Gumart1 Posted December 18, 2012 Share Posted December 18, 2012 Hi all, it's been a long while since I've been back here, and it's good to see some familiar names and great threads. My '98 LS just turned 336k miles and is still a champ. I've had a recurrent problem where there is no heat at idle even when the engine is warmed up. The temp gauge seems accurate and the car warms to temp without issue. I don't believe it is a thermostat issue at all. I bypassed the heater control valve by removing it but the problem persisted. The reservoir always stays full. Some would say heater core, BUT: I found that there was a huge amount of air in the system, and every year, I use a very long funnel with coolant at the water inlet and run the car for 15 min. and a few minutes at 2-3k rpm and this burps out the air. It works! This seemed to hold for a season, but this year it lasted just a month. How in the world do I find how this large amount of air is getting in the system, and how do I fix it for good? Quote Link to comment Share on other sites More sharing options...
landar Posted December 19, 2012 Share Posted December 19, 2012 You might try replacing the reservoir cap. Sometimes they go bad and do not hold the proper pressure on the system. Quote Link to comment Share on other sites More sharing options...
curiousB Posted December 19, 2012 Share Posted December 19, 2012 Maybe its the air handler box under the dash. Perhaps the core is getting hot but the air is being blocked from flowing over it. Is the cabin air filter plugged with dirt and grime? Is the fan not running or running at too slow a speed? Are the air dampers or related servos stuck closed? Quote Link to comment Share on other sites More sharing options...
Gumart1 Posted December 20, 2012 Author Share Posted December 20, 2012 Thanks for the ideas. The reservoir cap was replaced and definitely holds pressure as I found out during my impatience with no letting the car cool down before opening. Cabin filter is always replaced each year and my air flow is terrific at any speed. I think there is something related to the fact that after I bleed the system (and visibly watch large bubbles escape), it has great heat for weeks or months straight before the problem returns. Quote Link to comment Share on other sites More sharing options...
landar Posted December 20, 2012 Share Posted December 20, 2012 Your car has a lot of miles for any brand (336k miles) and perhaps something is not properly sealing in the cooling system. It sounds like you have covered all of the obvious bases. If air is getting into the system, coolant would have to be displaced. Are you losing any coolant at all? Have you checked for combustion gases in the coolant? Quote Link to comment Share on other sites More sharing options...
curiousB Posted December 20, 2012 Share Posted December 20, 2012 If you are constantly topping up coolant that is a sign of a leak. As rated in (good/better/best) scenarios: Lucky: a leaky hose, easy fix Not so lucky: a worn water pump (seal leaking), fairly costly but might still be worth it Bad news bears: Blown head gasket (coolant leaking into cylinder), forget about it, time to get a new car Quote Link to comment Share on other sites More sharing options...
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