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I will be ordering a 1.4 bar cap for my E53 asap.
I've just done a quick check on the 11 vehicles we have here (German, Japanese & American) and not one has a radiator cap or expansion bottle cap with pressure relief in excess of 1.5 bar. Does that say anything? I don't know, except it gets bloody hot over here and not one of my vehicles suffers from an overheating issue or has ever burst a hose or worse. Yes - there have been occasions where there has been some coolant leak visible, but that's usually because I've over-filled the system and it's vented through the radiator cap (before bursting anything else).
I'm inclined to agree with slickgt1 in this argument (discussion) to the point I'm going to swap over my cap to a 1.4 bar pressure.
Does anyone know what pressure cap is in the newer X5 or other BMW's that have a similar cooling system? Or is the E53 the only one with the 2.0 bar cap?

Quote:

Originally Posted by SlickGT1 (Post 1051814)

No it was new cap. And I am pretty sure I didn't over fill. I mean seriously. Not my first go around. I am well aware of bmw fluid limits lol.

I suspect the tank can only hold lets say 1.5 bar before going bye bye, maybe less. Not a brand new. I know for fact the new one held at over 1.7. So my 2 year old tank, at one point decided to split way before the cap did anything.

Note the leak after this expansion tank replacement was not at the expansion tank. It was at the Y fitting under the throttle body. The plastic fractured, not the little hoses or hose clamps. You can see that post here. The one hose I didn't change failed on me very shortly after tank replacement.

http://www.xoutpost.com/bmw-sav-foru...hing-else.html

Again, a lower bar cap, just lowers the failure point to the cap. It does not change operational temps or pressures. It just lowers the safety net. Our systems run at about 1 bar. Seeing my cap vent at 1.4 bar, will notify me of a problem way before a 2 bar catastrophic failure. Our cars to not run anywhere near 1.4 bar. There is no reason to be afraid of 1.4 bar cap.

Think of it like this. Lets say you have a leaky hose. Then is does not matter what bar your cap is, you are leaking fluid, that is your weakest point. 2 bar or 1.4 bar makes zero difference. Right.

Now lets say that your car is running at 1 bar. You shut down hot. Pressure builds, you hit 1.4 bar (normally not likely). At which point the 1.4 bar cap will vent. Agreed? But lets say you have a 2 bar cap, and your 2 year old expansion tank can only hold 1.4 bar. Boom, your tank split at the seam, and you are posting here saying the expansion tanks are shit.

Now lets look at it a different way. One of the plastic connections is failing, and can only sustain 1.3 bars, then again it won't matter if you have a 2 bar or a 1.4 bar cap. That connection will bust when your system hits 1.3 bar. In either of these scenarios, it doesn't make sense to run 2 bar caps.

If my system starts venting at 1.4, I know I have an issue. It should never get that high. I don't need to wait for 2 bars over pressure, and potentially blow out something huge. 2 bar cap does not add any cooling efficiency to our cars.

Look at the pressure chart below. At 1.14 bar, you are at operating temp. By the time you hit 1.7 bar, you will overheat, and your cap didn't do shit. Please explain the logic of this safety cap being at 2 bar.

KTMP Reading/PSI Reading
40C/1.5 PSI = 0.10 bar
45C/2 PSI = 0.14 bar
50C/2.25 PSI = 0.16 bar
55C/2.5 PSI = 0.17 bar
60C/3.0 PSI = 0.21 bar
65C/3.25 PSI = 0.22 bar
70C/3.5 PSI = 0.24 bar
75C/4.0 PSI = 0.28 bar
80C/5 PSI = 0.35 bar
85C/6 PSI = 0.41 bar
90C/6.5 PSI = 0.45 bar
95C/7.5 PSI = 0.52 bar
100C/9.0 PSI = 0.62 bar
105C/16.5 PSI = 1.14 bar

Only reason for us to have these pressures is to increase boiling point of the coolant. So that it does not boil over. That pressure keeps it a liquid, and not vapor. Vapor does not cool anything. I know the chart above doesn't show it, but at 1.4 bar, you can hit 260F (126C), sorry to tell you, but your shit is overheating at this stage. So again, the 2.0 bar cap doesn't do anything while driving. At 2 bar you are so far gone overheating, it isn't funny.

So why do we have a 2.0 bar cap?

I never said it changes operating temps. I don't know why we have a 2 bar cap and never claimed to know. I simply stated, as confirmed in your chart, that a lower pressure cap would lower the cooling thresh hold and that changing to a lower cap was a bandaid fix and that's it. According to BMW the cap IS the weak link and I choose to believe them over you. Maybe if we met and you showed me some real stuff I might buy in a bit, but, this is the internet dude.......

There's a lot of variables here, too many to make any real conclusions. So to me, some of your conclusions are false interpretations in my eyes. Like, you state there is no way an expansion tank will hold over 2 bars, but earlier stated your tested would not pump that high. What proof do you have that it will not hold this amount of pressure? It would be cool to set up a test to examine failure points on brand new parts...... You think BMW did this when they ran test on everything else? who knows.

In the mean time I'll continue to run my 2bar cap and you'll continue to run your 1.4bar cap and well both be happy campers:) Speaking of which, I'm stuffing my X full of camping supplies right now. We take off tomorrow for a week of fun in the X!

Quote:

Originally Posted by kvc (Post 1051833)

IMO, there is no reason to change the max. pressure of the cap from the original spec. That includes consideration of the environment. The caps of other vehicles of any make or model other than what you own is no indication of the appropriate cap for your vehicle. That also considers that some here have had expansion tanks go bad. Key word is some. As with anything where the question is what's good or bad, it is human nature to build a much longer list of negatives. Another reason we hear less from those that haven't experienced a problem s that input is often said to be anecdotal or they are drinking the BMW kool-aid.

IMO, if the design of the cooling system resulted in chronic failure of system components, it would have been corrected quickly within the warranty period. In addition, chronic parts problems or lack of longevity are usually addressed by aftermarket companies. I know of no aftermarket expansion tank or pressure cap marketed as addressing the weaknesses of the stock part.

A cooling system is designed to allow the engine to run at some specific range of temperature. Components are designed to deliver an acceptable life cycle in that temp range. The break point of components is in excess of the specified pressure release. One reason that is the case is that even if the overheating is noticed immediately it is no always possible to turn off the engine immediately so there is cushion from the warnings to likely catastrophic damage. If the system discharged fluid prematurely due to the pressure release that would increase the likelihood of and extent of damage.

FYI--I have replaced one hose that failed, the plastic pipe near the pressure cap (I broke it) but have not replaced an expansion tank.

Lol. I'm not here to convince anyone that my theory and logical conclusion is to make people switch.

I'm not the only one saying this. You know there are forums where there are shit load of other BMW owner who went this route. I'm not the creator of this. I'm actually conservative. People just go for the 1.2 bar cap from GAS. I have the e30 1.4 cap. It's identical by the way. People with 1.2 bar caps actually burp sometimes. Mostly when overfilled. I'm sure those people would rather burp a few ounces instead of dumping a few gallons. Suddenly people have cooling components last longer.

All I am saying there is no reason to be concerned with having a 1.4 bar cap if people want a piece of mind. Because sure as shit a 2.0 cap is not the weakest point.

And yes kvc. New BMW cooling systems are now with reasonable pressures. 1.2 -1.4 bars.

I follow you SlickGT1. 1.4 cap is my next "upgrade" for both my X5 and E39. I've read about 1.4 cap in the E39 forums but I think your explanation makes a lot of sense. Coupled with that, I recall one time my daughter, who is a senior in Electrical Engineering, pointing out to me that they had a discussion at school wherein the gist of the conversation was products are deliberately designed to fail. She called it something like "planned obsolescence". It happens where engineering meets capitalism. Products aren’t designed to last, so the brightest and most successful engineers don’t aim to create the best possible machine. They aim for maximum profit through steady sales. In other words, our Bimmers aren't the "Ultimate Driving Machine" after all :D

I'm saying. No one else finds it odd that people recommend replacing all hoses, tank, radiator, and coolant when your expansion tank breaks? I don't replace one hose and guess what happens.

Oh and I drive in NYC almost daily. AC on. The most ridiculous traffic ever. It took me 45 min to drive Lincoln tunnel to nyu hospital. .3 miles. Just throwing that out there as far as harsh driving environment and zero issues with e30 cap.

I think x5only. You split your tank because of improper mix. Possibly too much water. Boiling point too low, and you stressed out your tank. The real weak point. The cap would have saved your tank. It would have vented, and you would have seen it, and smelt it.

Back in the day (most likely even now), racers, track guys, would remove antifreeze (some tracks won't allow antifreeze), fill 100% water and water wetter. This would lower boiling point. So those guys would need a high pressure "race" cap. This would increase boiling point, and let the water survive the event. When said racers got the cap, it usually went from something like 1.1 bar, to 1.3 bar. Yea. That's it. Because beyond that, you blew cooling components up.

Quote:

Originally Posted by X5only (Post 1051882)

So the correct answer is now E) 2 Bar tank cap?

What did I win? :P

Quote:

Originally Posted by X5only (Post 1051882)

This is like a conspiracy therory here.

Let me clear something up, it would cost a manufacture MORE money to produce parts that deliberately fail. I work in a manufacturer setting and have been for some time. It just doesn't work this way. You guys that think bmw made a faulty part on porpose have never worked in a manufacture setting with engineers designing, with the other part of the company producing what was engineered. These company's are trying to beat the compition and you think designing faulty parts is a way to win......omg:)

Slick now you just stated that your research was indeed "a bunch of shit on the forums" right after BC and I explained how you are only going to read the bad. Find me an example of a guy who got 200k out of his cooling system. You won't because he's one of the serval million bmw drivers without cooling issues that are not posting on forums.

Well said BC.

Quote:

Originally Posted by B-M-W (Post 1051894)

Listen guy. Find another thread. This point on I'm just going to ignore your ass. You have provided nothing but shitty interpretation of every fucking word to your liking without adding anything to the discussion. You clearly need to get the last word in. Go ahead. Simple as that. Open up Google and do some research. Even simpler than that, follow the links I provided for your lazy ass. There are people attaching gauges to their cooling system on the e39 forum. All you are doing is trying add your 2 pennies of nonsense.

Only thing going your way in this thread is the cool aid you drank when you bought your whatever car. Don't preach shit to me. I guarantee you every item on mine is bought from dealer. Your research is shit, there is none of it. Find me a case where a lower bar cap has failed anyone and I will remove you from my ignore list. Adult discussion over. I entertained your ass long enough.