Hard Brake Air goes to defrost

[Uhohspaghettios]

I changed the coils in an 06 Limited and immediately following that the brakes are very hard and the air comes out of the defrost vents. That's got to be some sort of a vacuum screw up on my part but I have no clue what. Looks like all the hoses got plugged back up the way they should be. Had my dad look it over to see if I missed anything and we are stumped. Any ideas?

 

[Aspen03]

Like you said it has to be vacuum, assuming hooked up correctly the next step is to find the leak, or crack that was created while messing with them. These old trucks don't like to be touched. I have 2 2nd gens. Our navigator has this issue but it occurs at part throttle while cruising and my Expedition just did it today while having the cruise set on 71 on the hwy and a slight uphill grade. I'll be purchasing a smoke machine to track these down. Easiest way to pinpoint a leak.

 

[Uhohspaghettios]

Thanks for the reply! I decided to step away for a day and see if I got lucky on the internet, back at it tomorrow

 

[Hamfisted]

Can you post pics of the engine bay of your Expy ? Particularly the throttle body area where vacuum hoses run. The hot water valve also. Are you getting a check engine light, or any DTC codes ?






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[Uhohspaghettios]

301 and 308 before I changed the coils, nothing since. Will get pictures within the next hour- thanks much!

 

[Uhohspaghettios]

 

[Uhohspaghettios]

 

[Uhohspaghettios]

 

[Uhohspaghettios]

 

[Uhohspaghettios]

 

[Uhohspaghettios]

That hose that runs along the back is not in the best shape but with how dramatic the problem is I kind of thought I had put a hose somewhere it shouldn't go instead of it just being an older hose. Either way I'll be changing that one out tomorrow just because I'm out of ideas

 

[Hamfisted]

Yeah, I don't see anything obvious. You may end up having to check the intake and vacuum hoses with a smoke machine to find any leaks. The loss of vacuum only happens when you step on the brake pedal ? You could disconnect the booster's vacuum line and plug the hose, then with the engine running step on the brake pedal and see if the loss of vacuum problem goes away. That would kinda point to the brake booster diaphragm leaking. Do you hear any air noises from the brake booster when you or an assistant steps on the brakes?






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[Uhohspaghettios]

It's a very loud engine, can't really hear any issues. Running and idling is not noticably worse than it was before. I'm not sure about only loss of vacuum, more those are the symptoms I've noticed. The brake pedal is hard to push down and does not do anything until it's all the way down and the ac comes out of the defrost vents no matter what it's set on; both just started after the coil swap.

 

[Uhohspaghettios]

Does this look right coming off the brake booster?

 

[Uhohspaghettios]

 

[Uhohspaghettios]

Made a diy smoke test and the billowing smoke from behind the engine was enough to motivate me to get serious about where the back hose goes. Wriggled, twisted, and cussed til I got the hose back on it's little metal offshoot on the back of the engine. Skinny arms can access it from under the driver's side with a great deal of determination and nothing being removed.

 

[Hamfisted]

Did that seem to fix your issue ? Repeat the smoke test until all leaks are taken care of.





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[Uhohspaghettios]

My issue is definitely fixed and you're right I should repeat the test to get any less troublesome leaks taken care of. Honestly tonight I was just glad to have my ride functional again. I figure I should wait to do anything else til I've made it through the work week.