1989 BMW 535i Pressure Tank

Do you mean expansion tank?

Hi there,
The mechanic referred to it as a pressure tank but after looking it up on line and not finding that term I assume it is the expansion tank however I am far from qualified to determine. The part has to do with cooling the engine so again that appears to be called the expansion tank correct?

Yes, and thank you for the clarification. The expansion tank is shown in this link: http://www.realoem.com/bmw/showparts.do?model=HD13&mospid=47408&btnr=17_0001&hg=17&fg=05
The site is quite useful, dont you agree?
The $80 dollar part and the total time to diagnose and repair the car should have the bottom line at less than $150 bucks, is this close to their quote?

Thank you for replying and for the most helpful website! You are saving us over $100. They want to charge $281.27. They said we need to replace the tank plus the cap - can we use the old cap? The cap is only like $10 though. We are just going to order the part and the cap from Parts Geek and my husband is considering whether he can replace it himself.
The website is going to help him see how to attach the part so again thanks very much for your help!
Sincerely,
Betsy

It is going to possibly require bleeding the air out of the system too, the air bleed is on top of the T/stat housing, #9 in this link: http://www.realoem.com/bmw/showparts.do?model=HD13&mospid=47408&btnr=11_1118&hg=11&fg=35