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High tickover and low reading onTemp gauge


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GS 430. 05reg. 141000 mls. Near FLSH.   My car ticks over too fast for too long from cold. It takes about 6/7 miles before it drops to about 750 RPM.  The Temp Gauge in all circumstances only gets to quarter way up the gauge.  I'm thinking normal should be at least halfway. The heater does get warm to hot-ish. Maybe a change of thermostat and/or is there a temp sensor, and if so OEM or after market and/or clean the throttle body. I know the earlier V8's did have a TB problem solved.

Pictured is the air scoop (both sides are the same). Something's missing here. Can anyone fill me in on that. A grill, mesh or blank maybe. I surmise it's to direct air to the discs. Once again thanks for your help.  

IMG20211209110042_BURST000_COVER.jpg

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Don't think anything is missing its just that it should be black plastic. It looks as if the bumper has had some paint and the duct not masked so it has collected paint which has subsequently deteriorated making it more obvious to the eye.

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Certainly no expert but my guess would be the thermostat, if the temp gauge moves from cold but doesn't get to halfway then it's likely the thermostat isn't opening. My temp sensor failed recently and it caused erratic readings that were all over the place before getting pinned to hot even when the car had been sat cold for 3 hours, and then eventually it failed completely and set a check engine light. If yours is moving consistently but only so far then I'd think the most likely thing is the thermostat failing to open so the car can't warm up.

As with all things I would recommend a professional diagnosis rather than just throwing parts at the car as there are likely many things that can cause these symptoms other than the thermostat.

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The coolant sensor bolts on to the side of the engine: https://lexus-europe.epc-data.com/gs300_430/jzs160r/5048/electric/8404/

Thermostat can be found here: https://lexus-europe.epc-data.com/gs300_430/jzs160r/5048/engine/1603/

(Check the same sections with your vin# as I don't know if I selected the right options for your car)

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If you want to change the coolant sensor anyway it's relatively easy, I got one for mine for £20 from euro and it works perfectly. You can swap it over with coolant in the system just do it as quick as possible to avoid losing too much coolant, also be careful where it leaks out to, on mine the transmission was directly under the sensor but I only let a bit out and it didn't go into the vent. I had a bit of a mare trying to figure out if I'd over or under-tightened mine because I didn't have a torque wrench when I swapped it over, would strongly recommend looking up the torque spec and using a quality torque wrench. You really don't want to over-tighten it and crack something.

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On 12/29/2021 at 8:11 PM, 39buss said:

GS 430. 05reg. 141000 mls. Near FLSH.   My car ticks over too fast for too long from cold. It takes about 6/7 miles before it drops to about 750 RPM.  The Temp Gauge in all circumstances only gets to quarter way up the gauge.  I'm thinking normal should be at least halfway. The heater does get warm to hot-ish. Maybe a change of thermostat and/or is there a temp sensor, and if so OEM or after market and/or clean the throttle body. I know the earlier V8's did have a TB problem solved.

Pictured is the air scoop (both sides are the same). Something's missing here. Can anyone fill me in on that. A grill, mesh or blank maybe. I surmise it's to direct air to the discs. Once again thanks for your help.  

IMG20211209110042_BURST000_COVER.jpg

Thanks Paul, now I know.   I've painted the inside with matt black and it's practically invisible now.

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On 12/30/2021 at 6:09 PM, m4rkw said:

If you want to change the coolant sensor anyway it's relatively easy, I got one for mine for £20 from euro and it works perfectly. You can swap it over with coolant in the system just do it as quick as possible to avoid losing too much coolant, also be careful where it leaks out to, on mine the transmission was directly under the sensor but I only let a bit out and it didn't go into the vent. I had a bit of a mare trying to figure out if I'd over or under-tightened mine because I didn't have a torque wrench when I swapped it over, would strongly recommend looking up the torque spec and using a quality torque wrench. You really don't want to over-tighten it and crack something.

Thanks Mark. Very detailed reply. I'll have my trusty garage to diagnose the car and take it from there.

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