Sealed Cooling System

[djdr1988]

I'm sure there is already a thread on this, but I have an 89 Jeep Comanche that has constant overheating problems. I have check the water pump and I flushed it. still overheating I was wondering if it is possible to put a radiator with a cap in it without changing the whole system.

[djdr1988]

It is also losing coolant and I don't see any leaks or drips and its not going into my oil

[jimoshel]

Check your tail pipe. See if there is any moisture coming out of it. Pull your plugs. Look for one, or two adjacent ones that are cleaner than the rest.

[djdr1988]

I have checked the exhaust, I will pull the plugs here shortly

[1989 Eliminator]

I have the same system. That pressure cap could be possibly bad on the pressure bottle. You really have to bleed out the system to get it right. I say drive for awhile till it gets warm. Let it cool. Fill it up. Repeat.

[Eagle]

First things first:

 

We just did this a few days ago. At least you know that you have a closed system, and that the plastic bottle on the firewall is pressurized, right? And that plastic cap on that plastic bottle is your pressure cap.

 

If you still have your original plastic bottle and cap, it is now about 25 years old. Plastic gets brittle and changes size as it gets old. It's very possible that your bottle isn't capable of maintaining pressure any more. If that's the only problem, then a replacement bottle will cure it.

 

Second point -- how full are you filling that bottle? It should NOT be "filled." If you look down inside, you'll see a post sticking up. That's the fill mark. It should be HALF-full when cold. There is no overflow, so the coolant needs a place to expand. The upper half of the plastic tank is the expansion space.

 

Lastly, if you still have the original radiator, consider it beyond dead. It may not be leaking but I'll bet it's almost completely clogged. 25 years is a LONG time for a radiator. I bought my '88 Cherokee new, and it's now on its third (second replacement) radiator.

[djdr1988]

I am only filling it to the top of that piece. I replaced the bottle last year. I believe it is the original radiator in it. I have a newer radiator out of a jeep we parted out but it is for the breathing system and is my understanding that if input that in I have to change something with the heater hoses and I can no longer use that sealed bottle.

[Roadking99]

Try running it without the thermostat. I'd been having all kinds of problems since losing a radiator hose last week. Changed thermostat today, topped off engine and radiator thru t-stat housing. Forgot to put in t-stat, but engine now runs great. Some might disagree with my recommendation, but I am leaving my t-stat off, but being in South Texas, I should be okay.

[djdr1988]

I did take the thermostat out a couple weeks ago I have ran without before and the Jeep always ran cold but it still overheating now

[djdr1988]

I did take the thermostat out a couple weeks ago I have ran without before and the Jeep always ran cold but it still overheating now

[HOrnbrod]

Read these threads and do the cooling system checks detailed within. No use rehashing this crap over and over and over.

 

http://comancheclub.com/topic/38373-road-trip-a-little-hot/

 

http://comancheclub.com/topic/39639-cooling-system-testing/

[yxmj]

To answer the OP question, yes you can put an updated rad with cap in. I just installed a 2000 xj 4l rad in my 87 MJ.2.5

 

FYI if you had a 2.5 it would have come with a normal rad with a cap (looks like a CJ/YJ rad)

 

Another cooling trick i use in all mine, is with the secondary electric fan (if you don't have one they can be picked up at any JY) I put a cab mounted switch that activates a relay under the hood, then i run the lead for the secondary to the relay. I find it gives better control over cooling when wheeling, towing, or just sitting in heavy traffic.

 

Also if you run a secondary tranny cooler mount that in front of the electric fan to really give you control.

:thumbsup:

[Eagle]

I am only filling it to the top of that piece. I replaced the bottle last year. I believe it is the original radiator in it. I have a newer radiator out of a jeep we parted out but it is for the breathing system and is my understanding that if input that in I have to change something with the heater hoses and I can no longer use that sealed bottle.

 

I don't think the top of that post is the mark. Isn't there a notch, or a cut-away portion, below that? THAT's the mark. (I don't remember -- I've been running a Moroso surge tank in place of the plastic bottle for fifteen years.)

 

Do NOT run it without a thermostat. The thermostat is there for a reason, which is to keep the temperature UP to the proper operating range. If the system can't keep it from overheating beyond that range, removing the thermostat is not the answer.

[djdr1988]

Hey Guys. Sorry I Haven't Posted Back In A While. I Decided To Take Out The AC Condenser And I Pulled The Radiator And Flushed It Directly With A Hose And Reinstalled It Filled Up The System And Ran It With The Cap Off The Tank For About An Hour And A Half Filling As It Went Down. I Haven't Had Any Problems Since. I Think There Was Too Much Air Trapped In The System. Thanks For All The Advice. Sorry For Everything Being Capitalized. My Phone Is Being Weird.