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Unread 10-02-2011, 06:56 PM   #1
BlackPearl
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1996 XJ Cherokee 
 
Join Date: Oct 2008
Location: Scottsdale, Az
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Overheating Issues...seemingly tried everything

Okay, so I've been searching around and I am pretty much at a lose. So I broke the golden rule and let a non-Jeeper borrow my Black Beauty, clearly warning him of the possibility of overheating. Well sure enough he let it over heat and since then I can't get it to STOP overheating. I have a 1996 XJ 4.0 I6, 183,000miles

Since the overheating, I have changed/fixed lots of things:
New water pump
New T-stat
New 3 core aluminum HD radiator
Fresh coolant
New starter motor
New Battery
New IAC
Ran SeaFoam through the oil and fuel system(that was a first and I smoked out my neighborhood unknowingly haha)

The Jeep will heat up normally as it's supposed to. Then roughly 5-10 minutes into it running when it gets up to normal operating temps, it will just keep climbing and never look back. I have three electric fans on my radiator that are all working, a Fail-Safe t-stat but it just doesn't want to cool off in the least bit. Also when it starts up it idles really rough. When it gets up to about 2000rpm it will smooth as ever, but anything below that it rumbles and shakes and is on the verge of stalling.

What can I do to fix it? I've been told the head gasket is blown. What are your thoughts? I need to get my baby going again...it's been a few months now since she's been able to go more then just down the street

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Unread 10-02-2011, 08:03 PM   #2
djb383
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Have the cooling system pressure tested and maybe go back to stock rad fans with a new fan clutch? Maybe a motor tune-up?
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Unread 10-02-2011, 08:09 PM   #3
anony
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Compression test?

Pull plugs?

Sometimes removing injector connections or plug wires reveals leaks between cylinders ..

You might want to first rule out or replace the head gasket if it is leaking.

Last edited by anony; 10-02-2011 at 09:32 PM..
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Unread 10-02-2011, 09:14 PM   #4
kyledye25
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I have read that the fail-safe thermostats can go bad. And have been bad right out of the box. I would go with a Mopar one. Especially on something vital like that.

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Unread 10-02-2011, 09:18 PM   #5
kyledye25
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Map sensor could be bad. I had one go bad and it stumbled and ran rough till I got it up higher in the rpms. Then it ran awesome. Map sensor was sending to much gas. So ran like crap till the higher rpms could burn all or most of the fuel. Didn't make it over heat but it was winter. New map sensor, or used, may do the trick. But also a blown head gasket could be your problem. Are you losing coolant? White smoke at all?

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Unread 10-02-2011, 09:31 PM   #6
BlackPearl
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Quote:
Originally Posted by kyledye25 View Post
Map sensor could be bad. I had one go bad and it stumbled and ran rough till I got it up higher in the rpms. Then it ran awesome. Map sensor was sending to much gas. So ran like crap till the higher rpms could burn all or most of the fuel. Didn't make it over heat but it was winter. New map sensor, or used, may do the trick. But also a blown head gasket could be your problem. Are you losing coolant? White smoke at all?

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It's not spitting any smoke, other then when I ran SeaFoam through it. It will just heat up and keep getting hotter and hotter. I feel confident that it's not just a bad temp gauge either because when I shut the Jeep down after the gauge says its about to boil, I can smell the coolant like it's about to overheat. I don't think that I'm losing coolant. The overflow still says full and I don't see any leaking any where.

Would it be worth pulling the t-stat just to check to see if everything is flowing?...Something to rule out anyways.

Thanks for the tips so far. Hopefully I can crack it open next weekend.
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Unread 10-02-2011, 09:41 PM   #7
kyledye25
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I would pull the tstat and put in a Mopar. Make sure your water pump is spinning freely as well. Take the serp belt off and spin it. I'm sure there is a way to test the map sensor. I don't know how...but someone here does. My tstat cost me $10 at Mopar. So deff worth it. What kind of coolant are you using? Not that it would make a world of difference but qaulity coolant would help I'm sure.

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Unread 10-02-2011, 10:48 PM   #8
BlackPearl
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I usually use Prestone coolant 50/50 mix. Looks like I might take a trip to my Jeep dealership and get a MOPAR t-stat and try that. But that wouldn't explain the rough idle.

Any ideas on how much a new map sensor would cost?
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Unread 10-03-2011, 12:12 AM   #9
littleblackXj
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A blown head gasket would cause all of those symptoms. If the exhaust gas leaks into the cooling system it would cause it to over heat, which would also mean coolant is getting into the cylinder. At low rpms there would be too much water in the cylinder to fire, but at higher rpms it can overcome the water in the cylinder and combust. Also, a blown head gasket will increase the pressure in your cooling system and raise the coolant level in the resovoir.

You should do a pressure test on the cooling system and see if it will hold 13psi. Even with a blown head gasket it can still hold pressure though. Put 13 psi on the cooling system and leave it on there for a couple hours and pump it up if you have to. Then pull all your spark plugs and have a buddy crank the engine over and check for coolant coming out of the spark plug holes.

Does it feel like one cylinder is missing or a random misfire?
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Unread 10-03-2011, 10:33 AM   #10
BlackPearl
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I'm not sure if it feels like a cylinder is missing. I didn't have that thought in mind last I ran it but I can fire her up this afternoon and see what it's doing. Also after I run it, let it rev above 2,000rpms so it's running smoothly, if I just let off the gas all together it will drop to really low rpms and stall. Then it's difficult to get her running again unless I just let it sit for a bit. That gives me the clue of what you were talking about LITTLEBLACKXJ, about there being too much water in the cylinder for the it to combust.

Thanks for the tips. I need to get my Jeep running before the rains start here in NorCal...I don't like riding a motorcycle in the rain haha
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Unread 10-04-2011, 07:15 PM   #11
BlackPearl
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So I got the chance to get out and fire the Jeep up. She fired up after a few cranks. Right away I noticed something that I didn't before. First off I popped the hood and squeezed the coolant hoses when the engine was at about 210 degrees and they weren't hard, but kind of like a 3/4 full basketball. How hard are they supposed to be when the system is supposed to be charged?

Secondly, I heard what sounded like a sucking sound sound coming from the rear of the block, towards the firewall. Would that be from the blown head gasket? It definitely seemed to be in the right location because it sounded as if it was coming from right below the intake manifold.

Any ideas?
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Unread 10-04-2011, 07:42 PM   #12
banndit
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some simple stuff first, it sounds like you might have an air bubble in the system. If you run your heater on high, does hot air come out of the vents? If not, you have an air bubble in there. Also, just use water until you get the problem solved, or you're going to waste a lot of coolant. To quickly troubleshoot the air pocket idea, try this: the stock thermostat has a hole drilled in it to let some coolant flow when its warming up and to help get air out of the system. If your aftermarket one didn't have a hole in it, you can pull it and drill one, or if you really want to do some fast troubleshooting, take the thermostat out, gut the spring/ valve assembly and put the remains back in and button it up. Don't remove the thermostat entirely, as the system needs the restriction there to allow the coolant time to cool. Point the jeep nose up (driveway, ramps, whatever), take the cap off and run the engine. Turn the heat on full blast and top the radiator up with a hose and when it won't take anymore, put the cap on and watch the gauge. If it keeps overheating, you need to compression test and see if you have a head gasket issue. If you gut the thermostat, you won't have to wait very long to see what's up, but if you don't you will have to wait until the thermostat opens before you can actually fill the system to capacity. If you are looking at the water level, you will see it drop drastically as the thermostat opens.
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Unread 10-04-2011, 08:16 PM   #13
BlackPearl
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That sounds great, I'll give that a shot. The thing that confuses me is that when I checked the radiator cap it started to spit out coolant like it was pressurized...but the tubes still felt some what soft.
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Unread 10-05-2011, 05:51 AM   #14
unkajeffy
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Did you replace the bottom Rad. Hose? If you did, did the replacement have a spring in it? That is the intake to the water pump, and the spring keeps it from collapsing. And yes fail safe t-stats are crap! Check that hose and then do the nose up deal.
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Unread 10-05-2011, 06:44 AM   #15
banndit
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Quote:
Originally Posted by BlackPearl View Post
That sounds great, I'll give that a shot. The thing that confuses me is that when I checked the radiator cap it started to spit out coolant like it was pressurized...but the tubes still felt some what soft.
If you remove the cap with the engine cold and you have a geyser, you almost certainly have a blown head gasket. Again, with the engine cold, put your palm over the radiator cap opening, and if it builds pressure and you can smell compression gasses (hard to explain) coming through the coolant its time to get a head gasket or engine.
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