Brake Booster Leak - Early Warning Signs in EFI - and a Cautionary Tale

[sscanf]

I recently posted in my reliability update the my brake booster was leaking. Once it gets bad, its easy to diagnose: A sucking sound in the cabin when brakes are applied along with hard braking and engine surge during braking. Long story short: All of this goes away once the brake booster is replaced and everything is properly re-attached.

Early Warning Signs

What I didn't realize is that my Z was telling me for a few weeks that the brake booster was going bad. It did this with an occasional engine surge at idle (it would only go down to maybe 1500 rpm's at a stop light). When this happened though, I would give the throttle a quick kick and it would get back to normal. Because of this behavior I attributed the problem to my recently adjusted dashpot (prior to adjustment it was out of the picture) or a sticky linkage. I figured it was getting sticky and it was on my list of things to look at some day. During this period when the brake booster was going bad, there were no other braking problems. Braking was strong and there was not cabin noise while braking.

Fast forward to about 10 days ago and I get the classic brake booster issues: Hard braking, sucking sound in the cabin during braking, engine surge during braking.

So I replace the brake booster (see cautionary tale below) and the brakes work really nicely, classic symptoms are gone. But, now, also gone is my stop light slight engine surge. No more need to kick the throttle (yay!).

A Cautionary Tale

Some of you may have caught this on the Help Me board. I change the brake booster last week. Its really an easy job to do (maybe 2 hours, if that - you do have to be a little bit of a contortionist to get to the bolts under the dash).

Don't make the mistake I did: It turns out that the replacement booster was somewhat larger than the old one (and I can feel the difference in braking). When I went to hook up the master cylinder to the hard lines I was careless in alignment (I think maybe that the larger booster slightly changes the alignment of the hard lines to the master cylinder slightly) and I could not get the hard lines connected. In the end, I wasted more than a few hours recovering from this and I almost had to replace one of the hard lines but managed to dremel out the burr that I had created while thrashing with the lines.

So, be sure to always get those brake lines nicely square before attempting to connect them. If you search the Help Me forum for finger blisters, you can find the whole story.

Here it is all done though (I decided to paint the new booster, I think it looks good):

Edited August 4, 2014 by sscanf