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Old 11-16-2013, 01:43 PM   #1
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Radiator replacement

I'm going to be replacing my radiator with a OEM replacement. Is there anything I should know before I try and tackle this job, or is it pretty straight forward? 91 4.0 auto trans w/o A/C.
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Old 11-16-2013, 05:21 PM   #2
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Very easy, 4bolts on shroud, 4 on rad, two hoses. Make sure you purge the air out after you fill the new rad, shouldn't be much unless you change the thermostat at same time.

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Old 11-16-2013, 07:27 PM   #3
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Quote:
Originally Posted by reno92 View Post
Very easy, 4bolts on shroud, 4 on rad, two hoses. Make sure you purge the air out after you fill the new rad, shouldn't be much unless you change the thermostat at same time.
That's what I wanted to hear. Hopefully it's not stubborn. Thanks!!!
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Old 11-14-2016, 12:25 PM   #4
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Need to replace radiator on my 93 4.0 5spd. I put stop leak in a few months ago so I should probably flush the system first? How do you bleed the air out of the system? Just run with the cap off? No issues with over heating, temp gauge stays right at 180 once warm. Should i also replace thermostat or just leave it?
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Old 11-14-2016, 12:30 PM   #5
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1. Flush the system out to get as much of the stop leak out as possible.

2. You bleed the air out by "burping". All you do is squeeze the upper radiator hose until air bubbles stop coming out and the coolant level is stable.

3. 180 degree thermostats are ghetto fixes for overheating problems. Throw in a name brand 195 degree. With a 180 degree, you'll never reach operating temperature. A 100% stock cooling system is more than enough for a YJ with a factory engine.
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Old 11-14-2016, 01:19 PM   #6
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Quote:
Originally Posted by MudMagnetYJ View Post
1. Flush the system out to get as much of the stop leak out as possible.

2. You bleed the air out by "burping". All you do is squeeze the upper radiator hose until air bubbles stop coming out and the coolant level is stable.

3. 180 degree thermostats are ghetto fixes for overheating problems. Throw in a name brand 195 degree. With a 180 degree, you'll never reach operating temperature. A 100% stock cooling system is more than enough for a YJ with a factory engine.
MM hits the hammer on the nail here.
Once you have flushed the system and installed your new radiator & thermostat, fill the radiator as full as possible and start the engine with the radiator cap off. Once the thermostat opens, you can expect to see coolant circulating as you peer into the open radiator. Add pre-mixed coolant until it won't take any more. This is when you squeeze the top hose with a gloved hand. The hose will be hot enough to be uncomfortable but probably won't burn you. Once you have the system "burped" and ready for the road with the radiator cap in place, fill the overflow bottle to the warm mark and make a note of exactly where the fluid level is. A piece of masking tape works great to mark the exact level.
Then each time that you drive the Jeep, check the coolant level until you don't need to add any more.
What happens is that as the coolant warms up, pressure in the cooling system pushes coolant and residual trapped air out through the radiator fill cap and into the overflow bottle. Then as the engine cools after being shut off, lack of pressure draws coolant (without the air) back into the radiator.
It might take zero through three or four cycles to not have any residual air left in the system.

If you are on the margin of passing emissions and have a 180* thermostat, installing a 195* could make the difference.

Good Luck, L.M.
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Old 11-14-2016, 01:25 PM   #7
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Forgot to mention, with the radiator out, it's easy to change the lower hose.
Check all your hoses, upper radiator hose and three heater hoses while you have the system opened.

Make sure that if you replace the rear hose from the heater core to the back of the intake manifold (6cyl. engines) that the hose doesn't rub on the heater box bolt that protrudes through firewall. There is a Factory Service Bulletin about this from 1987.

Good Luck, L.M.
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Old 11-14-2016, 02:46 PM   #8
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Was reading online about radiator flush that involves putting a valve on the heater hose and flushing from there. Is this a good method? Appreciate LM and MM input on this forum. You guys are everywhere with great info
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Old 11-14-2016, 04:43 PM   #9
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No "flush" product will completely flush out the system. This summer, I did a complete cooling system flush. I had out every single cooling system component, and sprayed the block out with a hose until it ran clear. Then I used a blow gun hooked up to my air compressor and more crud came out.

If you have the lower hose and upper hose off, you can spray water in the system from top to bottom. Also flush the heater core out backwards and forwards.

If you want to use a flush product, they're just a bottle of white vinegar plus some other stuff. Pour in a quart of white vinegar and the rest distilled water if you wish. Then drain it and put in coolant the next day.
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Old 11-14-2016, 04:54 PM   #10
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Quote:
Originally Posted by moenmike23 View Post
Was reading online about radiator flush that involves putting a valve on the heater hose and flushing from there. Is this a good method? Appreciate LM and MM input on this forum. You guys are everywhere with great info
Negative.

Go to your local parts store and get a couple cans of radiator flush. Dump them in the (cool) radiator and drive the Jeep until it's thoroughly warmed up.
Drain the radiator and properly discard the old coolant.
Remove the radiator and thermostat. Attach your garden hose to the heater hose that runs to the heater core and turn the water on. Let it run until the water comes out clear. If a lot of crud comes out, reverse the flow until the water runs clear again.
Change whatever hose looks questionable. I would do the lower hose now because it's so much easier with the radiator out than with it in.

You can get pre-mixed coolant now at most auto parts store. Pick the coolant up when you buy the cooling system flush and whatever hoses and clamps that you need. Look in your Factory Service Manual for your cooling system capacity. Get a little extra.

Don't cheap out and attempt to salvage any of the old coolant. It has stop leak in it and could end up ruining your new radiator.

In my opinion, the valve that you install in a heater hose only does a partial job. I think it is an old time gas station gimmick that hasn't died out yet.

Good Luck, L.M.
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Old 11-14-2016, 05:05 PM   #11
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There you go Mike,

A couple of different opinions from knowledgeable posters.
A gallon of white vinegar is cheap at the supermarket. Probably cheaper than a couple cans of cooling system flush at the parts store.
I prefer the store bought stuff because maybe it will do a better job. There is no reason not to do both.
If you do both, do the store bought stuff first. That way the acidic vinegar has a better chance to bite and loosen the rust and crud so that it will wash out with the second hose flush.

Good Luck, L.M.
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Old 11-15-2016, 12:39 AM   #12
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Since you have stopleak and years of muck in there, I would recommend replacing the waterpump and, with that and the thermostat off, you can properly blast out the water jackets and head. There will be a lot of muck in the bottom of the block and head.





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Old 11-15-2016, 12:05 PM   #13
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DREDnot offers a good suggestion. If you don't minding spending a few extra bucks on a water pump and a few extra minutes doing the job, you will have a well serviced cooling system to begin the winter with. Attention to detail is important. Don't rush the job.
Look at DREDnots gasket surfaces in pic 2. Your auto parts store will have a tool that attaches to your drill. A wire brush or a fiber disc work equally well. Wear eye protection.

Pay the same attention to detail in getting the crud out of your cooling system. A little extra time spent now will save hours of heartbreak on the trail. Use that thinking in all you do, on your jeep in particular and in life in general.
"A stitch in time saves nine" said a mother of eight as she sewed up her husbands pajamas.

Good Luck, L.M.
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Old 11-15-2016, 05:25 PM   #14
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Thoughts on aluminum core radiator with plastic tank? You'll probably hammer me on that but it's a few hundred $$ difference. I see prices from about $90-$450. Had 180* thermostat when I bought it 2 years ago. In NJ because of the model year they don't even test my emissions now so no concern. What is the difference performance related running at a higher temp? I know my jeep runs stronger with cooler air temp so I'm a little confused by that
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Old 11-15-2016, 06:09 PM   #15
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Open up my 1993-95 manual in my signature. 95o Fuel Systems page 31.

See all of those modes that the PCM uses to run more efficiently? It will be stuck in open loop warm-up mode and will not read the oxygen sensors. The idle will be higher at idle as well. Only the open loop modes will be used, and not the closed loop.

Also, engines have less wear at operating temperature. Engine startup is always the time where most of the engine wear occurs, since it is 1.) cold and 2.) it does not have oil circulating.

As for the "cold air" I am not sure why exactly cooler air is supposed to make your engine run more efficiently, unless it prevents the fuel-air mixture from igniting prior to the spark, due to compression (like a diesel). I do know that one of our vehicles sits at 18 MPG in the summer and 16.5 MPG in the winter... Not sure what that's about.
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Old 11-15-2016, 08:53 PM   #16
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Don't know how to get to your signature. One reason mpg decline in winter here is addition of ethanol to the fuel. Lose about 10%. Thoughts on the radiator option? I use for dd and beach fishing only
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Old 11-15-2016, 10:12 PM   #17
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NAPA radiators tend to be the norm for stock configurations. That's if you don't want the Griffin for $300 ish... Go to Rock Auto. The NAPA radiator is the Spectra one. If you look at the product description then you should see Spectra or something like that.

Here it is, straight from the NAPA website:
"Innovative Engineering, Manufacturing Technology And Quality Control Ensure That Spectra Premium Radiators Meet Or Exceed The Performance Of The Original Equipment They Replace. That Extends To All Components, Including Engine And Transmission Oil Coolers."

My signature is below here... Last line where it says "Jeep Manuals".
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1990 Yamaha TW200.

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Old 11-16-2016, 09:39 AM   #18
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The hotter you run an engine (without over heating) the more efficient it is. Jeeps like 210 range. Alot of that has to do with keeping it at a constant temp, as large temp fluxuation causes expansion-contraction, and diferant alloys in your engine group and shrink at different rates. Keeping to the design temps is the way to go.
Cold air is more dense, therefore can contain more oxygen per cubic inch of volume, so you theoretically would produce more usable power. That being said, most cold air intakes just flat don't work, by poor design, or they are pulling mostly under hood air, or have really restricted or poor performance filters. It's been proven time and time again here and elsewhere that stock intakes and air boxes perform best.
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Old 11-18-2016, 04:14 PM   #19
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Quote:
Originally Posted by Ov yj View Post
stock intakes and air boxes perform best.
I still have the original air box but I took out, off, all the restrictions. Scoop off the front and the reducer inside. Seems to run better but I also did plugs wires cap and rotor about the same time. Definitely made higher rpm easier to attain.

MM, I'm using Mobile app,couldn't find your signature. Went to browser and there it is. Thanks
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Old 11-18-2016, 06:36 PM   #20
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The aluminum core radiator with the plastic tanks will work just fine. I have one in my Jeep and have never had a problem.
My wifes 2014 Cadillac SRX came with one from the factory. I think my Ford F-150 has an aluminum core radiator too.

For a regular Daily Driver the more expensive, multi core radiators are overkill. Just make sure that your fan clutch spins somewhat freely when cold and doesn't make any noise like a grind or grumble when you turn it by hand with the engine off.

Good Luck, L.M.

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HEI distributor with computer and all related relays and wiring removed.
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12K Badlands winch with dual batteries.
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