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1991 Lexus Ls400 Problems


JimmyTheHutt
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Hello All,

I figured I would introduce myself as well as seek some advice with my first post. I recently purchased a used 1991 Lexus LS400. So far the car has been great, with a few important issues. I had to replace the fuel tank, as the seam on the original one ruptured. I am worried about the replacement doing the same, as the fuel tank seems to heavily over-pressurize. If I do not use a vented gas cap and have it in the vent position, it routinely takes 1 minute or more for the tank to release pressure when I go for a fill up. I am concerned that this pressure caused the rupture on the first tank, and it will do it to the second one.

In addition to this problem, I also seem to get a Oil warning light when traveling over 75 miles per hour. Its the amber indicator, with the oil can and the wavy lines beneath it. However, my oil level is fine, right between max and fill. Is this the oil temperature light? The previous owner used synthetic 10W30 Oil, rather than the 5W30.

Any thoughts? Thanks in advance!

Sincerely,

Jimmy The Hutt

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Hello All,

I figured I would introduce myself as well as seek some advice with my first post. I recently purchased a used 1991 Lexus LS400. So far the car has been great, with a few important issues. I had to replace the fuel tank, as the seam on the original one ruptured. I am worried about the replacement doing the same, as the fuel tank seems to heavily over-pressurize. If I do not use a vented gas cap and have it in the vent position, it routinely takes 1 minute or more for the tank to release pressure when I go for a fill up. I am concerned that this pressure caused the rupture on the first tank, and it will do it to the second one.

In addition to this problem, I also seem to get a Oil warning light when traveling over 75 miles per hour. Its the amber indicator, with the oil can and the wavy lines beneath it. However, my oil level is fine, right between max and fill. Is this the oil temperature light? The previous owner used synthetic 10W30 Oil, rather than the 5W30.

Any thoughts? Thanks in advance!

Sincerely,

Jimmy The Hutt

It sounds as if the engine is "gunked" up and the oil is not returning, not "free-flowing" back into the sump fast enough.

I would drill a small hole in the gas cap or not use it at all until the problem can be ascertained.

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try replacing the gasket on the gas cap. the cap should be good. mine does the air pressure thing too if i let the gas get too low. when the tank is fuller there is less pressure.

The gasket is about a buck cheaper than the entire cap assembly, you need the vented cap as the ECM checkes for pressure in the tank or else throws a check engine light. My OBD2 96 Breeze will throw a code about 5 minutes after I leave the cap off or not tightened.

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Thanks for all the advice, everyone. I will see about the factory replacement gas cap, as the one that came with the car is not factory. In regards to the oil issue, I will add a small amount of oil to see if that changes anything, as my situation seems somewhat similar to one described on page 12. I will keep you all posted. Thanks again for the advice!

Sincerely,

Jimmy The Hutt

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On my 91, the low oil light will come in if the oil level is at all below the completely full mark. I've noticed that the amount of time the light will remain illuminated varies with just how "low" the oil is. One quarter down from full is about 15 seconds, half way down is about 30 seconds. I'd imagine that lower than that would result in longer "on" times, but I've never let it go that long.

Good luck!

Ed

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