foreste1

Hi Guys, my GX I live in Warm climate, Phoenix, and never use the heat in my GX. I went up to snow country and noticed no heat. I went back through the service history I have and see where prior owner right before he sold to me was at lexus and they stated possible heater core needed for no heat.
I am also wondering in the hot summer, my a/c sometimes will shut off when i sit in traffic and then start cooling perfectly when I start moving again. My fan and clutch are all good, and it the engine temp runs right at middle most of the time. I do notice in summer though when the a/c acts up, the temp gauge can climb a bit, but I have checked and the fan is running when that happens. Coolant level is good too.
I am wondering if the two are related, and if any simple fix for heat and then the a/c before summer comes again.

DiabloX22

If the heater core is clogged, the coolant isnt circulating through the system the way it should. Coolant over time actually turns into a acid and eats up the system from the inside out. If you ever seen a mechanic grab a coolant hose and squeeze it, thats what they are checking for, to feel if it collapses from the inside. They sell p.h. test sticks you can test the coolant level of balance. IMO NOTHING is "lifetime" as far as fluids go. Some manufactures claim the trans fluid is lifetime, then if you have a problem they tell you, you need a transmission.

Even though the level is good, is it clean? that can effect a few things. If its old and dirty, thats how the heater core got clogged, the coolant eating rubber and plastic components, over time they find a place to settle, the heater core pipes are small and have bends like a S shape.

As far as the A/C do you have it on automatic or manual setting? What is a "bit" high in regards to the temp? You also have a electric fan. Try to provide a bit more info, you may have a small leak as far as the freon in the A/C.

chiph9

I believe the coolant is on a 3-year change interval. Use only the Toyota-brand coolant.

So far as the A/C, it wouldn't surprise me if an 03 needed the refrigerant topped-up. I needed this done last year on my 04 and it was about $170.

Chip H.

foreste1

Hi Guys, thanks for the answers. The coolant looks clean and I added more red toyota/Lexus coolant into reservoir yesterday as it was a little low, but nothing really changed for heat. It does have luke warm heat I noticed yesterday, just not hot.
Anything you can run through system to un-clog anything in there?

On A/c its freezing cold most of the year its only when it gets up to 112-115 degrees in PHX and I am sitting in traffic that it all of a sudden goes to a sort of muggy warm coming out of vents, if I get moving it will kick back in and be super cold. I remember last year trouble shooting and was down to something inside the glove box area that I was thinking was the issue but seems like a big job, so I did not get into it, cant remember what that was.

One time I was stuck in a lot of traffic and had to sit for maybe 20-25 minutes and the air kicked off and the temp starting going up to 3/4 and I turned on heat and it went right back down. I remember last summer also thinking it had too much freon and had some removed and the fan worked great and I let it sit in my driveway for an hour in 115 degrees and it stayed perfectly cold and temp stayed half way, so thought it was fixed, but then it did it again a few days later in traffic.
Just trying to figure it out now before it so hot out and I have no a/c.

chiph9

If you've never changed the coolant ... that's bad because it's not the coolant that goes bad, it's the additives in it. And they're what protect the internals of the engine & heat exchanger from corrosion.

So far as the A/C - How is the airflow? Have you changed the cabin air filter recently?
And what do you mean - had some removed? The system needs a specific amount of R-134a and PAG oil. No more, no less. The technician will weigh the cylinder with the liquid/gas to make sure it's correct when filling it.

Chip H.

DiabloX22

The Temp gauge should not go to 3/4 high. Especially not sitting. I would start with a thermostat, and yes there are flushes to clean the system and block. Just make sure you tell who is doing the work you want the system and block done! If the system is done, then as soon as it circulates around the new and old will mix. So you basically have old again. Maybe look into a water temp sensor for the computer, not engine gauge You will have to do a bit of research to learn what it does.

If you are lucky with the flush and a new T-stat it may clear out the heater coil.

If the temp is hitting 3/4 I think the computer will shut off the A/C as a safety from over heating.

foreste1

Ok, I will order thermostat first and then do a flush/clean. That makes sense the temp goes up and the a/c kicks off, but it does it sometimes when temp is not rising, so will try flush and thermostat for now and see how it does.

I have changed cabin filter, on removal of some, I had an a/c guy remove some as it was too high they said.

I think I will also take back to a/c place and have then measure exactly, thanks for that info.

DiabloX22

Just my opinion, I would stay with OEM parts, MOST of them seem to be made very good. For the flush, IDK where you will have it done, but If they can get access to the hoses to the heater core, disconnect and run pressurized water through, it could clear it out. Dealer probably wont do that cause they are "remove and replace" mostly, idk. Also the flush, I used to own a shop and used BG products, not available at stores, never checked the internet or anything. Might want to consult with the shop, they might want you to add it and drive for a day. That gets it circulated, up to temp so it starts to eat the junk inside. Some say turn heat on say dont. Since you think your core is clogged, I would turn it on. Then replace the thermostat. OR again, depending where you take it, they should be able to hook it up to the computer and see exactly what is going on with all the sensors, temp gauges etc. Then inform you of the problem. It doesnt sound like it, but make sure the heater core isnt leaking. Carpet/floors are dry in front. If it is leaking, no sense of doing the flush. If you have any questions, just ask.

foreste1

Thanks, no floors are wet. I was going to install thermostat today but cant find anything on net where it is located, do you know? I think its right on top in front of motor, but not sure. I bought OE style at parts store, but I am seriously thinking I am going to go get Lexus/Toyota brand from dealer Monday and do this later in week. I dont want to have an issue because after market thermostat for sure!

DiabloX22

I THINK it is at the top of the engine, upper hose to a flange held on by 2 bolts. Hopefully 1 of the other guys will chime in and tell us if thats correct or not. I wouldnt put a new one in until after the flush. They will have to take it out to do a good job of flushing the block. I would buy 1 and a gasket and hand it to them. Ebay has Lexus thermostats. If it was me, I would go to your parts store and see what kind of coolant system cleaner they have. We already know you have a pretty bad clog in the heater core. Depending on when you are going to get the flush done & the directions of the system cleaner. I would buy some, put it in and drive around with cycling the heat on and off. You would have to make a educated guess depending on the directions. Meaning it it looks like strong aggressive stuff, or if it says for bad blockages leave in over night. I think you get the idea. Look at the color of the coolant before hand then check it once in a while, the dirtier the better!

chiph9

You want the Lexus-brand thermostat. If you buy from eBay or Amazon, check for counterfeit parts (Amazon is starting to have a problem with this). Safest place to ensure genuine parts is a dealer (there are some that sell online).

Agree that if the cooling system has never had the coolant changed, an additive may be required to clean out the scale & corrosion.

Something that hasn't been mentioned is the coolant pump. Sometimes corrosion will eat the vanes on the pump (I think this is from a GM):




Chip H.

foreste1

That makes good sense to run the cleaner through this week and then flush this next weekend and install the new OEM thermostat after. I did find where the radiator and cooling system was changed out about 60k ago at Lexus. I have all the history as I bought from original owner about 4 years back.
By the way Lexusdrivers.com is a great site if you input your vin you can get all history since new, just in case anybody does not know about it.
Coolant pump, not heard of that, need to check that as well, thanks! Been in garage tonight fighting with my SC marker lights, absolutely no fun!!! Cheers!

DiabloX22

He is referring to the water pump. I agree they can go bad, and break/disintegrate, a lot of German cars use plastic impellers, so the impeller or fins would look good but where they connect to the shaft was worn, the shaft would spin but the torque from trying to circulate the coolant would cause the impellers to stat still.

I would keep that in the back of your head for now, if you do add a flush and drive around, make sure to cycle the heat off and on a few times.

chiph9

Yes, water pump. Normally you change this as part of a timing belt service. Normally.

Chip H.

foreste1

Ok now I follow. I will drive for a while and then flush and change thermostat.