Not Smart Enough To Figure Out Climate Control

[billydpowell]

have your mechanic pressure test your cooling system, you must have a leak that allows air to be sucked in as your coolant cools off.

when we put motor mounts on my 99, we broke the HCV, I got one at a salvage yard for $15. working fine... here it is

[brian du4]

Well, here's an update. Took to a local mechanic who I've had do simple jobs before, and I now know why. He changed the thermostat, backflushed the heater core, and declared it working. I get to the first stop light, go to idle, and back to cool air. He then says I need to keep the air flow on recirc, instead of outside air, to get constant heat, and I just say ok and leave, knowing you fog out in a couple minutes unless you pull in outside air. I then take to my normal mechanic who is farther away, but at least has enough common sense to know how to operate your car's climate control. Anyway, he jacks front of car up, verifies no air in coolant system, verifies no leaks in system, verifies the heater control valve is switching and operating as it should, and then concludes what I was hoping against the whole time, that the heater core is partially plugged, so that at idle with low water pump flow there is not enough hot coolant going thru heater core to blow warm air, but when I rev up rpm's, pretty much instant heat as more hot coolant flow now is going thru what part of the heater core is not plugged. He didn't even bother with an estimate because of the size of the job. So I have put a call into Lexus dealership to see if any other options to try, such as chemical shocking or something similar, and their main man won't be in until in the morning, so I am calling back then. I don't know if I am up to removing the dash or whatever is required to get to the heater core, and even once getting to it could I remove it and remove scale and buildup from inside individual heat exchanger tubes. I did alot of that on a submaring in the navy many years ago, but they were much bigger and easier to get to. I may not have much choice after I hear the cost of any options, oh well.

[billydpowell]

We are very sorry not to have helped you overcome this... but keep us posted..

[brian du4]

I sure will, thanks for all your help so far, it has helped me narrow it down little by little. I have researched a little more on unplugging a heater core using compressed air, and then pouring in some CLR and letting it soak for a couple hours, then blowing all the crap out again, then several flushes with water to make sure all of chemical is out. I have a compressor and regulator, so I can maintain a pressure less than 20 or 25 psi just to make sure don't blow core out, but the guy on youtube used regular 125 psi shop air, and said he has never had a problem with that high a pressure blowing out the core, but I want to make sure I have a good path for flow first at a lower pressure before I crank it up to get out the stubborn stuff. Sound like a plan? We'll see!

[landar]

Did your mechanic completely bypass the heater control valve? I would do that first to verify that without a doubt, there are no external restrictions making it appear to be a plugged core.

Concerning flushing the core...I would want to try to reverse flush it. Probably take it to a radiator shop that specializes in cores and see if they could do something with it while still in the car.

But first, make sure the valve is not restricting the flow at idle via bypassing it.

[AzHotLS]

It would be interesting for you to do a climate control test and see if any codes come back. I think your heater core is partially blocked but doing the test can't hurt.

http://www.clublexus.com/forums/ls400/477602-a-c-control-assembly.html

[brian du4]

Well, here we go. Took heater hose off at heater control valve, verified internals working on valve ok by manually moving lever and seeing valve shift internally and no blockage. Then just left hose off and started car, and got no flow coming out of the hot coolant hose that leads to the heater control valve. Had wife increase rpm's and finally got a little flow, never really got a full stream that i would expect. Went back down to idle and no flow, and what had come out at high rpm was brown and dirty, like nothing had flowed thru this line in a while. Also, while hose off, hooked up garden hose to a flush t-fitting on the line coming out of heater core, pinched off hose so it wouldn't flow back towards engine, and put water flow backwards thru the heater core, and got good solid stream of water out of the heater control valve where i had the hot coolant hose off, so the heater core is clear and not blocked. The problem is with no flow coming thru the hot coolant line up to the heater valve. Anyway, here is where I screw up...I put the hot coolant line back onto the heater valve, and decide to idle engine to burn off all the coolant and water that was on the block. Went in house for a couple minutes, heard a big pop from the garage, and opened door to see hot coolant and steam at full pressure blowing all over everything. I ran thru the stream and shut the engine off, didn't feel real good. Kinda hot! I forgot to put the clamp back on the hose when i hooked it up to the water valve...actually i didn't forget, i left it off because i knew no flow was going up that line, and i would be taking it off later anyway...what a mistake...looks like that hot coolant line had plenty of flow going thru it when it blew off of the valve and started spraying down me and my garage. Couple observations...the coolant reservoir level has not dropped any after any of these recent maintenance activities...there is a lot of coolant on my garage floor, and yet the level says good on the tank. I am thinking of a complete drain, flush thru the t-fitting up near my heater valve, and fill from the high point near my water valve, filling the heater core and valve last to make sure no air, and try again. Is there a drain fitting near the bottom of radiator, or where?

[landar]

First off, I hope you did not sustain any burns. Steam contains a tremendous amount of energy.

There should be a drain plug near the bottom (passenger side I believe) of the radiator. Probably the reason that you did not see the reservoir level go down is because the engine has to cool down in order to pull the coolant from the reservoir into the engine AND you would need a sealed and completely air-purge system to do that. Your system after the "incident" was not sealed or purged. There is no magic trick (level-wise) going on here.

So, are you saying that you suspect a clog in the heater line leading from the engine to the heater valve? Sometimes a hose can get a kink or collapse.

[brian du4]

I guess I suspected a problem with the hot coolant line to the heater valve when I had it pulled off, and at idle there was zero flow coming out of the hose, and as I rev up rpm's flow increased little by little...but I doubt that is the problem now, because that mass of coolant that blew out all over the garage and me last night was coming out that same hose, so it definitely is not blocked. I believe when i tried venting all the air out a couple times earlier in this fiasco, that I never really accomplished that. The heater lines, valve, and core are all at the highest point in the system, and with the system low, it never really filled up or pushed air out, it would all just drain to the low point of the system, and leave all the heater lines empty. i have come across a little financial situation, and i need to sell the car, but i would not try to if i knew there was a problem like this...that is why i am hoping to fix it, so i can sell it...i'll keep workin' on it

[AzHotLS]

Went in house for a couple minutes' date=' heard a big pop from the garage, and opened door to see hot coolant and steam at full pressure blowing all over everything.[/quote']

That's probably when the thermostat opened up.

[brian du4]

Finally done! Drained and filled from the heater valve hose connection, vented thru fill plug and reservoir...once coolant there, then hooked up water hose to flush fitting on outlet of heater core, and filled backwards thru core until solid flow out of heater valve. Closed it all up, ran at 2500 for 5 minutes to get any residual air out...now have full heat at idle! Mr Powell was right all along about an air pocket, it just took me awhile to get there. Learned alot though... experience is one heck of a teacher.

[JWhite]

I have a 95 LS400 also and when I press the auto button AC comes on also. What I have found out is when you start up and want to warm the car while sitting in the garage or driveway just turn the heat on by pressing to > button (the one to increase the temperature) and the heat will come on and not the AC. Once the car is warm I now can press the front defrost and it works like a charm. Reading the other responses it seems like you had other issues, not sure. Hope this helps.

[landar]

Brian, glad to hear you now have heat even at idle. . According to a previous post, your mechanic apparently could not get the air purged so this is no simple feat (or your mechanic does not know the correct procedure). With all that has occurred, I am still unclear as to exactly what you did to finally get the air purged from the system. Can you summarize the procedure that you have learned?

[brian du4]

Since I could not elevate the front of car about 18 inches as mr powell suggested, I filled and vented from the highest point in the system, which is the heater valve and the coolant line supplying it. I took the hot coolant line off that goes to the inlet side of the heater valve, placed it in a vertical position straight up and down, found a funnel that fit snugly down into inside of hose, held hose vertical and filled with premixed coolant and water mixture. Before doing this, I had removed the fill plug bolt right behind the thermostat and the radiator cap to give air a path out. The car was not running at this time, I just let gravity fill the system since I was holding the hose at a high point, and filling from there. Once solid coolant flow out of fill plug vent behind thermostat, I put that bolt back in, continued filling, forgot about overflow tank level, but once i heard it overflowing there, put the cap back on. Continued filling slowly thru heater hose, until it filled up...then on the outlet hose of the heater core, i had installed a hose flush tee fitting, so i could hook up a water hose at that point, and backflow thru the heater core and out of the heater valve to make sure the heater core in full of water...while water coming out of heater valve, hooked up the hot coolant hose to the valve and hose clamped it onto the valve...turned water off that i was using to backfill the heater core, took the hose off the fill fitting, filled the small air pocket that left in that hose with some coolant, put the cap on the tee fitting, ran car at 2500 for a couple minutes, let cool down, level in reservoir ok...loosened hose clamp at hot coolant line on heater valve, slowly started taking it off and verified coolant started leaking out, since this is the high point of system, then reattached hose to valve...had to siphon some coolant out of reservoir from my initial fill when i overfilled it...yea, that's a lot of info, but basically by putting a t-fitting on the outlet side of the heater core that allows a garden hose hookup to backfill the heater core and doing all of the fill from the hot coolant hose that feeds the heater valve since this is the high point in the system, i finally succeeded...thanks for all the help everybody...anybody want to buy a nice pearl white 1995 LS400 with only 101k miles? have a small financial situation arise, and would help if i could sell the car...Brian at 859-457-1402 in kentucky, thanks

[brian du4]

oops, in my last post, I mentioned my car is now for sale, but I didn't realize as a new member I was not allowed to do this. I didn't mean to try and circumvent any policies and regulations, so I won't say anything else about it, and will wait until i am not considered a new member before I try and post it for sale on this site...i did not start the thread about my heater problems with any thought of selling the car, it has just worked out that way...sorry 'bout that.