I have a 2006 e350 passenger bus.

Last night I had a tire failure at about 40mph on rear outside dual tire. Now, before anything else happened, I noticed my bus was driving fine but the speedo read over 3k, very abnormal, and the engine didn't sound like the rpms were that high.


I made it to a gas station, removed the tire, and when I went to put air on the inside tire, which was low, once I hit about 45psi something shot out of the tire and it immediately went flat and the bus sank to the ground. So there was a shock to the bus's suspension, just mentioning this so I tell the complete story, but I don't think this caused anything to bind.

So to get rolling I switched a tire from driver side to passe get side, now rolling as a nor AL vehicle not a dually.

When I start the vehicle now, the rpms jump to 2k as the new baseline instead of 600 where it used to be. It appears to function normally other than that. This seems weird it happened when the tire blew. I mean it happened at the exact same moment.

Then, after driving a few miles, I suddenly lost power brakes and there is a severe hissing coming from my brake pedal. Now, my break pedal has been hissing since I bought this vehicle over a year ago, but now it's really loud. I am assuming the brake booster went bad, but this all seems very coincidental it happened at the same time. Could something else that happened last night cause this? Master cylinder is not leaking or losing fluid. I recently had to replace a seized caliper and bad brake line about 3 weeks ago but it has been running fine since then, until this.



Does anyone have any input?



Does anyone have any ideas?

 

Hopefully you will get some additional ideas to check.

We don't know at this time if you ran over something that caused the 1st tire to go flat.
We don't know what was ejected from the 2nd flat tire.

There is a pretty big vacuum leak to locate and this could all be just coincidence, don't know until everything is checked out.
I'm pretty sure you mean the engine RPM went pretty high and not the speedometer.
We also have to consider if whatever was run over hit any electrical wiring that now could cause incorrect readings,a thorough inspection is necessary to verify all systems are ok.
You didn't state what mileage was on the speedometer, but something is going on with the brake syst and really if was questionable to replace only the one caliper..
Which caliper was it? What wheel ?

 

Welcome to the site

No CEL?

Being you seem to hear the booster leaking vacuum (inside the van?) I’d start there.
If there’s a significant vacuum leak be it the booster or any engine related bleeds, it can affect fuel/air ratio, meaning a lean condition exists and idle speeds can raise when the system try’s to correct the lean condition by adding fuel to try and recover the ratio. But being you stated it had been leaking for some time, it should have trigger the check engine light (CEL) and set code/s
Generally with a failing booster, the pedal feel changes,, meaning stiff, tall, or high effort etc..
You might try removing and capping the booster vacuum supply hose to see if the idle speed issue corrects itself.. The tach reading 3k, if the engine wasn’t at that actual speed would be odd and doubt it would be related to vacuum leaks, nor anything tire related..

As for the tire, did the valve stem let go while inflating? Tire burst ?