PDA

View Full Version : Brakes go to the floor and when I pump them the idle drops and almost stalls.



JesseH
05-30-2021, 07:54 PM
I tried some searching about idle issues and brake issues but I could not find anything covering both issues. Sorry if I am missing an enlightening thread that has been posted already.
The brakes gave out a few days ago and pumping them up builds no real stopping power. It will drag a bit but the e brake is the main way to stop the van. (Just limped it home to know this)
I was sitting with the van running and I was pumping the brakes and watching the brake fluid level and nothing seemed to be dropping at all even after a lot of pumping, But that is when I noticed that the van would start to stumble and the idle drops from like 800 to about 250-300 when I pumped a lot.
Would a bad master cylinder do anything to the idle speed?
I would have thought some leaking fluid might be getting into a vacuum line to mess something up but... not see fluid loss makes me second guess this idea.
I tried to do a solo bleed on it today and nothing changed. I plan on doing a proper bleed with a buddy soon.
Any speculation why pumping the brakes affects idle speed?

JesseH
05-31-2021, 10:27 AM
Pulling the vacuum line off the brake booster and plugging the line keeps the idle solid while pumping. I’m getting a new master cylinder and I’ll report back what happens.

Ace MM
05-31-2021, 11:10 AM
sounds like a vacuum leak. check all lines while replacing the MC

JesseH
06-08-2021, 11:50 PM
So... The new master cylinder fixed it right up! I was really thinking I needed new vacuum lines or a booster to fix the issue but nope. The idle issue went away when I pulled the MC off and pumped the the brakes to no idle change (or master cylinder). Bench bleed the new one and it’s working great now. The MC I’m pulling out seems like a poor refurbishment of an OE master cylinder. Just want to leave some bread crumbs for anyone else searching about the odd idle thing. Have a good time vanning all!

SunnySlowLaneClub
08-26-2022, 11:29 AM
Hello! I have the same issue. Van wants to stall while pumping the brakes. I have only the back brakes not working, front ones work fine. I'm thinking about replacing the MC and checking the vacuum lines at the same time. I have a 1987 4x4 van. Where is the Master Cylinder located and how do I access it?
:cnfsd:

Gareth
08-26-2022, 05:35 PM
Installing a New Brake Master Cylinder
https://www.toyotavantech.com/forum/showthread.php?1550-Installing-a-New-Brake-Master-Cylinder&highlight=dash+removal