RJM Performance Clutch Pedal Assembly
11-08-2018, 10:39 AM
#316
In my 180sx, my clutch would be soft in the morning, but as I drove and pedal would firm up and at one point become super stiff. As soon as I adjusted the rod lower, the problem went away.
The following users liked this post:
Rochester (11-08-2018)
11-08-2018, 10:41 AM
#317
Administrator
Thread Starter
iTrader: (8)
I actually had something similar occur in my 180sx in the past. So when the clutch pedal is adjusted too far out, it cause something called 'pump-up' or something along that line . Its common in the 2g Eclipses. From what I understand, it has something to do with how the master cylinder bleeds pressure and when there isn't enough free play, the pressure builds.
In my 180sx, my clutch would be soft in the morning, but as I drove and pedal would firm up and at one point become super stiff. As soon as I adjusted the rod lower, the problem went away.
In my 180sx, my clutch would be soft in the morning, but as I drove and pedal would firm up and at one point become super stiff. As soon as I adjusted the rod lower, the problem went away.
Thank you.
11-08-2018, 02:55 PM
#318
@ projectpanda13 I think it depends *how* the pedal is adjusted. Is it adjusted by the mc plunger & limit switches, or by the 3 nuts/bolts that allow the pedal to be adjusted some without affecting the other 3. I suppose adjusting using the former can indeed create weird issues because one is changing the mc plunger dynamics.
@rochester, if you like the pedal higher, depending how those 3 bolts are adjusted, you might have more pedal adjustment left which shouldn't affect anything else.
@rochester, if you like the pedal higher, depending how those 3 bolts are adjusted, you might have more pedal adjustment left which shouldn't affect anything else.
11-08-2018, 06:37 PM
#319
Registered User
Good evening Rochester,It's a pleasure to hear from you again. I can definitely help explain things and will post this to your thread as well. This is actually one of the most common questions I get for tech support so in that respect I wish you’d of contacted me sooner as its about a 30 second fix most of the time.
The key to why the issue started up lies in your description of having found the AFP backed out and having reset it fully clockwise + back ½ turn or so. Anytime the AFP is adjusted the upper cruise switch must also be checked or adjusted to ensure it doesn’t prevent the pedal from returning fully as the pedal resting height rises slightly as a by product of AFP adjustment. This small rise in resting pedal height would prevent the master cylinder from fully returning if the upper switch was preventing the pedal from reaching it’s now higher resting point and is the root of the problem.
JSolo got it exactly right that the internal vent port in the master cylinder was being blocked before the new mechanic “lowered the pedal” however the issue was not a case of the pedal being too high if you will as the RJM pedal allows you to set the height however you see fit within the mechanical limits of the pedal. The real issue is the upper cruise switch wasn’t checked/adjusted accordingly after making the change to the AFP setting.
Now I understand you felt you were setting it back to where it was which technically wouldn’t require a change to the upper switch but ultimately the master vent port ending up blocked tells me that after this adjustment the pedal’s upper resting position was indeed a slight bit higher then it was in the past initiating the issue. The simple solution to this is the upper cruise switch just needs to be loosened and threaded upward a few threads to take any pressure off the master cylinder rod with the pedal fully up.
Your new mechanic in fact didn’t “need” to reduce the pedal height even though that did fix the issue by ultimately lowering the pedal’s top resting position to be lower again, thereby taking any pressure off the master cylinder rod.It’s for this exact common issue that after adjusting the AFP or the clutch rod especially the upper switch must always be adjusted to correct for the new pedal height after any adjustments.
As well with the later design Rev3.X units the upper switch has been moved to a pivoting switch mount that locks with just a single Allen bolt so adjusting the upper switch is literally a 30 second operation to loosen the lock, rotate the switch and retighten it while setting up the pedal. On the older Rev2 series units the upper switch is in a fixed mount so you’d need to loosen the two jam nuts and thread the switch up/down to adjust before retightening the jam nuts.
Now for the technical explanation of what happens when the vent port is blocked:The vent port is a very small port that gets uncovered at the very top of the internal piston’s travel. So it’s only open when the cylinder is 100% fully returned and closes again by moving the internal piston only about 30 thousands of an inch downward travel so it takes very very little pressure on the cylinder to cause the port to get blocked. This vent when open allows fluid to travel between the high pressure side of the cylinder and the fluid reservoir. So when the car is hot excess fluid from expansion of the clutch fluid is relieved and vents to the reservoir preventing any pressure build up in the clutch line when not pressing the clutch. Conversely when the car cools down again after driving the hot fluid in the lines begins to contract and creates a vacuum which pulls fresh fluid into the line from the reservoir to replace the lost volume pushed out while it was hot. It’s this cold contraction that leads to a low and squishy pedal after sitting overnight that may or may not resolve itself as the fluid that remains in the line re-expands in volume as it heats up. So blocking of the fluid port leads to the classic low pedal in the morning and slowly returning to normal pedal feel after driving a bit.
As for the GTR fluid, I agree the crap fluid Nissan originally put in these cars from the factory is completely used up and so full of moisture within a couple years of ownership that fluid boiling issues start to surface, especially on cars driven hard. That said ANY quality high dry boiling point fluid will do exactly the same thing as the GTR fluid (Nissan is just pushing their higher rated $$$.$$ fluid here) and in most cases even just flushing the system with basic gas station fluid would do just fine so long as it gets done yearly. Again Nissan just wants to see you once within the warranty period for this so they put the better stuff in that will hopefully get your thru until the warranty is up before it needs flushing again. I typically flush the clutch fluid on all my manual vehicles once a year, typically in the spring as just part of regular maintenance. Everyone knows to change the engine oil regularly but not many people flush the clutch or brake systems until something fails. Same goes for transmission and differential fluids as well, they rarely get checked or changed either.
Anyway, hope that helps explain things for your and anyone else inquisitive about the problem you encountered.Best Regards,
Ryan Morgan
RJM Performance Inc.
The key to why the issue started up lies in your description of having found the AFP backed out and having reset it fully clockwise + back ½ turn or so. Anytime the AFP is adjusted the upper cruise switch must also be checked or adjusted to ensure it doesn’t prevent the pedal from returning fully as the pedal resting height rises slightly as a by product of AFP adjustment. This small rise in resting pedal height would prevent the master cylinder from fully returning if the upper switch was preventing the pedal from reaching it’s now higher resting point and is the root of the problem.
JSolo got it exactly right that the internal vent port in the master cylinder was being blocked before the new mechanic “lowered the pedal” however the issue was not a case of the pedal being too high if you will as the RJM pedal allows you to set the height however you see fit within the mechanical limits of the pedal. The real issue is the upper cruise switch wasn’t checked/adjusted accordingly after making the change to the AFP setting.
Now I understand you felt you were setting it back to where it was which technically wouldn’t require a change to the upper switch but ultimately the master vent port ending up blocked tells me that after this adjustment the pedal’s upper resting position was indeed a slight bit higher then it was in the past initiating the issue. The simple solution to this is the upper cruise switch just needs to be loosened and threaded upward a few threads to take any pressure off the master cylinder rod with the pedal fully up.
Your new mechanic in fact didn’t “need” to reduce the pedal height even though that did fix the issue by ultimately lowering the pedal’s top resting position to be lower again, thereby taking any pressure off the master cylinder rod.It’s for this exact common issue that after adjusting the AFP or the clutch rod especially the upper switch must always be adjusted to correct for the new pedal height after any adjustments.
As well with the later design Rev3.X units the upper switch has been moved to a pivoting switch mount that locks with just a single Allen bolt so adjusting the upper switch is literally a 30 second operation to loosen the lock, rotate the switch and retighten it while setting up the pedal. On the older Rev2 series units the upper switch is in a fixed mount so you’d need to loosen the two jam nuts and thread the switch up/down to adjust before retightening the jam nuts.
Now for the technical explanation of what happens when the vent port is blocked:The vent port is a very small port that gets uncovered at the very top of the internal piston’s travel. So it’s only open when the cylinder is 100% fully returned and closes again by moving the internal piston only about 30 thousands of an inch downward travel so it takes very very little pressure on the cylinder to cause the port to get blocked. This vent when open allows fluid to travel between the high pressure side of the cylinder and the fluid reservoir. So when the car is hot excess fluid from expansion of the clutch fluid is relieved and vents to the reservoir preventing any pressure build up in the clutch line when not pressing the clutch. Conversely when the car cools down again after driving the hot fluid in the lines begins to contract and creates a vacuum which pulls fresh fluid into the line from the reservoir to replace the lost volume pushed out while it was hot. It’s this cold contraction that leads to a low and squishy pedal after sitting overnight that may or may not resolve itself as the fluid that remains in the line re-expands in volume as it heats up. So blocking of the fluid port leads to the classic low pedal in the morning and slowly returning to normal pedal feel after driving a bit.
As for the GTR fluid, I agree the crap fluid Nissan originally put in these cars from the factory is completely used up and so full of moisture within a couple years of ownership that fluid boiling issues start to surface, especially on cars driven hard. That said ANY quality high dry boiling point fluid will do exactly the same thing as the GTR fluid (Nissan is just pushing their higher rated $$$.$$ fluid here) and in most cases even just flushing the system with basic gas station fluid would do just fine so long as it gets done yearly. Again Nissan just wants to see you once within the warranty period for this so they put the better stuff in that will hopefully get your thru until the warranty is up before it needs flushing again. I typically flush the clutch fluid on all my manual vehicles once a year, typically in the spring as just part of regular maintenance. Everyone knows to change the engine oil regularly but not many people flush the clutch or brake systems until something fails. Same goes for transmission and differential fluids as well, they rarely get checked or changed either.
Anyway, hope that helps explain things for your and anyone else inquisitive about the problem you encountered.Best Regards,
Ryan Morgan
RJM Performance Inc.
Last edited by Northern G; 11-08-2018 at 06:47 PM.
The following 3 users liked this post by Northern G:
11-08-2018, 06:45 PM
#320
Administrator
Thread Starter
iTrader: (8)
I'm going to asses the fitment on my cruise switch ASAP.
This was an incredibly insightful post by Ryan at RJM.
This was an incredibly insightful post by Ryan at RJM.
Last edited by Rochester; 11-08-2018 at 07:39 PM.
11-08-2018, 06:55 PM
#322
Registered User
I personally use the Prestone Synthetic DOT3 "Ford" formulation as it has a slightly higher boiling point then regular DOT3 spec fluid and less then $8 a bottle off the shelf pretty much any corner auto parts place . The Ford stuff is a 500*F boiling point where the regular stuff is 450*F so no big deal at all and I think you'll be just fine with it. Like I said any fluid flush hands down beats having the factory fluid still in there that typically looks like black sludge 4-5 years on when it's drained from the slave end.
The following users liked this post:
saywat? (11-08-2018)
11-08-2018, 07:50 PM
#323
Administrator
Thread Starter
iTrader: (8)
So... when this new mechanic lowered the pedal, and by virtue of manipulating the entire assembly, are you saying he inadvertently created slack that was lacking against the cruise switch? That's a pretty narrow tolerance of cause & effect, but it does fit the problem description.
In any event, he saved me money not already spent. I did needlessly buy a new MC, but that's OK, it was only $100 and odds are I'll be using it someday, or selling it online. And I did just order a quart of GTR brake fluid, but I can use that for another fluid swap. Maybe next spring, when I'll be needing an inspection, and will be tapping this new shop for a motor mount install.
Pretty curious to check the cruise switch tomorrow. And to lift the pedal back up to where I like it.
In any event, he saved me money not already spent. I did needlessly buy a new MC, but that's OK, it was only $100 and odds are I'll be using it someday, or selling it online. And I did just order a quart of GTR brake fluid, but I can use that for another fluid swap. Maybe next spring, when I'll be needing an inspection, and will be tapping this new shop for a motor mount install.
Pretty curious to check the cruise switch tomorrow. And to lift the pedal back up to where I like it.
11-08-2018, 08:28 PM
#324
Registered User
So... when this new mechanic lowered the pedal, and by virtue of manipulating the entire assembly, are you saying he inadvertently created slack that was lacking against the cruise switch? That's a pretty narrow tolerance of cause & effect, but it does fit the problem description.
In any event, he saved me money not already spent. I did needlessly buy a new MC, but that's OK, it was only $100 and odds are I'll be using it someday, or selling it online. And I did just order a quart of GTR brake fluid, but I can use that for another fluid swap. Maybe next spring, when I'll be needing an inspection, and will be tapping this new shop for a motor mount install.
Pretty curious to check the cruise switch tomorrow. And to lift the pedal back up to where I like it.
In any event, he saved me money not already spent. I did needlessly buy a new MC, but that's OK, it was only $100 and odds are I'll be using it someday, or selling it online. And I did just order a quart of GTR brake fluid, but I can use that for another fluid swap. Maybe next spring, when I'll be needing an inspection, and will be tapping this new shop for a motor mount install.
Pretty curious to check the cruise switch tomorrow. And to lift the pedal back up to where I like it.
The following users liked this post:
Rochester (11-09-2018)
11-08-2018, 11:20 PM
#325
@Rochester Still have your installation instructions? I recall on one of those pages it mentioned anytime an afp adjustment is made, switches should be checked/readjusted.
Time to get more intimate with your car than relying on the mechanic
Edit: Updated first post to link to explanation above.
Time to get more intimate with your car than relying on the mechanic
Edit: Updated first post to link to explanation above.
11-09-2018, 06:19 AM
#326
Administrator
Thread Starter
iTrader: (8)
@Rochester Still have your installation instructions? I recall on one of those pages it mentioned anytime an afp adjustment is made, switches should be checked/readjusted.
Time to get more intimate with your car than relying on the mechanic
Edit: Updated first post to link to explanation above.
Time to get more intimate with your car than relying on the mechanic
Edit: Updated first post to link to explanation above.
Good idea, linking Ryan's comment from the first post.
11-09-2018, 12:01 PM
#327
^^I know where you're coming from. I've experienced a failed clutch on other vehicles. One motorcycle had the clutch cable partially fail ~20 miles from home. Few strands remaining. It was an interesting ride back to say the least. On a different bike I had weird hydraulic issues (similar to yours actually). Grab point would change. Sometimes it would grab normally, others with the lever almost at the bar (fully stock clutch with no modifications. Never did figure out if the issue was MC or slave related. Traded it in on a newer model with cable clutch, kept a spare with me at all times.
I think if I experienced this with a car, depending on severity, I'd probably just have it towed.
I think if I experienced this with a car, depending on severity, I'd probably just have it towed.
11-09-2018, 12:17 PM
#328
You didn't enjoy pulling the pedal up with your toe while the smell of burning clutch rolls into the cabin? Cars flying up on your bumper, becoming enraged, as you cost down the road; doing all you can to maintain momentum and limp home?
Yea me neither.
Yea me neither.
11-09-2018, 12:47 PM
#329
Administrator
Thread Starter
iTrader: (8)
In my case, I was pulling into a shopping plaza when it all went to hell. Coasted to a stop, called for a tow to the dealership. Very unpleasant moment, could have so easily been worse.