Guest bastaad525 Posted April 18, 2004 Share Posted April 18, 2004 Well I just waded thru months and months of posts on this subject with our friendly neighborhood search function and came away more confused than anything Was hoping to open the can of worms anew and get some better perspective on this. I've been trying a little 'experiment' lately. I figured out one day that if I open the radiator cap when the coolant is hot and let out all the excess pressure, and make it a point to ONLY open the cap when the motor is hot, that there will be NO pressure in the system, ever. No hiss of escaping air, no coolant bubbling out of the top. And of course, if I then try to open the radiator when cold, there is a loud pop as the vacuum pressure of the colder coolant is released. Now, I'm wondering, is this the better way to have it running? I mean with having no pressure built up in the system when hot? I have really come up with two opposing answers to this question. 1. that having no pressure in the system is BETTER, in that it prolongs the life of the radiator, hoses, etc, and keeps high pressure from creating leaks. However, I have not found ANY info that suggests this helps the system to cool better or to cool worse 2. that having high pressure is BETTER because it lowers the boiling point of the water. I'm assuming this will cause the water to remain cooler or increase cooling effectiveness? I know I like being able to open the radiator when hot and have no fear of anything pouring out or getting all over the place, and I like the idea of hoses lasting longer, as I've had a really bad histroy with all my Z's of hoses blowing ALL THE DAMN TIME. But, I'm also having a bit of trouble with my car running warmer than I would like (around 200-210* on a warm day in traffic) so I'd rather have it in a way that it was cooling more effectively. Also, has anyone used redline water wetter and does it really help keep temps down? And how much difference does running 50/50 coolant mixture make versus, say, 30% coolant to water? Quote Link to comment Share on other sites More sharing options...
80LS1T Posted April 18, 2004 Share Posted April 18, 2004 The pressure that you are refering too is caused by the coolant "instantly boiling" once you take off the radiator cap. Say the cap is a 15lbs cap, that means that water will boil at 45* degrees hotter(3* for every 1lbs of pressure increase). So instead of 212* it would be 257*. Most cooling systems run right around 200* so once you take that cap off the boiling point of that coolant instanly drops 45* to 212*. Thats why all the coolant comes rushing out. Im not sure off what you mean by a vaccum sound when its cold? I have never noticed any noise when I have taken off a radiator cap when the engine was stone cold? I dont think they make a cap that holds 0psi? Besides that you dont want your boiling point of the coolant to be 212*. If you ran your cooling system with no pressure you would "boil over" all the time. Most engines should be run at about 200* for the best performance. Mine runs betweeen 180*(cruising) and 200*(traffic). Once you go above say 225* then you should start wondering whats wrong with your cooling system. Heck the fans on a new Dodge Minivan dont even turn on till 221*(I am a Dodge Technican). As for the mixture, most coolant bottle say what the protection range is for a certain mixture. Im not too sure on what a 70/30 mixture will do for a heat range? Hope that helps some! Guy Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 18, 2004 Share Posted April 18, 2004 About the vacuum/popping sound, what I'm saying is... okay I open the cap when the coolant is HOT. The first time I do this of course there is pressure there and some air and coolant escapes.This releases all the excess pressure at the hot temp. Now, any time I open it HOT after that, there will NO sign at all of boiling or anything, no pressure will come out when I open the cap hot. However, of course the air 'shrinks' when the system is once again cold, and since there was very low or maybe even ZERO pressure left when I open it hot and then close it (still hot) and the air shrinks, there is then actually vacuum or suction force inside the radiator after that, so as soon as I open the radiator when cold, the cap is kind of hard to remove, stuck, and then with one good pull it comes off with a popping sound. i've been driving it this way for a while, and though i can't say I notice any increase in the cooling ability of the system, I do like the idea of low pressure in there and longer living hoses. I haven't had a problem with boiling over, running it like this. However, I think after reading your post that I'll run it the other way. That is to say, I'll open it when cold to set the 'cold pressure' to 0, and that way there will be 'normal' pressure in the system when it's hot. Quote Link to comment Share on other sites More sharing options...
80LS1T Posted April 19, 2004 Share Posted April 19, 2004 Your system is not running with out pressure in it if you open your cap when its hot and then put it back on. The pressure will build again. If you wait long enough that same pressure will be back. If you take off the cap and "release" the pressure and then put it back on and then take it back off right away, there will be no pressure right away. However if you leave it with the cap on and let the system build pressure again it will do the same thing. The pressure is caused by the coolant reaching is boiling point. So once it gets back up to 250*+ that pressure will be there again. Hope that explains it a little further! Guy Quote Link to comment Share on other sites More sharing options...
Dan Juday Posted April 19, 2004 Share Posted April 19, 2004 The reason you want pressure in your system is to raise the boiling point of the water, just like Guy said. You don't want the water in your motor to boil. Steam will not transfer the heat from the motor to the coolant like water will. You will get hot spots in your motor where the steam collects and your water pump won't pump steam so when the steam pocket gets to the pump no more flow, bad, very bad. Also, take a look at the bottom of your cap. There is a check valve there to let coolant back into your system from the overflow tank when your engine cools off and the pressure drops to less than atmospheric. This is why you want an overflow tank in the first place. Without one, or if it runs dry, the system will suck air in when the pressure drops. As far as the antifreeze mix 70/30 water/antifreeze is fine FOR CALIFORNIA ONLY. The antifreeze is there to lower the freezing point of the water so that when the temperature drops below 32F the water doesn't turn to ice, expand, and crack your block. We don't see those temps very often and a 70/30 mix should work fine all the way to about +10F I've heard good things about the Redline water wetter. It doesn't cost that much and if it lowers your water temp it's well worth it. I've never had a high temp problem so I've never used it myself. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted April 22, 2004 Share Posted April 22, 2004 To expand on what Dan said, you need a new radiator cap. The cap should act as a check valve to allow air back into the radiator as it cools. Just as importantly, it acts as a pressure regulator to keep it at the right pressure. Blowing hoses could mean excess pressure. Buy a new cap every few years. Antifreeze does more than just keep the water from freezing. It also prevents corrosion of the aluminum parts and most importantly (for a Z) it acts as a lubricant for the water pump. A corroded engine will do more to reduce the effectiveness of the cooling system than water wetter ever could so never run an engine without the proper amount of antifreeze. Also water expands as it heats up, even if it is well below the boiling temp. Thus once you take the cap off a hot engine, the only way pressure will build back up is if it gets even hotter. With a properly functioning cap the entire cooling system should be completely full of liquid with no air or steam. Steam doesn't transfer heat as well as liquid water. So like Dan says without the pressure from the cap, you run the risk of forming small steam pockets in the hottest parts of the engine. This makes those hot spots even hotter. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 23, 2004 Share Posted April 23, 2004 I just bought a new radiator cap about 3 weeks ago, didn't help at all. I better mention that I"m not running an overflow tank, if that makes any difference. The other day I did as Tim240z suggested again, to try to bleed any air pockets from the system. I jacked up the front of the car, topped off the radiator to overflowing, PUT THE CAP BACK ON (in caps because I"m still not sure if I'm supposed to do that or run it with the cap off), and ran the car to normal operating temp, then allowed it to cool off completely (overnight) before lowering the front. I then opened the cap and the level seemed to have gone down a bit. Now, another question... I always thought that if you weren't running an overflow tank that you didn't want to fill the radiator all the way, right? It should be about an inch or so lower than the full line right? I didn't know if I should top it off again after it cooled off. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted April 23, 2004 Share Posted April 23, 2004 Well, like Dan said, without an overflow tank the radiator will suck in air as it cools. So you can fill it to the top and after on heat up and cool down cycle it will be an inch or so lower. That is how much the water expanded as it heated up. That is why an overflow tank is such a good idea. It keeps the raditor completely full of liquid. Check the overflow tube coming off the top of the radiator where the cap installs. Make sure that is not blocked, because that is the path air takes coming back into the radiator. It is odd that the system will suck air back in after cooling, but maybe it is only a small amount and not worth worrying about. Are you sure you got the right sized cap? Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 23, 2004 Share Posted April 23, 2004 Pop-n-Wood pretty much covered it. The rad cap is a relief and reentry point to compensate for normal expansion and contraction. It should not go under a vacuum, it should allow air back into the system, or those littel capillary tubes in your radiator's core will suck down and collapse. They are very good at containing pressure, but NOT designed to operate under vacuum. I have some experience with collapsing them when I lived back east and had 90 degree+ diurnal variations and tried to outsmart the OEM in the radiator department....but I digress. My observations on Water Wetter: When I went to the ABQ convention one year with the 260, I consumed a gallon of coolant from "pukeover" after hot shutdown (no recovery tank). The next year on my trip to Canada's convention (roughly twice the mileage) I took two gallons of 50/50 mix w/ waterwetter in the car and refill. In 12,000 miles of hard driving I didn't use a DROP of coolant. ABSOLUTELY NO pukeover after hot shutdown. What I noticed with the system before (same cap, same radiator, same coolant mix as the previous trip except for the addition of WW) was that after shutdown I could hear steam popping inside the head towards the rear of the cylinder head. The car would ALWAYS puke a little coolant out after shutdown hot. After addition of the Water Wetter, this did not occur---ever! The only time my rad cap has lifted was after fifteen minutes of idling after an accident where I didn't realize the fan was in the radiator and was not turning! DOH! But thanks to WW, no head warping, and drove another 6K miles back home on that trip---well, Aluma Seal helped on that one, too... My conclusion was that the addition of water wetter was that it decreased the spot-boiling that occurred after shutdown during the heat soak period. Durinig operation, something it did was make the thing run cooler---I could see it on the gauge, and verified with my I/R thermo gun that it was running between 19 to 28 degrees cooler. I was running 110mph, in 103* heat, with the A/C on giving me a 75* interior temperature, and NEVER exceeded 195* with a three-core radiator and a 160* thermostat. (But early cars have overheating problems... yeh, riiiight!) Anyway, the pressure cap (radiator cap) only adds supplementary pressure to insure proper operation of the water pump. If you are blowing hoses, it's because of bad hoses---or the elimination of the bypass line and revving it during times of decreased flow while the thermostat is slightly closed. The water pump cranks 40 to 60psi in the water jackets, allowing a much higher boiling point, and cooling the engine more efficinetly. By running a lower pressure cap, you decrease the operating pressure in the block by a similar ammount, and greatly increase the possibility of cavitation and steam impingment within the engine. Steam formation inside the block during operation can/will errode metal! I have seen industrial engine liners that have pockmarked holes due to steam cavitation---and this is in an open system (no pressure on coolant to keep leaks down). I added a 5# relief valve to the "surge tank" for that particular engine, and the cavitation damage went away. Personally I have 16# caps on everything. I also modify all my 240's with the 280 Puke Tank for the radiator (this all occurred before I put water wetter in). With the puke tank installed, you can fill all the way to the top of the filler neck, and then there is NEVER any air in the system. Without the puke tank coolant recovery line, you WILL be running an air space due to expansion and contraction of the coolant. I just noticed the 260 (which still doesn't have a puke tank) has a full radiator but doesn't puke at all. This lends more credence to the contention that boiling at hotspots inside the engine after shutdown causes the overflow. With the Water Wetter and 50/50 I hear no "popping" after hot shutdown, and never see overflow. On the subject of the stregnth of the mixture...anything over 10% glycol will cause a decrease in heat transfer. But the tradeoff is FREEZE protection more than boilover. Many industrial glycol systems that require efficient transfer will dictate only pure water with inhibitors in it, and only the bare minimum of glycol to keep it all from freezing if that is required! Water with Water WEtter is a very efficient coolant, but without the corrosion inhibitors, water pump lubricants, etc.... it becomes a very high-maintenance way to cool your car! I did run water and Drewguard for a while, but the purple dye was a real beyotch if you got it on anything , so I went back to prestone.... which BTW is the Wal-Mart Tech 2000 coolant---half the price and the SAME thing. Compare lot numbers and sequencing on the containers some time! Aaaah, efficient batch tracking working for the informed consumer! Oh, and BTW, I have inspected JeffP's engine internal coolant passages. He has run STRAIGHT Glycol since new in his car. Everyone told him "NO, you can't do that, it hurts cooling performance!" But he doesn't have overheating problems, and I am AMAZED that after this much mileage, that there is ABSOLUTELY no corrosion WHATSOEVER in his coolant jackets, and his HEAD looks like new inside! No white powder, nuthin! Something to be said for "no water in the system" too, I suppose. Interesting the new generation of Propylene Glycol Coolants tout "no corrosion" as a benefit, and curiously they run with NO WATER in the system! Hope this shed some light on it. I've rambled on so long, I forgot the question... Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 23, 2004 Share Posted April 23, 2004 Wait a sec... so I'm NOT supposed to block off the little port on the side of the filler 'neck', the one that originally would go to an overflow tank?? I thought I needed to block that if I wasn't running the tank. You know... that's it I'm gonna go pick up one of those tanks today, well hopefully, if they aren't too much I'll get one. But if I dont end up getting one I should unblock that port?? Very interesting info Tony D!! Well you make as good a case as any for the Water Wetter. Ahhhh but the local 'Speed Shop' here carries all Neo stuff! Well I've heard good things about Neo's equivalent to the Water Wetter as well, and am going to give it a shot. I just clarified with Tim240z on the method he gave me for purging air bubbles from the system and am gonna try that one more time as well. Hopefully after doing all this my temps stable out a little bit! Quote Link to comment Share on other sites More sharing options...
Tim240z Posted April 23, 2004 Share Posted April 23, 2004 You BLOCKED OFF the overflow outlet!!!! No No No!!! If anything, just put on a 3 foot length of tubing so that it pukes on the ground, not on the engine.... Quote Link to comment Share on other sites More sharing options...
johnc Posted April 23, 2004 Share Posted April 23, 2004 I just spent two weeks doing very a intensive diagnosis and modification of the L6 cooling system. One day I'll do a writeup of what I learned regarding cooling a high horsepower L6. Until then, run 10 to 20% of any kind of coolant, Water Wetter is a waste of $7, purge all the air from the block and head when filling, and leave room in the radiator tank so that you can separate the steam from the water. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted April 23, 2004 Share Posted April 23, 2004 I would spend my money on a good temp gauge if I were you. I think you're making a mountain out of a molehill on this one Bastaad. I don't really worry about temp until it gets to about 215 or so. Aside from a broken fan belt, a stuck thermostat, and that header wrap incident I had last fall, I've never had problems even at the track in 114* weather. You can get a cheap overflow bottle for about $15 at the parts store, or I used one from a 280ZX parts car I had and just bolted it to an existing hole in the rad support. Get a good thermostat, consider replacing the rad cap, and run it. You've already got a bigger radiator. You should be fine. Seriously consider the gauge though. Cheap and you'll never have to wonder again. Jon Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 24, 2004 Share Posted April 24, 2004 I know for a fact my gauge is off, shows about 10-15* hotter, I verified this with a meat thermometer. I did go out and get an overflow tank from autozone today and installed it. I did also pick up a bottle of the Neo Keep Cool or whatever it's called, same kinda stuff as the Water Wetter. A friend of mine fully convinced me when he told me how he used to have cooling problems in his Civic which he races often, and adding this stuff helped quite a bit. About making a mountain out of a mole hill... yeah I'm taking this really seriously. The first reason is becuase it NEVER used to run this hot before... it was a very sudden change, which makes me think something changed to cause that. Even if that's not the case, I was only worrying about it getting so high (again, it's gotten as high as about 210*) because I have seen a few posts when I was going thru the archives on this subject, that made it seem like anything over 200* was enough to possible cause the head to warp. And even if I dont worry much when it gets up to 200, it seems to fluctuate a LOT with the air temperature, and summer is almost upon us in SoCal (90 deg + for like 6 mos straight) I just dont want this to become a serious problem at that point. I really do NOT want to have to pull the head again.... I do still feel that the most likely culprit was/is probably air trapped in the system, and that's why it remained an issue for me, as I know that can create lots of problems. Today I tried Tim240z's procedure again, I clarified with him on a couple things I had misunderstood, but this time I did it exactly the way he said, and I did see some bubbles come up as the thermostat opened, so I really hope that solves the issue once and for all. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted April 24, 2004 Share Posted April 24, 2004 Personally I would be concerned if my temperature rose to 210 or 215. that means your cooling system is out of control! The thermostat is supposed to regulate at it's setpoint. If the temperature goes higher, your cooling system is inadequate for the conditions. Either your radiator cannot dissipate the heat, the fan cannot move enough air, or you cannot circulate enough coolant. And of course the system must be free of air pockets. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 24, 2004 Share Posted April 24, 2004 it certainly seems to high to me.... even if it werent, the fact remains it had never done this before. Well, the overflow tank is installed, I put some of that Neo Keep Cool in the radiator, and took one more shot at bleeding any air out of the system. All last night and today it's been staying put at somewhere in the 185-190 range. So far, same as usual. Have to drive it when it gets warmer out, but I'm usually asleep during those times something tells me it wont have helped. If it hasn't that doesnt leave much... I'll have the radiator flushed I guess, and switch to the nissan t-stat... dont think it's an issue with the fan as it only happens at high speeds? Well I did test my fan clutch and it seems to be working fine, and again I'm using a fan shroud as well. After that I'm just gonna leave it be...., Quote Link to comment Share on other sites More sharing options...
Tim240z Posted April 24, 2004 Share Posted April 24, 2004 Is your fan running when you are at speed? It could actually be hampering air flow if it is.... Tim Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 25, 2004 Share Posted April 25, 2004 I assume that it is? It's just the regular clutch fan... isn't it running all the time? Quote Link to comment Share on other sites More sharing options...
Tim240z Posted April 25, 2004 Share Posted April 25, 2004 My bad...no sleep...don't mind me!!!!! Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 25, 2004 Share Posted April 25, 2004 Pulling all nighters getting the car ready eh? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.