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Heaters Blowing Warmish Air


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Recently had my thermostat changed as the heaters were blowing coldish air,

but this has not resloved the problem.

The car temp will warm up as normal and the fan kicks in, there is no airlock

in the system.

The radiator has been flushed several of times incase of a blockage,

all pipes are warm and firm.

There is no leaks or drips from the water pump. The car does not seem to loose water.

When the car is started from cold it makes a gurgling sound for a few seconds behind the centre consle,

as if there is water being poured.

Also the driver side heaters are blowing much warmer air compared to the passenger side.

Seem's that the water is not circulating properly or there is a problem within the heater matrix??

Any feedback would be appreciated


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sounds like you have an airlock - not worked on the lex cooling system but sometimes removing the thermostat and doing a reverse flush will clear any phsical blockages - airlocks are usually resolved with bleed screws or worst case scenario parking the car facing up a really steep hill and running it on tickover with the rad cap off so any air trapped in the system rises to the highest point ie the open cap and leaves the system - i would get it checked properly though or take it back and ask them to bleed the system again

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This has been done, parked on a steep hill facing up left the heaters on full/hot kept the water topped and ran it for several minuets, have not heard the gurgling noise yet seem's fine

Driver side heater's are fine, but passenger side is still blowing coldish air regardless of

the setting (feet/windscreen)

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this is funny you should mention this when i had my 200 i had a similar problem whereby when i had the air con on the passangers side would blow cold air as it should and the drivers side would blow warmish air out (as if the air con wasnt working) i had the air con system checked and there was no problem with it

the problem was ongoing for over a year and never found the problem

incidently the center vents which look like two seperate vents are actually one and went i undid the vent and put my hand in one side of it was cold and the other warm yet it was the same physical vent

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Had a deep look into this problem and the heater matrix is blocked,

the water is not circulating through it as it should.

The whole dashboard has to come off to replace this,

so im going to leave it for a while (until winter!)

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i would reverse flush it before ripping all the dash out mate - theory is that your water only circulates in one direction in your system as pumped by your waterpump, if you stick some radflush stuff in the system then after a day or so remove your thermostat so nothing impedes the flow of water and insert a hose into a removed radiator top pipe for example and force water the other way to normal thru the system and out the open orifice ( cos you have a pipe off) you will remove a lot of crud from the system - i have done this with a number of cars in the past with great and surprising results ( large lumps of stuff coming out) - it is quite simple to wrap a cloth round a hosepipe and stuff it in a hole - afterwards refit thermostat and antifreeze etc - much easier then removing dash and high chance of success in my opinion - please take advice from your mechanic as to my advice

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Agreed lexynik

Did put some radflush in and drove it for a few hours after i drained it out and put a hose pipe in the rad and took off the pipe on the other side, but did not cure the problem

The method that you have given i have not tried this with the thermo out, so this may do the trick'

and yes it will be much easier than to take the dash out

Will give this a go next week and see the result

Thanks for the advice...

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its worth a try mr leki - from the sound of it you succesfully flushed your rad but thats not where your blockage is - did any crud come out when you did that ? did it have antifreeze in it when you got it ? and if so what colour was it ?

remember REVERSE flush works best when going the opposite direction to normal so you will need to work out which way the water circulates for best results

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It is the heater matrix, i had the same problem on my 300 (detailed somewhere in an earlier thread) what i did was take off the two hoses where they join the heater matrix, under bonnet just in front of baulkhead on drivers side. I had bought a meter of new pipe that i cut in two and connected one to each side, i then poured radflush in and left it for an hour or so, if you keep the new hoses up high you can fill the matrix right up.

Then remove hoses and flush with hosepipe in reverse direction this washed loads of crap out. flushed both ways then reconected hoses turned heater on full and topped up water with engine running until termostat opened and all air was gone.

Result heating back on passenger side, total time about one hour work one hour while flush works just be delicate removing /replaceing hoses as the matrix is aluminium.



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Did not see any crud come out, water was brownish not sure of the antifreeze,

i presume the car was parked for a while

Will try both methods given by yourself and russell-H

Thanks will let you know of the result...

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Gave it a go this morning

Took off the two pipes on the left of the engine bay, got my hose pipe and directly

forced water into the top pipe then the bottom.

Amazed at the brownish water and gunk that came out, then blocked the

two pipes and took off my rad pipe and fed water through,

again gunk and brownish water

Connected the pipes back up and ran the car until it was warm

Then repeated this a few times until the water was completely clear

Also just to make the job thorough i removed the thermo and done the same

Put in a new pollen filter as the previous was heavily blocked

Refited the thermo/antifreeze and blead the system,

and RESULT the heaters are working (HOT) as they should equally

around the car

Thank you for the help and advice, this has saved me an awful lot work

(taking the dash out!)

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  • 3 months later...

Hi guys,

Nice thread, I'm hoping reverse flushing will help to resolve my heating issue.

My heaters dont work at all, either side. They blow fine and I've checked that all vents blow correctly.

Have checked the rad and that was a little low, so i topped it while on a hill and no air bubbles.

Just wanted to check i found the correct two hoses i need to remove to flush the heater matrix.


Are they the right ones?

If so do I need to take them off where the arrow points? Do i flush the side that is in the engine bay, or the other side - inside the car?

Any help appreciated.


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Im not 100 percent if they are the right hoses,, they do look like the right kind of thing tho - someone else will post up to confirm im sure - ideally flush both sides - if you have no warmth then your problem lies in the heater matrix which is inside the car (essentially a mini radiator) - so flush a hose in each way to be sure its reversed at some stage - ideally chuck a bottle of radflush or similar in the expansion bottle a couple of days before you fluch to loosen it all up a bit inside - you can use hosepipes to extend the pipes out and over the side of the car to save getting dirty water over everything - and dont forget once it all flushes clean,,youll know when,, to REFILL WITH CORRECT STRENGTH ANTIFREEZE- As winter is on its way

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Looks like this is becoming a fairly common problem and now I'm glad that its a fairly easy fix so I'll be getting onto this as soon as possible so the left side of my car can be nice and warm as well. I need to flush my rad anyway so killing 2 birds with one stone I suppose by clearing the whole system including the matrix. Wheres the thermostat by the way and why do you need to remove that to help with the flush?

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Wheres the thermostat by the way and why do you need to remove that to help with the flush?

Basically, while engine is cold (when you would be doing a flush) the thermostat would be closed and would prevent the coolant from circulating and flushing properly.

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Just wanted to post back an update.

I flushed matrix in both directions.

Used a whole bottle of Rad flush and left it to soak in matrix for about half an hour.

While that soaked, flushed rest of cooling system.

Connected back up, topped up with antifreeze and water.

Heaters working again!

So chuffed, this has saved me freezing all winter and possibly hundreds of pounds to get a garage to look into the issue!

Very happy Lexus owner :D

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Good to hear Rob.

As you know i had this problem a few months back, now unfortunatly the heater matrix is leaking. :crybaby:

Its building thick steam on the windscreen, loss of water, coldish air and a strong radiator smell.

Radweld & K-seal has been used but has not cured the problem.

Only way round is to take the dash off and replace it for a guaranteed fix.

Have not ordered the part yet,

still looking into more information on the best way to remove the dash but have not come across anything yet.

Will need a rough guide to assist me to make life easier, as it is a tricky job...

Heated seat is my only friend in the is200 now.... :unsure:

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Oh no....dont tell me that. I'll be paranoid that will happen to me too!

Doesn't sound good for you though. You got a mission ahead of you to take the dash out!

Thats exactly what i wanted to avoid!

Ive only ever had the clocks & AC Unit/stero out of mine. So i cant help you im afraid.

Good luck, let us know how you get on!

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