Car not blowing heat at idle also random temperature spikes
01-19-18, 04:51 PM
#1
Intermediate
Thread Starter
Car not blowing heat at idle also random temperature spikes
Car info: 1996 Lexus LS400 with 149,500 Miles
Hello
So since things have started to cool down in AZ I finally had the chance to use my heater. When I turn it on I realized it blows hot air while moving however when I come to a stop it starts to blow cold air. Not sure if these two issues can relate but the other night or two ago I was in the parking lot waiting for around 10 minutes and I noticed my temp gauge starting to climb. After about a minute it was almost near the 2nd bar near the red H. I turned the car off not too sure whats going on. After about 2-3 minutes I started to drive and the temp went back to normal as I drove. This is the 2nd time I noticed this. Last time it was about a half a year ago in the summer. What I also find odd is I tried to make the overheating issue occur again by sitting in my car for 10 minutes however it remained at the same normal temperature at idle. Anyone have any idea whats going on and how to fix the issue?
Also yes my coolant is full, water pump and timing belt along with a lot of other things were done at 120K when I bought the car.
Hello
So since things have started to cool down in AZ I finally had the chance to use my heater. When I turn it on I realized it blows hot air while moving however when I come to a stop it starts to blow cold air. Not sure if these two issues can relate but the other night or two ago I was in the parking lot waiting for around 10 minutes and I noticed my temp gauge starting to climb. After about a minute it was almost near the 2nd bar near the red H. I turned the car off not too sure whats going on. After about 2-3 minutes I started to drive and the temp went back to normal as I drove. This is the 2nd time I noticed this. Last time it was about a half a year ago in the summer. What I also find odd is I tried to make the overheating issue occur again by sitting in my car for 10 minutes however it remained at the same normal temperature at idle. Anyone have any idea whats going on and how to fix the issue?
Also yes my coolant is full, water pump and timing belt along with a lot of other things were done at 120K when I bought the car.
01-19-18, 10:14 PM
#2
Racer
Car info: 1996 Lexus LS400 with 149,500 Miles
Hello
So since things have started to cool down in AZ I finally had the chance to use my heater. When I turn it on I realized it blows hot air while moving however when I come to a stop it starts to blow cold air. Not sure if these two issues can relate but the other night or two ago I was in the parking lot waiting for around 10 minutes and I noticed my temp gauge starting to climb. After about a minute it was almost near the 2nd bar near the red H. I turned the car off not too sure whats going on. After about 2-3 minutes I started to drive and the temp went back to normal as I drove. This is the 2nd time I noticed this. Last time it was about a half a year ago in the summer. What I also find odd is I tried to make the overheating issue occur again by sitting in my car for 10 minutes however it remained at the same normal temperature at idle. Anyone have any idea whats going on and how to fix the issue?
Also yes my coolant is full, water pump and timing belt along with a lot of other things were done at 120K when I bought the car.
Hello
So since things have started to cool down in AZ I finally had the chance to use my heater. When I turn it on I realized it blows hot air while moving however when I come to a stop it starts to blow cold air. Not sure if these two issues can relate but the other night or two ago I was in the parking lot waiting for around 10 minutes and I noticed my temp gauge starting to climb. After about a minute it was almost near the 2nd bar near the red H. I turned the car off not too sure whats going on. After about 2-3 minutes I started to drive and the temp went back to normal as I drove. This is the 2nd time I noticed this. Last time it was about a half a year ago in the summer. What I also find odd is I tried to make the overheating issue occur again by sitting in my car for 10 minutes however it remained at the same normal temperature at idle. Anyone have any idea whats going on and how to fix the issue?
Also yes my coolant is full, water pump and timing belt along with a lot of other things were done at 120K when I bought the car.
how does your radiator cap look? My car also blows cold when coming to a stop sometimes but hasn't overheated or the coolant temp hasn't fluctuated ever since I bled it properly.
01-20-18, 08:30 AM
#3
Driver School Candidate
Check your thermostat. could be intermittent issue where it opens prematurely or does no open at all. Suspend it in a pot together with a temp gauge, add water and heat it up, check at what temp the thermostat opens at and compare with the manual.
01-20-18, 09:54 AM
#4
Pole Position
If your temp gauge is at normal, or even higher sometimes, then the thermostat is opening and closing as it should. It sounds like one of two things. Either there is air in the system, (even if you bled it, bleed it again) or you have a hole in your heater core. (which would give you air in the system anyway)
My 94 is doing the exact same thing (sometimes) and I know my heater core is bad b/c I get fogged windows in the morning from the coolant that leaks into the heat ducts. I changed the HC in my 93 and I aint doing that again.
I can live with it for now. I just wash the windows more now. 
My 94 is doing the exact same thing (sometimes) and I know my heater core is bad b/c I get fogged windows in the morning from the coolant that leaks into the heat ducts. I changed the HC in my 93 and I aint doing that again.
I can live with it for now. I just wash the windows more now.
01-20-18, 01:46 PM
#5
Intermediate
Thread Starter
my car did this after improperly bleeding my coolant. i was also about half a gallon low since I had just bought the car 2 days prior, and did the upper and lower rad. hoses.
how does your radiator cap look? My car also blows cold when coming to a stop sometimes but hasn't overheated or the coolant temp hasn't fluctuated ever since I bled it properly.
how does your radiator cap look? My car also blows cold when coming to a stop sometimes but hasn't overheated or the coolant temp hasn't fluctuated ever since I bled it properly.
If your temp gauge is at normal, or even higher sometimes, then the thermostat is opening and closing as it should. It sounds like one of two things. Either there is air in the system, (even if you bled it, bleed it again) or you have a hole in your heater core. (which would give you air in the system anyway)
My 94 is doing the exact same thing (sometimes) and I know my heater core is bad b/c I get fogged windows in the morning from the coolant that leaks into the heat ducts. I changed the HC in my 93 and I aint doing that again. I can live with it for now. I just wash the windows more now.
My 94 is doing the exact same thing (sometimes) and I know my heater core is bad b/c I get fogged windows in the morning from the coolant that leaks into the heat ducts. I changed the HC in my 93 and I aint doing that again.
I can live with it for now. I just wash the windows more now. [Everyone]
Ok, so I tried to see if the issue again would occur by sitting in my car for 10 minutes at idle and it did not. I also went to check to see if my heater would blow heat and guess what, it did
. So I'm not fully sure whats going on????
01-20-18, 03:37 PM
#6
Pole Position
If it is a small leak (like my 93 was) you wont notice a drop in the overflow tank. But you would notice the windows getting foggy from the coolant evaporating into the heat ducts, especially front defroster. On my 94 sometimes I can hear it hissing very lightly when I turn the car off after it"s warmed up and use of the heat.
01-20-18, 09:03 PM
#7
Lexus Champion
Car info: 1996 Lexus LS400 with 149,500 Miles
Hello
So since things have started to cool down in AZ I finally had the chance to use my heater. When I turn it on I realized it blows hot air while moving however when I come to a stop it starts to blow cold air. Not sure if these two issues can relate but the other night or two ago I was in the parking lot waiting for around 10 minutes and I noticed my temp gauge starting to climb. After about a minute it was almost near the 2nd bar near the red H. I turned the car off not too sure whats going on. After about 2-3 minutes I started to drive and the temp went back to normal as I drove. This is the 2nd time I noticed this. Last time it was about a half a year ago in the summer. What I also find odd is I tried to make the overheating issue occur again by sitting in my car for 10 minutes however it remained at the same normal temperature at idle. Anyone have any idea whats going on and how to fix the issue?
Also yes my coolant is full, water pump and timing belt along with a lot of other things were done at 120K when I bought the car.
Hello
So since things have started to cool down in AZ I finally had the chance to use my heater. When I turn it on I realized it blows hot air while moving however when I come to a stop it starts to blow cold air. Not sure if these two issues can relate but the other night or two ago I was in the parking lot waiting for around 10 minutes and I noticed my temp gauge starting to climb. After about a minute it was almost near the 2nd bar near the red H. I turned the car off not too sure whats going on. After about 2-3 minutes I started to drive and the temp went back to normal as I drove. This is the 2nd time I noticed this. Last time it was about a half a year ago in the summer. What I also find odd is I tried to make the overheating issue occur again by sitting in my car for 10 minutes however it remained at the same normal temperature at idle. Anyone have any idea whats going on and how to fix the issue?
Also yes my coolant is full, water pump and timing belt along with a lot of other things were done at 120K when I bought the car.
https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/846574-interior-temperature-sensor-1995-2000-ls400.html
Last edited by YODAONE; 01-20-18 at 09:07 PM.
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01-21-18, 09:58 PM
#8
Intermediate
Thread Starter
If it is a small leak (like my 93 was) you wont notice a drop in the overflow tank. But you would notice the windows getting foggy from the coolant evaporating into the heat ducts, especially front defroster. On my 94 sometimes I can hear it hissing very lightly when I turn the car off after it"s warmed up and use of the heat.
If going through process of elimination, then consider;
https://www.clublexus.com/forums/ls-...000-ls400.html
https://www.clublexus.com/forums/ls-...000-ls400.html
Could be possible my sensor is bad however it does seem to be stable when I pick a temperature. Like in the summer when it's 105F I set it to 72. After about 5 minutes the fans die down and the temperature seems to remain the same.
01-21-18, 10:03 PM
#9
Intermediate
Thread Starter
Also, may I note this is the 2nd time I have seen my car heat up like this. Last time was in the summer while waiting to pick someone up. AC was on max cold. Just thought I should point out that info too.
01-22-18, 02:41 PM
#11
Intermediate
Thread Starter
check out this running HOT story, it was mine and it happened..
https://www.clublexus.com/forums/ls-...-hot-help.html
https://www.clublexus.com/forums/ls-...-hot-help.html
01-22-18, 06:06 PM
#12
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Temp ***
Most temp flux is air and water leaks in systemi.
Bleeding might help,but air leaks back in and water eventually back out.
Leaks are tough to find I place a white mat under mine just at start up to look under car . Coolant is not hot enough to dry up as it slowly leaks Just a few drops ,hard to see on rough ground need smoooth surface.. Or wait to end of day of driving when really hot it will be trying to escape by the pressures in the system and show on the mat.
Mecanics have pressure pump to force water out of any leaks insystem. It pumps up the system to about 8 PSI about normal pressure when hot
Bleeding might help,but air leaks back in and water eventually back out.
Leaks are tough to find I place a white mat under mine just at start up to look under car . Coolant is not hot enough to dry up as it slowly leaks Just a few drops ,hard to see on rough ground need smoooth surface.. Or wait to end of day of driving when really hot it will be trying to escape by the pressures in the system and show on the mat.
Mecanics have pressure pump to force water out of any leaks insystem. It pumps up the system to about 8 PSI about normal pressure when hot
Last week I had this same problem after changing starter motor. I thought I had sealed the back coolant crossover pipe for coolant to crossover coolant from cylinder head to other head it stilled leaked Also the small hose to the overflow tank was separated no coolant getting from tank to engine. This is important cause hot coolant overflows to the tank to be saved and then on cool down overnight a vacuuming sucks it back to engine by the temp change IF NO LEAKS in system It needs no leaks to work right
Also obvious leaks show up as white paste around hoses the coolant travels through no wet spots just traces of paste
01-22-18, 08:41 PM
#13
Intermediate
Thread Starter
Most temp flux is air and water leaks in systemi.
Bleeding might help,but air leaks back in and water eventually back out.
Leaks are tough to find I place a white mat under mine just at start up to look under car . Coolant is not hot enough to dry up as it slowly leaks Just a few drops ,hard to see on rough ground need smoooth surface.. Or wait to end of day of driving when really hot it will be trying to escape by the pressures in the system and show on the mat.
Mecanics have pressure pump to force water out of any leaks insystem. It pumps up the system to about 8 PSI about normal pressure when hot
Bleeding might help,but air leaks back in and water eventually back out.
Leaks are tough to find I place a white mat under mine just at start up to look under car . Coolant is not hot enough to dry up as it slowly leaks Just a few drops ,hard to see on rough ground need smoooth surface.. Or wait to end of day of driving when really hot it will be trying to escape by the pressures in the system and show on the mat.
Mecanics have pressure pump to force water out of any leaks insystem. It pumps up the system to about 8 PSI about normal pressure when hot
Last week I had this same problem after changing starter motor. I thought I had sealed the back coolant crossover pipe for coolant to crossover coolant from cylinder head to other head it stilled leaked Also the small hose to the overflow tank was separated no coolant getting from tank to engine. This is important cause hot coolant overflows to the tank to be saved and then on cool down overnight a vacuuming sucks it back to engine by the temp change IF NO LEAKS in system It needs no leaks to work right
Also obvious leaks show up as white paste around hoses the coolant travels through no wet spots just traces of paste
01-22-18, 11:49 PM
#14
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No drop.
Mine was taking a couple months to drop before I created new leak with poor sealing job, but it was leaking somewhere else before I took the starter out This is when
I relized my overflow hose was separated from the engine so the oolant level in overflow never changes it’s above engine level Can’t escape out leaking hose Only engine coolant would leak here from hot water rising and pumped by engine water pump.
When I began taking stater out I only got less than a gallon from radiator
Should have been gallon and half at least When done with stater I ended up Putting about two gallons into engine not overflow tank cause it was full Engine was low but would not know if I did not have to drain it to repair starter
LS 215k miles1996
I relized my overflow hose was separated from the engine so the oolant level in overflow never changes it’s above engine level Can’t escape out leaking hose Only engine coolant would leak here from hot water rising and pumped by engine water pump.
When I began taking stater out I only got less than a gallon from radiator
Should have been gallon and half at least When done with stater I ended up Putting about two gallons into engine not overflow tank cause it was full Engine was low but would not know if I did not have to drain it to repair starter
LS 215k miles1996
Last edited by oneLSowner; 01-23-18 at 12:04 AM. Reason: Add LS
01-23-18, 12:36 AM
#15
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No drop
[QUOTE=winter4w;10090429]Reading a bit more online I am wondering if I have air stuck in my heater core. The only thing that is stumping me a bit is it seems when people have air in the cooling system their coolant levels drop. Mine doesn't drop, it still remains at the full mark (which is good).[/QUOTE
your engine could be pumping coolant to tank but the vacuum needed to draw back into engine is not there and engine level could be low
your engine could be pumping coolant to tank but the vacuum needed to draw back into engine is not there and engine level could be low
Have to remove large bolt on top of water pipe out let and fill with coolant