Camelwagon Posted September 12, 2005 Share Posted September 12, 2005 I took off the radiator cap and started my Suby and let it run and in about 1 minute the coolant started rising and overflowing out of the rad, is this normal?? Shouldn't it go into the overflow container? Thanks. Quote Link to comment Share on other sites More sharing options...
Petersubaru Posted September 12, 2005 Share Posted September 12, 2005 that is normal..put the cap back on and then it goes into overflow container... I took off the radiator cap and started my Suby and let it run and in about 1 minute the coolant started rising and overflowing out of the rad, is this normal?? Shouldn't it go into the overflow container? Thanks. Quote Link to comment Share on other sites More sharing options...
MorganM Posted September 12, 2005 Share Posted September 12, 2005 Radiator cap will hold back that pressure. Should only bleed off to the overflow when the pressure exceeds what the cap is rated for. Top off your coolant now from whatever spilled out Quote Link to comment Share on other sites More sharing options...
Camelwagon Posted September 12, 2005 Author Share Posted September 12, 2005 Cool, thats what I thought. This other guy was telling me that it was from bubbles in the system. but i didnt see any bubbles coming up or anything. Thanks. Quote Link to comment Share on other sites More sharing options...
Camelwagon Posted September 12, 2005 Author Share Posted September 12, 2005 OK this is what my friend says about rad caps and pressure... and i quote. "With the cap off, there is no backpressure created by rising water tempurature. What you have is like a bucket of water jumping out of the bucket. You have convulsions brought about by HOT AIR BUBBLES in areas where water is supposed to be. The overflow is air escaping when it comes to the top. It pushes the water ahead of it out of the way. 'Normal' overflowing only makes up the difference in water state at different temperatures. The size of the Overflow Container is designed to accomodate 'normal' overflow. When it exceeds that, there's another problem. And, no overflow occurs until pressure in the radiator exceeds 14-17 psi with the cap in place. When the cap is not in place, there's no backpressure at all. At least, normally. A properly operating system can run with the cap off and not spill a drop of water, if not run for long enough to exceed normal operating tempuratures. I can only suggest you study fluid dynamics." So what do you guys think of that? Not sure if I agree with him cuz when the engine is started cold, the coolant will rise and overflow cuz its building pressure and stuff, even though its not hot and not at normal operating temp. I dont know, i'm very confused. Quote Link to comment Share on other sites More sharing options...
zyewdall Posted September 12, 2005 Share Posted September 12, 2005 A properly operating system can run with the cap off and not spill a drop of water, if not run for long enough to exceed normal operating tempuratures. I am not sure that this is true for newer cars. Back in the 60's the radiator cap was always higher than the highest part of the engine/heating system, so if it was in an unpressurized state, it couldn't get out. They had a level indicator in the radiator neck sometimes because you weren't even supposed to fill all the way up to the cap. But when the radiator is lowered to give a lower hoodline, I think it may get low enough that it gets below other components in the system and can escape if you take the cap off -- even if it's not escaping just sitting there, the movement and flow head caused by pumping it could cause it to come out. If you look carefully, I think the "full" line on the overflow container might is higher than the radiator cap. Also, because the radiator isn't higher than the engine any more, you are more likely to get bubbles in the system too. I am not sure whether any of this applies to an '85 subaru though, or if it still has the radiator high enough to function like the old systems... Quote Link to comment Share on other sites More sharing options...
Bobby_boucher Posted September 12, 2005 Share Posted September 12, 2005 Im not sure you friends statment is completly true but let me make a couple of calls right quick and find out. Quote Link to comment Share on other sites More sharing options...
Bobby_boucher Posted September 12, 2005 Share Posted September 12, 2005 I asked a couple of diffrent mechanic buddies of mine and all of them said that thats very irregular and all 3 said it was most likley a headgasket blown. Quote Link to comment Share on other sites More sharing options...
azsubaru Posted September 13, 2005 Share Posted September 13, 2005 If it's normal for a radiator to not overflow with the cap off, even as it heats up, where is that extra volume of water going? Seems to me that water expands as it heats up and would easily overflow if not held in by pressure from the radiator cap. That's where the pressure comes from. Quote Link to comment Share on other sites More sharing options...
Bobby_boucher Posted September 13, 2005 Share Posted September 13, 2005 Sorry i should have mentioned, if its cold and you have the cap off when you start it and it over flows, they said somthing about the compression from the motor seeping through the head gasket??? Quote Link to comment Share on other sites More sharing options...
Camelwagon Posted September 13, 2005 Author Share Posted September 13, 2005 Ya I think I agree with you Zye. As for Bobby, hm not sure about headgasket, I'm not losing any coolant from the reservoir or the radiator, no white smoke... and if it was a headgasket, wouldnt the coolant be going down instead of overflowing since the engine would be burning it? Thanks guys. Quote Link to comment Share on other sites More sharing options...
subarubuddy Posted June 27, 2006 Share Posted June 27, 2006 Ya I think I agree with you Zye. As for Bobby, hm not sure about headgasket, I'm not losing any coolant from the reservoir or the radiator, no white smoke... and if it was a headgasket, wouldnt the coolant be going down instead of overflowing since the engine would be burning it? Thanks guys. i know this thread is from months ago, but i have the same deal where you start the car (cold) and the coolant slowly rises and overflows if you run it with no cap - takes about 30 seconds to a minute. i don't think its head gaskets because i'm not losing any coolant with the cap on, or any oil---i usually only have to add 1 quart between oil changes (3000-4000 miles). no smoke or anything and no overheating. although it does seem to run hot on the highway, but not quite in the red , and then go back down to normal--i'm thinking the tstat or clogged radiator on that one though. and i checked the compression today and this is what i got: 1--170. 2--175. 3--180. 4--175. seems good to me. oh yeah, its a 92 loyale 5speed i'm talking about here. Quote Link to comment Share on other sites More sharing options...
Petersubaru Posted June 27, 2006 Share Posted June 27, 2006 in my case the thermostate was not opening up until the last moment (hitting the red line)and then it would suddenly open..later I found out that the thermostate was not the one for a subaru...It was missing the "little wiggly" that lets the air out if the system ...if your thermostate has the wiggly on it, try running it without the thermo. and see what happens..if it runs cooler then it is thermostate related...a broken or wrong thermo i know this thread is from months ago, but i have the same deal where you start the car (cold) and the coolant slowly rises and overflows if you run it with no cap - takes about 30 seconds to a minute. i don't think its head gaskets because i'm not losing any coolant with the cap on, or any oil---i usually only have to add 1 quart between oil changes (3000-4000 miles). no smoke or anything and no overheating. although it does seem to run hot on the highway, but not quite in the red , and then go back down to normal--i'm thinking the tstat or clogged radiator on that one though. and i checked the compression today and this is what i got: 1--170. 2--175. 3--180. 4--175. seems good to me. oh yeah, its a 92 loyale 5speed i'm talking about here. Quote Link to comment Share on other sites More sharing options...
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