'94 LS400 Overheating- rplc'd thermostat
11-05-13, 01:48 PM
#16
if the head gasket is fine, and it is just an overheating issue, here are to most common reasons why an LS400 can overheat:
● bad fan clutch
● bad thermostat
● debris (leaves, bugs, plastic bags) on the A/C condenser (the condenser is the the large radiator looking item that people incorrectly refer to as the radiator when they point to it from the front of the car - it is sandwiched against the actual radiator, which is what you see from the backside view looking from the engine side)
● electric cooling fan motor out
● electric cooling fan motor relay out
● electric cooling fan motor coolant temperature sensor (in bottom corner of radiator)
● refrigerant overcharge
● smashed condenser or radiator fins
● clogged radiator (happens if someone used coolant other than Toyota red or with really high mileage, like over 300K) - replace, cleaning doesn't work well
● incorrect coolant (use 50/50 mix of Toyota red and distilled water)
● defective radiator cap
● bad fan clutch
● bad thermostat
● debris (leaves, bugs, plastic bags) on the A/C condenser (the condenser is the the large radiator looking item that people incorrectly refer to as the radiator when they point to it from the front of the car - it is sandwiched against the actual radiator, which is what you see from the backside view looking from the engine side)
● electric cooling fan motor out
● electric cooling fan motor relay out
● electric cooling fan motor coolant temperature sensor (in bottom corner of radiator)
● refrigerant overcharge
● smashed condenser or radiator fins
● clogged radiator (happens if someone used coolant other than Toyota red or with really high mileage, like over 300K) - replace, cleaning doesn't work well
● incorrect coolant (use 50/50 mix of Toyota red and distilled water)
● defective radiator cap
http://www.lexls.com/tutorials/cooling/coolant.html
11-06-13, 09:14 AM
#17
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Exhaust Gas Sniffer
I would have said the blown head gasket theory was bogus except that you mentioned it has severely overheated before, which possibly could cause this.
Find a mechanic who is good enough that he owns an exhaust gas sniffer and have him sniff the coolant overflow tank with it, that is the gold standard for determining a blown head gasket.
Find a mechanic who is good enough that he owns an exhaust gas sniffer and have him sniff the coolant overflow tank with it, that is the gold standard for determining a blown head gasket.
11-06-13, 09:22 AM
#18
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Air in coolant lines
i believe you forgot to include air in the coolant lines. i found that it takes awhile to really get all the air burped out of the system. air trapped in the lines makes the motor overheat. rid the cooling system of air bubbles and see if the problems go away.
http://www.lexls.com/tutorials/cooling/coolant.html
http://www.lexls.com/tutorials/cooling/coolant.html
11-06-13, 09:33 AM
#19
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Are you for real about the sniffer? ...lol...I have a hard enough time being a woman and getting a mechanic to take me seriously, I can only imagine how much harder it would be if the sniffer thing was a joke.
I am very aware of the air in the coolant lines....prior to replacing the thermostat the "Lexus Mechanic" my father was using didn't do this after the initial hose burst.....and this is where the problems all began....LOL....when ever you hear a bubbling sound upon shutting the motor off, it is a good sign that you have air in the lines...
)watch the premier mechanic in America, Paul "Scanner" Danner, perform the test for unburned hydrocarbons using "the sniff test":
Last edited by LScowboyLS; 11-16-13 at 01:52 AM.
11-06-13, 09:51 AM
#20
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it's no joke, and if you Lexus mechanic doesn't have the exhaust sniffing tool to sniff your coolant overflow tank, then perhaps it's time to get a mechanic who owns modern tools in order to properly diagnose your car!
not necessarily - if your thermostat is installed correctly (properly "clocked" with jiggler hole at 12 o'****) and you have a new condition radiator cap, and you filled the system at the "fill bolt" (located behind the thermostat) and you have the overflow tank filled to the proper lever as well, the the LS400 cooling system design is self-bleeding, it just takes a few hot/cold engine cycles (and you will notice the fluid level drop in the overflow tank as the air works it's way out! )
watch the premier mechanic in America, Paul "Scanner" Danner, perform the test for unburned hydrocarbons using "the sniff test":
How to test for a bad head-gasket - YouTube
not necessarily - if your thermostat is installed correctly (properly "clocked" with jiggler hole at 12 o'****) and you have a new condition radiator cap, and you filled the system at the "fill bolt" (located behind the thermostat) and you have the overflow tank filled to the proper lever as well, the the LS400 cooling system design is self-bleeding, it just takes a few hot/cold engine cycles (and you will notice the fluid level drop in the overflow tank as the air works it's way out!
)watch the premier mechanic in America, Paul "Scanner" Danner, perform the test for unburned hydrocarbons using "the sniff test":
How to test for a bad head-gasket - YouTube
11-06-13, 10:06 AM
#21
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I watched the video. Thanks I will call around and see if I can find a mechanic with one. The thermostat that was put in before the one that is on it now, the mechanic did a pressure test for 8 or 9 hours before I came and picked the car up. He said that it did not leak. The video stated that that a pressure test was not always accurate. thank you again for your help.
Sincerely,
Ms. Lyn
Sincerely,
Ms. Lyn
11-06-13, 10:10 AM
#22
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I would find one who is recommended by someone!
word usually spreads fast on who is the great and honest mechanic - if you can find one who specializes in Toyotas, that's even better!
there are so many incompetent and crooked mechanics out there, that I would not want to use one that did not come highly recommended!
PS - I personally prefer the real genuine Toyota thermostat for this car! - it can be had for a decent price online
word usually spreads fast on who is the great and honest mechanic - if you can find one who specializes in Toyotas, that's even better!
there are so many incompetent and crooked mechanics out there, that I would not want to use one that did not come highly recommended!
PS - I personally prefer the real genuine Toyota thermostat for this car! - it can be had for a decent price online
11-16-13, 01:43 AM
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overheating
Have you bleed the system?could be simple air lock ,front of engine 17mm bleed nut get car to running temp undo nut let out air till just water flows replace nut
11-16-13, 01:50 AM
#25
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if your thermostat is installed correctly (properly "clocked" with jiggler hole at 12 o'****) and you have a new condition radiator cap, and you filled the system at the "fill bolt" (located behind the thermostat) and you have the overflow tank filled to the proper lever as well, the LS400 cooling system design is self-bleeding, it just takes a few hot/cold engine cycles (and you will notice the fluid level drop in the overflow tank as the air works it's way out! )
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