dtob

Problem finally sovled. The car was in the shop to have the starter replaced so I had them flush the cooling system (among other things) and that got the air pocket out so I now have heat when idling. I was unable to resolve it using the method that others have suggested with running the motor with that cap off.

My issue is that I did run the car at 2500 RPM for 5 with the heat on MAX and topped it off to the fill line and still have the issue. Are you recommending I try it again? I thought for sure it would fix the issue given everyone else's success, but no dice for me. I wonder if draining it as you did would help.

I initially posted to this topic in Jan '09 with my '97 LS400 not blowing heat at idle. I tried to test the issue by first putting the heat to MAX but that didn't change anything. I then tried the simple approach to topping off, but it didn't need much and that didn't fix it. Last weekend i finally got around to topping off the correct way as described in this topic and on top of the reservoir, but I don't know where that 17mm bolt is and if it is necessary to fixing the issue. Anyway, that didn't fix it either, but did create one additional question. The directions on the reservoir say something like 'fill up to the bottom of the neck' but that is almost an inch higher than the FILL line on the side of the tank. I stopped at the FILL line, should I have gone higher? If not, should I move on to the thermostat, then the heater valve as described in another post or does anyone else have another suggestions before i get into that??

I just found this post. I too have a 96 LS400 with the same cold air blowing issue and wondered if the original poster fixed their problem - was it an vapor lock or sensor issue. I'm going to test tomorrow by setting my temp to MAX. I think I've done that in the past though, so I may be looking at a vapor lock.