marrap834 Posted February 7, 2007 Share Posted February 7, 2007 I've been having a probem with my car now for a couple weeks where my car overheats when I slow down or stop, then starts to blow out cold air, while the temp gauge goes up in the hot zone until I start moving fast or rev the engine quite a bit. I changed the thermostat, and checked the antifreeze level already so thats not the problem. Also, just recently my check engine light came on with an error for the knock sensor. Are any of these things related? I need help I'm really frusterated with the problem. Any info would be greatly appreciated. Link to comment Share on other sites More sharing options...
Manarius Posted February 7, 2007 Share Posted February 7, 2007 Worn out water pump? Blockage in the system? Link to comment Share on other sites More sharing options...
ScoobieRoo Posted February 7, 2007 Share Posted February 7, 2007 Headgasket? Heater Core? Link to comment Share on other sites More sharing options...
nipper Posted February 7, 2007 Share Posted February 7, 2007 So you recently changed the t-stat. Did you get all the air out of the cooling system. Did you use a subaru T-stat. Have you changed the radiator cap. If yes, you need to take the cap off and let the car run. Can you see bubbles? If not wait for the t-stat to open, the car will burp and spit up a bit. Top off the raditor and look for bubbles. Since th car over heats with a loss of heat, have someone watch the temp gauge for you. If the temp gauge still spikes, or you have bubbles, you have a blown Head gasket. nipper Link to comment Share on other sites More sharing options...
marrap834 Posted February 7, 2007 Author Share Posted February 7, 2007 I don't know... All i know is that as long as my foot is on the gas and a decent speed, there is no problem. It only starts overheating and blowing out the cold air as soon as i come to a stop or slow down enough. And as far as the knock sensor thing I'm not sure if that would have anything to do with it or not? Link to comment Share on other sites More sharing options...
marrap834 Posted February 7, 2007 Author Share Posted February 7, 2007 I'm not sure what T-state it was ... I went to advanced auto and told them my make and model and they gave me one. The cap hasnt been replaced yet Link to comment Share on other sites More sharing options...
marrap834 Posted February 7, 2007 Author Share Posted February 7, 2007 As far as getting all the air out of the system... what is the best method for doing that...I thought I did by taking off the bleeder cap on the top of the radiator and waited for the antifreeze to come out then replaced. Link to comment Share on other sites More sharing options...
ccrinc Posted February 7, 2007 Share Posted February 7, 2007 Check to see if your fans are working when you're at a stop. Emily http://www.ccrengines.com Link to comment Share on other sites More sharing options...
nipper Posted February 7, 2007 Share Posted February 7, 2007 OK we need to back up. There are very few parts in a subaru that should come from subaru, the Thermostat (Tstat) is one of them. The others are the Head gasket, the front o2 sensor and the timing belt. First thing is to replace that Tstat. I get the air out the old fashiones way, by letting the car run with the cap off for 15 minutes, and constantly topping off the radiator, and in 5 subarus never had a problem. The way you should do it is by having the car on ramps to do the same thing. The knock sensor can affect performance, may even make the car run hot, but only one thing kills the heat, and thats air in the cooling system. That air can come from trapped air or a bad head gasket. Air in the cooling system from filling the cooling system wrong can blow a HG also. nipper Link to comment Share on other sites More sharing options...
ScoobySchmitty Posted February 7, 2007 Share Posted February 7, 2007 Had this problem on my 91 Legacy before I fire-sold it. Ran it for 15 minutes one day, hoping to get the air bubbles out, but it was still throwing bubbles out of the top of the cap. I should have really pushed to get the money to fix it, I regret ever selling my poor old Roo. Get that baby fixed, she deserves it! Link to comment Share on other sites More sharing options...
WAWalker Posted February 7, 2007 Share Posted February 7, 2007 All I have ever done for the last 10 years to bleed a Subaru cooling system is...............remove air bleed screw, fill through radiator till full, replace bleed screw and rad cap. Start engine, stop engine, top off radiator, Start engine, test drive, allow to cool, top off. Buy filling with bleed screw out there has NEVER been enough air left in cooling system to cause a problem, in my experiance. You have other problems. Knowing the 2.5L DOHC as I do, I would recommend you have the cooling system checked for the persence of hydrocarbons (by someone who knows Subarus), in order to confirm or rule out head gaskets. Get to the bottom of the problem before you destroy the engine. A bad t-stat will not cause a loss of heat. Unless it is stuck open, in which case you would have an over heating problem. But you should use an OEM t-stat all the same. Loss of heat is a coolant flow problem in the engine. In rare cases this could be caused by a bad water pump, or glazed timing belt slipping on water pump pully. It can be caused by low coolant level (which you say you have ruled out). It can be caused by air in cooling system (which you seemed to have ruled out). It can be caused by combustion gases in the cooling system. Link to comment Share on other sites More sharing options...
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