Preventative maintenance

[Beedub]

Hey guys, I'm replacing my coolant cap as part of my preventative maintenance, and came across this....

http://germanautosolutions.com/bmw_solutions/cooling_system/12_bar_coolant_cap/product_bmw_12_bar_cap.php

Anyone got any input they'd like to add, it's basically a lower vent pressure and according them helps longevity of the plastic components and doesn't alter cooling efficiency at all.

Their logic makes sense to me but maybe someone with more knowledge of cooling and pressure could chime in.

 

[chrissrush]

According to: http://www.engineeringtoolbox.com/boiling-point-water-d_926.html

At 2.0 Bar "pure" water boils at 120 C
At 1.2 Bar it will boil at 105 C

With antifreeze in the system the boiling point is raised higher than that of water alone.

I don't see any harm in it, the pressure cap is intended to allow the water to "run hotter" any excess of pressure will vent coolant to the expansion tank, and, when it cools suck it back into the system.

http://auto.howstuffworks.com/cooling-system3.htm

Suggests that a 1 Bar pressure cap would raise the boiling point by 25 C which in a 50/50 mix would apparently) give you a coolant boiling point of 131 C!

Surely that's hot enough!

I guess you could check the expansion tank when fully hot and see how much it's vented?

On the other hand I guess you need to bear in mind that with the extra power I believe you run so the demands on the cooling system will be higher.

 

[simonlpearce]

Personally i would have said to leave well alone. I had issues with a replacement coolant cap that was non OEM on my E36 M3 in that it just didn't hold pressue.

However the above argument is much more thought out and sensible than mine.

 

[Ewazix]

Sounds a bit snake-oily to TBH, exactly what INTERNAL plastic component in the system is subject to pressure other than the expansion bottle?? Impeller blades and other internals may be plastic but are contained within the closed circuit so shouldn't be pressure stressed (other than by the dynamic flow). True that the bottle is a weak point but leaky cracks are relatively easy to spot and fix with a replacement.

On the flip side IF you can run at lower pressures without boiling over that has to be a good thing for seals etc so maybe using waterless coolants like Evans Power Cool which runs to 180 C deg could provide a solution, it also reduces corrosion. I've read about it over the years but never tried it, but wondering why not? :scratchhead:

Come to think of it the Evans sounds a bit snake-oily as well - any users out there?

 

[Beedub]

interesting stuff.

 

[tertius]

Personally I would replace with OEM and do it regularly.

This was a well known issue with Elises, such that most people (well some) would replace them annually, and quite often you'd look at an Elise to see the date Tipp-Ex-ed onto the expansion cap so you knew when to replace it.

What is the cost of an OEM cap?

 

[andysat]

Personally I would replace with OEM and do it regularly.

This was a well known issue with Elises, such that most people (well some) would replace them annually, and quite often you'd look at an Elise to see the date Tipp-Ex-ed onto the expansion cap so you knew when to replace it.

What is the cost of an OEM cap?

Probably about £400 :roll:

 

[tertius]

Personally I would replace with OEM and do it regularly.

This was a well known issue with Elises, such that most people (well some) would replace them annually, and quite often you'd look at an Elise to see the date Tipp-Ex-ed onto the expansion cap so you knew when to replace it.

What is the cost of an OEM cap?

Probably about £400 :roll:

OK, then maybe I wouldn't ...

 

[andysat]

Personally I would replace with OEM and do it regularly.

This was a well known issue with Elises, such that most people (well some) would replace them annually, and quite often you'd look at an Elise to see the date Tipp-Ex-ed onto the expansion cap so you knew when to replace it.

What is the cost of an OEM cap?

Probably about £400 :roll:

OK, then maybe I wouldn't ...

 

[tertius]

What is the cost of an OEM cap?

£8.81 on BMMiniparts.com