Rotax 912 Coolant Pressure Cap

[skippydiesel]

Here's a conundrum -

 

Commissioned 2000, 912 ULS 750+ hrs, Third Owner (done most of the hours).

 

Another thread prompted me to check out my Radiator Cap next time I had my cowl off (today).

 

Cooling system has always worked very well. No complaints. All required rubber (hoses etc) replacement done on time.

 

Existing radiator cap 0.9 BAR (13 psi) - possibly never changed (certainly not by me). Cap appears to be in good functioning condition.

 

Rotax manual (and other thread referred to above) recommend replacement cap 1.2 BAR (17.4 psi).

 

I have the new cap but if I fit it, the internal /operating pressure of my cooling system will increase by 0.3 BAR (4.4 psi).

 

I fear the increased pressure in my now quite old system.

 

What would you do??

 

 

[microman]

I think you are worrying about nothing - I fitted the later cap to my old 2000 hr Rotax without any problems and, worst case scenario, the increased pressure might show up a problem somewhere in the system that otherwise mightn't have been noticed. If you have done the hose replacement requirement as per the maintenance manual cant see that you would have a problem.

 

 

[skippydiesel]

I think you are worrying about nothing - I fitted the later cap to my old 2000 hr Rotax without any problems and, worst case scenario, the increased pressure might show up a problem somewhere in the system that otherwise mightn't have been noticed. If you have done the hose replacement requirement as per the maintenance manual cant see that you would have a problem.

Thanks Microman - that's the sort of reassurance I am looking for - 2000 hr's without a problem "way to go!"

 

Got to say though - its the "showing up a problem" that concerns me a little. There may be no problem at 0.9 BAT with the coolant pump seal, but 1.2 BAR may be too much for it. Same goes for the radiator. Suddenly life becomes expensive (as always with aircraft).

 

 

[bstrachan]

If your cooling system is working fine and the old cap is holding pressure, why change it? You probably know, the reason for pressurizing the cooling system is to raise the boiling point of the coolant. Take a look at this article Things you should know about coolant | hellafunctional As long as you have the correct mixture of "antifreeze" and water your .9 BAR cap should be fine. So why did Rotax recommend the change? You'd have to ask Rotax. Good luck in getting any info out of them.

 

"If it aint broke don't fix it"

 

 

[skippydiesel]

If your cooling system is working fine and the old cap is holding pressure, why change it? You probably know, the reason for pressurizing the cooling system is to raise the boiling point of the coolant. Take a look at this article Things you should know about coolant | hellafunctional As long as you have the correct mixture of "antifreeze" and water your .9 BAR cap should be fine. So why did Rotax recommend the change? You'd have to ask Rotax. Good luck in getting any info out of them."If it aint broke don't fix it"

Yeah! that's kind of the way I feel. Due (about 30 hrs) for its 5 year rubber (carbi, hoses etc) replacement might try the new radiator cap after all the new stuff has been fitted.

 

 

[Downunder]

You will only "blow off" at 1.2 bar if it reaches that pressure/temperature.

 

If the engine runs perfectly well and not hot, then I don't think you will see much difference.

 

Rotax probably upped the pressure to prevent very hot engines "dumping" the coolant.

 

 

[skippydiesel]

You will only "blow off" at 1.2 bar if it reaches that pressure/temperature.If the engine runs perfectly well and not hot, then I don't think you will see much difference.

Rotax probably upped the pressure to prevent very hot engines "dumping" the coolant.

I like your logic/reassuranc