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Head gasket sealers?? Minor leak...maybe

scot4free

NAXJA Forum User
Location
Sacramento
So, my 92 XJ temp gauge is funny. Replaced sending unit twice. The rad and wp are new.
Since the temp unit is by #6, could there be a small leak that heats up the coolant at the sending unit? It does get to "red zone" after 2 miles, then drops really fast when thermostat opens.
Daily driving, gauge reads almost to the white line before red, which is what? 225, 235,245?? I have no idea. My infrared thermo on the hoses, housing and radiator all read 100% normal.
No residue on oil cap, coolant not disappearing enough to notice. no white smoke.
I'm shamefully thinking of trying a Bars type product, since I feel if there is a leak, it's very minor.

Any thoughts given my situation?
 
Or maybe there's a lot of scale build up in the head. Maybe a flush is needed with a good cleaner in between. I've never done this before, but there are threads about what to use to clean the water passages
 
Why would you put that sealer crap in there if you have no evidence of a leak? Or for any other reason for that matter.

What is status of thermostat? OEM is best or Stant Superstat. I installed a Superstat about two months ago for the first time and after a little less than two miles the temp gauge locks in at 210* and never, ever moves regardless of what I do or in what ambient temps until I turn the motor off. I couldn't believe it the first few times. Not necessarily suggesting you will have similar experience.

I have heard of some people getting defective Superstats out of the box so don't know if quality control has slipped.

If the IR thermometer shows normal at all times, there is a reasonable chance you still have a sender problem. My gauge read a bit high while highway driving a couple of years ago (not near the red though) while the IR gun showed normal. I finally gave up and got an OEM sender that fixed it. Again, my experience, not necessarily your fix.

Just some thoughts.
 
get a block testing fluid kit from any parts store, you pull some of the fluid out of the cooling system and add it to a testing chemical (pretty much your basic high school chemistry class pH test) and it will tell you if there are combustion chamber gasses present in the coolant. this will tell you if you have a problem.
 
Gonna spend the $40 and get a block tester from napa. I realize flushing may help, but if I do have a Gasket issue, what a waste of time flushing.... thanks!
 
OK OK OK... temp spike solved. I bought jeep Non-driving. Replace temp gauge sender twice with BWD units. 1st one stripped, so i never used it. 2nd on, was installed, brass threads came up when installing, so clearly stripping also. But, left in anyway.
Gauge would get to just before red zone after 2 miles, drop very fast when thermo opens, but always read between 210 and the white line before 260 redzone.
Well, I bought an MOPAR sender and problem solved. I have not been over heating like feared. Nor any head gasket issues.
The block test kit was negative and no milky oil, so I figured the sender. USE MOPAR on this part for sure. 92 XJ
 
I had issues with a gauge sender earlier this month. My temp were reading unusually low 180-195 on 95+ heat. I assumed the PO installed a 180 thermostat. While changing a power steering pump, I went to disconnect the hire to the sender and the unit broke in half. It corroded from the inside out. I replaced it the same day and my temp were running 205-215 consistantly. I got wierded out so I got an IR gun and sure enough, the new one was reading true. Although I knew the head was recently replaced by a reputable local shop, I also found out I had a 630 head on my 96 in the process.....this is my first XJ.
 
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