sc3dreamz

After reading countless threads of heating problems, I thought it might be a good idea to compile a list for some of the new people and anyone else who runs across these problems.
Heating related threads:
https://www.clublexus.com/forums/sea...archid=1045043

Summary:

Main problem: No heat. A/C working, fan speeds are normal.
Solutions to date in order, starting with the easiest and progressing.
The first 3 steps tie-in together.
1. Make sure all your coolant hoses are connected, especially around the firewall, inspect them to ensure they are not rotted from being so old. Check your vaccum lines running to the heater control valve, inspect the hoses going into the heater control valve:

This is your heater control valve. You can see a coolant line on the right and there is one underneath. Inspect the vacuum lines running from the HCV.

2. Make sure your radiator isnt rusted out, leaking ect ect. This was one of my problems and I was constantly leaking coolant. The most common place to see cracks in the radiator is the end tanks and around/underneath the cap because its made out of plastic. At the same time, inspect your radiator cap to see if the seals on the inside are still good. If you just have leaks on the end tank(plastic part) you can do a quick patch or order a new radiator, an all metal radiator. I'm not promoting but I bought mine from radiatorbarn.com for around $180. If you just want to try a quick patch then its off to auto zone for some jb weld. They make a product specifically for radiators. Follow instructions and patch. You can also get a radiator cap there, that is where I bought mine: 0.9 is the one you need to get if you need one.

3. Check the coolant level in the radiator and not the overflow tank. It gets said everytime so it must be important. Others have just simply not had enough coolant. Of course OEM coolant is recommended, I'm sure a little 50/50 wont hurt.

Now after all that is done check the heat again, make sure the car has warmed up. If you still have no heat, then lets continue.

4. You can knock out two birds with one stone on this one. You can check the heater control valve itself and the thermostat. I did both in about 45min-1hr. Not a big deal, a new thermostat was only around $8 bucks at autozone or advanced auto, which ever your prefer. Honestly though, the thermostat did not help me, I wasnt overheating to begin with but it was suggested to check and it didnt hurt any. If you dont know where it is, follow your lower radiator hose into the block. It is not hard, there are a couple 10mm bolts to remove on the neck/housing your lower radiator hose is connected to, just make sure you have the right tools and something to catch coolant in b/c there will be plenty. I do not recommend the jug method...didnt work to well. Get an oil drain container from your local auto parts store and use that.
A. Heater control valve:
This item is controlled electronically to open and close thus allowing coolant to flow through to the heater core. Make sure the car is warm when testing this. The first method is to reverse the vacuum lines.
Obviously borrowed from two other threads, so its proven and it can work if this is your problem. Look in the picture and reverse the lines that it points to.
A. If this solves the problem, you have a bad heater control valve, you can order a new one or find one used on the boards here. Or leave it as is and just reverse the hoses in the summer so the A/C will work more efficiently
B. If you still do not have heat, you can manually open the valve. On the bottem there is a plunger, zip tie the plunger in the up position. If this solves the problem, you may still have a vacuum leak, bad hcv or possibly a short. The vacuum leak you can trace down, the hcv would get replaced even if method A. worked. If you believe it to be electrical, you might want to take it to a pro. So far as I know, no one has experienced an electrical problem or vacuum problem associated with heat...YET! If they do then, it will be me.
C. If you still have no heat......before you move on, you can by-pass the hcv all together. Just disconnect the coolant lines and run them together. You will need a male connector which you can get various places, just size up the hoses and buy the one that fits the best..thats obvious. I did this last night and now I have heat!
D. If you do not have heat after this.......lets move-on

5. Checking to see if your heater core is bad, plugged up, ect ect. This is lengthy...it is not for the faint of heart...it is not quick....
here is the link to that thread below:
https://www.clublexus.com/forums/sho...r+core+removal
you will also need this link:
https://www.clublexus.com/forums/sho...r+core+removal
more good threads:
https://www.clublexus.com/forums/sea...archid=1045132
https://www.clublexus.com/forums/sea...archid=1045142

I would like to ask if the mods could stick this...its not that uncommon. It should also alleviate any more heating threads. If I left anything out, please edit, I'am not a master heating lexus guru. I just had the same problem.

jgdynamics

iTrader: (16)

this is a really good thread man, goodluck, i still dont have heat either, ima try that plunger thing, thanks... i suggest stickying this as well.

yelloa3gti

nice write up.. used this to fix mine

morris

iTrader: (2)

Thats for no heat at all right?

It doesnt address the heat on one side and not the other issue correct?

sc3dreamz

that is correct, this is for no heat at all. Although, if you have heat on one side and not the other, I would have to lean towards one of the vent doors not opening.
Behind the radio, and glove box is where all the vents connect. It could be as simple as its blocked up, fell off, or the door on the actual vent is broken and closed.
When you start adjusting the heat control, there is a door that works on an actuator behnd the radio, actually there are three little doors back there that work on actuators. One could be not functioning correctily, one of the arms could have worked its way off, there are several little things it could be.
I would start with the side that is not getting any heat, check the vents and make sure it is open and just trace back from there.
Check the little things though before you go taking the cd player and all that mess out, it is not fun....its not hard but its just not fun. Working on older sc's is like surgery on geriatric's, you never know what else is going to break in the process.lol.

morris

iTrader: (2)

Quite a few of us are having an issue where we get cold air BLOWING out of one side of the car, while heat is blowing from the other side. This occurs even when both sides are set to the same temp like 85

jgdynamics

iTrader: (16)

well update, the plunger thing/ changing the hoses didnt work for me, but i felt all the hot water in the hoses... sooo whuts the problem?

sc3dreamz

you have pm. I know it sounds dumb but make sure your coolant levels are good.

O. L. T.

iTrader: (17)

https://www.clublexus.com/forums/performance-and-maintenance/71094-heater-blows-cold-even-on-manual-set.html

03 was a good year for info. Lot's of people from the old school then.

sc3dreamz

Yeah that was a pretty good thread, just none of that fixed my problem and I did all of it. I've had heat for 3 days now and doo-doo..doo-doo-doo..im lovin it!

HalfBaked

Sorry to bump old thread, was doing some searching and couldn't quite find an answer to my problem. I'm sure this is a n00bie question but I really don't know these cars as well.

In my 98 sc400 I started leaking coolant and after the leak got a bit worse I've lost heat. Even if I refill the coolant there is no heat and it still leaks. Is it the heater core itself? Or probably a hose connecting it? Also if its a hose is there a place I get a diagram to see what to replace and check.

Thanks.