Heating Problem

finest1 · November 15, 2010

hi all,

i wonder if you guys can help.

my car is the lexus gs300 sport MK1. this morning no hot air would come out or the heating system although i had the car running idle for 20 mins! i turned it up to 30 degrees, and it still blew out hot air. because of this it couldn't demist the windows which meant i couldn't drive it today.

any ideas as i need to trouble shoot this asap. the heating was working last week, but it was playing up a bit. it was working sunday , but not today.

thanks

finest1

TigerFish · November 15, 2010

There is a flow control valve in the bulk head (pretty much in line with the back end of the engine). Check that the cable hasn't come adrift or loose. Is the antifreeze up to scratch, maybe the heater matrix froze? Or possibly the matrix needs a flush which can be done by disconnecting the two hoses at the Bulk head and flushing with a hoze. If you do flush, be careful not to let water spill on top of the spark plug covers, as it can fill the plug wells with water and cause some serious misfiring.

finest1 · November 16, 2010

hi rick,

yes, coolant is one of those summer coolant/antifreeze liquid type products.

this bulkhead part, would i see it looking down on the engine or do i need to check it from underneath?

i take it behind part of the engine, you mean towards the windscreen. if you got a picture of a basic diagram i'll check it out. its blooming cold out there!!

thanks for your response

finest1

TigerFish · November 16, 2010

No, you can do it all from above. The only picture of mine I can find with the part in is one I did for the tps sensor. Ignore the big red arrow (that is the tps sensor). The flow control valve is circled in green, and you can see the operating cable in the pic.

Check the cable is still clipped on. As you adjust the temp inside the car, you can see the cable operating the valve. Just because it is moving the valve, doesn't neccesarily mean it is set correctly though. You can unclip the cable and move the valve manually to check the operation. i.e. disconnect the cable, put the interior fan on (once the car cooling system has warmed up of course) and operate the valve manually over different positions and check whether you get heat or not. If you establish you can get heat, put the interior temp up to max (so the cable moves to the max position) and then clip the cable back on with the valve in the max heat (from previous test) position. It should then work correctly again when you tirn the temp up and down.

If need be, you can flush the matrix by either undoing the pipes at that valve, or by following them to the bulkhead and disconnecting there. Like I mentioned, do be carefull not to p*ss water all over the top of the engine, as water down the plug wells is a pain to get to and dry out (don't ask me how I know ).