[6Inarowmakesitgo!]

My old cap was not holding pressure properly, you could squeeze a hose and hear it hiss out from under the cap. The original one was a 1.4 bar opening pressure. I ordered a new one, same manufacturer, but it states 2 bar opening pressure, a significant increase of pressure. The entire cooling system is new except for the heater core. 2 bar seems a little excessive at just a hair under 30psi. Car runs great. No drops in coolant levels and no mixing of oil/coolant/trans fluid.


What do y’all think? Try to find another 1.4 bar cap? or stick with the 2 bar cap and run it.

[Efthreeoh]

I'd go with the stock pressure version of the cap. It works fine and reduces the risk of heater core rupture by increasing the pressure of the cooling system in case of an over-heating event.

About six years ago I had the same issue, loosing coolant level over time, with a leak-free system. I replaced the car with an OE BMW part and stopped loosing coolant at the faster rate I was previously experiencing.

[6Inarowmakesitgo!]

Originally Posted by Efthreeoh

I'd go with the stock pressure version of the cap. It works fine and reduces the risk of heater core rupture by increasing the pressure of the cooling system in case of an over-heating event.

About six years ago I had the same issue, loosing coolant level over time, with a leak-free system. I replaced the car with an OE BMW part and stopped loosing coolant at the faster rate I was previously experiencing.

It ran fine with the high pressure cap, but man being anywhere near those hoses at full operating temp gave me a really uneasy feeling. Stuck the old one back on it for now and it doesn’t seem to be venting at all. It maintains pressure overnight which is odd.

[smass]

OE part is $20. Not worth going aftermarket.

[Welcome to NBA Jam]

Originally Posted by 6Inarowmakesitgo!

It ran fine with the high pressure cap, but man being anywhere near those hoses at full operating temp gave me a really uneasy feeling. Stuck the old one back on it for now and it doesn’t seem to be venting at all. It maintains pressure overnight which is odd.

Grab yourself another 1.4 bar cap from Rein. The E46 used a 2.0 bar cap and people actively sought out a 1.4 bar Landover cap because E46 expansion tanks had a nasty habit of catastrophically cracking under pressure. Granted the E90 tank is a different design, it's originally fitted with a 1.4 bar cap. A 2.0 bar cap will only increase your risk rather than help it.