82 CJ5 Engine Running Hot! - JeepForum.com
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post #1 of 17 Old 09-14-2021, 08:57 PM Thread Starter
Wingnut74
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Cj 82 CJ5 Engine Running Hot!

82 Cj5, 258ci 4.2l, So what I have done.... New rebuilt/recored Radiator, New 190* thermostat and housing, New Water Pump-Proper Rotation, Flex Fan and Fan Shroud, New Hoses, and Flushed out the Eng Block when I had the pump off. I didn't trust the OEM gauge so I installed an aftermarket gauge and attached the sensor at the Intake Manifold. Dam thing runs 225*f, I'm considering changing the Radiator to a Direct fit Aluminum 3 core. When I installed the Thermostat I tested it to be sure it opens in a pot of boiling water on my stove.

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post #2 of 17 Old 09-14-2021, 09:06 PM
KevinCJ7Jeep
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You might check your timing. Timing too retarded can cause an engine to run hot. Quick and easy to check

My distributor hold down clamp loosened up and caused timing to retard.
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post #3 of 17 Old 09-14-2021, 09:25 PM
Girth83
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You put in a new sending unit, with the new gauge, not just hooked new gauge to old sensor?

Thanks for reminding me though. In the middle of a radiator/pump/thermostat swap myself. Forgot I needed to test the thermostat. Wife was just looking at me like I was crazy, as I'm checking the temp of the heating water. She sounded excited when she saw it. "It's moving!"
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post #4 of 17 Old 09-14-2021, 09:27 PM
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Is the sensor matched to the gauge? I know in the marine world there are different sensors for different gauges, get them mixed up and you get false readings. Did you reconnect the original gauge? While they may be inaccurate, it would give you some indication if you're running too hot or normal.

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post #5 of 17 Old 09-14-2021, 09:31 PM Thread Starter
Wingnut74
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Yes, New aftermarket gauge with the temp bulb on it from the mfg... Threaded into the intake manifold. So i have the original gauge still giving a hot reading, and the aftermarket sits just below 230*.
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post #6 of 17 Old 09-14-2021, 09:33 PM Thread Starter
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I have been meaning to buy a timing gun.. Guess this now gives me a reason... I will look into the timing degrees setting. Ty
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post #7 of 17 Old 09-15-2021, 07:46 AM
jeepdaddy2000
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Have you verified the temps with an IR gun?
Always the first step.

Paperwork will ruin any military force.
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post #8 of 17 Old 09-15-2021, 10:18 AM
bob4703
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We are talking about Jeep engines 8 years difference in age. The TSM for my 74 says that I'm supposed to be using a 205* thermostat in the 258 which does not fully open until 228*. The 304 uses a 190* which fully opens at 218*.

A thermostat doesn't keep the temperature at its rating. That is when it starts opening and depending on conditions can reach higher temps. 225* isn't running hot. You also must match your sending unit to the temp gauge nor an accurate reading.

You can go here and download the TSM for your 82 and check the specs for that year.

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post #9 of 17 Old 09-15-2021, 10:19 AM Thread Starter
Wingnut74
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No, I have not used an IR gun on it. I figured the second gauge also running hot was enough to convince me. Also, when its at temp, at idle or when the engine is returning to Idle off a higher RPM, you can hear some chatter from the prolly the lifters/rockers top of the head. I have known to hear that when an engine is running hot as well. I will double check with an IR gun as well. TY
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post #10 of 17 Old 09-15-2021, 11:02 AM
devildog80
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Check your radiator cap, and be sure it is working properly, as a stuck/old cap can cause overheating issues too.
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post #11 of 17 Old 09-15-2021, 02:15 PM
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post #12 of 17 Old 09-16-2021, 07:56 AM
bob4703
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Quote:
Originally Posted by bob4703 View Post

You can go here and download the TSM for your 82 and check the specs for that year.
It appears I didn't get the link to the TSM to take or I forgot to put it in.

https://oljeep.com/edge_82_tsm.html

It is he!! getting old. JEEPFELLER will say it is a sign of senility. I used to know what that means but somewhere back up the road I forgot.
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Last edited by bob4703; 09-16-2021 at 08:02 AM. Reason: I forgot to include something.
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post #13 of 17 Old 09-16-2021, 08:12 PM Thread Starter
Wingnut74
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BOB4703.... Ahhhhh, I did not think there could be a difference in mfg suggested thermostats... I have always just installed 190* thermostats... I will look into some manuals I have see if they make a temperature recommendation, and adjust accordingly.
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post #14 of 17 Old 09-16-2021, 09:24 PM Thread Starter
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So I purchased a set of Service Manuals for my 82 Cj... I have been reading into the (Notes) and I have learned a couple things I took for granted in my years of working on various vehicles. First, My thermostat is recommended to be a 195* to begin opening, and to be fully open at 218*. Also the concentration percentage of Anti-Freeze to water is required to be at no more than a50% to a max 68%. 100% antifreeze can cause the engine to overheat due to the specific heat of anti-freeze is lower than that of water. It is recommended to test your anti-freeze with a Hydrometer "Anti-Freeze" tester. Note to self.... Look at adding an air bleed screw/valve at the line from the water pump to the heater core to purge air from the lines. So i have a few items to go and double check according to the trouble shooting section of the manual. 1- Check anitfreeze % to verify below 68%. 2- Check Ignition timing, 3- Install new 195* thermostat and flush block.
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post #15 of 17 Old 09-16-2021, 11:50 PM
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Before getting a new thermostat, get an IR gun thermometer, about $10.

Then I would check at the thermo housing, the top hose, down through the radiator to the bottom hose.

Radiator cap should be holding 12-15psi. With 44% glycol mix this would give a boiling point of 257F to 262F

You should see a minimum 20 degree drop across the radiator. Temp at the thermostat housing can be up to 250F, bottom hose 230F and it will still function. I would be a lot happier if it was slightly above the opening temperature, say 200 for a 190F thermostat. Why? Because it means the radiator is leaking as much heat as the engine makes, and the thermostat is only just open.

Have you a thermostatic fan clutch? When was it last replaced? They lose about 2% power transfer ability each year.

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1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1951 Willys CJ3A/MB/M38 - Little Willy
1995 Cherokee 4.0 - CHEROKEE
1980 Land Rover Series III 109" troop carrier - ROVER
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