Hard brake pedal solved - Vacuum issue -
 

This may help anybody else who replaced their brake booster and check valve for a hard brake pedal and got no improvement. I was finding it very hard to come to a stop going down a hill without standing hard on the pedal. I've been round and round with this problem and read every hard brake thread.

As a last resort I took it to the Toyota dealer to get a diagnosis. They were stumped, and wanted to replace the master cylinder and brake booster: $$$

I replaced the check valve and then the brake booster myself. Did not fix the problem. So I took it to a friend's mechanic who asked me a lot of questions I couldn't answer about testing vacuum. I left it with him and he called me back in a hour.

- He said there was vacuum through the hose going to the booster but Just not enough volume.
- Possible fixes:
1. clean out and VAT the intake section on top of engine. about 300 to 400 bucks.
2. he routed a vacuum hose from another source to the booster. Brakes working GREAT. I guess this is temporary fix till I do #3>
3. He suggested a cheap fix would be mounting a Vacuum cannister to route vacuum from. Maybe 50 bucks.

I'm not a mechanic and may not be using the right terms but passing this along if it helps anybody . . . . and the dealer don't know s%#t.


http://webgreen.com/vacuum.jpg

Why no one has commented is beyond me - this is awesome!

For the cheap price, I might just try #3 to see what it’s like.

OP what MY ya got? On some later models like mine the metal connection tube used for your 'fix' is not a part used in my 01.

I wonder what the other end on yours connects to? Was the input to the booster end an existing port or made?

Luck and enjoy the Runner. :cowboy:

Instead of routing from the brake booster to it's usual vacuum source on the side of the engine intake manifold,(the nipple next to and just below that diagnostic plug-in), he routed from the booster to a metal vacuum tube on top (see red line in original post). He then routed from that now open intake manifold nipple to the charcoal canister box (whatever the hell you call it). See blue line in attached image.

I bought a vacuum cannister off amazon and my plan is to mount that today and try return to sourcing the vacuum from the original and weaker position on side of intake. Only place I see to mount it other than removing the front grill, is maybe in the space down between battery and engine.

Also will use Sea Foam treatment first to clean out the intake manifold and see if that also helps vacuum volume.

http://webgreen.com/vacuum2.jpg

oh, forgot to reply that this is a 2000 4runner SR5.

>>>>Was the input to the booster end an existing port or made?

Goes to an existing port of top of intake manifold.

Looks like something anyone can do in a few minutes to determine if your braking problem is a vacuum problem instead of Booster or check valve.

2000 sr5 here too, and if I recall on my stock booster I do not have a check valve. Maybe try cleaning the metal tube and port on intake mani with a pipe cleaner or small round brush. Swapping vacuum hoses is a band aid, I would find out why you have low vacuum at that port, and fix the issue. Pulling the upper half of the intake isn't hard at all. Probably could use a cleaning. Have you ever cleand the throttle body or intake mani? It's free and easy to do.

Yea, probably a good idea to manually clean port and return to original routing. I'm also going to do the Sea Foam treatment.

I installed the Vacuum can this afternoon but haven't connected it yet. Couldn't hurt.

What’s the report?
Which can did you opt for?

Thanks for this post. I've been chasing a hard pedal issue on my 05 Sequoia with the 4.7. Sounds like your exact issue. Both the brake booster and the check valve are fine (brakes firm up when the truck is off, then release when starting the truck and holding the brakes down).
I'll look into a low vacuum issue on the air plenum side, I never even thought about that. Vacuum, but just not enough.

I put in a 32 buck vacuum can from Amazon. But can't say that it helped my brake booster a noticeable amount. Though I got some improvement before putting in the can by routing vacuum from a different port, I'm still not 100% happy with my braking. So, bottom line, Consider your vacuum assist to the brake booster as an option to test if you've tried everything else because it's cheap and easy to try. Now wondering if my rebuilt brake booster from O'Reily's is good. Saw another thread where a guy said he had a bum rebuilt unit and had to get another.

I saw this as a way to check your brake booster: " Hold brake pedal in when you turn off car and pedal should not move for 30 seconds"; mine starts pushing back up almost immediately. Is that test legit?

Not entirely. Even after you turn off the car the brake pedal has a bit of give in it. Pump it a couple times until it firms up and THEN hold it. There should be no give at all unless there's a fluid leak or vacuum leak in the booster.

I'm thinking that you may be able to use the spray version of SeaFoam in all your vacuum hoses, specifically the proper brake hose.
Do it slowly, and if there's anything clogging up the hose or the port on the manifold, it'd clear it out.

I know that those vacuum canisters are usually used for old muscle cars with big cams that by default had low vacuum at idle. I don't think there's any reason to replace the cams on a 3rd gen 4Runner (with either the 2.7 or 3.4), but has your engine had any work done to it, by chance?
By that note, would out of spec valves cause a vacuum issue?

No engine work done except for the timing belt and water pump replacement at 200m. The vacuum hoses are clear. I guess I could try some SeaFoam spray directly into the ports.

Hey Greeney - did you ever solve this. I have the same exact issue on my 99. Haven't checked the vacuum yet, will do as soon as I get a gauge though.

Thanks!