efseiler Posted January 8, 2015 Share Posted January 8, 2015 I have an '01 Forester with an EJ251 engine. Last night it got super-cold and although it started up fine this morning the cabin vents would blow cold even after the engine was completely warmed up. So I parked it and nervously waited thinking that an overheat was imminent due to the blockage. However, after waiting 15 mins. I started it up and the heat started working again. I'm thinking that the thermostat got stuck due possibly due to the cold but I really don't know how it works in those vehicles. Can anyone give me a clue? Thanks! --Damien Quote Link to comment Share on other sites More sharing options...
mikaleda Posted January 9, 2015 Share Posted January 9, 2015 Its possible that it just stuck cause of the cold. I would just keep an eye on the tempature gauge just in case though Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted January 9, 2015 Share Posted January 9, 2015 Low coolant level would be my first guess. Double check that in the morning before you start it. Quote Link to comment Share on other sites More sharing options...
jp98 Posted January 9, 2015 Share Posted January 9, 2015 I agree with low coolant or a air lock in the heater hoses. If it was the thermostat you would of seen a overheat or very little movement of the temperature gauge Quote Link to comment Share on other sites More sharing options...
lmdew Posted January 9, 2015 Share Posted January 9, 2015 Have your anti freeze checked to make sure it will handle the cold temps. 3 Quote Link to comment Share on other sites More sharing options...
efseiler Posted January 10, 2015 Author Share Posted January 10, 2015 Another symptom was the fan was running even tho it was sub-zero temps outside but the temp gauge was not high. I'm guessing this one, too has the doomed headgasket, anyway. That's what you get for 2300 bucks! My brother bought it at auction thinking it was some sort of 'awesome deal' not knowing any better. I found this interesting theory after some digging----> http://www.subaruoutback.org/forums/88-head-gasket-issues/17264-no-subarus-dont-have-problems-their-headgaskets-print.html Quote Link to comment Share on other sites More sharing options...
mikaleda Posted January 10, 2015 Share Posted January 10, 2015 Wow that theory is totally wack. If that was true the 2.2l would have the same faikure rate as the 2.5l which is not the case. Also the coolant conditioner Subaru reccomemds is to prevent EXTERNAL head gasket leaks and has nothing to do with the heater core. Also your cooling fans kicking on at cold temps is not a sighn of head gasket failure. If you are worried about an internal leak do a block test, don't screw around with these unproven theorys. Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted January 10, 2015 Share Posted January 10, 2015 At least he understands the way the system works. His idea that the cooling system causes head gasket failures is out of line though. This type of cooling system design is intended to regulate coolant temp in a much more even manner and prevent head gasket problems. Most aluminum block/aluminum head engines these days use a cooling system design similar to this. In the days of old, the engine warms up the coolant and the thermostat opens for a little while until cool coolant from the radiator makes its way up through the block. Then the thermostat closes until the now cold coolant in the engine warms up to the operating temp of the thermostat. It opens again and the cycle repeats itself. Hot, cold, hot, cold, hot... Eventually, if you sit still long enough, the coolant temp levels out and the back and forth smooths out. But once you start driving the process starts all over again. The engine temp changes along with coolant temp. So the engine is also going back and forth heating and cooling, heating and cooling. The Subaru system eliminates this back and forth cycle by mixing hot coolant from the heater core with the incoming cold coolant from the radiator. The engine warms up to 170° quickly, and the thermostat opens slightly, just enough to maintain a steady temperature that will slowly and evenly continue to rise. Eventually the whole cooling system will warm to the same temperature, and the thermostat will be wide open at 190°F. When you start driving or the cooling fans turn on and air flow over the radiator cools the coolant coming into the engine, the thermostat closes slightly but the 190° operating temperature is maintained because of the coolant flow from the heater core. Another symptom was the fan was running even tho it was sub-zero temps outside but the temp gauge was not high. This indicates coolant temp at the sensor was above the fan turn on temp which is around 200°F. For the fans to turn off coolant temp must then drop below 194°F. This can be either due to low coolant level or in very cold weather can be a sign of a partially clogged heater core. I've also seen this caused by improper ratio of coolant to water, usually more than 60/40 coolant to water. 1 Quote Link to comment Share on other sites More sharing options...
efseiler Posted January 10, 2015 Author Share Posted January 10, 2015 Well I took it for a spin today. I noticed that the coolant level was low so I added some of that Radweld conditioner and topped it off. When I came back I inspected the OF tank and there no was no sign on bubbling at all nor any exhaust gas smell. Heater was working fine, too. So maybe I'm a lucky guy after all. There was some evidence of coolant leaking but it seemed to be coming from the top of the radiator nearest the cap. Maybe there's a small crack in there or something. I also noticed that one of the hoses to the fuel rod? was seeping gasoline so I tightened the screws on it. That may explain why the ECU was generating an EVAP code. Quote Link to comment Share on other sites More sharing options...
keith3267 Posted January 10, 2015 Share Posted January 10, 2015 Imdew had the best answer. You may need to have a mix a little richer than the typical 50/50, maybe go 60/40 or richer. I think one possibility is that the coolant in the heater hoses froze. I think it would have worked eventually whether you shut down or not. But there is one other possibility that has not been brought up yet and that is the blend door got stuck. This fits your scenario a little better as when you restarted the engine, the blend door cycled and worked the second time. There might have been a little moisture or condensation that froze around the blend door the first time it was supposed to cycle. Quote Link to comment Share on other sites More sharing options...
mikaleda Posted January 11, 2015 Share Posted January 11, 2015 (edited) You may need to have a mix a little richer than the typical 50/50, maybe go 60/40 or richer. I think one possibility is that the coolant in the heater hoses froze. I've also seen this caused by improper ratio of coolant to water, usually more than 60/40 coolant to water. At a 50/50 mix the coolant would have to see -34 to even start to gel Like fairtax said too much antifreeze could be causing the problem, and I would lean more twords that conclusion Edited January 11, 2015 by mikaleda Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted January 11, 2015 Share Posted January 11, 2015 (edited) Let me clarify. When you use more than 60/40 antifreeze to water, the antifreeze is less able to dissipate heat. Antifreeze has to be mixed with water so that it transfers heat more efficiently. Using 100% antifreeze will cause overheating because the antifreeze can't get rid of heat fast enough. In the range between 60/40 and 40/60 the heat dissipation really isn't affected enough to matter for most engines. Mixing 70/30 antifreeze to water WILL cause the engine to run hotter than normal, and could possibly cause the fans to come on, then not be able to turn off because the coolant temp will not go back below the fan cut-off temp. Edited January 11, 2015 by Fairtax4me 1 Quote Link to comment Share on other sites More sharing options...
keith3267 Posted January 11, 2015 Share Posted January 11, 2015 When ever I change the coolant in any of my vehicles, I always use a 2:1 mix antifreeze:distilled water and have never had a problem with overheating, even when pulling the grade out of Death Valley into California when it was 126°F at the ranger station in Furnace Creek and running the AC. I agree with over 70% being bad, I would not do that, but even the undiluted antifreeze has about 4% water in it, going up to 70% as measured by mixing the antifreeze and water myself ( and not by lab analysis) would be OK. If I was mixing in a lab where the concentration could be definitively determined by analysis, I would not exceed 67%. Quote Link to comment Share on other sites More sharing options...
efseiler Posted January 11, 2015 Author Share Posted January 11, 2015 Let me clarify. When you use more than 60/40 antifreeze to water, the antifreeze is less able to dissipate heat. Antifreeze has to be mixed with water so that it transfers heat more efficiently. Using 100% antifreeze will cause overheating because the antifreeze can't get rid of heat fast enough. In the range between 60/40 and 40/60 the heat dissipation really isn't affected enough to matter for most engines. Mixing 70/30 antifreeze to water WILL cause the engine to run hotter than normal, and could possibly cause the fans to come on, then not be able to turn off because the coolant temp will not go back below the fan cut-off temp. Well, water does have a high heat capacity but that doesn't necessairily make it a better heat dissipator. I checked again today and the tank was bubbling away so I don't know. That car does many things but at least overheating isn't one of them. I have to drive it cuz I'm an official Subaru test mule! Cheers! --Damien Quote Link to comment Share on other sites More sharing options...
mikaleda Posted January 11, 2015 Share Posted January 11, 2015 (edited) Well, water does have a high heat capacity but that doesn't necessairily make it a better heat dissipator. Antifreeze is made to be mixed 50/50, or at least close to that mixture.50/50 is the optimal mixture for freeze/boiling pritection without compromising flow. At a thicker than 60% mixture the antifreeze will gel at tempatures that are below freezeing, technically it has a lower freezing temp and higher boiling temp but it is to thick to flow properly Edited January 11, 2015 by mikaleda Quote Link to comment Share on other sites More sharing options...
keith3267 Posted January 12, 2015 Share Posted January 12, 2015 I've never had a flow problem at 2:1. The 2:1 ratio is used in Alaska all the time at temps below -50F and they don't have any flow problems. Until you reach the freeze point for the mix, the viscosity of antifreeze is not significantly different than for water. Quote Link to comment Share on other sites More sharing options...
mikaleda Posted January 12, 2015 Share Posted January 12, 2015 I've never had a flow problem at 2:1. The 2:1 ratio is used in Alaska all the time at temps below -50F and they don't have any flow problems. Until you reach the freeze point for the mix, the viscosity of antifreeze is not significantly different than for water.I have seen on service pro antifreez that 50/50 is recommended and 2:1 is the maximum recomened mixture rate At 2:1 you would probably be fine, but unless your seeing below -30 or above 120 degrees anything over a 50/50 mixture is unnecisary Quote Link to comment Share on other sites More sharing options...
keith3267 Posted January 13, 2015 Share Posted January 13, 2015 You get more corrosion protection at 2:1, but that only counts if you forget to change it at 5 years, which I have on occasion. 1 Quote Link to comment Share on other sites More sharing options...
efseiler Posted January 14, 2015 Author Share Posted January 14, 2015 Well last night it got super-cold again. When I started my Forester up it basically repeated the same behavior. Warmed up quickly...but it took some time before there was heat in the cabin. There was no sign of any frozen coolant even though the temps got down to -20 F. Is there any flow to the heater core when the thermostat is shut? Quote Link to comment Share on other sites More sharing options...
keith3267 Posted January 15, 2015 Share Posted January 15, 2015 In older designs, coolant flowed through the heater core if the heater control valve was open, it bypassed the thermostat. There are several designs in use today including some that use two thermostats and the heater core is used to help keep the engine temperature more even. These do not have a heater control valve and the coolant always flows through the heater core. Blend doors under the dash in the hvac ducts control the heat and cold. I'm am kinda suspecting that the blend doors may be getting frozen and I'm not sure there is much you can do about that. If by very cold, you mean -30F or lower, you may need to add a little pure antifreeze to your system. Have you tested it yet for concentration? Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted January 15, 2015 Share Posted January 15, 2015 Well last night it got super-cold again. When I started my Forester up it basically repeated the same behavior. Warmed up quickly...but it took some time before there was heat in the cabin. There was no sign of any frozen coolant even though the temps got down to -20 F. Is there any flow to the heater core when the thermostat is shut? Subarus run full flow through the heater core no matter if the thermostat is open or closed. Either the coolant level in the block is low, or the heater core is partially blocked. Quote Link to comment Share on other sites More sharing options...
efseiler Posted January 15, 2015 Author Share Posted January 15, 2015 Well my theory was that when it's super-cold like that it takes a while for the thermostat to open and allow the coolant to flow more freely. I visually inspected the coolant and there was no sign of any ice crystals so I figured freezing was not the issue. I think the mixture is closer to 60/40. I just want to make sure I'm not missing something obvious or doing something stupid. Quote Link to comment Share on other sites More sharing options...
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