99 XJ cooling issues (still) - JeepForum.com
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post #1 of 22 Old 07-11-2017, 12:43 AM Thread Starter
Deakerdoke
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Xj 99 XJ cooling issues (still)

First post, out of frustration....I guess.

New 3 core radiator, new stat, new temp sensor, new fan clutch, new water pump, new rad. cap & hoses......electric fan operates at correct temp.

Temp gauge runs normally about 210-ish. Freeway speeds the temp climbs to 220 and seems to stabilize. Adding a little more load, like a hill or a mash of the throttle, the idiot light illuminates and the temp spikes to 240 (2 seconds).

After panic wears off and backing off the throttle for a few min. And staring at the needle, the temp slaps back to 220 and all seems good.

I read a previous post (by CJ7 Tim) that touched on this, but haven't had any luck solving the issue.

My next thought has been the fact that the upper radiator hose is above the cap, creating an air-gap in the system that needs to be "burped", and there is a steam pocket that develops.

Thoughts?
Thanks in advance.

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post #2 of 22 Old 07-11-2017, 05:53 AM
CJ7-Tim
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Did you install a 16 lbs radiator cap ? Is the radiator cap a good brand name like Stant or genuine Jeep from the Dealership ? The symptoms suggest a momentary loss of pressure in the system. If there is a radiator cap, the system is self burping after just a few drives.

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post #3 of 22 Old 07-11-2017, 08:01 AM Thread Starter
Deakerdoke
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No, Orilleys special. I'll try a quality cap today.
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post #4 of 22 Old 07-11-2017, 09:59 AM
bluejunior
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Quote:
Originally Posted by Deakerdoke View Post
No, Orilleys special. I'll try a quality cap today.
The premium store brand option from NAPA is a re-branded stant super-stat if that helps you track one down.

That said, the hopping gauge does seem consistent with an air pocket, you can often get those to burp out by removing the rad cap (to provide an outlet) and then squeezing/releasing the upper and lower rad hoses to provide a bit of a pumping action in the system.

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post #5 of 22 Old 07-11-2017, 10:21 AM Thread Starter
Deakerdoke
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Sounds good, I'll try that too.
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post #6 of 22 Old 07-12-2017, 11:19 AM
JellybeanFTW
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Deakerdoke: I hate that you're having problems and hopefully it's something as easy as burping needed or low quality rad cap. Question for you though. Would you mind to explain what issues you were having before replacing all of the listed stuff?

Now, this is probably not the issue. But something to nibble on in the future maybe. You mentioned that the new radiator is a 3-core. While 3 is usually better than 2, there 'can' be a trade-off for the extra core. Mostly, the cores in a 3-core can be smaller than the cores in the 2 core. If you bought a quality, trusted name-brand radiator, this probably won't be an issue for you. But if it's some cheap deal, they may have made the cores smaller than needed so that they could fit them in there and call it a "3-core". That could restrict flow.

But as mentioned above, a spike like you have is much more likely air bubble related or something. And since you may have used an el-cheapo radiator cap (not that Stants are expensive!), I've got to ask: Which thermostat did you get? Most folks will recommend the Stant Superstat in the stock 195 degree variant which is not very expensive but good quality. I wonder if it's possible to get those spikes if a bad thermostat is stuck half way open or something? If a Stant cap and extra burping doesn't fix your problem, I'd say the Stant thermostat would be the next and easiest way to go. Keep us posted as to what you find!

Last edited by JellybeanFTW; 07-12-2017 at 11:29 AM.
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post #7 of 22 Old 07-12-2017, 01:01 PM
DerrtyD750
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Hello. I have heard a lot about air locks in the 4.0. Some suggest taking the upper heater hose off of the thermo housing. Would i be correct in saying that his needs to be done while the engine is stopped and cold? I recently went wheeling in colorado and had a lot of overheating issues climbing the mountains at high altitude. I removed the thermostat but did not idle without the radiator cap on or anything else. I saw a lot of sediment and the overflow liquid looks unhealthy. What are the opinions on how to be sure I have no air after I flush my cooland and replace my thermo and cap with the 195* and a good 16lb cap?
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post #8 of 22 Old 07-12-2017, 01:43 PM
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DerrtyD750: Before I go on with my reply... Yes. The system needs to be cool before removing hoses, thermostats, radiator caps!

There are a couple of options for coolant berping kits (AKA Spill Free Funnels) out there. While they are handy sometimes, I don't find them completely necessary.

My suggestion for you:
-Get all of the old coolant out of that system. If there is floating sediment and serious discoloration then you have, at the very least, some corrosion inside your block, heater core, or radiator. On the other end of the scale, you may have serious deterioration of your water pump, radiator, and serious rust in your block.

If you have a garden hose and plenty of spare time, I'd recommend taking the thermostat out (ONLY WHEN COOL!) and re-installing the housing. Take the rad cap off (and maybe loosen the petcock drain). Then, take off the heater hose (going from the water pump to the firewall), sticking the hose in there, and turn the hose on (just medium pressure is fine). After not very long, you'll see water coming out of the top of the radiator. Keep this up until clear water comes out. You may still see particles with the clear water. If so, keep going. Once the water is clear with no particulate left, replace the thermostat with a 195 degree Stant Superstat and replace the rad cap with regular Stant as well. Also remove and wash out the overflow bottle at this point and re-install.

To purge the system of air:
I usually park on a slight incline with the front going up hill. Take the radiator cap off (when cool!), fill with 50/50 (mix your own with distilled water for best price!) till you can see fluid, then start the engine. You may notice that the coolant level drops in the radiator to where you can't see it. Fill it a little more. And repeat. Eventually the engine will reach operating temperature and the coolant level won't dip any more. Turn the engine off. Reinstall radiator cap. Fill over flow tank to between lines.

Now drive as normal. But every day for a few days, or twice a day if you are paranoid, check the coolant level (when cool) under the rad cap. Can't see it? Fill it up. If it's turning brown again, flush the system again. If you are still over heating, now's the time to start replacing water pump most likely. Maybe the radiator as well depending on condition.

If all is well after this, start a routine of simply changing the coolant ever 1-4 years. A lot of parts depend on quality/clear coolant to operate properly.
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post #9 of 22 Old 07-12-2017, 04:50 PM
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if your thermostat does not have a tiny hole drilled in it, drill about a 3/32 drill, not larger. Drill a hole in the thermostat below the gasket line. Deburr. Additionally, watch out for the gasket itself. Make sure you have it placed correctly, not covering up the flow on the right side. Place the thermostat with the hole at the top. Fill, squeeze the upper hose a few times, refill. Run, let cool, keep filling the coolant expansion tank. If this does not do the trick, have your coolant system checked for combustibles (possible head gasket leak). If the freeze plugs were replaced and just knocked it in the block, this another possibility. I am in the hottest area of arizona, running a aluminum stock radiator with a 195 degree thermostat. All Ok
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post #10 of 22 Old 07-13-2017, 11:11 AM
DerrtyD750
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@JellybeanFTW Thanks for the great tips! I will try this approach and see how it goes.
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post #11 of 22 Old 07-13-2017, 04:02 PM
JVP729
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I have had cooling issues with my 99 XJ over the past two years. I have found that the three row radiators are waste of money. The stock radiator is just as good. I replaced the thermostat housing with a High Flow model. Minimum difference. A quality Radiator cap. Minimum difference. I have a clean system with good hoses, and good quality water pump.


The key is Air Flow! These 4.0 motors run hot. I would suggest you replace the Fan Clutch on the Blade side and replace the Electric Fan on the other side. Even if the these two items appear to be working, they may not be running at the proper RPM's due age. Make sure the Electric Fan Switch is working with the A/C and the Fan should kick on when the temp gets around 210 degrees without the A/C on.
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post #12 of 22 Old 07-14-2017, 08:02 PM Thread Starter
Deakerdoke
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Purchased a quality rad. cap and popped it on. Much better (tighter) fit. Seems to have helped. Drove around and temp stayed under 220. Will road trip tomorrow to put some load and time on the system. I did purchase a NAPA "PREMIUM" 195 thermostat, didn't install yet, going to try the cap first to attempt to narrow the solution.
Keep the info coming!!
I'll post tomorrow with results.
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post #13 of 22 Old 07-14-2017, 08:16 PM Thread Starter
Deakerdoke
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Mikehunter, I'm in AZ too, and it is hot. So if this thing will cool here, it will cool anywhere! Working on it.
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post #14 of 22 Old 07-18-2017, 08:08 AM
azlivn
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An xj in az can be a fun game to play. I've pretty much parked mine until it cools some. My 96 has a clean cooling system, but the OE radiator still in place. Was looking loooking to upgrade, but reading results from others definitely vary. When it was 120 last week, I was running 234+ on my easy 8 mile drive from work. Throw a hill in that and I'd be way too hot I'm sure. Considering the radiator discussed in the " non tech" forum right now. I want an aluminum radiator.
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post #15 of 22 Old 07-23-2017, 03:58 PM
SouthSeaPirate
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IIRC is there not springs that are to be put in the lower hose to keep it from collapsing?
I agree with above that the system just needs be burped, but also make sure that hose isnt collapsing.
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