RandyV

I have learned that the 460 has no low coolant warning system.

How is that acceptable on this flagship Lexus!?

Luckily my wife was able to park the car after seeing steam coming out from under the hood before damage to the engine occurred.

Now I've set a reminder to check coolant level every month.

That is total BS!

jdanielca

the engine temperature gauge is supposed to tell you that, if coolant was low it would the gauge would have started creeping past the middle mark on your dash.

Also people are supposed to check their fluid levels once a week. Engine oil, coolant etc.

RandyV

^^^ I don't think so dood.

I've never owned any other car that didn't have a low coolant warding system. This is just ludicrous!

jdanielca

MODERATOR EDIT. Jdanielca exit this thread. You can disagree without rude commentary

if you can’t do that, do not post here.

gymguy79

I have a related problem in my 1993 LS400. I did a timing belt job about 5 years ago. Replaced water pump, belt, ignition wires, plugs, water hoses, thermostat, etc while in there. Worked fine until 6 months ago and started getting coolant low indicator.
Saw that level was low so refilled with about 4 ounces water to bring up to level. Ran for several miles and rechecked coolant level which was to the top of the tank. Took a 150 highway trip and checked level again and level was low about 4 ounces. No engine overheating but had to refill about 4 ounces. This pattern has continued for the last 6 months. Replaced radiator cap but behavior continues. Never overheats but appears that something is forcing the tank to overfill and possibly venting out the cap. There is no leakage under the car when stopped for a long period of time. Could the thermostat not be opening properly when the pressure reaches design temperature? It is relatively easy to change the thermostat. Advice would be appreciated.

DerrickM

This is not my area of expertise, but my understanding is the cooling system has an overflow tank that it offloads coolant into when it needs to due to thermal expansion. As the coolant cools, it draws it back in. I would check the overflow tank and the connecting hose.

Doublebase

No visual signs of a loss of fluid usually means a head gasket, but I’ll tell you, just because you can’t “see” the coolant leak externally doesn’t mean it’s not happening.

Take a really close look at the seams on the radiator - check for even the slightest of coolant residue/staining - that would indicate that your radiator is leaking. Check for some staining and wetness under the water pump as well. Another place to check is under the throttle body, just a tiny bit of sea page out of the coolant hoses under there can be hard to detect.

Another thing is smell...coolant smells like maple syrup...take a walk around the front of the car after a long drive, if it’s leaking you’ll get a little hint of maple syrup smell coming from the engine bay.

And yeah, it could be a head gasket. Head gaskets can leak and not cause overheating (although it’s unlikely). It shouldn’t be a thermostat, whether it’s stuck open or closed, it won’t cause a coolant loss.

EastTNLex

As stated, the thermostat itself would not cause loss of coolant. You have a leak somewhere and should check those areas as mentioned above. Good luck.

SW17LS

You should never be low on coolant unless there is some reason why you're losing coolant.

gymguy79

As I stated there is no sign of leakage anywhere except a small amount of moisture around the pipe exiting the radiator cap underneath the car. Note that I said the overflow tank will fill completely to the radiator cap and then would presumably out through the pipe going underneath the car after the car runs for several miles. If the thermostat is not opening properly or is obstructing flow through the coolant system the water would have no place to go except back into the coolant tank and would force the radiator cap to vent. Note that there are 2 levels indicated on the coolant tank, one for cold the other for hot but in this case the tank is filled completely up to the radiator cap. This is the reason why I am hoping that the thermostat is causing a build up in pressure that forces coolant back into the coolant tank.

Yeah, I know about the head gasket problem as I had one on another car that I diagnosed because pressure from the pressurized water system when the engine was off would force water into the cylinders. This would cause stumbling when it was first cranked up until the water was burned off and then it would run fine. Boy, I hope it is not a head gasket. I'm just not up for doing that kind of a job. A water pump would be bad enough.

RandyV

On mine it turned out that the water pump was leaking, resulting in low coolant and system over pressure, also resulting in a damaged radiator. There was no indication of a water pump leak - no coolant under the car when parked.

Luckily no head gasket damage, but dang, should be made aware of a low coolant situation before getting into an overheating situation.

SW17LS

Well, there certainly would be an indication of a water pump leak, but it would require you to look at the water pump, which is something that should be done routinely in a 13 year old car. Coolant is easily checked under the hood.

In order for there to be enough coolant loss to cause it to overheat it had to be a BIG leak, or it was leaking and unchecked for a very long time.

Nospinzone

Steam might be emitted from a leak before either the coolant is low or the engine is overheated. That's not a defect with the vehicle.

I bet if she didn't see the steam, the vehicle would have thrown an error code in time for her to prevent damage to the engine.

RandyV

Thats why I'm perplexed.

Nope, nor warning code and no obvious leak.

texas008

I've seen this happening with one of my car that is not Lexus. A lower radiator hose popped out of the connection (not fully seated in the spring loaded connection) and within 5 seconds "low coolant" warning sign showed up, and within 20 seconds the engine temperature reached 125 C with the whole dash flashing with red message "engine overheat, shut off engine".