Overheating again! - JeepForum.com

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post #1 of 18 Old 07-11-2011, 01:51 PM Thread Starter
mtnracer190
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Overheating again!

I went to the OBX 2 weeks ago and the temperature gauge kept climbing up to 230F at which point I would pull over and let it cool back down. I realize these guages are far from accurate so when I got back I replaced the thermostat, temp sending unit in the back of the block and the temp sending unit in the thermostat housing. I also replaced the fan clutch and bought a radiator barn 3 row all metal radiator. While the radiator was out I flushed out all of the coolant passages. I started it today and everything seemed normal but I started driving it around and it kinda appears that the overheating problem has gotten worse. I also have a mr gasket thermo cap in the top of the radiator that seems to hang around 240F which seems pretty high. I put a 195F thermostat in when I replaced it.

Im pretty much out of ideas so any help is appriciated. The exhasut does not smoke at all, but could it still be a head gasket problem? I also have checked the waterpump and it does not leak at all and has no play whatsoever in the pully or shaft.

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post #2 of 18 Old 07-11-2011, 01:52 PM
Andywear
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Quote:
Over heating again
I thought it was Express again

Used to have a good sig but Mod threated to ban me...


Errrrrrr, Will complain else where - &y
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post #3 of 18 Old 07-11-2011, 01:54 PM
MONSooNmonkey
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you could have bad bearings that is causing the overheating, regardless of how much you mess with the cooling system it only cools the sleeves of the pistons not the bottom end.

Pull the oil pan and check your bearings.

Sadface :(
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post #4 of 18 Old 07-11-2011, 03:00 PM Thread Starter
mtnracer190
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okay that is one thing to check. Any other ideas?
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post #5 of 18 Old 07-11-2011, 06:38 PM
4.7stroker
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Your engine oil cools the bottom end, if there was that much friction in your bearings your engine would frag in short order.
Normal operating temp is ~220*f so I would not worry about 230*f 240 is getting worrying though.
What oil do you run? Synthetics can bring the temps down some.
Is the new stat operating right? They have been known to be bad out of the box.
Do you have any air pockets? They can happen after opening the cooling system.

Dwayne
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post #6 of 18 Old 07-11-2011, 06:41 PM
50rck
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You hit about everything you could with the cooling system. The biggest problem I have always had with these YJ's (been driving them for over 20 years) was purging all the air. They would always get a little hot for the first few weeks after a flush, or a rebuild (rebuilt or replaced 3 of these motors, both the 4 and 6 cylinders) while that air worked its way out. I never let them get over 230 for more than a few seconds.

The head gasket is not necessarily hard to check, or to replace. The replacing just takes a day or so. You can always drain the oil into a clear jug and let it sit for a few days, see if any coolant separates. If there is oil in the coolant, you should see it in the radiator.

You could check the bearings, I wouldn't rule it out, but that's not where I would put my $$.

Another silly thought, did you put the fan back on facing the right way? I took mine off once, repainted it and forgot which way it went back. I had to post a request for a pic in the forum.

1991 YJ, rebuilt 4.0L in spring 2009 at 234,000 miles, no lift yet, slightly offset wheels, 235/75/15 tires for now, rag top, sold the hard top. Over 35,000 miles on the rebuild and counting.


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post #7 of 18 Old 07-11-2011, 07:08 PM
moonshinefuel
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Does it do this on the highway, or in stop and go traffic, or both?
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post #8 of 18 Old 07-11-2011, 07:38 PM
moonshinefuel
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You can run your own test if you believe this is a cylinder head/gasket problem possibly. Rent/borrow from a parts store a radiator pressure tester. Pressurize the radiator to no more than 15lbs. After 2 minutes of the system holding pressure, you should not lose more than 1 or 2 lbs of pressure. You can also leave the pressure tester on the radiator for an extended period of time. After some time has passed, take the tester off, pull all the spark plugs, turn the engine over, if you see that coolant spray out of any given spark plug hole or holes, that would pretty much pin point the problem. You know but its not limited to this testing as fractures can super heat the coolant also.
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post #9 of 18 Old 07-11-2011, 08:06 PM Thread Starter
mtnracer190
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Im 99% sure it is not the head gasket. There was no coolant in the oil when I changed it. I run mobile 1 sinthetic to answer the oil question. I am 100% sure all of the air was out because I had worked it all out. The only thing I did find is that it only overheats over 220F with the AC on. I forgot to mention that my jeep has factory AC installed on it. It also overheats more when on the highway then when sitting still.
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post #10 of 18 Old 07-11-2011, 08:18 PM
moonshinefuel
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Ok well are you sure your radiator is good? Did you have it taken apart and rodded out, or just flush? Sometimes flush is not enough, it would not have worked on my 3 row, a simple flush.. It took the guy time just to rod each core passage manually, no way flushing would have done the job in my case.
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post #11 of 18 Old 07-11-2011, 08:36 PM
soonermatt
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You can start running a water hose into some sections if you need to isolate independent variables.

Running cold water straight into the block or forcing it into the heater could help out. I had to do this after replacing all hoses, water pump, etc. I had air pockets as others had mentioned.
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post #12 of 18 Old 07-11-2011, 08:48 PM
littleredjeep
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Is your a/c condensor in front of your radiator? Are both the radiator and condenser fins cleaned out or nothing shoved in between them so you could get good air flow to cool it off?

88 YJ 4.2, 5-speed, 4"RC lift, 5/8 booms, herced tub, and cavi seats

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post #13 of 18 Old 07-11-2011, 10:08 PM Thread Starter
mtnracer190
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Quote:
Originally Posted by moonshinefuel View Post
Ok well are you sure your radiator is good? Did you have it taken apart and rodded out, or just flush?
I’m not familiar with the term rodded out, however the radiator is brand new. Yes the condenser does sit in front of the radiator and after further Google searching it does appear that many people have cooling issues on the highway after installing the AC condenser. On a side note the fins on my condenser and new condenser are so close together that you can hardly even see light through them. I’m thinking this condenser is the culprit so now I just need to figure out what to do about it. With the triple digit temps we have been having lately, I’m not giving up the AC so I guess I will keep searching for solutions.
Thanks for all the suggestions and help, any further help with this issue is appriciated
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post #14 of 18 Old 07-11-2011, 10:17 PM
moonshinefuel
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Sounds good. If the radiator is new, that's good, that's not the problem then. Good observations on that condenser!
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post #15 of 18 Old 07-12-2011, 07:02 AM
Apollo12227
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Quote:
Originally Posted by mtnracer190 View Post
I realize these guages are far from accurate so when I got back I replaced the temp sending unit in the back of the block.
That right there is your problem my friend. If your purchased your sending unit from either Advance Autoparts or Autozone, they read 30* hotter than actual temp right out of the box. I have had 3 seperate sensors from seperate stores confirm this. One from Advance Autoparts and 2 from autozone, all read the same incorrect temperature.

I spent over $1,000 on my cooling system, perform flushes, pressure tests, replacing hoses, heater core, water pump, thermostat, coolant, radiator (3-core replacement), and a $300.00 flex-a-light black magic cooling fan.

After all that money, it turned out that the senders that Autozone and Advance were selling were reading 30* hotter than actual temp.

I replaced mine with one from the dealership. Go to any local Chrysler dealership and pick one up. They are exactly twice as much as the Autozone replacements, however my jeep has never "overheated" again since I replaced it.

I will post a link to my thread in a moment.

HERE
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