'94 LS400 Overheating- rplc'd thermostat
10-30-13, 01:26 PM
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'94 LS400 Overheating- rplc'd thermostat
Hi guys I'm new to the web site...I am ready to pull my hair out, can someone please help...My '94 LS400 has been a great car until last spring...A hose burst and the car overheated, no big deal had the car towed to the mechanic's....got the car back and kept having to put antifreeze in it every 3 days +-....finally found a leak in the radiator, fixed it...transmission went out and I replaced it ....then car began to overheat while idling and the AC was on I could drop it down a gear and get the rpms above 2600 and temp gauge would drop.....then one night the temp gauge began to rise as I accelerated so I pulled over and let it cool down...(before it had only boiled out of the reservoir 2 times I had always been able to get the temp down before it got that far) replaced clutch fan and the mechanic made it idle high so the electric fan would pretty much stay on....this still didn't work he tried to tell me that the head gasket was blown....I may a female but I drag raced as a teen and have been around cars most of my life...I took it to a friend of mine for a second opinion...he replaced the thermostat and the seal (it was too small) and repaired a small leak at the thermostat housing....he also pressure tested the car for 10 hrs after the repair.....car did fine for a month until this weekend and I had to run to Atlanta and back got there and the temp gauge started rising while I sat in the drive thru....immediately parked and shut it down....chilled out for about 2 hrs...when I began trip home and got to interstate temp gauge began to rise dropped it down a gear and it went down....did fine for 1.5 hr trip back until I got off the interstate....took off from the light and the same thing...maintained for steady ride for 20 mins til I got to town and took off from the light....please someone give me a clue as to what I need to check next....Water pump? Radiator? (it keeps great pressure and the cap is in good shape.)
Single mom and only ride....
Single mom and only ride....
10-30-13, 05:53 PM
#2
Where is the coolant level after you let it cool down? A blown head gasket can cause this issue. There is a test you can do to see if exhaust gas is present in the coolant. Another question is how old is the waterpump? Pull the covers off the timing belt, see if its wet.
10-31-13, 08:57 AM
#4
Lexus Champion
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.
10-31-13, 12:13 PM
#5
Welcome to Club Lexus.
Many areas to look into, my initial thoughts:
Fan clutch and an unobstructed air flow to the radiator. One member in the GS section had leaves and other debris accumulate between the A/C condenser and the radiator. Once that was cleared, his temperature issues went away.
Many areas to look into, my initial thoughts:
Fan clutch and an unobstructed air flow to the radiator. One member in the GS section had leaves and other debris accumulate between the A/C condenser and the radiator. Once that was cleared, his temperature issues went away.
11-02-13, 04:03 AM
#6
One more thing to do, it does not take too much effort, but helped in my case:
The cooling system has some small passages here and there (in the engine block AFAIK), and it could be that there is some dirt/rust there from bad coolant. A lot of times people use green coolant, or anything that's red in color, but not necessarily Toyota... that's a BIG no-no. The fact that your transmission is goners, possibly means that even when your temperature seemed OK, the cooling did not work properly as transmission fluid is cooled by the cooling system.
I would dump whatever coolant you have, use Prestone dual action cooling system flush (around two bucks at Sears), put that in, add about two gallons of distilled water (check exact capacity, I don't remember off top of my head), and drive like that for about 100 miles, hopefully over a period of around two-three days.
Then dump that, and you will quite possibly see brown liquid coming out, flush a couple of times (hopefully with distilled water) and finally fill up with genuine Toyota red coolant. In my case this procedure did wonders. The transmission now shifts like a new car, the engine purrrs so lovely that I am absolutely in love so much that my wife is jealous
and I am one happy camper!
Just make sure you unscrew all three bolts on the bottom of the engine when flushing the coolant or later that Prestone/water combo - there are two on the block itself, one for each bank of cylinders I believe, and one more to the front. Opening just one or two of those will not do.
The cooling system has some small passages here and there (in the engine block AFAIK), and it could be that there is some dirt/rust there from bad coolant. A lot of times people use green coolant, or anything that's red in color, but not necessarily Toyota... that's a BIG no-no. The fact that your transmission is goners, possibly means that even when your temperature seemed OK, the cooling did not work properly as transmission fluid is cooled by the cooling system.
I would dump whatever coolant you have, use Prestone dual action cooling system flush (around two bucks at Sears), put that in, add about two gallons of distilled water (check exact capacity, I don't remember off top of my head), and drive like that for about 100 miles, hopefully over a period of around two-three days.
Then dump that, and you will quite possibly see brown liquid coming out, flush a couple of times (hopefully with distilled water) and finally fill up with genuine Toyota red coolant. In my case this procedure did wonders. The transmission now shifts like a new car, the engine purrrs so lovely that I am absolutely in love so much that my wife is jealous
and I am one happy camper! Just make sure you unscrew all three bolts on the bottom of the engine when flushing the coolant or later that Prestone/water combo - there are two on the block itself, one for each bank of cylinders I believe, and one more to the front. Opening just one or two of those will not do.
11-02-13, 04:16 AM
#7
http://www.northerntool.com/shop/too...FStxQgodHVMAWg
check both radiator hoses...if 1 is much much hotter than the other u have blockage...its not the water pump as the impeller would have to have completely deteriorated or come apart.
check both radiator hoses...if 1 is much much hotter than the other u have blockage...its not the water pump as the impeller would have to have completely deteriorated or come apart.
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11-02-13, 01:12 PM
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I have searched this forum and many others for a couple of months and I tried many of the suggestions and some did help but not for long...now I've reached the end of my line I have to find something to work before destroying my motor so I'm asking now for help...so yes I did search for an answer
11-02-13, 01:17 PM
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Welcome to Club Lexus.
Many areas to look into, my initial thoughts:
Fan clutch and an unobstructed air flow to the radiator. One member in the GS section had leaves and other debris accumulate between the A/C condenser and the radiator. Once that was cleared, his temperature issues went away.
Many areas to look into, my initial thoughts:
Fan clutch and an unobstructed air flow to the radiator. One member in the GS section had leaves and other debris accumulate between the A/C condenser and the radiator. Once that was cleared, his temperature issues went away.
11-02-13, 01:25 PM
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One more thing to do, it does not take too much effort, but helped in my case:
The cooling system has some small passages here and there (in the engine block AFAIK), and it could be that there is some dirt/rust there from bad coolant. A lot of times people use green coolant, or anything that's red in color, but not necessarily Toyota... that's a BIG no-no. The fact that your transmission is goners, possibly means that even when your temperature seemed OK, the cooling did not work properly as transmission fluid is cooled by the cooling system.
I would dump whatever coolant you have, use Prestone dual action cooling system flush (around two bucks at Sears), put that in, add about two gallons of distilled water (check exact capacity, I don't remember off top of my head), and drive like that for about 100 miles, hopefully over a period of around two-three days.
Then dump that, and you will quite possibly see brown liquid coming out, flush a couple of times (hopefully with distilled water) and finally fill up with genuine Toyota red coolant. In my case this procedure did wonders. The transmission now shifts like a new car, the engine purrrs so lovely that I am absolutely in love so much that my wife is jealous and I am one happy camper!
Just make sure you unscrew all three bolts on the bottom of the engine when flushing the coolant or later that Prestone/water combo - there are two on the block itself, one for each bank of cylinders I believe, and one more to the front. Opening just one or two of those will not do.
The cooling system has some small passages here and there (in the engine block AFAIK), and it could be that there is some dirt/rust there from bad coolant. A lot of times people use green coolant, or anything that's red in color, but not necessarily Toyota... that's a BIG no-no. The fact that your transmission is goners, possibly means that even when your temperature seemed OK, the cooling did not work properly as transmission fluid is cooled by the cooling system.
I would dump whatever coolant you have, use Prestone dual action cooling system flush (around two bucks at Sears), put that in, add about two gallons of distilled water (check exact capacity, I don't remember off top of my head), and drive like that for about 100 miles, hopefully over a period of around two-three days.
Then dump that, and you will quite possibly see brown liquid coming out, flush a couple of times (hopefully with distilled water) and finally fill up with genuine Toyota red coolant. In my case this procedure did wonders. The transmission now shifts like a new car, the engine purrrs so lovely that I am absolutely in love so much that my wife is jealous
and I am one happy camper! Just make sure you unscrew all three bolts on the bottom of the engine when flushing the coolant or later that Prestone/water combo - there are two on the block itself, one for each bank of cylinders I believe, and one more to the front. Opening just one or two of those will not do.
I will let you know how it turns out thank you for replying to my post
11-02-13, 02:00 PM
#11
I really think you need to follow cowboys suggestion and find out for sure about the blown head gasket. do this first. once we know for sure it is still sealed, and will hold a pressure test, no internal or external leaks, and that your cooling fans are working properly. all you have to deal with is coolant..... providing your temp sensor is true.
so get started and report..
PS: dont go on any past test, start over and do it as listed.
so get started and report..
PS: dont go on any past test, start over and do it as listed.
Last edited by billydpowe; 11-02-13 at 02:10 PM. Reason: ps
11-02-13, 04:01 PM
#12
Lexus Champion
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
11-03-13, 04:28 PM
#14
Since you have replaced the fan clutch I would take it to a radiator shop and ask them to take a look the tubes inside the radiator to see if they are clogged. If so replace the radiator don't try and clean it you will be wasting your time you can't get the build up out by flushing it. Also if you do replaced the radiator drain the block of coolant there is a drain plug on the side of the block for that reason. I have been using Toyota red and distilled water 50/50 mix changing it every 3 years and never a heating problem. My 91 LS 400 went 300,000 miles on the original radiator and when I change it out it busted the top out and it was 35-40% clogged I also have had a trans cooler on the trans since 40,000 miles to save the trans. It is the biggest I could fit in my car about 28,000 pounds rated or used in a motor home for cooling. I also have found using mobile one trans fluid seem to help the trans to work fine I now have 307,000 miles and no problems living in So Cal with the heat and heavy traffic on the freeway some time I crawl 2-3 hours in the heat in Palm Spring at 110-115 degrees using the AC and the car does just fine. Always drain the block when you drain your radiator this way you have about 95-99 % new antifreeze in the car.
