1HZ (HZJ80) Temperature Gauge and Thermostat (1 Viewer)

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Joined
Oct 6, 2022
Threads
3
Messages
10
Location
Malaysia
Hello! I have a 1995 Land Cruiser HZJ80 with a manual with only 105000km. I have recently flushed the entire cooling system and put in Toyota Red, I have also changed the radiator cap (Denso), upper and lower radiator hoses (oem toyota), Aisin water pump.

I have also replaced the water temperature gauge sender(oem toyota) and the connector. I have also replaced the thermostat to the oem toyota 76c (90916-03089) which starts opening at 76c and fully open at 90c.

What I noticed is the temperature gauge sits very low, barely 1/4 and quickly drops to cold when driving at higher speeds such as highway. (See attached photo) I have check the ground at the sender and it pegs all the way to hot when grounded. Battery terminals are also brand new. I also tighten and check for corrosion for the ground screw nuts behind the gauge and they are tight.

So I went to an automotive electrical shop expert and they said it is the the thermostat opening too early which explains the drop the temperature at higher speeds. So I put in a oem toyota thermostat with the same size and diameter which is rated at 82c. (90916-03100) which starts opening at 82c and fully open at 95c. After I change the thermostat to the 82c the temperature sits at 1/3 and does not drop at higher speeds anymore. (See attached photo)

I know the oem temperature is by no means the most accurate gauge but I could use some insights and opinions on this. I would really appreciate it if any of you with a 1hz show me where your gauge sit when fully warmup and what thermostat are u using. This vehicle is operated in a tropical climate with 32-35c ambient temp during the day and 24-29c during the night. Thanks! PS. The rpm gauge is sourced from a 1hdt because my old one is broken.

IMG_20221218_130727.jpg


IMG_20221228_170526.jpg
 
Hello! I have a 1995 Land Cruiser HZJ80 with a manual with only 105000km. I have recently flushed the entire cooling system and put in Toyota Red, I have also changed the radiator cap (Denso), upper and lower radiator hoses (oem toyota), Aisin water pump.

I have also replaced the water temperature gauge sender(oem toyota) and the connector. I have also replaced the thermostat to the oem toyota 76c (90916-03089) which starts opening at 76c and fully open at 90c.

What I noticed is the temperature gauge sits very low, barely 1/4 and quickly drops to cold when driving at higher speeds such as highway. (See attached photo) I have check the ground at the sender and it pegs all the way to hot when grounded. Battery terminals are also brand new. I also tighten and check for corrosion for the ground screw nuts behind the gauge and they are tight.

So I went to an automotive electrical shop expert and they said it is the the thermostat opening too early which explains the drop the temperature at higher speeds. So I put in a oem toyota thermostat with the same size and diameter which is rated at 82c. (90916-03100) which starts opening at 82c and fully open at 95c. After I change the thermostat to the 82c the temperature sits at 1/3 and does not drop at higher speeds anymore. (See attached photo)

I know the oem temperature is by no means the most accurate gauge but I could use some insights and opinions on this. I would really appreciate it if any of you with a 1hz show me where your gauge sit when fully warmup and what thermostat are u using. This vehicle is operated in a tropical climate with 32-35c ambient temp during the day and 24-29c during the night. Thanks! PS. The rpm gauge is sourced from a 1hdt because my old one is broken.

View attachment 3204375

View attachment 3204376
@Radd Cruisers
 
Verify your coolant temp with either an infrared heat gun, thermometer, or a temporary gauge that gives you a temperature reading, not just a mark on the gauge

if you shorted the gauge, you might have bumped the needle out of its normal position. Some gauges don't like to be shorted out.


I'd stick with the OEM thermostat that you had originally.
 
Verify your coolant temp with either an infrared heat gun, thermometer, or a temporary gauge that gives you a temperature reading, not just a mark on the gauge

if you shorted the gauge, you might have bumped the needle out of its normal position. Some gauges don't like to be shorted out.


I'd stick with the OEM thermostat that you had originally.
😦😦, I thought grounding out the sender wire is normally what is done to diagnose any problem with the sender wire and gauge. Still does not explain why the gauge will drop with the 76c thermostat. But I will try checking with an infrared heat gun.
 

Users who are viewing this thread

Back
Top Bottom