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lucymiao

My 1997 Lexus Ls400 Only Gets 13 Mpg

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I got my 1997 lexus LS400 recently. It is a decent car, but I realize that I do not like its fuel consumption and slow A/C heating.

I do not use this car extensively, only for grocery shopping and other shoppings. I use 89 octane ( plus blended), about 2.8 dollar per gallon in Kentucky. I put about 30 dollars every time, about 10.8 gallons. It takes me 10 days to consume it. I only get 130 miles before I have to fill it up again. so I get about 13 mpg. However, all other people can get about 17 or even 19 mpg in city for Lexus LS400.

Another thing bothers me a lot is the slow A/C heating. Since winter is just around the corner. I start to use the heating now. It has to take about 15-20 minutes before it can blow warm air. I asked the previous owner about it. He said it was like these for him all the time. but most of my trip is less than 10 minutes. so I assume that A/C is useless for me at all. Is it true for owners of LEXUS LS400 1997, the heating is always so slow to heat up, or my car has a problem?

Please help me on this. thank you a lot!

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I have found two causes of problems with my heat in my 95 LS400. One cause is the use of the wrong type of engine coolant. Lexus specifies a particular type of coolant which is different than other cars. The other cause I've had is that the system needs to be pressurized and all air bled from the system. One mechanic solved this by putting the car on a lift and lowering the rear of the car to force the air up and out. He called it burping the system.

As for the mileage, I can tell you that my 95 with 145,000 miles still gets about 18 city and 25 on the road.

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Well lucy, your car has all the classic symptoms of a thermostat that is stuck open. No, it is not normal to take 15-20 minutes to blow warm air. Should be around 5 minutes tops, especially at this time of year in Kentucky. And a cold engine uses more fuel, hence your poor mileage. So, I would investigate that item first. It is pretty easy to change the thermostat and I would recommend using an OEM Toyota stat at the dealer along with a new gasket. Will cost you about $35 in parts if you can DIY ($15 for thermostat and $20 for a gallon of antifreeze. labor will be extra).

And...you really should be using 91 octane fuel although this alone is not causing your heating issues.

Also, where does the temperature needle point (middle or below) on your dash readout when fully warmed?

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Yes, it could also be a temp sensor issue as well or in combination with the thermostat. That is why I asked about the behavior of the temp gauge. May contain some clues.

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It would do your car a world of good to get it out and the Interstate and run it for a couple hundred miles. A little run up to about for awhile and after it is warmed up, get off and back on and accelerate heavily until fear of accidents of fear of cops overcomes you. You may see black smoke coming out the exhaust in your mirror which would be the carbon buildup departing. All that driving around town on shorts trips is not the best environment for your car. Use TOP TIER premium fuel and avoid discount gasoline, yeah I know it costs more. My 90 LS gets around 17 in the city but I often come off the light hot just because I can. I could probably do 19 if I was conservative with the accelerator but again, I am not.

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Thank you very much for all your replies. I took my car to the mechanic today. He said the slow heating may be caused by water pump, which maybe worn out. While the car parked, he press the gas pedal, until the rmp is at 2 or over, the car can blow very warm air, very nice. But when I just start the car normally in morning, the rmp is about 1, or 1.2, so it never warms up quickly. so his conclusion is that something is wrong with the water pump. To change the entire water pump, including parts and labor, may cost about 300-400 dollars.

The previous owner has timing belt and water pump done at 83511 miles, currently the odometer is 135000 miles. So the water pump can be easily wear out at about 50000 miles?

I find an ebay seller sells water pump for about 60 dollar. so if the labor cost is not so expensive, i might buy it from ebay, and ask a mechanic to change it.

How do you think?

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Thank you very much for all your replies. I took my car to the mechanic today. He said the slow heating may be caused by water pump, which maybe worn out. While the car parked, he press the gas pedal, until the rmp is at 2 or over, the car can blow very warm air, very nice. But when I just start the car normally in morning, the rmp is about 1, or 1.2, so it never warms up quickly. so his conclusion is that something is wrong with the water pump. To change the entire water pump, including parts and labor, may cost about 300-400 dollars.

The previous owner has timing belt and water pump done at 83511 miles, currently the odometer is 135000 miles. So the water pump can be easily wear out at about 50000 miles?

I find an ebay seller sells water pump for about 60 dollar. so if the labor cost is not so expensive, i might buy it from ebay, and ask a mechanic to change it.

How do you think?

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No, Like many have already said, its most probably you thermostat. Cost about $50 to replace. Find another mechanic or do it yourself.

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Again, where does the temp needle point when this warm air is flowing or when the car has been driven for approx. 1/2 hour?

BTW, its RPM, not "rmp". :)

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I just changed my water pump at 90k miles and the pump impeller looked brand new. I think its stainless steel so resistant to corrosion. So the worn pump theory is a bunch of nonsense. Most common water pump failure is leaking water seal anyway.

Find another mechanic. Better still just go to a mechanic and ask them to change thermostat and see what happens. Won't cost much and is 90% likely to be your problem.

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Plus a pump issue is going to cause overheating, but underheating.

I say Thermostat as well...

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When water pumps go, they go. They either leak, or sieze and that is it for them, no more pumping. Thermostat, hands down.

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Thank you for your suggestion. The previous owner did timing belt and water pump at a shop specializes Toyota in 2005. I still have the receipt, which is the transferred from the previous owner. I called the shop. they said it could be the problem caused by heat cord restriction. the water pump shall be fine.

When the rpm is about or more than 2 rpm, the air blows warm, the thermostat needle points to the middle. so I think thermostat shall be good. also, on Oct.12,2010, the mechanic did back flush heater. not sure what does back flush heater mean? is it means back flush the heat cord restriction? the previous owner did back flush heater in winter on 2007, 2009, and 2010. Is it normal to do heater back flush every one or two years?

Also, i hear quite some noisy under than hood? not sure what is the next problem. I need some bless for this car, which i just bought for one month. thank you all.

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about the thermostat:

when I just start the car, the needle points to c(cold), and after I drive, it slowly goes up to 20% -40% of the gauge, and 50% at the most, and never go more than half of the gauge. since I drive in city, the rpm is usually between 0-1, and 1-2, and rarely goes beyond 2. but as long as rpm>2, it can blow nice and warm air. so what do you think the problem is?

in addition, the noise under the hood maybe just normal, and it is me being paranoid.

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about the thermostat:

when I just start the car, the needle points to c(cold), and after I drive, it slowly goes up to 20% -40% of the gauge, and 50% at the most, and never go more than half of the gauge. since I drive in city, the rpm is usually between 0-1, and 1-2, and rarely goes beyond 2. but as long as rpm>2, it can blow nice and warm air. so what do you think the problem is?

in addition, the noise under the hood maybe just normal, and it is me being paranoid.

Ok, so we get the needle info I was wanting. A temp needle pointing to approx. halfway is correct operation. The temperature should get there in about 10 minutes of normal driving in cold weather (sooner if above freezing). Usually when the heater does put out correct heat at higher RPM's but cools down at lower RPM's, it points to air in the cooling system or low on coolant or both. In particular, air may be trapped in the heater core area.

You might:

1) Buy a new "radiator" cap and install(it is located on the coolant reservoir). This will ensure that the cooling system pressure is correct.

2) burp the system by making sure the coolant reservoir is full, bringing the engine up to operation temp and keeping RPMs above 2k for a few minutes. Let the engine cool and repeat if necessary. I believe there are instructions in your engine compartment.

Did you just post the same issue in a new thread? :chairshot:

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landar's suggestion to buy a new radiator (reservoir) cap is a good one. To expand on his "burping" instructions....

With the car cool:

1) Remove the tank cap

2) Set heater temp on high (85)

3) Let engine warm up to normal operating temp (to open the thermostat)

4) Rev engine between 2000 and 2500 RPM for 5 minutes (at some point you may see some fluid "blurp" (technical term) out as the air escapes)

5) Turn off engine and let engine cool

6) Add fluid to the tank as coolant is drawn back into radiator (don't let tank get empty)

7) When engine is totally cool, add fluid to full level

8) Replace cap

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lander, sorry. I did put a new thread, with a different wording. sorry, I was too nervous about this problem. I spent whole last night to study the cooling system. I will follow your procedure. Also, I put some white paper under the hood this afternoon to check for any leaking. Previously, the high pressure hose of power steering was leaking and it was replaced. just make sure no more leaking.

Thank you all for the information. I will update you with my progress.

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lander, sorry. I did put a new thread, with a different wording. sorry, I was too nervous about this problem. I spent whole last night to study the cooling system. I will follow your procedure. Also, I put some white paper under the hood this afternoon to check for any leaking. Previously, the high pressure hose of power steering was leaking and it was replaced. just make sure no more leaking.

Thank you all for the information. I will update you with my progress.

It's ok, lucymiao. I can understand your frustration.

It is hard to diagnose problems via the internet w/o actually seeing and hearing the issues first hand. With all the information you have provided so far, you may have several things to fix. I am still not convinced that your thermostat is working correctly. It may be but it might be a good idea just to have it replaced. Some owners replace them on a periodic basis, like 30-40k miles, regardless of whether the thermostat is showing signs of failing. BTW, I checked my LS this morning for heating. It took 7 minutes (about 5 miles) of gentle driving to reach full operating temperature at an ambient of 45 degrees F. Yours should be similar. If it takes much longer than that(say 10-15 minutes), just replace the thermostat.

The reason the previous owner kept flushing and flushing the heater core is precisely because of this heating issue. He obviously never got it fixed probably because it is not a clogged core.

Keep us updated and follow AZHotLS's directions for burping the system after you get a new cap.

...and, read this thread carefully, much the same advice -> http://us.lexusownersclub.com/forums/index.php?showtopic=44432&hl=%20garage%20%20heater&st=0

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thank you lander. I will change my thermostat since it has never been changed. An excellent advice. Also, I have been calling two mechanic shops. their labor rate is 80 dollar per hour, and 50 dollar for a diagnostic check. So I think I will change the coolant and thermostat, before I engage to more repairs.

I check more about my car. The coolant is dirty. When I put a stick to the reservoir, and I realize that something blackish from the bottom of the reservoir. So I believe the coolant is dirty, and i shall change it.

Secondly, I placed white paper under the hood last night, I checked today that there was leak. I toughed it with my finger,it is oily and the color is very light brownish or light reddish, not greenish for sure. Also, I check the engine oil, it line is between Full to low, but more toward Low line.

Sorry to bother fellow members so much.

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what is the right type of coolant?

sorry for my inexperience. I read from the manual, it saying ethylene-glycol coolant (do not use alcohol type), 11.0L. So what brand and where I can get this type of coolant?

I think I need to buy coolant before I do the burping of the cooling system, although my current coolant reservoir is at full.

also, the radiator cap is the same as the coolant reservoir cap?

AzHotLs, 1) Remove the tank cap? which tank you are talking here? is it the coolant reservoir tank?

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what is the right type of coolant?

sorry for my inexperience. I read from the manual, it saying ethylene-glycol coolant (do not use alcohol type), 11.0L. So what brand and where I can get this type of coolant?

I think I need to buy coolant before I do the burping of the cooling system, although my current coolant reservoir is at full.

also, the radiator cap is the same as the coolant reservoir cap?

AzHotLs, 1) Remove the tank cap? which tank you are talking here? is it the coolant reservoir tank?

You need Toyota Factory Red Fluid with Ethylene Glycol and Diethylene Glycol. Full strength. You can get it at your Toyota or Lexus dealer for around $20 USD. You will need approx. 1 1/2 gallons (6 L of non-diluted coolant).

Then you will need distilled water to dilute it to the proper concentration. Do not use regular tap water because it has too many contaminants that will eventually corrode your cooling system.

Yes, the cap is the coolant reservoir cap. There is no cap on the radiator itself as it is a "sealed" unit.

I would drain your existing coolant completely by opening the radiator drain !Removed! and both left and right engine block drains. While empty, remove and replace your thermostat and gasket.

Then refill the system via the top-center fill hole and proceed to purge the system.

If you want to know more about draining and thermostat replacement, see these tutorials on the early LS. Very similar to your year however. http://www.lexls.com/tutorials/cooling/

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lander, thank you for your information, especially the tutorial, so helpful. The current coolant I have is actually greenish, not sure this is the right coolant or not since it was the previous owner did it. I think I shall get the reddish one from Toyota dealer.

Something weired happened to me today. Two or three days ago, I checked my coolant reservoir with a chopstick since I do not know how to check whether the coolant is full or not, and the end of chopstick took out some blackish mushy soft sediment. But today, when i checked my coolant again, it only has about 25% of the tank capacity, and there are two black tiny rubbers. 2.5 cm in length,0.5mm in diameters, not totally round though, like part of a seal or something coming up, so I took it out. Also, on the ground there is a fresh puddle of leak, which I assume it is coolant since it is not oily, the puddle is right beneath the coolant tank.

something really funny is that when i start my car, and I let it idle for two or three minutes, without touching the gas peddle and rev up to 2000rpm, and there is warm air. This is so rare after I have this car for about 40 days now.

I will have to book a mechanic to flush the cooling system and install a new thermostat and gasket next week.

BTW, refill the system via the top-center fill hole? what is the top-center fill hole, and where is it?

thank you numerously.

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BTW, refill the system via the top-center fill hole? what is the top-center fill hole, and where is it?

thank you numerously.

Make sure the mechanic does a thorough flush on the entire coolant system to get the old junk out. You do not want any old residue mixing with the new.

Concerning the fill hole, here is a pic of a 98 LS400 location. It is slightly left of center. But beware, it may not be exactly the same on the 97.

post-41820-0-67782400-1290611079_thumb.j

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