Nitsujeep

Hey Guys, Let me fill you in on all of my info and also state my problem. I have a 1990 cherokee 4wd 5sp 2 door with a 4.0 renix system engine. I bought it about a year ago with 98,000 miles on it for $800. I know a steal right. Well the night I bought it I was about 10 miles from home and got about 3 miles away and noticed that i was running a little hot (and it just happened to be nighttime PITA right). Well over the next week I tore apart the front of the motor and replaced the Water Pump, all hoses( bottom did not have the spring in it) Electric fan, belt, clutch fan, resivour, thermostat,and thermostat housing. I also Manually flushed the radiator( which i should mention was full of mud and decent size rocks. At this point The jeep runs great and I love it, I have always been a gm guy and still am but the jeep is my new love. Anywho I drive it and it gets to 210 then drops as the thermo opens. Then It starts climbing and climbing slowly past 210 until i shut it off Please help!!!!!! P.S. I Have the aux fan hard wired to run all of the time. Thanks Guy And I look forward to being part of the family.

caged

either bad rad, bad fan clutch or air in the system.
you are sure the belt is on correctly i assume.
to burp a closed system found in the renix era, you need to get the pressure bottle up higher than the rad. i parked mine on a hill, kinda like in a ditch with the *** end up the hill.
then i removed the pressure bottle cap and let it idle for a while.
that was after i replaced the rad, fan clutch, water pump and thermostat.

Nitsujeep

Yes sir i verified that the belt was on correctly the fan clutch is new, so that leaves air in the system and the rad, is there a way to test the rad? When Idling while parked in the ditch what happens if it over heats during do i shut it off? Does the heat need to be on high? Will I be able to see/notice the air escaping through the pressure bottle?

Thanks Man I really appriciate the help!!

cruiser54

Try replacing the cap on the coolant bottle with one from a Volvo. Part number 703-1396 at Napa.

Nitsujeep

whats the reasoning in the new cap?

cruiser54

First off, yours may not be sealing well. The Volvo cap is rated at higher pressure and fits tightly even on chinese bottles where the chinese caps don't. If you can't hold pressure, it will boil and get hot....

Nitsujeep

I will definitly try it but it never boils in the resivor does that matter?

Nitsujeep

And it never loses water

tjwalker

cruiser54 is well versed in Renix vehicles; he used to be a Service Manager at a Jeep dealership. I'd take his advice on this one.

Nitsujeep

Nuff Said, No disrespect this thing has been making me so frustrated since it started. Thanks Man

tjwalker

Completely understood; you will get this figured out. Lots of RENIX owners here! I'm a bit rusty as I don't work on them as much as I
did when I owned my 88 Comanche!

Burping the air out though is critical though on the Renix. They don't "self-burp" in 3-4 heat up/cool down cycles like the 91 and newer XJs do.
Check out this link from my friend lunghd. I am a moderator on the Jeeps Unlimited forum with lunghd. But this darn XJ addiction brings me to all forums relating to the XJ!

http://www.lunghd.com/Tech_Articles/...BurpAirMod.htm

And I've heard others that have tried that Volvo cap that cruiser54 recommended, so I'd consider that. And a new radiator (if you plan on keeping the XJ) is not at all expensive and it sounds like you are handy with a wrench.

Once you get everything new, (and you are very close, so why not finish it up??) it's just a matter of burping the air out!

Some perform the conversion to the open system as well. Another thing to consider. SEARCH for both pros and cons about doing this. Cruiser; please chime in about your thoughts on the conversion; I know you have an opinion on this which I would respect.

But if this cooling system was abused and it sounds like it was, I'd recommend multiple flushes with fresh coolant until you get to a point where the coolant STAYS green. One flush for an abused system like yours is almost assuredly not sufficient. I'd consider using a citrus based flushing agent, available at any parts store. I've found that a citrus mix is strong enough to do the job for most cases and can really help get the crud out. Follow the instructions on the bottle. I'd use conventional (green) coolant all the way along. And for your final mix, be sure to use a 50-50 mix of distilled water as it doesn't have the minerals that tap water has. Verify strength with a hydrometer as it is easy to get the final mix too diluted.

Also know that the heater control valve on the 87-90 is a very weak link. Woefully under-designed and lamely manufactured. I'd recommend getting a new one on there as a matter of course as they are very susceptible to blowing apart, which leaves you with an overheat and possible cylinder head damage. They are very inexpensive! Buy one.

Good luck!!!!

blenny

I had the same problem, and replaced everything including the radiator.... A $7 autozone cap fixed everything.

cruiser54

Something to do regardless. For under $10 you can eliminate this as a contributing factor in your higher than normal temp situation. Many times we must make sure what isn't before we can determine what is.

Nitsujeep

Very True, as soon as payday hits it will be the first thing i buy. I appreciate every body donating there time to help me out with my problem.

5-90

Typical service life for the OEM RENIX radiator seems to run 150-180Kmiles, with some variation outside of that range (you may get up to 200K.)

This is irrespective of maintenance - although better maintenance will allow you to run to the longer end of the range.

Even the Jeep service techs would replace the OEM with a qualify aftermarket part around here (typically Modine or Performance Radiator,) and that would take care of that little annoyance.

When you replace the RENIX thermostat, drill two small holes (1/16"-1/8") in the flange, 180* apart, on opposite sides of the centre poppet valve. Install with one hole at 12:00 and the other at 6:00 - this allows the system to purge itself of air, with minimal intervention on your part.

Also note that an initial overheat on any closed cooling system (not just RENIX) can cause a "steam void" behind the thermostat - which will insulate it against coolant, and prevent the thermostat from opening. Drilling the thermostat flange helps to avoid this, and can save you some expensive repair work later! (Not bad for two minutes' work...)

The steam voids and eventual OEM radiator failure seem to be about the most common cooling system malfunctions found in the RENIX system, so I'd check those first.

The fan clutch gets replaced every four or five years, and I tend to write the date on one of the fins with either a Sharpie pen or an engraver, so I can keep track of it. Any maintenance part I know I have to replace at intervals gets the initial install date written on it for my own reference for later. I find it helpful - if I suspect a part, the first thing I do is check the date on it. If it's more than five years old, it's probably due for replacement, so that gets done out of hand. Further troubleshooting PRN.

Check your hardware stores - General Tools makes a nice battery-powered pencil engraver for less than twenty dollars that is very useful for this sort of thing.