Brake Booster Check Valve

[ZMARKUS]

Can the brake booster check valve be individually replaced on the 1999 Q45 and where is it located? Brakes are becoming somewhat harder to press, early in engagement. Plus,a sound of air escaping or sucking, is coming from interior dash, where brake booster is located, when pedal is pressed. Break fluid level remains unchanged. Hoping it's a check valve issue as opposed to brake booster.

[EdBwoy]

The 99 Q seems one of those convenient ones where the check valve can actually be individually replaced. As a rule of thumb, they are usually located in the only line that goes from the brake booster to the intake manifold (popularly used by people running seafoam cleaning into their engines).

The symptoms make sense. Test it to see if it's leaking by.
The manual should be helpful too. Page 15: https://www.nicoclub.com/FSM/Q45/1999_Q ... Q45/br.pdf

[ZMARKUS]

Thanks, that's good to hear. I suppose that will be a dealer only part, as search results have been non existent. Yet, I've seen availability of this part for previous generation Q.

[EdBwoy]

Well, slight correction. I suppose it's not uniformly replaceable in all Qs. This website seems to indicate later production models have the part integrated into the hose: https://www.infinitipartsdeal.com/parts ... ?PNC=47210

Either way, both can work with a discrete check valve (I don't see why not), and 47478-6P100 is the original part number. It has been superseded but should still be available at some dealers.
The other option is grabbing any check valve off the shelf that fits the tubes, but I'd rather stick to a properly designed and sized unit.


Of course, test the thing first so you don't waste time/money on an unnecessary replacement.

[ZMARKUS]

Thanks for the diagram. I've been searching for something detailed as that. Appreciate the info.