i just replaced my master cylinder with a remanufactured one. bolted everything together and started the car, and the idle quickly shoots up to 3k, and it wont go any lower

*edit* car is a 91 civic std, DPFI

any ideas?!?


Modified by srswarts3 at 3:28 PM 7/2/2005

 

look for a vacuum leak

 

probably a vacuum leak at the booster, your mc might not have had a gasket on it or your old gasket stuck to the booster and there are 2 on now

 

When I replaced my MC I had strange idle problems like you mentioned. What I found happened in my case was that the leaky, old MC had leaked brake fluid into the brake booster which destroyed the seals.

I new booster fixed my problems.

 

i knew there was a gasket that went in between there....duh

thanks for the help dudes.

 

no, no gasket... i had a bad leek between my mc and booster... i replaced them both while i was at it, but there is no gasket you can just buy, sorry

 

so your saying there is no gasket that is supposed to go there?

why is there such a huge vacuum leak then?

 

Here is a image of the brake booster.

http://www.honda.co.uk/owner/C...5.pdf

If there is air leaking around the MC where the brake booster meet then you have a leak in your booster from the leaking brake fluid.

I think a replacement booster is about $70.

Chris

 

there is no air or fluid that transfers between the booster and the MC. There is just a shaft! there are vaccum tubing around there. Look around your throttle body too. I know I disconnected one while changing mine. When I put my hand down on the valve cover knocked off one. It is like chris said if there is air comming out around there then you have a leaky brake booster. You can usually hear the air by stomping on your break petal.

 

when you replace the MC you wil lose the Vac in the booster. just let it run for a little to build vac.

If you had no vac in the booster your brake would be a brick.

 

i have a hissing noise under the hood, it is around the area of the booster/mc, i figured replacing the mc would fix this.

now when i start the car, the hissing has gotten worse and now i have a monster vacuum leak

before replacing the hissing noise was quite loud, and you could hear it when the brake pedal was pressed while bleeding the brakes (motor off)

so basically i need a booster?

 

Is your brake peddle a brick???? Hissing, I would say yes, you do need a new Booster.

 

the is 1 rubber seal between the master and booster. if you have none or two of them in there...you will have a vacuum leak.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by egtwincam &raquo;</TD></TR><TR><TD CLASS="quote">the is 1 rubber seal between the master and booster. if you have none or two of them in there...you will have a vacuum leak.</TD></TR></TABLE>

Yup. Your mc should have come with a new one. If you have two and put the new one on top of the old one the mc won't sit flush causing the leak.

 

okay, so there is a seal between the booster and m/c?

i didnt get one with the reman unit nor did one come off my old m/c...im confused??

 

So the old one is probably still there. You should check its condition. A new one should have been provided to you with the reman unit.

 

did you replace the vaccum hose that runs to the booster? usually there is one on there.

 

im guessing i need part #9??

 

bump, before i replace the booster

 

when you change your master....the seal is usually stuck on the brake booster side. clean it up and youll see. FYI: its very unlikely that your brake booster is bad. ...unless you drilled a hole in it.