yuri.ber

iTrader: (7)

Really weird. I always give my car at least 5 min to warm up but for a few days now the rpm stays at over 1000-1100 rpm even when the warms to the first quarter of the guage. When a needle rises to the middle of the temp guage rpm is 800. When I start driving and turn on the heater the needle drops! Like heater takes most of the engine heat. When you drive the needle stays in the middle, as soon as you stop a needle falls by about half a quarter quarter of the guage. What gives?

Cleanshots

iTrader: (2)

um well when you use the heater the coolant cools better cause the heater core is like another radiator. and that keeps the temp a bit lower.

Jabberwock

I'd have your termistat checked - but I'm not sure if these cars have a mechanical or electronic controlled termistat

TJW98LS

iTrader: (1)

I would check coolant levels. If they are fine then it is a Thermostat issue. Does your heater get very hot when turned on?

yuri.ber

iTrader: (7)

It does not get too hot. It's as usual. Question: Which color antifreeze has to be in the system green or red? I got green.
You're 100% right, it was like that last winter. Now the temp goes down significantly, like a full quarter of a temp guage.

TJW98LS

iTrader: (1)

My LS400 had Red coolant. But I'll check my LS430 when I get off work.

V8_Fan

Does the temp gauge move up and then suddenly drop?

yuri.ber

iTrader: (7)

Yes! Exactly. Do you know what it is?

LiCelsior

iTrader: (32)

sounds like the thermostat is stuck open..

GRAND_LS 4

iTrader: (2)

Yup, replace t-stat and gasket and you're good to go.

V8_Fan

Had the exact same problem on my old 4runner after installing a heavier-duty 3-row core radiator vs. the factory 2-row core. Anyways, it's because the heater is removing enough heat from the engine core that the thermostat doesn't open. Once the engine heats up sufficiently (with your heater going), the thermo opens and the gush of cold coolant from the radiator into the engine will cause the temp gauge to drop. The thermostat was working fine, too. My guess was the engine temp gauge is located where the coolant actually circulates in the block while the thermostat is located on the other end of the input hose to the top of the radiator near the throttle body, so the coolant there doesn't heat up at the same rate as the coolant circulating around in the block lines. The only thing you can try is another OEM thermostat. PS: there are often different temp rating thermos from Toyota. On my 4runner, whenever I requested the thermo for that model & year, I got a 88C thermo, but that always ran hot (even with engine warmed up, needle was in the middle or slightly above). I then got another toyota P/N for a 85C thermo and the needle would then ride between 1/3 and 1/2 from cold (even in 107F temps, it would be in the middle).

Although I tried 3 different OEM thermos, I never did completely solve the issue. It never had negative consequences, as the needle will drop down to the middle/normal once the engine warmed up. I drove like that for years until I sold the car this year. Also make sure you aren't losing any coolant. That's a different problem.