Overheating, of course

[invisiongrafix]

88 Jeep Cherokee, 4.0, 4 wheel drive. The radiator has been replaced. The water pump has been replaced. The reservoir and cap have been replaced. Today I put in a 180 thermostat (with the air hole) and burped the system. Didn't notice any air. My coolant is 100%, not 50/50. Even after this it ran about 215+ around town and I had to stop twice going up the mountain to get home as it was about 250.

Anything I'm missing?

Bill

[Saudade]

Does the top radiator hose feel hot when the engine is hot? (Be careful!). If not, you still have air trapped. It took me several heat/cool cycles and run at high RPM's to purge the air out of mine.

Did the electric fan kick on?

[invisiongrafix]

I'll continue to burp it. Should I notice the air come out?

The electric fan comes on at about 240 to 250 (I'm guessing). Just put in a new sensor.

[JDPascal]

Should not be running 100% antifreeze in the cooling system. It is not as effecient at removing heat as the 50/50 mix and if you are in a cold climate, it will gel and not circulate at a warmer temperature than the 50/50 as well.

Best freezing protection is a 60(af)/40(water) mix and for other climates a 50/50 is the best.

JD

[Saudade]

WOW. That's really high. When mine was low on coolant, it overheated quite easily. I had to run the a/c to keep it cooler. Turns out that the a/c also turned on the electric fan.

If you search this forum for "trapped air" you'll get lot's of hits for different methods. Try the one that suits you. I just left the cap off the bottle and ran the engine at 2000 rpm ad watched the flow out of the return line (or lack of flow). Once I shut down and cooled off, I filled the level up to the mark and started it up again (cap still off). Got it hot, rev'ed her up, shut 'er down, filled 'er up. Knew I was making progress when the top radiator hose (around the a/c compressor) was blazin' hot too. Kept it up until I didn't need to add anymore coolant.

Now I run around 195-200 (hard to tell with stock guage) and the electric fan kicks in around 210 which it does only under heavy load, extended idling or hot weather.

[Saudade]

Oh, and what JD says. Best to run a proper mix and not 100% antifreeze.

[canucklpuk]

I had the overheating trouble for about a year and it turned out that there was a small crack in the radiator, have also heard that older cherokees heat up due to excessive radiator clogging???? i dont know something to check

[invisiongrafix]

Ran it with the cap off and watched it spit and sputter. Didn't put the cap on before turning the engine off and it "boiled up" out of the reservoir. Won't make that mistake again. Lots of spitting and sputtering though. Is that the air coming out? If so, how much could possibly in there? Also, diluted the mixture. Does all of this sound right?

[Saudade]

If it's spitting and sputtering, then that's the air coming out. I get a steady trickle of antifreeze coming out at idle and a solid flow at higher rpm's.

Some of the other suggestions I've seen include parking on an incline (front end down) to raise the bottle higher. Or remove the temp sensor at the rear of the head (next to the valve cover) to allow air from the block to escape.

Anyway you do it. It's a pain. However once done, it works just fine for me.

And sorry, I forgot to mention about replacing the cap at shutdown.

[invisiongrafix]

I noticed that when it cooled down this time the coolant stayed up at the same level. Didn't need to add any. I this a good sign?

[capt. apathy]

I went through a lot of crap with mine.

in the end it came down to flushing the radiator, removing the air trapped in the upper hose and head (due to the completely incompetent design of the cooling system), and adding a coolant additive. I think the additive was called 'water-wetter' or something like that. I was running without a thermostat and the operating temp dropped 10-15 degrees after using the additive.

IMO the best way to remove the excess air is nose-down and temp sensor method. the lines that go to the bottle leave the engine near the center of the engine and not all coolant routs through it. so even if you let your engine run hot enough and fast enough to circulate the air bubble, only a small % of it will make it's way to the bottle as it passes through the pump.

besides the air trap a few other problems with the design are-

the fan switch. my jeep would be at over 245 degrees and the fan wouldn't come on. as mentioned in an earlier post turning on the A/C will activate the fan (thats the only way mine ever came on). the big problem is the switch is located near the radiator outlet. so instead of your electric fan coming on when your operating temp reaches 220, it comes on when the coolant entering the engine reaches 220 (After the radiator has already cooled it down some).

the plastic bottle/cap. fine for an overflow but as part of the pressure system they suck. once it over heats you will never get them to hold pressure again. not realizing this I left the old ones and it promptly over-heated again. so I got a new cap, but the previous overheats had screwed the threads on the bottle, so it over-heated again. so I replaced both, somewhat better than having the older ones but you still have to be careful, the cap must be snug but if you over tighten it at all it jumps a thread. if that happens time for a new cap/bottle.

after all the time, money and BS I dealt with on the cooling system, I would have saved a lot of time, headaches, and about $150 if I'd just removed it all and put in a conversion cooling system with a regular cap and over-flow bottle.

thats what I'd recommend to anyone dealing with the overheat. anything else is just a temp fix until you can afford to replace it or get tired of fighting it.

[invisiongrafix]

I plan on the conversion as soon as the funds come in, hopefully January. Till then, need to be able to drive and work. What is the best way to tell if the clutch fan is bad? Not sure if this has been replaced.

[capt. apathy]

Originally Posted by invisiongrafix

I plan on the conversion as soon as the funds come in, hopefully January. Till then, need to be able to drive and work. What is the best way to tell if the clutch fan is bad? Not sure if this has been replaced.

if it's stock it should be temp activated. so if you try to turn the fan by hand with the engine hot it should have more resistance to turning than cold.

for a cheap temporary fix, you could try the aditive or by-pass the the fan temp switch and put a toggle in the jeep so you can turn it on manually. I've done this in other cars with good results but have never tried it in the jeep.

[scuba4321]

NEVER,NEVER,NEVER run 100% antifreeze, it will actualy reduce boilover temp, and increase the temperature it will freeze. would not even bother checking anything else until you drain 1/2 of the system and fill, with water.

[invisiongrafix]

Originally Posted by scuba4321

NEVER,NEVER,NEVER run 100% antifreeze, it will actualy reduce boilover temp, and increase the temperature it will freeze. would not even bother checking anything else until you drain 1/2 of the system and fill, with water.

Already fixed the coolant mix.