I always seem to run into odd problems. The brake booster rubber boot from the brake pedal rod is hissing. Its only when I dont use the brakes. If I step on the brake pedal enough it will slow the hissing, and more it will completely eliminate it. This doesnt seem to affect engine operation, would this be considered a vacuum leak as it is only there when the engine is running. But it is on the opposite side of the booster from the vacuum source.

Would it be ok to smear some silicone sealer or something on the boot to seal it? If any sealer got into the boot and further what could it damage? Booster, master cylinder?
How hard is replacing that rubber boot?

thanks
take care
Luke

I had to replace the brake booster in my 245 earlier this year. When it began to fail, it only made a whistling sound when the brake pedal was pushed very hard. But the noise did get progressively worse over time and eventually in impaired the effectiveness of the braking system. Also, it was very clear that the defective booster was venting engine vacuum because the engine would "sputter" during hard braking. I replaced it with an aftermarket booster made by Bendix($160) The installation took me about 2hrs.

that seems odd.... Just for kicks when the engine is running spritz WD-40 at it and listen to the engine... Mac

thanks I will give that a try.