Early failure mode on brake hydraulic boost pump

During the last week, or slightly less I suddenly started hearing the brake boost pump running much more frequently than normal in my 2008 and is also producing a "knocking" noise along with its run noise which increases in frequency as the pump speed increases. No problems with the engine coolant pump for the thermos, and the inverter pump was replaced yesterday along with a replaced "bolt" in the steering column for the recall.

I had the dealership (Toyata West in Columbus, Oh.) check the boost pump while it was there (by the way no error codes (yet) on my scangauge or the dealers scanner. Just the increased noise and run time. No fluid leaks noted. Pump current while on is approx. .8 amps (via the scangauge). With the car parked and the ICE off, the pump still continues to run intermittently and for quite a bit more than the 5 seconds or so it did prior to this, perhaps 15-20 seconds +. Still runs quite a few times after the car is turned fully off too.

I have quite a bit of suspicion that the Service Department yesterday was playing a bit of "hear no evil, see no evil"... because no outright failure has happened, and they know that its an expensive part and a chore to get to and replace AND I still have the extended warranty. 45,000 now on the odo.

Thoughts anyone?

I think I'll run a similar note up to Toyota Corporate and see if I can get a response.

 

Still researching. Narrowed to my best S.W.A.G. as the accumulator or related component internal leakage. Had the resident "prius guy" at a nearby dealership lend his ear for a few minutes, who then announced that he was sure it was normal... just like the 08' they had a couple of bays down. From the look of the accumulated leaves, dust/dirt under the bonnet, the owner of that one would have considered this area "The Unknown Country" and considered any unusual noise as "normal" short of having a complete failure of the engine mounts and scraping the engine assy. along the tarmac.

 

Thanks Patrick

I suspect that is the case, and in the case of the dealership I had do the two recalls for inverter pump and steering column, I also suspect that the tech (if he was worth his salt) also knew this but as you say wasn't required to do anything until a warning code appears.

I did manage to find a reference online to DTC C1391/69 (abnormal leak of ACC Press.) and how to read out that pressure sensor value (apparently an analog voltage) with the "Hand Held Tester" and monitor that reading for either a steady reading or a decreasing value which indicates a leak (and replacement of the Brake Actuator Assy.).

I'm going to check around and see if I can find a service dept. willing to perform that test and even if they can't replace it before an error is flagged, I want that attached to the vehicles "history" so that I can point it out if they balk at a warranty replacement later...