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post #1 of (permalink) Old 10-04-1999, 03:44 AM
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Overheating 258

'80 CJ7 258, recently replaced thermostat, hoses, flushed and filled radiator, but now am experiencing higher temperatures with interstate driving (60 mph sustained for 30 min). I'm ok if the ambient temp is cool enough. Even had overflow of antifreeze (no reservoir) x2 tonight. I did notice quite a bit of corrosion still in the radiator. Suggestions?


Dirt is good. Speed is good. Scabs are good. Life is good.
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post #2 of (permalink) Old 10-04-1999, 07:54 AM
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Re: Overheating 258

Natually many following posts will say "ya-gotta get a radiator shop to rod clean the thing"...... but I seemed to notice that you failed to mention replacement of the radiator cap. This would also explain your symptoms if it were defective. Beyond that, among a multitude of other things that others will surely make you aware of, "ya-gotta get a radiator shop to rod clean the thing" ...[img]/wwwthreads_images/icons/smile.gif[/img]

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post #3 of (permalink) Old 10-04-1999, 08:50 AM
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Re: Overheating 258

[img]/wwwthreads_images/icons/laugh.gif[/img] Yeah, and by the way, do you clean up after getting in the dirt, or do you track dirt into the ER?[img]/wwwthreads_images/icons/frown.gif[/img] You know, the radiator may look OK, but are the vertical tubes actually making good contact with the fins! Sometimes some corrosion can put a tiny partition between the two, and cancel out the "heat sink" effect of the fins. Inspect the vertical tubes closely to see if there is some crud showing at the tube-fin interface. If so, maybe a bath will help...otherwise it's a new radiator.[img]/wwwthreads_images/icons/frown.gif[/img] I can send over a crew of little moon guys [img]/wwwthreads_images/icons/crazy.gif[/img][img]/wwwthreads_images/icons/smile.gif[/img][img]/wwwthreads_images/icons/wink.gif[/img][img]/wwwthreads_images/icons/cool.gif[/img]to help if you need it.[img]/wwwthreads_images/icons/wink.gif[/img]

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post #4 of (permalink) Old 10-04-1999, 12:11 PM
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Re: Overheating 258

My 1980 suffered similar woes. Cured by advancing the timing (at the distributor) to 10 degrees BTDC. Still no knocking. I had gone through the regular check list of likely things. The fix that did the most good turned out to be the easiest. I don't know if there are any related problems tha advancing the timing will cause but all has been fine through this past summer. Maybe it would help you too. John

post #5 of (permalink) Old 10-04-1999, 11:14 PM
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Re: Overheating 258

Thanks for all the input. I'm in the process of backflushing the entire cooling system(used a handy kit from Prestone), which displaced a lot of junk beyond just draining the radiator, and treating with an anticorrosion agent (something else from Prestone). I did happen to replace the radiator cap with one closer to OEM (had been only 7 psi). Looks like I better inspect the fins more closely tomorrow. Actually this vehicle has had very little off road time to this point so it's pretty clean.

Thanks for all the input.

Dirt is good. Speed is good. Scabs are good. Life is good.
post #6 of (permalink) Old 10-06-1999, 11:07 PM
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Re: Overheating 258

I may be a little late here but if you haven't put the treatment in yet, put in one gallon of white vinegar (the
cheap stuff). Fill with water and run for a couple hours, drain and flush. The vinegar is mildly acidic and
will get a lot of the gunk out.


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