[Cooling System Upgrade] 1-BAR Radiator Cap

Originally Posted by mkodama

lol, why are your panties in a bunch? I haven't insulted you yet, nor have I even responded to you.

Hmm... Big internet ego hiding behind cliche forum lingo, and threatening to insult over the internet: "I haven't insulted you YET, but I can, consider yourself warned!"

Sorry that I don't have time to right a "long post" this time. Or was that not me you were responding to when you referred to somebody writing and/or having time to write long posts? Twice

Originally Posted by mkodama

Ok, if people aren't going to argue with me, I'm just going to leave.

Sorry to disappoint, try others if you're looking for arguments.

Originally Posted by mkodama

I disagree with what I put in bold. Metal warps from dissimilar expansion, not just heat. Heat metal evenly and it expands and contracts evenly with no stresses. A good example is people popping out dents with the spray from a computer duster bottle turned upside down.

Though the temperature of the coolant may not go passed the boiling point, the formation of vapor drastically reduces heat transfer from the metal of the engine to the coolant, so the engine will get much hotter than the coolant. Once a vapor bubble or pocket forms, the heat transfer rate goes from 0.58 watts per meter-kelvin to 0.016 , 97% slower. So pretty huge difference in cooling if there is a vapor pocket somewhere.


lol, why are your panties in a bunch? I haven't insulted you yet, nor have I even responded to you.


Ok, if people aren't going to argue with me, I'm just going to leave.

Are you also an engineer, or just someone who is mechanically/mathematically inclined?

SeanC, chill dude. You're reading too deeply into people's posts on teh interwebz.

thread is hilarious. you guys have chased OP out of here and convinced him that his thermostat was stuck open when he's trying to get some test results on an aftermarket expansion tank cap. Hope he listens!!! So much for his results holding any validity if he's got the thermostat stuck open.

Originally Posted by trizzuth

thread is hilarious. you guys have chased OP out of here and convinced him that his thermostat was stuck open when he's trying to get some test results on an aftermarket expansion tank cap. Hope he listens!!! So much for his results holding any validity if he's got the thermostat stuck open.

yeah if you look at it from that perspective...

Sent from my SGH-I997 using Bimmer App

Poor OP.

Originally Posted by WDE46

Are you also an engineer, or just someone who is mechanically/mathematically inclined?

SeanC, chill dude. You're reading too deeply into people's posts on teh interwebz.

Before I answer, why do you ask and why do you think I'm either of those two?

For those that don't know, the 1.4bar cap is 17-11-1-742-232. I checked my coolant level last night and found that it was almost empty, but the only coolant stain I can find is in my stock 2bar cap past the o-rings. I've looked at everything else with my mirror and light, and don't see any signs. No stains coming down my expansion tank either, which is strange considering the rad cap. Did a pressure test at 19psi and checked for leaks, found nothing and the pressure didn't drop during the 5 minutes I had it on for. Picked up a 1.4bar cap today instead of a new 2bar. Will do a more thorough search this weekend when I'm on the hoist.

^^ That is correct. The new cap reads 140 instead of 200 and it's what the local stealership recommended when I went in to get parts for my cooling system overhaul.

^ Nice find! So, 1.4 bar cap is actually a BMW part number! So, by default we need 2.0 bar, but 1.4 is official too. Lol, all that arguing and the lower bar cap is already available from bmw

not quite, the lower rated cap was intended for the e30 but I'm guessing unofficially some dealerships have been using them for awhile now.

some more info here http://forums.bimmerforums.com/forum....php?t=1805206 (sorry mods if not allowed to link to other boards)

I see, that makes sense, there is no reason to doubt BMW engineers on that one

Originally Posted by mkodama

Poor OP.


Before I answer, why do you ask and why do you think I'm either of those two?

Just curious and the work you did was better than most people are capable up.

Originally Posted by hanna

^ Nice find! So, 1.4 bar cap is actually a BMW part number! So, by default we need 2.0 bar, but 1.4 is official too. Lol, all that arguing and the lower bar cap is already available from bmw

interesting info

as a head's up, the vendor i've been working with this on is working on both a 1 BAR and 1.2 BAR cap. he's going to send me whichever one is going to be the production cap, so that i can test it, datalog, record results, etc.

Originally Posted by WDE46

Just curious and the work you did was better than most people are capable up.

I'm a mechanical engineering student and work part time doing CAD for an engineering and manufacturing company.

Originally Posted by trizzuth

thread is hilarious. you guys have chased OP out of here and convinced him that his thermostat was stuck open when he's trying to get some test results on an aftermarket expansion tank cap. Hope he listens!!! So much for his results holding any validity if he's got the thermostat stuck open.

cooling system was completely replaced on 10-16, still awaiting coolant cap to test from vendor

Originally Posted by bryce-o

cooling system was completely replaced on 10-16, still awaiting coolant cap to test from vendor

So, if 1.4Bar is already available from BMW, what the hell you even need to bother with any unproven 1BAR or 1.2BAR?

If you get NPG+ coolant, then worrying about the coolant boiling with a 1.4 or 1.0 bar cap is in the past. It's $40 a gallon and is a bit of a hassle to convert your cooling system to, but it's great stuff - it also is a long-lasting coolant. It is a waterless coolant.

http://www.bavauto.com/shop.asp?HC1=...p&hdept_id=417

Originally Posted by SeanC

Great, looks like people in the community has too much "street" knowledge, but when it comes down to actually calculating numbers, there is only WDE46, Terra and myself who are doing the work. I will look forward to your proof.



In my calculation of the pressure (without taking into account expansion), I used ideal gas law (PV=nRT), along with the knowledge of maximum operating temperature of 96 degrees Celcius. This gives a pressure of 1.3614 bars as the operating pressure (i.e. 0.3614 cap should suffice). For details and justification, read my posts above.

Now that we have an interval for the expansion (235-325 mL, we still don't know the absolute fill, hence we don't know the absolute expansion), we can start thinking about how this will effect the pressure that was calculated to be 1.3614 bars without taking into account the expansion. I still don't think it will effect it much, unless you're a clueless BMW owner (as most are), and top off your coolant as you would do on a domestic car.

So at this point, it seems to me that BMW is trying to minimize a possible premature ET failure by using a 2 bar cap. However, that's a good reason only for those clueless owners who tend to top things off, and I fail to see the advantages for the rest of us.

Ideal Gas Law can't be applied to water/steam You bleed the system of air, so there's very little that occupies the overall volume that you could even apply the ideal gas law too. And that little bit of air remaining is likely humid given the fact that if you open your cap when it's still warm there's quite a bit of condensation on the bottom of the cap along with a bit of steam.

Originally Posted by briangl92

Ideal Gas Law can't be applied to water/steam You bleed the system of air, so there's very little that occupies the overall volume that you could even apply the ideal gas law too. And that little bit of air remaining is likely humid given the fact that if you open your cap when it's still warm there's quite a bit of condensation on the bottom of the cap along with a bit of steam.

1. I wasn't applying to water/steam
2. You don't know what you're talking about.

Originally Posted by SeanC

1. I wasn't applying to water/steam
2. You don't know what you're talking about.

Stop responding like a dick head. The point I was trying to make is the high humidity in the volume you're considering affects the applicability of the Ideal Gas Law.