1985 cj7 overheating - JeepForum.com
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post #1 of 17 Old 07-10-2020, 11:07 AM Thread Starter
sk8brdtoday1
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1985 cj7 overheating

My cj7 is slightly overheating. I do not have a fan shroud, should the cj7 have a fan shroud? Thanks

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post #2 of 17 Old 07-10-2020, 11:12 AM
shadoow
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what's 'slightly'?


have you verified temps with other indications (e.g. an infrared temp measuring tool)?



did this just start?


have you check coolant level?



have you checked for coolant leaks?


have you filled out your profile??
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post #3 of 17 Old 07-10-2020, 11:26 AM
Nucking1Futs
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Quote:
Originally Posted by sk8brdtoday1 View Post
My cj7 is slightly overheating. I do not have a fan shroud, should the cj7 have a fan shroud? Thanks
For optimal cooling, yes.
What engine do you have, what modifications have you (or previous owner) done? You left a lot of holes in your particular scenario for people to assist you with you problem. Please provide all the details of your Jeep.
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post #4 of 17 Old 07-10-2020, 03:28 PM Thread Starter
sk8brdtoday1
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Hey,
So the radiator is full, the overflow tank is empty, no leaks. I will check the temp with a temp gun tomorrow.I had an old school gauge on before, but recently switch over to speedhut GPS speedo with temp gauge. Before the temp was fine no issue. If you look at the gauge, and say on a 0-100% scale normal should be ~50%, it is 75-80% to H. and the dummy light comes on. Also, its a 258 that is stock. Jeep is lifted on 37's pretty much only mod driving mods.
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post #5 of 17 Old 07-10-2020, 04:22 PM
Nucking1Futs
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Quote:
Originally Posted by sk8brdtoday1 View Post
Hey,
So the radiator is full, the overflow tank is empty, no leaks. I will check the temp with a temp gun tomorrow.I had an old school gauge on before, but recently switch over to speedhut GPS speedo with temp gauge. Before the temp was fine no issue. If you look at the gauge, and say on a 0-100% scale normal should be ~50%, it is 75-80% to H. and the dummy light comes on. Also, its a 258 that is stock. Jeep is lifted on 37's pretty much only mod driving mods.
No issues before gauge swap, issues after gauge swap. First thing I would suggest is to verify which gauge is working correctly, assuming one is correct.

Assuming that you are not the original owner and the P.O. may have modded the Jeep, how long have you owned the Jeep? When was the last time that the radiator was flushed? Last oil change? Last spark plug/wire tune-up? How is your fuel-air mixture? Running rich/lean? What is your base timing? Is your EGR working? Does your engine ping under load?

Are you in an area that checks tail pipe emissions? If so, what were the readouts from the test?

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post #6 of 17 Old 07-10-2020, 04:44 PM
pedal2themetai
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Hi You do have a leak.. the overflow tank should have fluid in it.. I suspect your radiator cap is the problem.. If the cap does not hold the proper pressure it well let to much fluid out of the motor into the over flow tank and in turn on to the ground viva its over flow tube and on to the ground as you drive, that's why you see no leaks. Now that your overflow tank is empty you system is low. I believe if you look on the side of the overflow tank their well be marks for fluid level.

The coolant system works like this. As the coolant heats up it expanse and creates pressure when it reaches the max pressure of the cap it is pushed out of the radiator into the overflow tank.. then as it cools when shut off the coolant is drawn back into the radiator. If the cap does not hold the proper pressure it well allow to much coolant to be pushed out and eventually lost out onto the ground and eventually you start having overheating problems with no sign of a leak.

Have the cap pressure tested it should hold 13 to 14 lbs.. if not replace it..

good luck
tim
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post #7 of 17 Old 07-10-2020, 04:45 PM Thread Starter
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Owner for 3 years, brand new radiator and flushed over this past winter. Oil change a month ago or so. Not sure about the other things. No emissions testing here. And the garages goes from 0(cold) to heating up. I think the gauge works properly. I was thinking maybe the gauges temp setting is off? Or the addition of the fan shroud might drop the temp a few degrees
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post #8 of 17 Old 07-10-2020, 04:55 PM
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I had similar issues a few years ago. 1980, 258 engine. I thought it was overheating because the gauge said so. I tried a fan shroud (no change), purchased new aluminum radiator, switched to electric cooling fans (ford contour conversion), ... turned out to be the temp gauge. Inaccurate temp gauge. (It’s all good though, I love the aluminum radiator and electric fans, I would recommend doing it anyway.)

Get a temp gauge with numbers on it, and a large sweep so it is more precise and you can actually see what the temperature is. Some gauges have a short sweep, so the precision is poor, and you still have to guess.
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post #9 of 17 Old 07-10-2020, 05:32 PM
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Quote:
Originally Posted by sk8brdtoday1 View Post
Owner for 3 years, brand new radiator and flushed over this past winter. Oil change a month ago or so. Not sure about the other things. No emissions testing here. And the garages goes from 0(cold) to heating up. I think the gauge works properly. I was thinking maybe the gauges temp setting is off? Or the addition of the fan shroud might drop the temp a few degrees
Is it a digit or analog reading? Take a picture of it at operating temperature.

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post #10 of 17 Old 07-10-2020, 06:07 PM Thread Starter
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Yeah I need to add a numbers gauge to it. Here is a pic at the “overheating” temp
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post #11 of 17 Old 07-10-2020, 06:59 PM
pedal2themetai
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HI Have you replaced OR checked the pressure cap?? if it does not hold the proper pressure it can cause the loss of coolant without you seeing a leak.. and in turn overheating...
good luck
tim
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post #12 of 17 Old 07-10-2020, 07:02 PM Thread Starter
sk8brdtoday1
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Hey, pressure cap. As in the radiator cap? I think it’s also brand new when I replaced the radiator
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post #13 of 17 Old 07-10-2020, 07:04 PM Thread Starter
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And what is the standard/stock pressure? 16lbs?
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post #14 of 17 Old 07-10-2020, 07:26 PM
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Here is the chart to test out the new sending unit that came with the new speedo w/ temp and fuel. Warm some water over the stove and using a good candy thermometer check the resistance of the sender at 180 degrees. Make sure the sender is suspended in the water and not touching the pan as that will throw off the reading. If it reads the correct 120 or so ohms, then the next step is to heat some water up in the garage to 180 and with the sender plugged into the gauge, see where the needle is at. Also, that is a universal sender and there is a mark up to where you can shorten the probe to. Make sure that it isn't too long and touching and metal that can cause a false reading.
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post #15 of 17 Old 07-11-2020, 01:34 PM
andysbarker
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Quote:
Originally Posted by sk8brdtoday1 View Post
And what is the standard/stock pressure? 16lbs?
Yes, the stock cap is 16 psi.
I have a champion radiator, specific for the Jeep, that came with a 13 psi cap. I called and asked them about it and they said their radiator tends to run better with a 13 psi, and it does in fact run just right with a 13 psi cap. The point is, if you have an aftermarket radiator, you may be better with a different cap. But yes, the stock cap is 16 psi.
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