Brake issue - Reaction valve hissing

Prepping the e-type for the new year and when I took it for a drive, I noticed a high pitched hissing sound when I modulated the brakes. The brakes worked as always but the sound was unexpected. I opened the bonnet and could hear a hissing sound coming from the reaction valve. When I turned the engine off, there was a continued hissing at the reaction valve that sounded different but did sound like an air leak that slowly stopped after a short time. One more potentially linked event. During the drive, I had to stop suddenly and applied the brakes very hard. The engine died. That had never happened before. Would it be linked to a much larger vacuum/air leak due to aggressive application of the brakes? Is my problem with the reaction valve or elsewhere? The hissing sound is coming from the reaction valve but could the problem be elsewhere and just making a sound at the reaction valve air vent?

I suggest you tighten all the hose clamps.
Either one is loose or a vacuum brake hose is cracked and leaking, or there is a vacuum leak somewhere
Dennis
69 OTS

I guess what you’re saying is it’s probably not the reaction valve itself. I will check the hoses and tighten the clamps. Any thoughts about the booster being the issue? I sure hope not but want to consider any and all options. One more question. If the issue is a hose or hose clamp, why is the hissing coming from the reaction valve? Shouldn’t the sound be coming from the leaking clamp / hose?

It sounds to me that the reaction valve is not sealing properly. I would start with a visual inspection.
Tom

I have a reaction valve kit on the way. That will be a reasonably easy place to start, particularly if I don’t find any suspect hoses or clamps.