1994 Cadillac SLS my car overheats when it wants

1994 CADILLAC SLS
145,000 MILES • V8 • 2WD • AUTOMATIC
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TORISMOMMY24
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I have a 94 cadi, sls and it overheats when it wants. It doesnt matter if I am stopped, on the freeway or climbing a mountain. Sometime it overheats really bad and sometimes it overheats a little and then goes back down or sometimes I have no problems at all. I have changed the thermostate twice, water pump, radiator fan, flushed radiator, block/pressure test, all done and it is currently in the shop and they have no idea what is causing it. They even ran it for 4 hours straight and could not get it to overheat. PLEASE HELP!!!! Any ideas?
Sep 26, 2009 at 6:32 PM
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RASMATAZ
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Is it actually overheating/boiling over or just the temperature gauge that's indicating it -If so could be the coolant temperature sensor out of calibration-Could also be air lock in the cooling system, try bleeding it
Sep 26, 2009 at 9:42 PM
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FACTORYJACK
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If it is in a shop, have them block test it for combustion gases in the cooling system. This can be done with an exhaust gas analyzer. After a good roadtest, place the analyzer at the tank as the radiator cap is removed. Anything over 30 ppm hydrocarbons suggests internal leakage.
Sep 26, 2009 at 11:31 PM
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RASMATAZ
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I have changed the thermostate twice, water pump, radiator fan, flushed radiator, block/pressure test, all done and it is currently in the shop and they have no idea what is causing it.

You said they did the block and pressure tests right-Yea the 5 gas analyzer will catch it by sniffing it out of the radiator open this is our way of being a certified emission control I/M specialist-The gas machine does a lot of wonders to include a vacuum gauge-
Sep 26, 2009 at 11:37 PM