As an OG Lurker, I felt I needed to post this public service announcement, as I have not seen anything of recent on the topic, or I am just missed the posts.
Drove my 03 in the morning, prior heat wave afternoon, to keep the battery charged and internals lubed, got home everything was fine. Went out to make sure the cars/yard were secure for the night and noticed my brake lights were on? Checked the light switch and tried to start the car, battery had enough energy to try and crank. Did the initial troubleshooting at the car, no joy. Got on the computer and found that my issue is 90% a grommet for the brake switch. Sure enough, went out and checked the floorboard and remnants of a plastic were found under the pedal.
My post is for those, like me that weren't aware of the deterioration of the grommets on the brake and clutch pedal.

 

Thanks for the heads up

 

This is actually a fairly common issue depending on the mileage and climate the vehicle has lived in. I checked all my pedal bump stops when I installed my RJM clutch pedal, being a CA vehicle, they're all still in good shape, none of them have hardened up (turned into brittle plastic) yet. There are some really cheap/easy DIY fixes for these, like using those universal plastic pop rivets you see holding fender liners and the like on various make/model vehicles. Anyway, if you ever see your brake lights stuck on, this is the number one cause. You can also experience issues starting your vehicle if it's the clutch pedal bump stop that crumbles/fails on a 6MT.

Definitely something to be aware of as these cars start approaching the 25 year mark. Rubber and plastic don't last forever and that lifespan is heavily dependent on climate and usage.
Cheers!
-Icer

 

Just happened to me this past weekend. Walked outside to toss the trash out and all my brake lights were glowing. Did a quick check and couldn't find any issues, so I began frantically searching online. Went back outside and found crumbled plastic in the floor mats. Just ordered the replacement from Z1 and now just need time to replace the old one. I really wish they'd make an aluminum version of these grommets instead of using the plastic ones.

 

Happened to me a couple weeks back, too. I saw where some people used a threaded bolt as a quick fix or more temporary solution, but it seems like the raised head of the bolt would not be as flush as the grommet.

 

I just went thru the brake Grommet replacement. No problem.
Then the grommet came out again. My son ordered a kit with correct Grommet
and Brake light switch ( I think ) Brake lights are no longer on. BUT, now my brakes are dragging.
What's up with that ? Why are my brakes suddenly dragging and how do I correct that problem. ?
Thanks.

'04 Nissan 350Z
6 speed manual trans

 

YES - same exact thing happened to me, too. I made it about a half mile from my house and noticed something was definitely not right. On the side of the road, I disconnected the brake switches above the pedal (which caused my brake lights to illuminate constantly), but then there was no more brake drag. I made it back home and plugged the switches back so the brake lights would shut off.

I let it sit. A couple days later, I took it for a test drive and the brake pedal was extremely sensitive. Like zero travel and then the brakes would engage HARD. But, there was no more brake drag.

Haven't driven it since and I have not had time to troubleshoot the issue, but a similar thread on here made it seem like it could be a failing brake booster. https://my350z.com/forum/brakes-and-...l#post11086169

Between the two of us, maybe one of us will figure out the issue shortly. I hope to have some time this weekend to tackle it unless life gets in the way again.

 

Thanks for that information.
I'm headed to work now but will try that when I get home this afternoon.
Again, thanks.

 

Since the brake booster is dependent on intake vacuum, I'm wondering if this issue could be related to the learned idle value? I believe there's a check valve on the brake booster line. If the check valve is holding "higher" than normal vacuum, that might cause this problem. The missing brake pedal grommet might have done something to the engine idle setting or something with the ABS module which resulted in the brakes dragging.

Just something to try, no idea if this will have an effect. Try doing a throttle position and idle air volume relearn (easiest with a bi-directional OBD2 tool). With the engine off, disconnect the vacuum line from the booster to bring back to atmospheric pressure (essentially a reset). Fire up the engine and see if the issue persists.
Cheers!
-Icer

 

Read through the linked thread. It very well could be a bad booster. I'm just trying to wrap my head around how a failing booster would cause the brakes to drag. Usually the vacuum diaphragm rips or tears on boosters and causes a loss of power brakes, not the other way around. I suppose it all depends on the internal design of the booster and how the vacuum boost is controlled.

Did a little reading, found this article (LINK).

I didn't realize that vacuum is applied to both sides of the diaphragm.
"The engine creates a partial vacuum inside the vacuum booster on both sides of the diaphragm. When you hit the brake pedal, the rod cracks open a valve, allowing air to enter the booster on one side of the diaphragm while sealing off the vacuum. This increases pressure on that side of the diaphragm so that it helps to push the rod, which in turn pushes the piston in the master cylinder.As the brake pedal is released, the valve seals off the outside air supply while reopening the vacuum valve. This restores vacuum to both sides of the diaphragm, allowing everything to return to its original position."

In a nutshell, a faulty valve inside the booster could be causing a vacuum imbalance when the brake pedal is released, this can prevent the the brakes from fully releasing and result in drag.

The more you know!
Cheers!
-Icer

 

Best thing to use is a plastic fender liner button. works great and no deteriation.

 

Thanks for the valuable input and insight as always Icer!

Looks like rain is (finally) in the forecast this weekend, which means garage time for me. This is basically my plan of attack - of course, let me know if you think I'm missing anything or have any other suggestions:

Reset the ECU with a 24h+ battery disconnect.

Reconnect and test whether the pedal travel feels normal at idle.

If not, test the pedal travel with the engine on and off by depressing the pedal to change the vacuum to atmospheric pressure.

Inspect the check valve in the brake booster line which runs close to the battery compartment. It's in the U-shaped bend right before the line attaches to the intake manifold. I've got a handheld vacuum pump, so I'm going to follow the procedure in the FSM and test the vacuum from the booster side and then make sure it's not holding any vacuum from the intake side.

Remove brake booster and check the output rod length by applying vacuum to the booster.

In the event I need a new booster, I searched around and apparently there are different boosters depending on the trim level with or without VDC/TCS. The OEM booster seems either impossible to find or $1,000+. There are aftermarket replacements that are much cheaper, and then many used boosters available secondhand on fleabay which also include the MC. It appears the booster is made by Bosch. The master cylinder has the same bore size of 1-1/16" regardless of base brakes or brembo, so that should be universal.

OEM on my '05 were the crappy base brakes, but I swapped over to the Akebono BBK a while ago. No issues since then. Not sure if this contributed to the issue or if it's just a coincidence.

It does seem odd that there have been more than a few instances of people experiencing the brakes dragging after the grommets fail. Did the failing booster make the grommets fail, or did the failing grommets make the booster (if that is the issue) fail. Or, is it just the ABS module on the fritz after the grommets crap out?

 

I think you have a good plan of action. The more I think about it, the booster is most likely at fault. The grommet failing may just be a coincidence.

Also, I believe you can upgrade to a 370Z MC + Booster combo with minimal effort. I haven't done in depth research on this, but as an example, my buddy with a 94 300ZX TT upgraded to an R35 MC + Booster. He did need to increase the diameter of the hole in the firewall for the pedal connection and adapt the brake line flare nuts for the larger size on the R35 MC, but otherwise it was a simple swap/upgrade.

I think you can purchase a 370Z Booster/MC combo cheaper New vs. 350Z (more available stock, less demand).
Cheers!
-Icer

 

Thanks for the input. Not sure if this is 100% accurate or not, but from what I found, I think the bore size of the 370Z MC is 1" as opposed to 1-1/16". The R35 MC bore size is 1-1/16". It appears that Nissan used a 1-1/16" bore MC on Z32's built prior to Jan 1991 and then they switched to a 1" bore MC which was the OEM setup on your friend's '94 Z32 TT.

From some quick internet searching, I don't think it matters too terribly much about the difference in the MC bore size on our Z33s, but the main thing I need to be concerned with when replacing the booster is with a model that's compatible with the TCS/VDC which is on my '05.

 

Good point, but I don't think the booster or MC have much to do with TCS/VDC, that's controlled through the ABS module (AFAIK). The electrical connection on the MC is only for the reservoir level sensor I thought, I would need to read up on this in the FSM. Path of least resistance would be to procure a good low mileage used one from a Nissan specialized dismantler/wrecker. I'm still shocked that a new OEM booster is retailing for $1000+.
Cheers!
-Icer

 

I finally got some time to research more and found this. Since replacing the switch is what started my problem, I didn't think the brake booster was bad.
I found this video and it makes perfect sense. This could actually be the problem with my dragging, overheating brakes. ( MAYBE )
It may be a slow process with all the adjust- test,-repeat. But, it's worth a shot.

 

After watching the video and applying what I learned, the problem I was having is no longer a problem.
The fix was quick and simple.
My Convertible top is working ( actually it was working before but after removing the parts and reinstalling them, they had to be adjusted also.)
I hope this helps someone else.
Heel Til I Die, thanks for taking the time to answer my post. Perhaps this video will cure your problem as well. Icer and the rest, Thank you also.
Now, what am I going to spend that $1,000 on now that I don't have to buy the new Brake Booster ?

 

I didn't even think about one of the brake pedal switches being bad or incorrectly adjusted, these switches are very reliable and rarely fail, but as these cars age, it's completely within the realm of possibility. It's for sure good information and something else to check. If you have a fancy scan tool you can actually monitor the switch positions (open vs. closed), making it very easy to do a quick test/check if you have a bad switch. Alternatively you can do what the guy in the video suggests & use a multimeter. If you're in a bind and don't want to wait for a replacement part, you can take these switches apart, clean them, and put them back together. The cover piece is a snap fit, you just need to be gentle to release the tabs. The contacts inside can get sooty over time. Simply clean them with a little sand paper and bend the metal contacts as needed. I also like to add a little dielectric grease to the pushrod to ensure smooth/quiet operation.

As for the adjustment, if you decide to replace a failed grommet/bump-stop with something different from the original design (something thicker/bulkier), there is a chance the depth adjustment on the switches will be different and cause the brakes to drag. (Prevents the pedal from fully extending back to it's parked/released position). As seen in the video, the switches both have locking ribs for quick and easy depth adjustment, so make sure to re-adjust the switches as needed if you choose a more home-brew grommet repair option.

Although I never had this specific problem with the brakes or brake lights, I did install cruise control on my old Base model 350Z and part of the process was adding the CC specific switches to both the clutch and brake pedal assemblies. It's just not fun working under the steering column!

Cheers!
-Icer

 

Brilliant. Thanks for taking the time to find and post this!

I had a stinking suspicion it was an issue with the brake switch since I had normal pedal feel/travel once I disengaged the brake light switch, but who knows.

I'll add it to one of the first things on my troubleshooting list and report back!

But not looking forward to squeezing under the steering column.

 

Or, in laymen's terms, the simplest explanation is usually the best one.

TLDR - adjust the stop lamp switch if you experience your brakes dragging after replacing the worn/missing out pedal grommets.

This applies to my M/T '05, but it should also apply to other years. If it's A/T, then there will be more than two pins on the sensors since a signal is also sent to disengage the interlock when shifting out of park.

From the FSM:

The stop lamp switch on the brake pedal is a simple plunger type switch which interrupts the circuit when the plunger is out (brake pedal depressed) and completes the signal when the plunger is in (brake pedal released).




If your Z is equipped with cruise control (ASCD), then there will be another plunger type switch which cancels cruise control when it is engaged with a tap of the brake pedal. The stop lamp switch is located under the ASCD cancel switch as shown in the diagram below.



Probably a good first order of business to confirm the play and clearance amounts:




Below is the diagnostic procedure according to the FSM to determine whether the switch is operating correctly or not and verify that power is being routed to the wiring harness connector leading to the switch.





As shown in the last step, a quick and easy way to test the plunger switches is to use a multimeter and verify continuity.

When the plunger is fully extended (representing the brake pedal depressed/engaged), there should be a break in the circuit (or no continuity / OL (open line)).




With the plunger depressed signifying the brake pedal has been released and brakes are not engaged, there should be continuity and the loop is closed.



After confirming the switches are OK, time to reinstall them (correctly this time).

The easiest way for me (and because I have somewhat freakishly long arms), was to do the following: I backed in the Z into my garage so I could see the red glow from the brake lights when they were illuminated against the wall. I inserted the stop lamp switch into the clip or collar without yet turning it clockwise to set it. With the stop lamp switch not seated into the clip and the plunger fully elongated, the rear brake lights should be illuminated. With one hand on the switch and looking towards the rear of the Z, I slowly started to push in the stop lamp switch into the collar, depressing the plunger switch, until the brake lights went out. I then tested it and with the brake pedal play (3-11 mm), the brake lights would illuminate. This probably would have been fine, and convenient to brake check anyone tailgating me without the brakes actually engaging, but I adjusted it correctly by pushing in the switch a tiny bit more. The brake lights should no longer illuminate with only the play in the brake pedal.

As for the ASCD cancel switch (if so equipped), I found that the plunger length did not have to be set as precisely as the stop lamp switch. Initially, I inserted the ASCD switch until the plunger barely contacted the grommet on the pedal - similar to the stop lamp switch. On a test drive, cruise control did not set. I then inserted the switch significantly more than the stop lamp switch (maybe about half of the plunger was depressed), and cruise control would properly set. I also verified it would cancel upon depressing the brake pedal. So, it would appear that the plunger on the ASCD cancel switch needs to be inserted a little more than the stop lamp switch to for cruise control to work properly.

Picture of switches installed properly below (sorry for the orange glow - footwell lighting). Notice that that there is less of the threaded portion visible on the ASCD cancel switch (top) than the stop lamp switch (bottom).



Thanks to shooter45 and icer5160 for pointing me in the right direction. Hopefully this helps anyone else who has this issue!