I have an 88 Cherokee LTD, inline 6, 4.0. Last week it started over heating and spewing hot coolant out of resevoir. Did what seemed rite and replaced thermostat and Water Pump. With both installed I am getting same issue. (note also ran without a thermostat for test of flow). With new parts installed, once jeep gets to normal 210 the coolant begins to boil out, and she over heats after this. I am no pro when it comes this stuff, but have a little knowledge. If any one has an idea what I can look for next I would be thankful.

Thanks in advance....

 

are your fans working

 

The Main Cooling fan is running with motor, and the electric fan is on a switch, which I have on.

 

Do you have a good 50/50 mix?

You might want to check for a leaking head gasket (compression test, cooling system pressure test).

 

Isn't the "rad cap" on a Renix in the pressure bottle? Is that stuff in good shape?

 

Your system isn't pressurizing correctly. Water boils at 212*. Could be a bad cap or a leak somewhere. Could be a cracked bottle. Do a pressure test on your system. Check bottle, hoses, and connections for the obvious coolant leaks. Check your oil for coolant. Replace your cap.

 

so guys i'm starting to get frustrated with my jeep i havent had it a year yet and im on my fourth new car battery. thank god for warranty's. this week we got allot of rain so me and some friends decided to take the jeep mudding after work. on my way home my check gauges light came on and my dash showed my battery was below 9 volts. i didnt think much of it at first turned the car of and turned it back over quickly. then when i started home my rpm's went below 1,000 and my car started puttering and died. i thought i had sucked water. let it sit for a day cleaned all the filters and recharged my battery and it ran fine but then it happened again after turning it over a couple more times. i went and had my battery tested and they told me it was dead and gave me a new one under warranty. but the problem continued. every time it iddles it reads 12 volts and as soon as i go above 30mph or 3500 rpms my check gauges light comes back on and my battery is showing dead again. ive cleaned all the mud off and i dont know what else to try. is it the computer? the alternator?

 

I would assume its the alternator. With a bad alternator the battery is not continuously being charged while you're driving. So your motor, all accessories, stereo, wipers, lights etc... Are running off of a 12 v battery. So if your battery just keep dying, ... Alternator.

 

Brian...don't hijack; start a new thread. Your problem is not related to this one. You will get more accurate replies with your own thread and so will the OP for this thread.

 

The best replacement for that cap is a 703-1396 cap from Napa. Fits the threads better, holds higher pressure, and has a lower profile so it doesn't hit the underside of the hood when the bottle expands.

 

Ok so I found a crack in the resevoir that is blowing out steam almost instantly at engine start...(Going to replace) sealed the crack to test, no more leak but still boils over. Tonight I will be flushing the Rad. and refilling to make sure my mix is perfect. I will post my results.

I want to thank everyone for taking the time to offer helpful tips.....I will post again tomorrow!

 

Use the Napa cap on the new bottle.