Low Coolant - Possible Causes??
03-02-09, 12:30 PM
#31
One thing that I haven't seen mentioned is the HCV (heater control valve). It will cause a coolant leak with no drips, and on my car ('93) ~1hour of highway driving with the windshield defroster on is enough to drop the coolant level to a point where the coolant light comes on (~2" below the cold fill line).
In the engine bay on the passenger side, behind the throttle body, there is a valve assembly mounted to the firewall. It has several coolant lines coming to it, look for any signs of coolant where they connect to this valve.
~$65 for the part, supposedly pretty easy to replace yourself. I've had the replacement part for over a year and haven't bothered installing it yet, I never use the heat unless I need to de-fog the windshield
In the engine bay on the passenger side, behind the throttle body, there is a valve assembly mounted to the firewall. It has several coolant lines coming to it, look for any signs of coolant where they connect to this valve.
~$65 for the part, supposedly pretty easy to replace yourself. I've had the replacement part for over a year and haven't bothered installing it yet, I never use the heat unless I need to de-fog the windshield
03-02-09, 05:15 PM
#32
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One thing that I haven't seen mentioned is the HCV (heater control valve). It will cause a coolant leak with no drips, and on my car ('93) ~1hour of highway driving with the windshield defroster on is enough to drop the coolant level to a point where the coolant light comes on (~2" below the cold fill line).
In the engine bay on the passenger side, behind the throttle body, there is a valve assembly mounted to the firewall. It has several coolant lines coming to it, look for any signs of coolant where they connect to this valve.
~$65 for the part, supposedly pretty easy to replace yourself. I've had the replacement part for over a year and haven't bothered installing it yet, I never use the heat unless I need to de-fog the windshield
In the engine bay on the passenger side, behind the throttle body, there is a valve assembly mounted to the firewall. It has several coolant lines coming to it, look for any signs of coolant where they connect to this valve.
~$65 for the part, supposedly pretty easy to replace yourself. I've had the replacement part for over a year and haven't bothered installing it yet, I never use the heat unless I need to de-fog the windshield
03-26-09, 09:01 AM
#33
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UPDATE: The coolant stopped disappearing. I had to top it off the few times mentioned in earlier posts, and it's held at the same level since. Possible air pocket(s) from work done previously? No idea. Have to say, I can live with this "best possible" outcome!
03-27-09, 09:41 AM
#34
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also, an update to the update. earlier on this thread, i mentioned that i'd seen brown, very viscous 'gunk' on the inside of the sensor cap. one mechanic i showed it to at a lexus dealership(!) said "i've never seen anything like that". i cleaned off as much as i could. weeks later, another certified lexus mechanic (works at a indie shop now) said, "oh, they ALL have that. i don't know what it's for, but they put that there, maybe to protect the wires". i said: "are you sure?". he then told me he had been working on lexi for 25 years. make of this what you will.
03-27-09, 10:48 AM
#35
the coolant tank on my old '90 had the same 'problem' (gunk seeping out from under sensor cap).
when I got my '93 the coolant tank was cracked, I swapped the tank from the '90 to the '93 and am still using the tank with the gunked up sensor. Still sets off the coolant light when I'm 2" below cold fill line, and has had that gunk on it for at least 6 years now.
I'd be inclined to agree with your mechanic, nothing to worry about.
did you check those coolant lines running to the HCV? I haven't lost any coolant in the last few months either, but a highway drive in the rain with defrosters on will still drop the level several inches.
when I got my '93 the coolant tank was cracked, I swapped the tank from the '90 to the '93 and am still using the tank with the gunked up sensor. Still sets off the coolant light when I'm 2" below cold fill line, and has had that gunk on it for at least 6 years now.
I'd be inclined to agree with your mechanic, nothing to worry about.
did you check those coolant lines running to the HCV? I haven't lost any coolant in the last few months either, but a highway drive in the rain with defrosters on will still drop the level several inches.
03-27-09, 12:16 PM
#36
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the coolant tank on my old '90 had the same 'problem' (gunk seeping out from under sensor cap).
when I got my '93 the coolant tank was cracked, I swapped the tank from the '90 to the '93 and am still using the tank with the gunked up sensor. Still sets off the coolant light when I'm 2" below cold fill line, and has had that gunk on it for at least 6 years now.
I'd be inclined to agree with your mechanic, nothing to worry about.
did you check those coolant lines running to the HCV? I haven't lost any coolant in the last few months either, but a highway drive in the rain with defrosters on will still drop the level several inches.
when I got my '93 the coolant tank was cracked, I swapped the tank from the '90 to the '93 and am still using the tank with the gunked up sensor. Still sets off the coolant light when I'm 2" below cold fill line, and has had that gunk on it for at least 6 years now.
I'd be inclined to agree with your mechanic, nothing to worry about.
did you check those coolant lines running to the HCV? I haven't lost any coolant in the last few months either, but a highway drive in the rain with defrosters on will still drop the level several inches.
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