had just means it is more capable of a stronger load then what your xj was spec'd for and has to work less hard.

As far as the valve cover is concerned, don't bother with a cork one. Get a tube of the appropriate RTV and make your own. Some new valve covers come with RTV pre applied and no other gasket. The directions are on the tube but you basically squeeze it onto the cover then put the cover on the engine but you're supposed to wait for a while to tighten the bolts down so it has time to cure. That is what I did and it hasn't ;eaked for 2 years since I did it.

Here did this to help:

*note not all 4.0 beltss are set up the exact same way but the water pump is always (to my knowledge) located in the same spot from the 90 I work on to the 97. This seams to be a custom job but the water pump is still the same*
1. Water pump (you need to remove the pully attached to it inorder to easily remove the pump from the block.
2. The small hole that is supposed to tell you when the seals/berrings are bad is located in this area under the pully.

If you do replace it I would buy an actual gasket. The RTV works but can be a pain where this is located. I didn't have trouble with the cork gasket.

12.4 at the battery with the car running soudns like a bad alternator to me, should be closer to 14.

I had a couple of hunting trips ruined when I had my 96 XJ due to overheating too. Now I have a very beaten up 90 XJ for a ranch jeep, but here's my .02 on overheating, as I spent countless hours getting my 96 to run normal.

1. Make sure your head gasket's not bad due to prior overheating. This will cause overheating once it's blown.

2. Check the fan clutch. When the engine is hot, you should not be able to spin the belt fan by hand. If so, then clutch is going bad. 20 years on an OE one is a very long time.

3. Check your water pump. I've seen pictures of water pumps after less than 10 years where the blades have corroded off. You're is probably not pushing fluid through efficiently.

4. Put back an OE 195* t-stat. Use the the OE one with the little bleed hole. It makes a difference.

5. Make sure your heater core/hoses aren't blocked. Disconnect hoses in/out to heater core in firewall. Blow into the "in" hose and make sure fluid comes out of the "out" hose. If not, you can bypass the heater core (read "no heater") by looping the "in" hose to the "out" hose.

6. Of course check your radiator to make sure it's not plugged up. If you put Alumaseal or similar in it to cure a leak, it could be clogged.

7. Make sure there's no air in the cooling system. Burp out any air that may be in there. A small amount of air will make the temps skyrocket immediately.

That's all I can think of. You want your Aux electric fan to work, but this time of year, a properly running XJ shouldn't get hot enough to engage the electric fan and it's not needed with the AC on or defroster. I think it goes on at 218*.

1. Your Delco-Remy alternator is internally regulated. You should be reading 13.0 to 15.3 volts between the battery's terminals with the engine running.

2. If you are still running the OEM closed system there are a few tips/tricks. First, buy a Stant 10244 pressure bottle cap--lower profile so it isn't getting smacked by the underside of the hood; it WILL screw down tight and seal on any OEM or Chinese pressure bottle; it has a higher psi rating and that will raise the boiling point of your coolant. Check all those little hoses off the pressure bottle and the coolant control valve. The coolant bypass hose likes to plug up and that will cause an overheat. Don't overfill the pressure bottle--1/4 to 1/3, the rest of that room is for coolant expansion. Use a Stant SuperStat Premium thermostat, 195 degree. It has a built in V-notch so you don't have to hunt down the hokey stock thermostat with the jiggle valve or drill the thermostat flange. Read here: http://www.stant.com/brochure.cfm?brochure=205&location_id=168 Make sure you burp the system to get all of the air out--park nose down attitude, pull the temperature gauge/idiot light sending unit from the back of the head and then pour coolant into the pressure bottle until all of the air is forced out of the system.

we need a little more info on what conditions are when over heating. you say 20 degree weather on the highway. is this over heating only when climbing hills, or flat ground? on the highway in 20 degrees, you don't need a fan. your getting enough flow all ready by the forced air. so if you have a circulating coolant, you shouldn't be over heating at all. unless something is heating the coolant, like your transmission. if this is an automatic, then your transmission can very well be overheating by a bad/worn/slipping torque converter. climbing the mountain during a snow storm i over heated when my trans was ready to go out. engine was fine, trans was toast, = over heating big time. when your jeep over heats, have you tried coming to a stop but letting it idle for a few minutes?(maybe even a high idle) if the cooling system is working properly it will cool back down pretty quick if it is the transmission heating it up. if it doesn't cool down, then you probably have a coolant flow problem. anything from needing to be burped, or a faulty water pump, to a bad lower radiator hose. by the way, make sure your lower radiator hose doesn't collapse when it gets hot. a weak hose looks fine untill it gets hot and will close up on you while driving.

guys i apologize about my slowness in response, if i aint been at work, i've been in the garage. anyways, forget everything i said about the alternator-problem fixed. bit the bullet, new alternator, passed all my tests and runs all 8 lights/interior lights/radio/winch at the same time with no problems. such a relief not having to charge a battery every night.

the cooling system is another story. more happenings there. making a new thread actually to cover my newest, biggest problem. look out for it.

90xjay, i appreciate you taking time out of your day to show me that example. my water pump was recently replaced and seems to check out fine, check out my new thread, hopefully you can give me some insight there.

again, i appreciate it guys

Glad to hear your electric system is up and running. Post up the link to your new thread when you get a chance.