pcolt94

I wasn't looking for a brake problem, I was looking for a vacuum leak perhaps related to my "hesitation" problem. I was de-pressurizing and checking all the vacuum lines that connect to the manifold. The last check was the booster and the initial findings of it led me to keep digging deeper. Basically I did not like the sound of the swoosh of the pedal and it did not have the 3 characteristic pumps before it got hard. But the real clincher was when I was monitoring the manifold vacuum with a gauge and pressing on the brake pedal. The vacuums dropped 2 or 3 pounds and just stayed there as long as the pedal was down.

I hadn't noticed any real bad braking with the car but has noticed the brakes might not has been as good as it was at the slower speeds few years ago. Thought it might have been pads and not really a problem so had not got my attention yet. So going to replace the booster and see if these problems clear up.

It would be real nice if this clears up my hesitation problem if luck is with me. If this fixes it, I'll post the information and details of the "fix".

antfarmer2

if that does not do it and you would like to clear up your hesitation problem I would change your front two 02s.

SJW

I'd say there's an excellent chance you'll kill both problems in one shot. All indications are that your booster diaphragm has developed a leak, and the unmetered air it will admit to the intake will disrupt the trims. If you have anything that'll read them, check your LTFT and STFT numbers before and after the booster swap. Should be revealing.

Live well,

SJW

pcolt94

So I received the part and went to install this morning. Booster was only 5 years old and still in full warranty no charge. Wiggled the thing in and got it thru the firewall. Got the first nut started and decided to slide the rod on the stud for the pedal. I immediately noticed the pedal was nowhere near the 2 push switches, I could see the adjustment wouldn't even come close and the pedal was way too low. Made sure the booster was all the way flush to the firewall and rechecked it all again. Remove the booster and concluded the rod was too short. Went down to the part store which still had my old booster to compare the rods. Sure enough there was about a 1/4+ inch difference in length. Also I did notice the rod diameter was thinner and less hunker than the original rod but that was not really an issue but the length is.

I knew even while driving back to the store that the part was made wrong or packed wrong and the manufacture. I ended up going to another store also to check their part and was wrong also (of course). So the second manager called the manufacture, and the first store manager is ordering another booster with a different part number (2+ hours of effort today). The managers who I know for years both were trying to solve the problem with good effort. So the vette apart for now and waiting to see where this all goes and how long it will take. I did get my original booster back. Good thing I have other things to drive.

Darn

SJW

I'd suggest you hold onto the old booster until you're fully satisfied that you have a new one that's good to go. Good luck with it. Let us know how the story ends.

Live well,

SJW

pcolt94

In response to your suggestion while I'm waiting to resolve the booster problem, I have had this hesitation problem for some time now. Some parts got changed for normal maintenance, and a couple for the actual problem. Have had couple threads on it (and is appreciated), but was no real help or things I had not done already. Have looked at the fuel trim numbers more times than I can count. When I can I drive around with my Tech1 looking at various sensors and readouts. O2, TPS, MAP, MAF flow, Fuel trim and all the others that might be related.

Nothing is ever out far enough to chase. Fuel numbers are always couple points of 128 which was some of the things I looked at again and again. Any sensor that had a voltage out reading I verified it against the Tech1(and vice versa). Fuel pressure was the only symptom I had which dropped when the engine hesitated which was not at initial acceleration, but about 1/2 second later. FPR and pump were changed.

But I did not know if the pressure was really dropping, or a change in vacuum to the FPR caused the pressure to drop. So couple days ago decided to do a real hard core check of the vacuum system and that’s where I am today finding a leaking booster.

The hesitation problem I only work on from time to time since it is an annoyance rather than a big problem. Maybe this is the last time I'll have to deal with it.

SJW

If your FP was dropping as described, even after replacing the FPR, there's a very strong probability that manifold vacuum was behaving abnormally. This could be consistent with a leaky booster diaphragm that would be returning to its relaxed position after you released the brake pedal. I'm betting a leak-free booster will resolve your hesitation.

Live well,

SJW

pcolt94

So a lot of water under the bridge at this point, but to be brief. The situation was moving too slowly for me so I took as much as I could into my own hands. I called every part store in my area to see if they had a booster and to check with their own stores and hubs who had one. Whoever I did asked on the phone to make measurements were all the wrong part. (I was ready to install my old booster Just to get the car on the road)

Last phone call I found O'Reilly parts in town had one so I bought it out right and sat on it. The same day I called AutoZone and found out there was still one more at the hub where the last two from them were the wrong part. He measured the last one for me and it sounded good which we had it transferred to my local store.

In doing some additional research earlier, it looked like those wrong boosters were really for the earlier cars before 1992 which used the shorter rod and thinner rod.

The root of the problem was Cardone packaging or making the booster with the wrong rod and distributing them to all the parts houses. Problem is currently being worked.

So I got the booster installed today from AZ and did go for a test drive. The vacuum problem was corrected that I had and all appeared normal. On the test drive TCC lock up and cruise did not work consistently. Had to re-adjust the 3 part switch which took care of the problem (brake lights worked OK though).

Need to put some time on the car to see if the hesitation is still there since it is subtle and only does it when you're not looking, we'll see and chime back in.

antfarmer2

good job

Ricks94vette

Hi Pcolt94,

I too have a '94 and in need of a brake booster. Hard pedal and a definite hissing when applying the brakes.

Would you mind providing the correct part#, manufacturer, and where you purchased. I believe you stated AZ?

pcolt94

In response to your PM

The part number was 54-71405 which is the part number most part stores use which is the Cardone manufactures number. Make sure the rod matches the rod of the booster you bring in. the thinner rod is the wrong length also. It's got to match. Took me 6 days to finally get the proper one and a week of grief and a learning curve I did not need. I got it at AutoZone cause it was a warranty replacement.

A 7mm socket, small torx drivers, 1/4 inch ratchet set with universities and extensions, 13mm socket and wrench and general tools.

Master has got to be pulled back. ASR (3bolts) have to come out so it can be moved, drivers kick panel has to be removed, clip on brake pedal, and nuts holding booster which is the challenge. When putting booster in it will take some wiggling but inner (left) stud goes in first.

There is a 3 switch assembly on the brake pedal. One is for stop light, one is for cruise and one is for TCC lock up. The plunger needs to be pushed in 90% of the way for all switches to close. There has been lots of cruise problems related to the cruise switch being open or just dirty. It can cause no cruise engage or just might work on and off.

SJW

Hesitation gone now?

Live well,

SJW

pcolt94

Seems like the hesitation is still there. Starting a new thread for it with some additional information. The vacuum leak is corrected and the vacuum does not drop anymore where pedal is depressed. Brakes working normal now no problem.
New hesitation thread

https://www.corvetteforum.com/forums...post1591028452

Ricks94vette

Awesome and thanks for the tips on the R&R!
I'll check into the booster at AZ but was also referred (by a AZ manager) of a local shop here which rebuilds. I called them......$160 to rebuild mine so i wouldn't have to worry about miss matched parts. They said every replaceable part is replaced, not just a torn diaphragm. I was also informed the external housing "may" be made of plastic so that is stress tested for leakage. Additional $50 if it needs replacing.

But if it doesn't work out, I'll use the part number you provided for a replacement. Thanks again!