Replaced power brake booster - still no brakes
 

Here we go again. 88 BII, 2.9, 4WD. My brakes were slowly fading and would go to the floor. At times I could pump the pedal and it would come back for a little bit, then it would start again. It happened on my drive home from work (62 miles). There is NO fluid leakage anywhere. The reservoir is full. I changed the power brake booster and it is worse. The pedal goes to the floor with minimum resistance. Now the engine runs at a higher RPM. When I first start it it hits 2,000 then after a few seconds it drops to about 1,500. When warm it is 1,000. When I hit the brakes there is a slight change in engine speed, about 100-200rpm up, then it settles down to 1,000. I pulled the codes and it passes. Like I said this all happened in one day. Any suggestions would be greatly appreciated.

Dave

If the pedal goes to the floor and there are no leaks I would replace the master cylinder.I have replaced a lot of Honda master cylinders,they leak internally.As far as the idle quality.I would recheck for vacuum leaks.Carl

Since you're not finding any leaks at the wheel cyylinders/calipers it sounds like the master cylinder is leaking internally. I'd replace it.

Do you have a vacuum leak, the rpms sound odd.

I've noticed sometimes that my RPM's change a little when I press on the brake before shifting into reverse of OD. I don't mean to derail this but, Ken, do you have any vaccum diagrams of the engine compartment for a 2.9L? I've found a few hoses not connected to anything and my RPM's have been getting higher, so I found where some noise was coming from and I plugged it with tape. Lowered RPM's but I need to know where all the hoses go, and what leaks to check for. Thanks

Don't have one right now so from memory... The fitting on the drivers side of the engine has ports for the brake booster, cruse control, climate control, and auto tranny. The one on the passengers side should go to the MAP and the air box. The ones on the throttle body should be the the PCV system. Please correct me if I'm wrong.

What is MAP? I've heard it in several forums, but never asked.

The MAP monitors manifold vacuum. High vacuum at idle & the injectors supplyless fuel. Low vacuum at full thottle & the injectors supply more fuel Ignition timing & EGR are also changed according to MAP input.

Ken,

That's what it looks like on mine.

Update: Changed the master cylinder and got my brakes back, thanks to those who gave me the tip. Still have the high idle problem. Can't find any vacuum leaks. Think it could be the MAP sensor?

Dave

Glad to hear you got the brakes fixed.

Pull the electrical connector off the IAC, rpms should drop or stall. If it doesn't you have a vacuum leak or someone messed with the stop screw.

I'll try that today when I get home, Ken.

I did something that I don't like to do. I "shotgunned" my troubleshooting and as usual it did not fix the problem. I just replaced the MAP sensor and PCV valve. It made it run smoother, but the rev's are still at about 1,200 in park at idle and around 1,000 in gear.

Dave

Have you taken a couple of minutes to pull the trouble codes.

87XLT,

It passes the KOEO test and I get codes 13 and 21 in the KOER mode. 13 has to do with idle not within self test range(no kidding!) and 21 has to do with coolant temp sensor or on the distributorless system the crankshaft position sensor.

Ken, haven't checked the IAC yet, hope to get to it this weekend. Will update when I do.

Dave

could have gotten code 21 if you did not let the engine warm up to operating temperature also.

Okay, I got the problem with the high idle fixed. It seems that the person (me) who removed and installed the brake booster knocked the vacuum line off the driver's side manifold vacuum plug :o :o :D The wife and I kept hearing the vacxuum leak, but with all the other noises I got I really could not pinpoint it until I took a good look around. Thanks to all for the suggestions. I appreciate the help.

Dave