PDA

View Full Version : Whats so special about BMW coolant??



PhilipJCaputo
06-25-2004, 06:53 PM
Other than its blue, and normal stuff is usually green...

I'm just about to replace the thermostat, thermostat housing (and thermo gasket)... and I'm not too thrilled with my bentley telling me that the entire system hold 12.5 liters of coolant! I'm going to have to go to the stealer and buy 3 jugs of bmw coolant at 15 bones a jug... which will double the cost of this fix.....

any alternative to BMW coolant?

Paul in NZ
06-25-2004, 08:06 PM
but the school of thought here is that it is cheap compared to a head gasket job.It is formulated to bmw specifications which means that its chemical make up is compatible to all the materials found in your cooling system.I beleive there is a vavoline? alternative but it is hard to find......personally i beleive any NEW coolant is better than any OLD coolant....but for the ammount you will save why not?????Next time mine is due for a change i will go for the blue stuff,which hopefully will tone in with some blue powder coating work on my vave cover....... :)

ryan roopnarine
06-25-2004, 08:07 PM
the only coolant that comes anywhere in equivalency is the mercedes/g-05, and that isn't EXACTLY the same. pentosin makes an equivalent, but it is likely MORE expensive than buying a jug of bmw at 15 a pop (at my orlando ger. auto parts store it is). anyway....3.78*2=7.xx, multiplied by two is 15 something litres, more than enough to service your system at a generous 50% mix....i'm not sure why you mention three bottles. it is highly unlikely that you will get ALL of the flush water out.....its likely that some water will remain in the system and dilute any solution you put in. You likely WON't be able to fit 12.x litres of anything into your cooling system.

Unregistered
06-25-2004, 08:12 PM
YOU DON'T NEED THREE JUGS. REMEMBER, YOU NEED TO MIX 50/50 (COOLANT/WATER). BMW COOLANT IS CONCENTRATE. YOU NEED TO ADD DISTILLED WATER TO COOLANT. SO, IT'S NOT TOO BAD!



Other than its blue, and normal stuff is usually green...

I'm just about to replace the thermostat, thermostat housing (and thermo gasket)... and I'm not too thrilled with my bentley telling me that the entire system hold 12.5 liters of coolant! I'm going to have to go to the stealer and buy 3 jugs of bmw coolant at 15 bones a jug... which will double the cost of this fix.....

any alternative to BMW coolant?

Tiger
06-25-2004, 09:01 PM
Actualy... do 70 water/ 30 coolant

PhilipJCaputo
06-25-2004, 09:06 PM
OK, the BMW stuff I bought isn't a its not a 50/50 mix like I thought (its the concentrate)... and I've got about 3 quarts of it left.. :-) This isn't going to be as bad as I thought.

I was thinking the 13 quarts because thats that the bentley manual says the capacity is.

but I think I'll be ok.... and if everyone says BMW... what I can I do... I'll stick with the BMW coolant, it was this initial idea i had where I was going to spend another 45 bucks on coolant which wasn't making me too thrilled.


On a side note, I just fixed my twisted passenger seat issue :)

Unregistered
06-25-2004, 10:20 PM
Hey Tiger,

Are you sure about 70 water / 30 coolant? I always thought you put 50/50 or 70 coolant / 30 water (for very cold winters / very hot summers). Never heard of 30 coolant / 70 water...



Actualy... do 70 water/ 30 coolant

Paul in NZ
06-25-2004, 10:52 PM
the water is the important cooling fluid.you only need more "anti freeze" where the temperatures get really low.In NZ where i live you dont need anti freeze at all but it has important anti corrosion and some lubricant properties......I guess there are instruction on the mix related to the temperature but i always go 70 h20 30 "anti freeze"

Unregistered
06-25-2004, 11:53 PM
Well, if you look at any coolant jug, it says otherwise... You will notice that if you put more antifreeze, antifreeze/coolant would withstand higher temp. It says on the jug. If very cold or very hot, use 70 coolant / 30 water for optimal performance. Cars operate in a wide variety of temperatures, from well below freezing to well over 100 F (38 C). So whatever fluid is used to cool the engine has to have a very low freezing point, a high boiling point, and it has to have the capacity to hold a lot of heat. The fluid that most cars use is a mixture of water and ethylene glycol (C2H6O2), also known as antifreeze. By adding ethylene glycol to water, the boiling and freezing points are IMPROVED SIGNIFICANTLY! The temperature of the coolant can sometimes reach 250 to 275 F (121 to 135 C). Even with ethylene glycol added, these temperatures would boil the coolant, so something additional must be done to raise its boiling point. The cooling system uses pressure to further raise the boiling point of the coolant. Just as the boiling temperature of water is higher in a pressure cooker, the boiling temperature of coolant is higher if you pressurize the system. Most cars have a pressure limit of 14 to 15 pounds per square inch (psi), which raises the boiling point another 45 F (25 C) so the coolant can withstand the high temperatures. Don't you think 70 coolant / 30 water is a better way to go? I would NEVER run straight water. Also, you need to use only distilled water and not tap water. Tap water containes too much minerals and bad for the system.



the water is the important cooling fluid.you only need more "anti freeze" where the temperatures get really low.In NZ where i live you dont need anti freeze at all but it has important anti corrosion and some lubricant properties......I guess there are instruction on the mix related to the temperature but i always go 70 h20 30 "anti freeze"

Paul in NZ
06-26-2004, 12:08 AM
thanks for the info...i thought water was unbeatable in its ability to absorb heat....

Unregistered
06-26-2004, 01:27 AM
In the US, BMW coolant is Valvoline Zerex G48:

https://www.valvoline-technology.com/data/VALV/ValvExtSecurity.nsf/fsZerex?OpenFrameSet

G-man
06-26-2004, 02:00 AM
How about the G-05 is that OK to use?...it seems no one has the G48 in my area since the G-05 came out.

bill g
06-26-2004, 04:24 AM
There is a coolant available here in Australia called Nulon Long Life which I found has very similar specs to BMW coolant, at about half the price. The stuff is green colour.

George M
06-26-2004, 05:44 AM
Bottom line is....compare G-05 specs to G-48 a.k.a. BMW blue coolant. I like the specs of the Mercedes approved G-05 better than the G-48 and it is half as expensive and much more available. Why I run the G-05 in my big six.
George

Bellicose Right Winger
06-26-2004, 06:40 AM
70/30 is very good for cooling performance, since the coolant has poor heat transfer properties relative to water. The downside is it prevents you from getting a full dose of corrosion inhibitors. Settling for a partial dose of corrosion inhibitors seems to contradict conventional wisdom which says use ONLY BMW coolant to minimize corrosion problems.

Paul Shovestul



Actualy... do 70 water/ 30 coolant

MicahO
06-26-2004, 06:41 AM
The other downside is reduced freeze protection, though 70/30 is probably enough for at least 360 days per year in 90% of the US......

MicahO
06-26-2004, 06:48 AM
Adding coolant to water does increase the boiling point, and therefore decrease the danger of boil-over.

However, water does have a better capacity to transfer heat than does coolant. So as a straight cooling fluid in a system that does NOT EXCEED the boiling point of that system, water alone is superior to a water/coolant mix. Because of this, many race engines that do not need to worry about the lifespan of the system components will run just water or mix with Water-Wetter. But those guys can toss their water pumps after a day or a weekend, so they don't need the other protective measures found in coolants.


Well, if you look at any coolant jug, it says otherwise... You will notice that if you put more antifreeze, antifreeze/coolant would withstand higher temp. It says on the jug. If very cold or very hot, use 70 coolant / 30 water for optimal performance. Cars operate in a wide variety of temperatures, from well below freezing to well over 100 F (38 C). So whatever fluid is used to cool the engine has to have a very low freezing point, a high boiling point, and it has to have the capacity to hold a lot of heat. The fluid that most cars use is a mixture of water and ethylene glycol (C2H6O2), also known as antifreeze. By adding ethylene glycol to water, the boiling and freezing points are IMPROVED SIGNIFICANTLY! The temperature of the coolant can sometimes reach 250 to 275 F (121 to 135 C). Even with ethylene glycol added, these temperatures would boil the coolant, so something additional must be done to raise its boiling point. The cooling system uses pressure to further raise the boiling point of the coolant. Just as the boiling temperature of water is higher in a pressure cooker, the boiling temperature of coolant is higher if you pressurize the system. Most cars have a pressure limit of 14 to 15 pounds per square inch (psi), which raises the boiling point another 45 F (25 C) so the coolant can withstand the high temperatures. Don't you think 70 coolant / 30 water is a better way to go? I would NEVER run straight water. Also, you need to use only distilled water and not tap water. Tap water containes too much minerals and bad for the system.

Tiger
06-26-2004, 09:28 AM
Yes... Water is the main heat transfer agent. Coolant is a modifier and additive. You do have to make sure that ratio is enough for your coldest day. Now, some of you say with more coolant, your boiling temperature is boosted to higher point like 275 degree... WELL if your coolant ever get that high, your engine is kaput! Our thermostat opens at 190 degree...

I had 50/50 in my car... it never overheats in BMW... but on MB, temperature always seem higher than normal... once I dilute it lower, the car run more normal temp. The car runs cooler with higher water content because of it's ability to shed heat better than coolant itself.

Then you say corrosion protection is lower with more water... yes... but not by that much especially if you do change you coolant every 2 years...

George M
06-26-2004, 09:51 AM
agree with Paul...will take the corrosion protection of 50/50 to the added cooling benefit of 30/70 any day of the week...but I don't live near the equator either.
George

Bill R.
06-26-2004, 11:24 AM
bullhead city driving at highway speeds. I always use the stock bmw coolant since its not that pricey and i always use it at 50/50 concentration. Corrosion protection is my big concern and the raised boiling point. And Tiger motors will survice 275 just fine if they are using a synthetic oil that will continue lubricating just fine at higher temps. 250 temps are fairly normal on newer cars here and they run just fine at that temp. Straight water does have the greatest capacity for heat transfer but thats not an issue since the cooling system is already sized for a 50/50 glycol antifreeze and easily handles the heat load if everything else is in shape. And the typical racing motor actually has lower operating temps than the motor in a street car since the race car usually has a large oil cooler, radiator sized accordingly, a lower temp thermostat, no ac or few belt driven acc. to increase heat load on the cooling system and a richer fuel mixture since they don't have to run lean for emissions purposes. Street engine frequently work under harsher conditions including neglect..
So i'd use bmw coolant 50/50 just like the engineers designed it for.





agree with Paul...will take the corrosion protection of 50/50 to the added cooling benefit of 30/70 any day of the week...but I don't live near the equator either.
George

Unregistered
06-26-2004, 01:36 PM
Yes, water is unbeatable in its ability to absorb heat but we're talking about engine and cooling system protection. It is recommended that you use at least 50/50 to fully protect your car (in Arizona or in Alaska). Like Bill R. said, race cars are not street cars. You would be surprised that street cars put more strain on cooling system than race cars. Antifreeze/coolant is cheap so why not use them as they are recommended?



Adding coolant to water does increase the boiling point, and therefore decrease the danger of boil-over.

However, water does have a better capacity to transfer heat than does coolant. So as a straight cooling fluid in a system that does NOT EXCEED the boiling point of that system, water alone is superior to a water/coolant mix. Because of this, many race engines that do not need to worry about the lifespan of the system components will run just water or mix with Water-Wetter. But those guys can toss their water pumps after a day or a weekend, so they don't need the other protective measures found in coolants.

Unregistered
06-26-2004, 01:53 PM
Also, BMW coolant might just be propaganda by BMW to buy their product. I seen many companies do this... Look at Microsoft. Really, what makes BMW's engine and cooling system any different than other German cars? Since BMW coolant doesn't cost that much, I still use it but are they puting one over on us? The properties of antifreeze/coolant is the same. What additives did they put in the coolant to protect it better than another quality brand? My friend's 1989 BMW used Prestone antifreeze/coolant since 1992 and never had a problem with cooling system. You be the judge...



Other than its blue, and normal stuff is usually green...

I'm just about to replace the thermostat, thermostat housing (and thermo gasket)... and I'm not too thrilled with my bentley telling me that the entire system hold 12.5 liters of coolant! I'm going to have to go to the stealer and buy 3 jugs of bmw coolant at 15 bones a jug... which will double the cost of this fix.....

any alternative to BMW coolant?

rickm
06-26-2004, 02:03 PM
How many "failures" has the BMW coolant had? I'd rather spend the extra few bucks for BMW coolant than take a chance on getting relabeled Dexcool.

Unregistered
06-26-2004, 03:16 PM
Hey, I don’t want to offend anyone who uses BMW coolant here. I too used BMW coolant for my 1995 BMW 525i. I’m just saying what PhilipJCaputo has brought up. What’s so special about the BMW coolant? I would like to know why, not because some company recommends it by gaining their own interest. Seriously, BMW is a business like any other. All companies claim their product to be the best. BMW isn’t in the business “solely” to make the “ultimate driving machine”. They are in the business to sell their product and make money. I like to know the facts… If all manufacture start to do this and we follow their guidelines without real facts, we would be the “suckers”.



How many "failures" has the BMW coolant had? I'd rather spend the extra few bucks for BMW coolant than take a chance on getting relabeled Dexcool.

rickm
06-26-2004, 03:25 PM
Search the forum for coolant, that will keep you busy for a while :) One thread I read mentioned that the reason why (or one of the reasons why) is that the properties of the coolant factored in the makeup of the engines. I guess it's one of those "better safe than sorry" things...maybe Bill or Winfred could chime in.

Unregistered
06-26-2004, 03:47 PM
The way I look at it, these cars were $40-50K brand new. 12-15 years ago, I would have said you be nuts to not use BMW coolant, why risk it on an expensive car.

However, your car, and I mean ALL OF YOU, are worth what - maybe $5K? 6K? If you really like the car and you some how "fry" your engine because you didn't use BMW coolant, its what $3K or so for a rebuilt!

At this point, if you really don't want to spend the $18-24/gal (yikes, its really expensive in the SF Bay Area) to use BMW coolant, don't. What the hey, these old ass cars have seen their best days. Go on down to wal-mart, target, kragen/checkers or pep boy and get that "$2.99 special" and be done with it. Just remember to change every 2 years....

PhilipJCaputo
06-26-2004, 03:53 PM
Thanks for all the input.... I only drained about half the cooland out.... (only opened the plug on the radiator) So I was able to use the rest of my bmw coolant I had left over.... mix'n with a little distilled water, and its good as new!

I just hope I never have to do that job again. Anyone try to replace the thermostat on the M60?? You can't even really see the bolts on the engine side of the thermo housing.. Plus there are other cords in the way... Plus with a cracked housing, EVERYTHING around there has this slippery layer of coolant all over it. Makes it hard to guide sockets into place

And when they reccomend to remove the radiator fan... its probably a good idea, I fought with that thing the entire time I was change'n the thermostat & housing!

good news is.... no more coolant leak! (that I've noticed)

Unregistered
06-26-2004, 03:54 PM
O.K. I searched the forum for “coolant” and only found people having problems with cooling system. When BMW recommends only to use their coolant, is it from BMW bulletin, manual, or is it on the jug? Could someone tell me exactly what it said about BMW coolant (word for word if possible)? It’s hard to believe the BMW coolant contains special additive(s)… Or is it just been tested to be O.K. (compatible). If second, companies comment phrase in a way for the public to believe or perceive certain way without legal liability of false statement. Look at “NO PRESERVATIVE” compare to “NO PRESERVATIVE ADDED” on food product. One might think it contains no preservative to both but is it? “NO PRESERVATIVE” means no preservative. “NO PRESERVATIVE ADDED” means no preservative added by this company but might contain preservative. What's does it say? Thanks for putting up with my crap… You guys are a trooper!



Search the forum for coolant, that will keep you busy for a while :) One thread I read mentioned that the reason why (or one of the reasons why) is that the properties of the coolant factored in the makeup of the engines. I guess it's one of those "better safe than sorry" things...maybe Bill or Winfred could chime in.

PhilipJCaputo
06-26-2004, 03:59 PM
in my bentley service manual it says this..

"Always use genuine BMW coolant or its equivalent ot aviod the formation of harmful, clogging deposits in the cooling system. Use of other antifreeze solutions may be harmful to the cooling system"

I guess it could be less likely to form deposits/clogs....

Unregistered
06-26-2004, 04:08 PM
YES, THERE IT IS!!! "Always use genunine BMW coolant or ITS EQUIVALENT". "ITS EQUIVALENT" means anything comparable, right? O.K., enough said...



in my bentley service manual it says this..

"Always use genuine BMW coolant or its equivalent ot aviod the formation of harmful, clogging deposits in the cooling system. Use of other antifreeze solutions may be harmful to the cooling system"

I guess it could be less likely to form deposits/clogs....

lee
06-26-2004, 04:21 PM
unknown states:

<YES, THERE IT IS!!! "Always use genunine BMW coolant or ITS EQUIVALENT". "ITS EQUIVALENT" means anything comparable, right? O.K., enough said...>

It should be noted that PhilipJCaputo was quoting from his *BENTLEY* service manual, not from any "official" BMW source, so take it for what its worth....

Unregistered
06-26-2004, 05:00 PM
Then, could you provide BMW "official" statement that comments on using ONLY BMW coolant.



unknown states:

<YES, THERE IT IS!!! "Always use genunine BMW coolant or ITS EQUIVALENT". "ITS EQUIVALENT" means anything comparable, right? O.K., enough said...>

It should be noted that PhilipJCaputo was quoting from his *BENTLEY* service manual, not from any "official" BMW source, so take it for what its worth....

Unregistered
06-26-2004, 05:12 PM
as McEnroe says "you can't be serious!"

Unregistered
06-26-2004, 05:43 PM
“You should've kept your rice burner and green coolant”??? Where did you come across this??? Please be more constructive! You probably don’t know any better…



as McEnroe says "you can't be serious!"

Unregistered
06-26-2004, 05:56 PM
Wow, this is unbelievable! I’m trying to find an answer and some people get upset. Why is that? I find this forum to be very useful and answered many of my questions but why would anyone write a negative remark like this guy? Sign of immaturely? Maybe! Do I have a rice burner? NO. Do I use green coolant? Sometimes. You know, people who rip on you like this are the people of ignorance. If you want to be smart, write something more constructive! And yes, I’m serious!



as McEnroe says "you can't be serious!"

MBXB
06-26-2004, 06:12 PM
Here's the thread where Tiger and others have a pretty good explanation of coolant differences.

http://www.bimmer.info/forum/showthread.php?t=308&highlight=coolant

Unregistered
06-26-2004, 06:59 PM
Thanks for the link, Ramon. However, I didn't find any hard facts that prove one way or the other. Also, people were discussing about the type, NOT brand (BMW). I’ve been using BMW coolant because I presume it to be high quality and NOT because I have no other choices.


Here's the thread where Tiger and others have a pretty good explanation of coolant differences.

http://www.bimmer.info/forum/showthread.php?t=308&highlight=coolant

Unregistered
06-26-2004, 07:10 PM
I'm sorry guys, I've just been babbling on because I don't have a clue nor an
identity.











Thanks for the link, Ramon. However, I didn't find any hard facts that prove one way or the other. Also, people were discussing about the type, NOT brand (BMW). I’ve been using BMW coolant because I presume it to be high quality and NOT because I have no other choices.

Unregistered
06-26-2004, 07:20 PM
Hey, looks who's talking!!! I'm registered and it's Rick L!!! I prefer to use this forum not logged in because it is easier for me to read different threads. So, if you want to criticize my comments, you could do so! IT IS RICK L!!! O.K.
Grow up!!!


I'm sorry guys, I've just been babbling on because I don't have a clue nor an
identity.

Unregistered
06-26-2004, 07:23 PM
No wait, I'm just kidding I'm not really Rick L, darn these multiple personalties! I thought I had that under control.






QUOTE=Unregistered]Hey, looks who's talking!!! I'm registered and it's Rick L!!! I prefer to use this forum not logged in because it is easier for me to read different threads. So, if you want to criticize my comments, you could do so! IT IS RICK L!!! O.K.
Grow up!!![/QUOTE]

ryan roopnarine
06-26-2004, 07:23 PM
what is the difference between Green regular and German???? the most important reason is that green american coolants are BUFFERED as to make them phosphate free WRT pH. BMW and others actually ARE phosphate free, and contain the minimum silicates necessary that the water pump and other components are happy. water in an engine application undergoes changes in chemistry when exposed to the water jacket materials, rust, et cetera, heat. these coolants are made as to make these interactions as innocuous as possible when they inevitably happen...IE, a real world application would be water pump bearing death, or thermostat failure (or any other number of things that deal with chemistry) as a result of excess silicates (green stuff), or retarded rust buildup with time as a result of a more compatible chemistry of coolant. If myself, (or someone driving my car) avoids an unexpected coolant failure because the coolant is "workable" for another 20k miles or so, that's worth the extra $$$ to me, especially since most people today would drive a car with temps in the red to get to their destination.


The way I look at it, these cars were $40-50K brand new. 12-15 years ago, I would have said you be nuts to not use BMW coolant, why risk it on an expensive car.

However, your car, and I mean ALL OF YOU, are worth what - maybe $5K? 6K? If you really like the car and you some how "fry" your engine because you didn't use BMW coolant, its what $3K or so for a rebuilt!

At this point, if you really don't want to spend the $18-24/gal (yikes, its really expensive in the SF Bay Area) to use BMW coolant, don't. What the hey, these old ass cars have seen their best days. Go on down to wal-mart, target, kragen/checkers or pep boy and get that "$2.99 special" and be done with it. Just remember to change every 2 years....

Tiger
06-26-2004, 07:56 PM
U mean the headgasket won't cook at sustained 275 degree whereas stock temperature is 190 degree?

Rick L
06-26-2004, 08:17 PM
hehehe... You're a funny guy. If you behave, I might have a doggy biscuit for you.



No wait, I'm just kidding I'm not really Rick L, darn these multiple personalties! I thought I had that under control.






QUOTE=Unregistered]Hey, looks who's talking!!! I'm registered and it's Rick L!!! I prefer to use this forum not logged in because it is easier for me to read different threads. So, if you want to criticize my comments, you could do so! IT IS RICK L!!! O.K.
Grow up!!![/QUOTE]

lee
06-26-2004, 09:52 PM
Unregistered states:


<Wow, this is unbelievable! I’m trying to find an answer and some people get upset. Why is that? I find this forum to be very useful and answered many of my questions but why would anyone write a negative remark like this guy? Sign of immaturely? Maybe! Do I have a rice burner? NO. Do I use green coolant? Sometimes. You know, people who rip on you like this are the people of ignorance. If you want to be smart, write something more constructive! And yes, I’m serious! >

Why do you need some sort of "confirmation" that your BMW is required to use *only* BMW coolant? As the Vavoline site states, Zerex G48 is *BMW approved*. If that is not good enough, don't use it, period. Its your car, put in straight water, green, yellow, purple, or rainbow if you want.

If you don't wanna pay BMW prices, it appears that Jaguar, Saab, Volvo, VW and even RR coolants are also Zerex G48. Those might be cheaper, use them (OK, RR might be more expensive!). Alternatively, if you think "Mercedes approved" G05 is the same, use that. Just remember to change your coolant every 2 years....

Rick L
06-27-2004, 11:51 PM
Here’s something for the curiosity at mind… ;) Listed are all the patents for antifreeze/coolant going back to 1935.

US Patent – 02/1935

www.delphion.com/cgi-bin/viewpat.cmd/US01992689__MODE=fstv&OUT_FORMAT=pdf (http://)

US Patent – 02/1949

www.delphion.com/cgi-bin/viewpat.cmd/US02462694__?MODE=fstv&OUT_FORMAT=pdf (http://)

US Patent – 06/1951

www.delphion.com/cgi-bin/viewpat.cmd/US02558030__?MODE=fstv&OUT_FORMAT=pdf (http://)

US Patent – 05/1963

www.delphion.com/cgi-bin/viewpat.cmd/US03090757__?MODE=fstv&OUT_FORMAT=pdf (http://)

US Patent – 03/1970

www.delphion.com/cgi-bin/viewpat.cmd/US03502578__?OUT_FORMAT=pdf&MODE=fstv (http://)

US Patent – 09/1973

www.delphion.com/cgi-bin/viewpat.cmd/US03758493__?OUT_FORMAT=pdf&MODE=fstv (http://)

US Patent – 01/1976

www.delphion.com/cgi-bin/viewpat.cmd/US03932303__?OUT_FORMAT=pdf&MODE=fstv (http://)

US Patent – 01/1976

www.delphion.com/cgi-bin/viewpat.cmd/US03935125__?OUT_FORMAT=pdf&MODE=fstv (http://)

US Patent – 12/1976

www.delphion.com/cgi-bin/viewpat.cmd/US04000079__?OUT_FORMAT=pdf&MODE=fstv (http://)

US Patent – 08/1980

www.delphion.com/cgi-bin/viewpat.cmd/US04219433__?OUT_FORMAT=pdf&MODE=fstv (http://)

US Patent – 06/1984

www.delphion.com/cgi-bin/viewpat.cmd/US04452758__?OUT_FORMAT=pdf&MODE=fstv (http://)