Have Toyota Questions? Ask a Mechanic for Answers ASAP
Hello I will help you with your question,
I am not sure what seal you had changed but the hissing noise is the vacuum leaking out of the power brake booster. Even though you have power function at this time it is leaking and needs to be replaced.
Please let me know if you have further questions
Yes, if the booster is leaking when you unseat the rear seal by stepping on the brake it should be replaced.
List price for the booster is $750 and it requires 2 hours of labor to replace.
An aftermarket booster is available for about $170 but the quality may not be up to standard. Your shop would have to make that determination.
I don't know the shop labor rate in your area but here it ranges from $80 - $120 per hour.
I am always glad to help, please let me know if you have further questions
Are you able to clean the area and see where the oil is coming from?
Spray brake cleaner works well for this. Clean and dry the area and run the engine for 10 minutes then shut it off and look for the highest wet spot to see what is leaking.
Let me know what you find
Great, let me know what you find