Question about 1991 Lexus LS 400

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I have a 91 lexus ls400 and its overheating. the only problem i can find is both electric fans dont kick on (i can wire them to a relay to bypass the factory wiring). i took the hoses off the engine and filled the radiator up with water and blew in one end and it flowed through. i did the same with the block. i also filled the block back up with the hoses off and cranked the car and water just drizzled out. does this mean i have a bad water pump or is the problem just a result of the fans not working.

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  • cgreen36352 Aug 02, 2010

    I took the thermostat out of the water neck. That was the first thing that I did. By the way do you know which way the water flost through the radiator (top to bottom or ?) and the direction the water pump flows the water through the system (does it push water through the block or pull it out?) thanks for all of ur help!

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Would have repaced the thermastadt. most commen cause of those fans not turning on because thr thermostadt is not letting the hot water flow into the radeattor .by passing the wiring and relays can only lead to bigger problems , but you have proven your fans work. water just drizled out of the block cause you had no water in the house to the pump ( no water to pump) thermostadts, temp sensors or temp sending unit .simple check for themostadt fill up with all houses attached with rad cap off run engine fill rad as needed keep feeling top hose to radiator it should get hot all of the sudden thats your thermostadt opening( working) go to next step check sensors or sending unit. realy best if you get a haynes or chilton at the half priced book store or auto parts storeand go to trouble shooting for over heating

Posted on Aug 02, 2010

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  • brad miller Aug 02, 2010

    sorry not familure with your vehicle

  • jazzylexus96 Aug 30, 2010

    hi i have a lexus ls 400 1991 and it was doing the same thing, i found out this system cannot have air in the coolant at all if it does it will overheat, if you remove the silver bolt on the top of the thermostat housing and fill it will coolant or water, till nothing but coolant comes out then replace the bolt, and keep filling the overflow unit till full, it may resolve your problem, it did mine, these cars run great when they are maintained well, but when they go out they really go out. good luck, loren

  • Ricky Gittins
    Ricky Gittins Apr 18, 2011

    Did you check the fan clutch? it should be pulling a lot of air thru the radiator, I just replaced mine, when you shut the car off the fan should not keep spinning (a few revalutions are ok). my temp gauge was only reading 1/2 way, now the temp gauge reads 1/4 and the aircondition now reads 31 degrees coming out the inside vents, the electric fans kick on when the a/c is on. FYI.

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