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.

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

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.

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

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?

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!

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.

See if this makes any sense...after bleeding air several times out of coolant, and still maintaining the same symptoms of good heat when I rev the rpm's up enough to increase water pump speed, which increases flow enough to push water thru the heater core, then the air leaves during the high rpm time, and then air pocket returns as speed decreases? to once again provide enough resistance to flow to stop hot coolant thru the heater core. Maybe I need to tell that air bubble to find another "happy place" besides my heater core so I can vent him back to atmosphere. I hope you understand I am just cutting up here, not trying to be sarcastic, gotta make fun of myself when an air bubble gets the best of me (just ask my wife, ha ha, get it?) Anyway, how hard to change the heater valve? I'm assuming that is next in line...when i troubleshoot at work, we go from the most common and easiest fix up the line to the next harder and so on. They don't look too expensive from the price I saw at "the parts bin", an online store. By the way, where is best site to buy Lexus parts, not necessarily OEM, but good aftermarket better priced parts? Thanks again for all your help, it is really appreciated!

Tried the bleeding thru the bolt trick, with not much luck it seems. Was done in my garage, not on a hill, roads too slick. I let engine warm up, put some towels under the bolt, had wife rev up to approx 2500 rpm, cracked open for a couple minutes and got a little bit of bubbles, not much, and then coolant came out after that. if I opened bolt too much then I guess it lost pressure, and nothing came out. Had to just barely keep bolt cracked for any flow of coolant to come out. Anyway, enough came out to soak two paper towels and some of a small rag. Heat went away as the rpm went back down to idle, well actually it stayed a little warm for awhile, so I shut it down, waited 5 minutes, went back out and at idle it blew cold air. Just so I get a better idea of the principle I am trying to pull off here, how does air in the coolant not allow the warm water to flow back into the heater core. There is pressure in the system, because I went to take radiator cap off after this, and it spewed pretty good...so if pressure is building up, shouldn't that be enough to force the coolant to take the lines to the heater core? Just asking and trying to learn. 25 years ago I was a nuclear plant operator on a nuclear submarine, so I understand heat transfer and theory, although things are slowing dimming away as far as the memory bank goes. Thanks for the help, though.

Yea, I feel confident enough to do this, just have to wait for ice and snow to clear off roads enough to get the car out on a hill without getting stuck...I am a maintenance technician at a large automobile plant/factory, so I understand some on heat transfer, mechanical drives, use of lots of tools and so on, just no experience on cars, just experience on welding robots, conveyores, PLC's, motor wiring and controls etc...all the equipment used to build the cars. Will let you know how it goes, thanks.

I made sure coolant level high enough, which it was...the engine was up to normal range, and i had the heat on max...no heat on idle, but with rpm's up the heat came back...went back down to idle, and the heat slowly faded away...installed a new radiator cap, and tried next day, and still blows cold at idle...the only thing I didn't do was jack up front of car, I have a small one car garage, and really not feasible to do this...the only thing I have noticed is that my coolant level seems to never change, whether hot or cold, i don't know if that is tipping off a problem or not, just wanted to let ya'll know some other symptoms...if the hot coolant line that goes to the heater is the one that runs most of the length of the firewall, then that line feels warm as the engine warms up, but the warm coolant is not making it into the heater core...hot water valve to heater partially clogged or not opening unless rpm's high, or the heater core partially plugged as someone else suggested? Or still the possibility of air in system that needs to be further pursued, as billy suggested by bleeding air out the bolt in his picture? Thanks again.

I talked to my mechanic on the phone, and he said to bleed coolant system of air to let engine warm up, then keep around 1500 rpm for 4 to 5 minutes with the radiator cap off to bleed air out of coolant. After doing that, when the engine returned to idle, the heat stayed on instead of fading away like it normally does...i let car idle for about 5 minutes, and the heat stayed on the whole time, and i thought i had the problem solved. 2 days later I go out, start car up, engine temp warms up nicely, but once again no heat coming out of vents. I increases rpm, and sure enough the heat returns. I didn't try burping air again, I just got frustrated and shut engine off...so it seems like it will keep heat at idle, but only after I have run rpm's up for awhile...it will not put out heat at idle after starting the engine from cold condition. Radiator cap? Suggestions? Thanks, Brian

I tried your simple test, landar, and sure enough as I brought the rpm's up, heat started coming out of the vents, and as soon as it returned to idle, the heat went away. I'm assuming this is due to more vacuum at higher rpm's allowing the valve to open that sends hot coolant to the heater core. I sound like I know what I'm talking about, I really don't, but I just want to know what to tell my mechanic when I have him look at it. Thanks for any more help, it's appreciated!

Thanks for the simple test, landar. I will have to wait and try that tmrw after church. I will post and let you know how it goes, thanks again. I will also click on your posted link, mr powell, tmrw when I have more time to read it.

The engine temp warms up pretty quickly, the needle goes to midrange, yet no matter how I switch and try different things, it continues to blow cool air, yet the only two times I have gotten it to work, was when I left the system in auto and the car was in motion...I left everything in the same position, so when I started up the next time it would pick up where it left off, but no luck. Being new to all this forum stuff, I am not for sure how to search other forums for this issue, and took me forever just to find these replies to my initial post. Maybe I should take the time to go through the welcome stuff, but adopting a fulltime granddaughter tends to take up a lot of time, so I am looking for simplicity in most things. Thanks for all your replies, though, it is greatly appreciated.