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    Unsolved cooling problem.

    Unsolved cooling problem.

    The quick summary is that my engine in my '91 ix is getting too hot, or at least the sensor in the thermostat housing says my coolant is getting too hot. However my radiator core is not. Less than 10k on water pump, no leaks, 72 degree thermostat, and the coolant in the expansion tank is over 40degrees warmer than my radiator core. New thermostat housing and sensors also.

    What I have tried so far. My car first started to overheat when idling when we got a heat wave in May. I went after the usual suspects. I did the newspaper fan clutch test and it failed, so I decided to do the auxilliary fan switch switch mod from an e36 to take care of my cooling problem. I had a cooler switch from my e36 when I did the fan delete mod on that. I hooked everything up, nothing, still overheating and the fan never came on. No big deal, the wiring that goes to the switch looked frayed, or maybe my aux fan was toast, no biggie.

    I then got the 72 degree thermostat installed it, and I cracked the thermostat housing when I used the wrong o-ring to seal it. PITA. I ordered a new one from bavarian auto recycling and it came with sensors and everything. Installed it, and also installed a 1300cfm spal slimline fan and an adjustable fan relay, 160 degrees and up.

    Installed everything, burped ALL (took a while) the air from the cooling system, and same thing, almost overheating when idling, the coolant temp goes up past 3/4ths. I am very frustrated at this point, I turn off the engine and 2 minutes later, the fan comes on. Weird. I thought it might be a bad temp sensor in the relay unit, so I got a trusty digital thermometer, tested it in boiling water and it was 211.5 which was close enough. Brought down the boiling water, it was only 193 when I got it to the car, immersed the sensor and the fan turned right on stayed on untill 159, then it shut off. I did it again, played with the adjustments, everything worked great. Finally i just stuck the meat thermometer into the radiator, turned on the engine and let the thing almost overheat, the fan turned on at 160 radiator core temp, the temp guage in the dash was almost in the red, and that fan sucked the whole thing back down to 3/4th, then shut off, and it would just cycle that way. I took the thermometer off and stuck it in the expansion tank after relieving the presure, and the coolant was still at 195 degrees. Why is my radiator so darned cool even with no airflow?

    #2
    I'm no expert on cooling issues.

    Check your hoses. It's a long shot, but the bottom hose could be "sucking closed" and preventing circulation.

    When you bled the system for air, you did squeeze the hoses, had the heater running full blast, and repeated the bleeding every other day for a few days (not necessarily standard procedure, but it works)?

    Sarcasm is a body's natural defense against stupid.
    When a man talks dirty to a woman, it's sexual harassment. When a woman talks dirty to a man, it's £3.95 per minute.
    "My mother never saw the irony in calling me a son-of-a-bitch." Jack Nicholson"
    Old age and treachery will always overcome youth and skill.



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      #3
      I have squeezed the top hose but not the bottom, that seems like a good thing to try. I open the bleeder valve everytime I park, which gets my strange looks at the supermarket, hoping air will come out, but only nice clean coolant does.

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        #4
        Bottom hose was normal. Is it possible that there is a blockage in my radiator? If so how would I test for it. It is possible that the water pump went bad very quickly, but how would I test for that also?

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          #5
          If it were my car, to eliminate the radiator as the source of the problem I'd take it out of the car, down to the rad shop and have it flushed and flow-tested. Their equipment is better than yours for performing that operation.

          I went the all-stock way to fixing my cooling system -- got it from marginal to very good. new thermostat (old one busted wide open), new fan clutch (old one wouldn't engage, causing the car to heat up to 3/4ths at stoplights), new aux fan resistor and radiator temp switch (resistor was bad, old temp switch was probably good but the new one is lower temp). New hoses are going in next week (although the old ones are allowing good flow, they have cosmoline (!) on them). And I did the flush and flow test to my radiator along the way (it needed it!). The radiator service cost me $28.00, and afterwards I was able to see a definite lowering of operating temps.
          The current fleet:
          1992 325ic: 148k-171k miles
          1999 Chevrolet Tahoe LT 4WD, 114k-142k miles
          1984 MasterCraft Stars and Stripes Powerslot (not a car :D) PCM Ford 351W, 904 hours

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            #6
            Yea, have the radiator checked. If that comes up ok. Then make sure the T stat isn't in backwards. Not sure if its possible. but wouldn't hurt to check.
            Then remove and inspect the water pump.

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              #7
              It is possible to install the t-stat backwards....and I did(should have looked closer at bently), but that was a while back in my troubleshooting. I think the next step is bringing my radiator in to get flow tested. Sticking a hose in the top and watching it come out the bottom is probably not scientific enough to diagnose anything.

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                #8
                This sounds like it could be a bad thermostat. Pull it and test it to see if it opens when it should.
                The car makes it possible, but the driver makes it happen.
                Jim Levie, Huntsville, AL

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                  #9
                  There is a block somewhere. Whether it's the thermo stat or crud in the radiator/block/head, who knows.

                  Since you replaced the thermostat, I would move on to checking the radiator.

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